jack1/jackd/engine.c

/* -*- mode: c; c-file-style: "bsd"; -*- */
/*
    Copyright (C) 2001-2003 Paul Davis
    Copyright (C) 2004 Jack O'Quin

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

 */

#include <config.h>

#include <math.h>
#include <unistd.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <sys/stat.h>
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdarg.h>
#ifdef HAVE_STDINT_H
#include <stdint.h>
#endif
#include <dirent.h>
#include <signal.h>
#include <sys/types.h>
#include <string.h>
#include <limits.h>

#include <jack/thread.h>
#include <jack/uuid.h>
#include <jack/metadata.h>

#include "internal.h"
#include "engine.h"
#include "messagebuffer.h"
#include "driver.h"
#include "shm.h"

#include <sysdeps/poll.h>
#include <sysdeps/ipc.h>

#ifdef USE_MLOCK
#include <sys/mman.h>
#endif /* USE_MLOCK */

#ifdef USE_CAPABILITIES
/* capgetp and capsetp are linux only extensions, not posix */
#undef _POSIX_SOURCE
#include <sys/capability.h>
#endif

#include "clientengine.h"
#include "transengine.h"

#include "libjack/local.h"

typedef struct {

	jack_port_internal_t *source;
	jack_port_internal_t *destination;
	jack_client_internal_t *srcclient;
	jack_client_internal_t *dstclient;
} jack_connection_internal_t;

typedef struct _jack_driver_info {
	jack_driver_t *(*initialize)(jack_client_t *, const JSList *);
	void (*finish);
	char (*client_name);
	dlhandle handle;
} jack_driver_info_t;

jack_timer_type_t clock_source = JACK_TIMER_SYSTEM_CLOCK;

static int      jack_port_assign_buffer(jack_engine_t *,
					jack_port_internal_t *);
static jack_port_internal_t *jack_get_port_by_name(jack_engine_t *,
						   const char *name);
static int  jack_rechain_graph(jack_engine_t *engine);
static void jack_clear_fifos(jack_engine_t *engine);
static int  jack_port_do_connect(jack_engine_t *engine,
				 const char *source_port,
				 const char *destination_port);
static int  jack_port_do_disconnect(jack_engine_t *engine,
				    const char *source_port,
				    const char *destination_port);
static int  jack_port_do_disconnect_all(jack_engine_t *engine,
					jack_port_id_t);
static int  jack_port_do_unregister(jack_engine_t *engine, jack_request_t *);
static int  jack_port_do_register(jack_engine_t *engine, jack_request_t *, int);
static int  jack_do_get_port_connections(jack_engine_t *engine,
					 jack_request_t *req, int reply_fd);
static int  jack_port_disconnect_internal(jack_engine_t *engine,
					  jack_port_internal_t *src,
					  jack_port_internal_t *dst);
static int  jack_send_connection_notification(jack_engine_t *,
					      jack_uuid_t,
					      jack_port_id_t,
					      jack_port_id_t, int);
static void jack_deliver_event_to_all(jack_engine_t *engine,
				      jack_event_t *event);
static void jack_notify_all_port_interested_clients(jack_engine_t *engine,
						    jack_uuid_t exclude_src_id,
						    jack_uuid_t exclude_dst_id,
						    jack_port_id_t a,
						    jack_port_id_t b,
						    int connect);
static void jack_engine_post_process(jack_engine_t *);
static int  jack_run_cycle(jack_engine_t *engine, jack_nframes_t nframes,
			   float delayed_usecs);
static int   jack_run_one_cycle(jack_engine_t *engine, jack_nframes_t nframes,
				float delayed_usecs);
static void jack_engine_delay(jack_engine_t *engine,
			      float delayed_usecs);
static void jack_engine_driver_exit(jack_engine_t* engine);
static int  jack_start_freewheeling(jack_engine_t* engine, jack_uuid_t);
static void jack_compute_all_port_total_latencies(jack_engine_t *engine);
static void jack_compute_port_total_latency(jack_engine_t *engine, jack_port_shared_t*);
static int jack_check_client_status(jack_engine_t* engine);
static int jack_do_session_notify(jack_engine_t *engine, jack_request_t *req, int reply_fd );
static void jack_port_rename_notify(jack_engine_t *engine, const char* old_name, const char* new_name);
static void jack_do_get_client_by_uuid(jack_engine_t *engine, jack_request_t *req);
static void jack_do_get_uuid_by_client_name(jack_engine_t *engine, jack_request_t *req);
static void jack_do_reserve_name(jack_engine_t *engine, jack_request_t *req);
static void jack_do_session_reply(jack_engine_t *engine, jack_request_t *req );
static void jack_compute_new_latency(jack_engine_t *engine);
static int jack_do_has_session_cb(jack_engine_t *engine, jack_request_t *req);

static inline int
jack_rolling_interval (jack_time_t period_usecs)
{
	return floor ((JACK_ENGINE_ROLLING_INTERVAL * 1000.0f) / period_usecs);
}

void
jack_engine_reset_rolling_usecs (jack_engine_t *engine)
{
	memset (engine->rolling_client_usecs, 0,
		sizeof(engine->rolling_client_usecs));
	engine->rolling_client_usecs_index = 0;
	engine->rolling_client_usecs_cnt = 0;

	if (engine->driver) {
		engine->rolling_interval =
			jack_rolling_interval (engine->driver->period_usecs);
	} else {
		engine->rolling_interval = JACK_ENGINE_ROLLING_INTERVAL;
	}

	engine->spare_usecs = 0;
}

static inline jack_port_type_info_t *
jack_port_type_info (jack_engine_t *engine, jack_port_internal_t *port)
{
	/* Returns a pointer to the port type information in the
	   engine's shared control structure.
	 */
	return &engine->control->port_types[port->shared->ptype_id];
}

static inline jack_port_buffer_list_t *
jack_port_buffer_list (jack_engine_t *engine, jack_port_internal_t *port)
{
	/* Points to the engine's private port buffer list struct. */
	return &engine->port_buffers[port->shared->ptype_id];
}

static int
make_directory (const char *path)
{
	struct stat statbuf;

	if (stat (path, &statbuf)) {

		if (errno == ENOENT) {
			int mode;

			if (getenv ("JACK_PROMISCUOUS_SERVER")) {
				mode = 0777;
			} else {
				mode = 0700;
			}

			if (mkdir (path, mode) < 0) {
				jack_error ("cannot create %s directory (%s)\n",
					    path, strerror (errno));
				return -1;
			}
		} else {
			jack_error ("cannot stat() %s\n", path);
			return -1;
		}

	} else {

		if (!S_ISDIR (statbuf.st_mode)) {
			jack_error ("%s already exists, but is not"
				    " a directory!\n", path);
			return -1;
		}
	}

	return 0;
}

static int
make_socket_subdirectories (const char *server_name)
{
	struct stat statbuf;
	char server_dir[PATH_MAX + 1] = "";

	/* check tmpdir directory */
	if (stat (jack_tmpdir, &statbuf)) {
		jack_error ("cannot stat() %s (%s)\n",
			    jack_tmpdir, strerror (errno));
		return -1;
	} else {
		if (!S_ISDIR (statbuf.st_mode)) {
			jack_error ("%s exists, but is not a directory!\n",
				    jack_tmpdir);
			return -1;
		}
	}

	/* create user subdirectory */
	if (make_directory (jack_user_dir ()) < 0) {
		return -1;
	}

	/* create server_name subdirectory */
	if (make_directory (jack_server_dir (server_name, server_dir)) < 0) {
		return -1;
	}

	return 0;
}

static int
make_sockets (const char *server_name, int fd[2])
{
	struct sockaddr_un addr;
	int i;
	char server_dir[PATH_MAX + 1] = "";

	if (make_socket_subdirectories (server_name) < 0) {
		return -1;
	}

	/* First, the master server socket */

	if ((fd[0] = socket (AF_UNIX, SOCK_STREAM, 0)) < 0) {
		jack_error ("cannot create server socket (%s)",
			    strerror (errno));
		return -1;
	}

	addr.sun_family = AF_UNIX;
	for (i = 0; i < 999; i++) {
		snprintf (addr.sun_path, sizeof(addr.sun_path) - 1,
			  "%s/jack_%d", jack_server_dir (server_name, server_dir), i);
		if (access (addr.sun_path, F_OK) != 0) {
			break;
		}
	}

	if (i == 999) {
		jack_error ("all possible server socket names in use!!!");
		close (fd[0]);
		return -1;
	}

	if (bind (fd[0], (struct sockaddr*)&addr, sizeof(addr)) < 0) {
		jack_error ("cannot bind server to socket (%s)",
			    strerror (errno));
		close (fd[0]);
		return -1;
	}

	if (listen (fd[0], 1) < 0) {
		jack_error ("cannot enable listen on server socket (%s)",
			    strerror (errno));
		close (fd[0]);
		return -1;
	}

	/* Now the client/server event ack server socket */

	if ((fd[1] = socket (AF_UNIX, SOCK_STREAM, 0)) < 0) {
		jack_error ("cannot create event ACK socket (%s)",
			    strerror (errno));
		close (fd[0]);
		return -1;
	}

	addr.sun_family = AF_UNIX;
	for (i = 0; i < 999; i++) {
		snprintf (addr.sun_path, sizeof(addr.sun_path) - 1,
			  "%s/jack_ack_%d", jack_server_dir (server_name, server_dir), i);
		if (access (addr.sun_path, F_OK) != 0) {
			break;
		}
	}

	if (i == 999) {
		jack_error ("all possible server ACK socket names in use!!!");
		close (fd[0]);
		close (fd[1]);
		return -1;
	}

	if (bind (fd[1], (struct sockaddr*)&addr, sizeof(addr)) < 0) {
		jack_error ("cannot bind server to socket (%s)",
			    strerror (errno));
		close (fd[0]);
		close (fd[1]);
		return -1;
	}

	if (listen (fd[1], 1) < 0) {
		jack_error ("cannot enable listen on server socket (%s)",
			    strerror (errno));
		close (fd[0]);
		close (fd[1]);
		return -1;
	}

	return 0;
}

void
jack_engine_place_port_buffers (jack_engine_t* engine,
				jack_port_type_id_t ptid,
				jack_shmsize_t one_buffer,
				jack_shmsize_t size,
				unsigned long nports,
				jack_nframes_t nframes)
{
	jack_shmsize_t offset;          /* shared memory offset */
	jack_port_buffer_info_t *bi;
	jack_port_buffer_list_t* pti = &engine->port_buffers[ptid];
	jack_port_functions_t *pfuncs = jack_get_port_functions (ptid);

	pthread_mutex_lock (&pti->lock);
	offset = 0;

	if (pti->info) {

		/* Buffer info array already allocated for this port
		 * type.  This must be a resize operation, so
		 * recompute the buffer offsets, but leave the free
		 * list alone.
		 */
		int i;

		bi = pti->info;
		while (offset < size) {
			bi->offset = offset;
			offset += one_buffer;
			++bi;
		}

		/* update any existing output port offsets */
		for (i = 0; i < engine->port_max; i++) {
			jack_port_shared_t *port = &engine->control->ports[i];
			if (port->in_use &&
			    (port->flags & JackPortIsOutput) &&
			    port->ptype_id == ptid) {
				bi = engine->internal_ports[i].buffer_info;
				if (bi) {
					port->offset = bi->offset;
				}
			}
		}

	} else {
		jack_port_type_info_t* port_type = &engine->control->port_types[ptid];

		/* Allocate an array of buffer info structures for all
		 * the buffers in the segment.  Chain them to the free
		 * list in memory address order, offset zero must come
		 * first.
		 */
		bi = pti->info = (jack_port_buffer_info_t*)
				 malloc (nports * sizeof(jack_port_buffer_info_t));

		while (offset < size) {
			bi->offset = offset;
			pti->freelist = jack_slist_append (pti->freelist, bi);
			offset += one_buffer;
			++bi;
		}

		/* Allocate the first buffer of the port segment
		 * for an empy buffer area.
		 * NOTE: audio buffer is zeroed in its buffer_init function.
		 */
		bi = (jack_port_buffer_info_t*)pti->freelist->data;
		pti->freelist = jack_slist_remove_link (pti->freelist,
							pti->freelist);
		port_type->zero_buffer_offset = bi->offset;
		if (ptid == JACK_AUDIO_PORT_TYPE) {
			engine->silent_buffer = bi;
		}
	}
	/* initialize buffers */
	{
		int i;
		jack_shm_info_t *shm_info = &engine->port_segment[ptid];
		char* shm_segment = (char*)jack_shm_addr (shm_info);

		bi = pti->info;
		for (i = 0; i < nports; ++i, ++bi)
			pfuncs->buffer_init (shm_segment + bi->offset, one_buffer, nframes);
	}

	pthread_mutex_unlock (&pti->lock);
}


static int
jack_resize_port_segment (jack_engine_t *engine,
			  jack_port_type_id_t ptid,
			  unsigned long nports)
{
	jack_event_t event;
	jack_shmsize_t one_buffer;      /* size of one buffer */
	jack_shmsize_t size;            /* segment size */
	jack_port_type_info_t* port_type = &engine->control->port_types[ptid];
	jack_shm_info_t* shm_info = &engine->port_segment[ptid];

	one_buffer = jack_port_type_buffer_size (port_type, engine->control->buffer_size);
	VERBOSE (engine, "resizing port buffer segment for type %d, one buffer = %u bytes", ptid, one_buffer);

	size = nports * one_buffer;

	if (shm_info->attached_at == 0) {

		if (jack_shmalloc (size, shm_info)) {
			jack_error ("cannot create new port segment of %d"
				    " bytes (%s)",
				    size,
				    strerror (errno));
			return -1;
		}

		if (jack_attach_shm (shm_info)) {
			jack_error ("cannot attach to new port segment "
				    "(%s)", strerror (errno));
			return -1;
		}

		engine->control->port_types[ptid].shm_registry_index =
			shm_info->index;

	} else {

		/* resize existing buffer segment */
		if (jack_resize_shm (shm_info, size)) {
			jack_error ("cannot resize port segment to %d bytes,"
				    " (%s)", size,
				    strerror (errno));
			return -1;
		}
	}

	jack_engine_place_port_buffers (engine, ptid, one_buffer, size, nports, engine->control->buffer_size);

#ifdef USE_MLOCK
	if (engine->control->real_time) {

		/* Although we've called mlockall(CURRENT|FUTURE), the
		 * Linux VM manager still allows newly allocated pages
		 * to fault on first reference.  This mlock() ensures
		 * that any new pages are present before restarting
		 * the process cycle.  Since memory locks do not
		 * stack, they can still be unlocked with a single
		 * munlockall().
		 */

		int rc = mlock (jack_shm_addr (shm_info), size);
		if (rc < 0) {
			jack_error ("JACK: unable to mlock() port buffers: "
				    "%s", strerror (errno));
		}
	}
#endif  /* USE_MLOCK */

	/* Tell everybody about this segment. */
	event.type = AttachPortSegment;
	event.y.ptid = ptid;
	jack_deliver_event_to_all (engine, &event);

	/* XXX need to clean up in the evnt of failures */

	return 0;
}

/* The driver invokes this callback both initially and whenever its
 * buffer size changes.
 */
static int
jack_driver_buffer_size (jack_engine_t *engine, jack_nframes_t nframes)
{
	int i;
	jack_event_t event;

	VERBOSE (engine, "new buffer size %" PRIu32, nframes);

	engine->control->buffer_size = nframes;
	if (engine->driver) {
		engine->rolling_interval =
			jack_rolling_interval (engine->driver->period_usecs);
	}

	for (i = 0; i < engine->control->n_port_types; ++i) {
		if (jack_resize_port_segment (engine, i, engine->control->port_max)) {
			return -1;
		}
	}

	event.type = BufferSizeChange;
	event.x.n = engine->control->buffer_size;
	jack_deliver_event_to_all (engine, &event);

	return 0;
}

/* handle client SetBufferSize request */
int
jack_set_buffer_size_request (jack_engine_t *engine, jack_nframes_t nframes)
{
	/* precondition: caller holds the request_lock */
	int rc;
	jack_driver_t* driver = engine->driver;

	if (driver == NULL) {
		return ENXIO;           /* no such device */

	}
	if (!jack_power_of_two (nframes)) {
		jack_error ("buffer size %" PRIu32 " not a power of 2",
			    nframes);
		return EINVAL;
	}

	rc = driver->bufsize (driver, nframes);
	if (rc != 0) {
		jack_error ("driver does not support %" PRIu32
			    "-frame buffers", nframes);
	}

	return rc;
}


/* Modified to use the new double-linked list of clients in execution order
 * FA 08/2015
 */
static jack_client_internal_t*
jack_process_internal (jack_engine_t *engine, jack_client_internal_t *client,
		       jack_nframes_t nframes)
{
	jack_client_control_t *ctl;

	ctl = client->control;
	ctl->state = Running;
	engine->current_client = client;

	DEBUG ("invoking an internal client's (%s) callbacks", ctl->name);

	/* XXX how to time out an internal client? */

	if (ctl->sync_cb_cbset) {
		jack_call_sync_client (client->private_client);
	}

	if (ctl->process_cbset) {
		if (client->private_client->process (nframes, client->private_client->process_arg)) {
			jack_error ("internal client %s failed", ctl->name);
			engine->process_errors++;
		}
	}

	if (ctl->timebase_cb_cbset) {
		jack_call_timebase_master (client->private_client);
	}

	ctl->state = Finished;

	if (engine->process_errors) {
		return NULL;
	} else {      return client->execlist_next; }
}


#ifdef __linux

/* Linux kernels somewhere between 2.6.18 and 2.6.24 had a bug
   in poll(2) that led poll to return early. To fix it, we need
   to know that that jack_get_microseconds() is monotonic.
 */

#ifdef HAVE_CLOCK_GETTIME
static const int system_clock_monotonic = 1;
#else
static const int system_clock_monotonic = 0;
#endif

static int
linux_poll_bug_encountered (jack_engine_t* engine, jack_time_t then, jack_time_t *required)
{
	if (engine->control->clock_source != JACK_TIMER_SYSTEM_CLOCK || system_clock_monotonic) {
		jack_time_t now = jack_get_microseconds ();

		if ((now - then) < *required) {

			/*
			   So, adjust poll timeout to account for time already spent waiting.
			 */

			VERBOSE (engine, "FALSE WAKEUP (%lldusecs vs. %lld usec)", (now - then), *required);
			*required -= (now - then);

			/* allow 0.25msec slop */
			return 1;
		}
	}
	return 0;
}
#endif


#ifdef JACK_USE_MACH_THREADS

/* Modified to use the new double-linked list of clients in execution order.
 * Unlike the Linux version, this just returns the next client in the list,
 * as did the original. I'm not sure if I understand how this works and
 * can't test it, but it seems to be correct.
 * FA 08/2015
 */
static jack_client_internal *
jack_process_external (jack_engine_t *engine, jack_client_internal_t *client)
{
	jack_client_control_t *ctl;

	engine->current_client = client;
	ctl = client->control;
	// a race exists if we do this after the write(2)
	ctl->state = Triggered;
	ctl->signalled_at = jack_get_microseconds ();

	if (jack_client_resume (client) < 0) {
		jack_error ("Client will be removed\n");
		ctl->state = Finished;
	}

	return client->execlist_next;
}

#else /* !JACK_USE_MACH_THREADS */

/* Modified to use the new double-linked list of clients in execution order.
 * FA 08/2015
 */
static jack_client_internal_t *
jack_process_external (jack_engine_t *engine, jack_client_internal_t *client)
{
	int status = 0;
	char c = 0;
	struct pollfd pfd[1];
	int poll_timeout;
	jack_time_t poll_timeout_usecs;
	jack_client_control_t *ctl;
	jack_time_t now, then;
	int pollret;

	engine->current_client = client;
	ctl = client->control;
	/* a race exists if we do this after the write(2) */
	ctl->state = Triggered;
	ctl->signalled_at = jack_get_microseconds ();

	DEBUG ("calling process() on an external subgraph, fd==%d",
	       client->subgraph_start_fd);

	if (write (client->subgraph_start_fd, &c, sizeof(c)) != sizeof(c)) {
		jack_error ("cannot initiate graph processing (%s)",
			    strerror (errno));
		engine->process_errors++;
		jack_engine_signal_problems (engine);
		return NULL; /* will stop the loop */
	}

	then = jack_get_microseconds ();

	if (engine->freewheeling) {
		poll_timeout_usecs = 250000; /* 0.25 seconds */
	} else {
		poll_timeout_usecs = (engine->client_timeout_msecs > 0 ?
				      engine->client_timeout_msecs * 1000 :
				      engine->driver->period_usecs);
	}

again:
	poll_timeout = 1 + poll_timeout_usecs / 1000;
	pfd[0].fd = client->subgraph_wait_fd;
	pfd[0].events = POLLERR | POLLIN | POLLHUP | POLLNVAL;

	DEBUG ("waiting on fd==%d for process() subgraph to finish (timeout = %d, period_usecs = %d)",
	       client->subgraph_wait_fd, poll_timeout, engine->driver->period_usecs);

	if ((pollret = poll (pfd, 1, poll_timeout)) < 0) {
		jack_error ("poll on subgraph processing failed (%s)",
			    strerror (errno));
		status = -1;
	}

	DEBUG ("\n\n\n\n\n back from subgraph poll, revents = 0x%x\n\n\n", pfd[0].revents);

	if (pfd[0].revents & ~POLLIN) {
		jack_error ("subgraph starting at %s lost client",
			    client->control->name);
		status = -2;
	}

	if (pfd[0].revents & POLLIN) {
		status = 0;

	} else if (status == 0) {
		/* no events, no errors, we woke up because poll() decided that time was up ... */
		if (engine->freewheeling) {
			if (jack_check_client_status (engine)) {
				return NULL;
			} else {
				/* all clients are fine - we're just not done yet. since
				   we're freewheeling, that is fine. */
				goto again;
			}
		}

#ifdef __linux
		if (linux_poll_bug_encountered (engine, then, &poll_timeout_usecs)) {
			goto again;
		}

		if (poll_timeout_usecs < 200) {
			VERBOSE (engine, "FALSE WAKEUP skipped, remaining = %lld usec", poll_timeout_usecs);
		} else {
#endif
		jack_error ("subgraph starting at %s timed out "
			    "(subgraph_wait_fd=%d, status = %d, state = %s, pollret = %d revents = 0x%x)",
			    client->control->name,
			    client->subgraph_wait_fd, status,
			    jack_client_state_name (client),
			    pollret, pfd[0].revents);
		status = 1;
#ifdef __linux
	}
#endif
	}

	now = jack_get_microseconds ();

	if (status != 0) {
		VERBOSE (engine, "at %" PRIu64
			 " waiting on %d for %" PRIu64
			 " usecs, status = %d sig = %" PRIu64
			 " awa = %" PRIu64 " fin = %" PRIu64
			 " dur=%" PRIu64,
			 now,
			 client->subgraph_wait_fd,
			 now - then,
			 status,
			 ctl->signalled_at,
			 ctl->awake_at,
			 ctl->finished_at,
			 ctl->finished_at ? (ctl->finished_at -
					     ctl->signalled_at) : 0);

		if (jack_check_clients (engine, 1)) {
			engine->process_errors++;
			return NULL;            /* will stop the loop */
		}
	} else {
		engine->timeout_count = 0;
	}


	DEBUG ("reading byte from subgraph_wait_fd==%d",
	       client->subgraph_wait_fd);

	if (read (client->subgraph_wait_fd, &c, sizeof(c)) != sizeof(c)) {
		if (errno == EAGAIN) {
			jack_error ("pp: cannot clean up byte from graph wait "
				    "fd - no data present");
		} else {
			jack_error ("pp: cannot clean up byte from graph wait fd (%s)",
				    strerror (errno));
			client->error++;
		}
		return NULL;    /* will stop the loop */
	}

	/* Move to next internal client (or end of client list) */
	while (client) {
		if (jack_client_is_internal (client)) {
			break;
		}
		client = client->execlist_next;
	}
	return client;
}

#endif /* JACK_USE_MACH_THREADS */


/* Modified to use the new double-linked list of clients in execution order.
 * FA 08/2015
 */
static int
jack_engine_process (jack_engine_t *engine, jack_nframes_t nframes)
{
	/* precondition: caller has graph_lock */
	jack_client_internal_t *client;

	engine->process_errors = 0;

	for (client = engine->execlist_head; client; client = client->execlist_next) {
		jack_client_control_t *ctl = client->control;
		ctl->state = NotTriggered;
		ctl->timed_out = 0;
		ctl->awake_at = 0;
		ctl->finished_at = 0;
	}


	client = engine->execlist_head;
	while (client) {
		DEBUG ("considering client %s for processing", client->control->name);

		if (!client->control->active ||
		    (!client->control->process_cbset && !client->control->thread_cb_cbset) ||
		    client->control->dead) {
			client = client->execlist_next;
		} else if (jack_client_is_internal (client)) {
			client = jack_process_internal (engine, client, nframes);
		} else {
			client = jack_process_external (engine, client);
		}
	}

	return engine->process_errors > 0;
}


static void
jack_calc_cpu_load (jack_engine_t *engine)
{
	jack_time_t cycle_end = jack_get_microseconds ();

	/* store the execution time for later averaging */

	engine->rolling_client_usecs[engine->rolling_client_usecs_index++] =
		cycle_end - engine->control->current_time.usecs;

	//jack_info ("cycle_end - engine->control->current_time.usecs %ld",
	//	(long) (cycle_end - engine->control->current_time.usecs));

	if (engine->rolling_client_usecs_index >= JACK_ENGINE_ROLLING_COUNT) {
		engine->rolling_client_usecs_index = 0;
	}

	/* every so often, recompute the current maximum use over the
	   last JACK_ENGINE_ROLLING_COUNT client iterations.
	 */

	if (++engine->rolling_client_usecs_cnt
	    % engine->rolling_interval == 0) {
		float max_usecs = 0.0f;
		int i;

		for (i = 0; i < JACK_ENGINE_ROLLING_COUNT; i++) {
			if (engine->rolling_client_usecs[i] > max_usecs) {
				max_usecs = engine->rolling_client_usecs[i];
			}
		}

		if (max_usecs > engine->max_usecs) {
			engine->max_usecs = max_usecs;
		}

		if (max_usecs < engine->driver->period_usecs) {
			engine->spare_usecs =
				engine->driver->period_usecs - max_usecs;
		} else {
			engine->spare_usecs = 0;
		}

		engine->control->cpu_load =
			(1.0f - (engine->spare_usecs /
				 engine->driver->period_usecs)) * 50.0f
			+ (engine->control->cpu_load * 0.5f);

		VERBOSE (engine, "load = %.4f max usecs: %.3f, "
			 "spare = %.3f", engine->control->cpu_load,
			 max_usecs, engine->spare_usecs);
	}

}

static void
jack_engine_post_process (jack_engine_t *engine)
{
	/* precondition: caller holds the graph lock. */

	jack_transport_cycle_end (engine);
	jack_calc_cpu_load (engine);
	jack_check_clients (engine, 0);
}


static jack_driver_info_t *
jack_load_driver (jack_engine_t *engine, jack_driver_desc_t * driver_desc)
{
	const char *errstr;
	jack_driver_info_t *info;

	info = (jack_driver_info_t*)calloc (1, sizeof(*info));

	info->handle = dlopen (driver_desc->file, RTLD_NOW | RTLD_GLOBAL);

	if (info->handle == NULL) {
		if ((errstr = dlerror ()) != 0) {
			jack_error ("can't load \"%s\": %s", driver_desc->file,
				    errstr);
		} else {
			jack_error ("bizarre error loading driver shared "
				    "object %s", driver_desc->file);
		}
		goto fail;
	}

	info->initialize = dlsym (info->handle, "driver_initialize");

	if ((errstr = dlerror ()) != 0) {
		jack_error ("no initialize function in shared object %s\n",
			    driver_desc->file);
		goto fail;
	}

	info->finish = dlsym (info->handle, "driver_finish");

	if ((errstr = dlerror ()) != 0) {
		jack_error ("no finish function in in shared driver object %s",
			    driver_desc->file);
		goto fail;
	}

	info->client_name = (char*)dlsym (info->handle, "driver_client_name");

	if ((errstr = dlerror ()) != 0) {
		jack_error ("no client name in in shared driver object %s",
			    driver_desc->file);
		goto fail;
	}

	return info;

fail:
	if (info->handle) {
		dlclose (info->handle);
	}
	free (info);
	return NULL;

}

void
jack_driver_unload (jack_driver_t *driver)
{
	void* handle = driver->handle;

	driver->finish (driver);
	dlclose (handle);
}

int
jack_engine_load_driver (jack_engine_t *engine,
			 jack_driver_desc_t * driver_desc,
			 JSList * driver_params)
{
	jack_client_internal_t *client;
	jack_driver_t *driver;
	jack_driver_info_t *info;

	if ((info = jack_load_driver (engine, driver_desc)) == NULL) {
		return -1;
	}

	if ((client = jack_create_driver_client (engine, info->client_name)
	     ) == NULL) {
		return -1;
	}

	if ((driver = info->initialize (client->private_client,
					driver_params)) == NULL) {
		free (info);
		return -1;
	}

	driver->handle = info->handle;
	driver->finish = info->finish;
	driver->internal_client = client;
	free (info);

	if (jack_use_driver (engine, driver) < 0) {
		jack_remove_client (engine, client);
		return -1;
	}

	engine->driver_desc   = driver_desc;
	engine->driver_params = driver_params;

	return 0;
}

int
jack_engine_load_slave_driver (jack_engine_t *engine,
			       jack_driver_desc_t * driver_desc,
			       JSList * driver_params)
{
	jack_client_internal_t *client;
	jack_driver_t *driver;
	jack_driver_info_t *info;

	if ((info = jack_load_driver (engine, driver_desc)) == NULL) {
		jack_info ("Loading slave failed\n");
		return -1;
	}

	if ((client = jack_create_driver_client (engine, info->client_name)
	     ) == NULL) {
		jack_info ("Creating slave failed\n");
		return -1;
	}

	if ((driver = info->initialize (client->private_client,
					driver_params)) == NULL) {
		free (info);
		jack_info ("Initializing slave failed\n");
		return -1;
	}

	driver->handle = info->handle;
	driver->finish = info->finish;
	driver->internal_client = client;
	free (info);

	if (jack_add_slave_driver (engine, driver) < 0) {
		jack_info ("Adding slave failed\n");
		jack_client_delete (engine, client);
		return -1;
	}

	//engine->driver_desc   = driver_desc;
	//engine->driver_params = driver_params;

	return 0;
}

#ifdef USE_CAPABILITIES

static int check_capabilities (jack_engine_t *engine)
{
	cap_t caps = cap_init ();
	cap_flag_value_t cap;
	pid_t pid;
	int have_all_caps = 1;

	if (caps == NULL) {
		VERBOSE (engine, "check: could not allocate capability"
			 " working storage");
		return 0;
	}
	pid = getpid ();
	cap_clear (caps);
	if (capgetp (pid, caps)) {
		VERBOSE (engine, "check: could not get capabilities "
			 "for process %d", pid);
		return 0;
	}
	/* check that we are able to give capabilites to other processes */
	cap_get_flag (caps, CAP_SETPCAP, CAP_EFFECTIVE, &cap);
	if (cap == CAP_CLEAR) {
		have_all_caps = 0;
		goto done;
	}
	/* check that we have the capabilities we want to transfer */
	cap_get_flag (caps, CAP_SYS_NICE, CAP_EFFECTIVE, &cap);
	if (cap == CAP_CLEAR) {
		have_all_caps = 0;
		goto done;
	}
	cap_get_flag (caps, CAP_SYS_RESOURCE, CAP_EFFECTIVE, &cap);
	if (cap == CAP_CLEAR) {
		have_all_caps = 0;
		goto done;
	}
	cap_get_flag (caps, CAP_IPC_LOCK, CAP_EFFECTIVE, &cap);
	if (cap == CAP_CLEAR) {
		have_all_caps = 0;
		goto done;
	}
done:
	cap_free (caps);
	return have_all_caps;
}


static int give_capabilities (jack_engine_t *engine, pid_t pid)
{
	cap_t caps = cap_init ();
	const unsigned caps_size = 3;
	cap_value_t cap_list[] = { CAP_SYS_NICE, CAP_SYS_RESOURCE, CAP_IPC_LOCK };

	if (caps == NULL) {
		VERBOSE (engine, "give: could not allocate capability"
			 " working storage");
		return -1;
	}
	cap_clear (caps);
	if (capgetp (pid, caps)) {
		VERBOSE (engine, "give: could not get current "
			 "capabilities for process %d", pid);
		cap_clear (caps);
	}
	cap_set_flag (caps, CAP_EFFECTIVE, caps_size, cap_list, CAP_SET);
	cap_set_flag (caps, CAP_INHERITABLE, caps_size, cap_list, CAP_SET);
	cap_set_flag (caps, CAP_PERMITTED, caps_size, cap_list, CAP_SET);
	if (capsetp (pid, caps)) {
		cap_free (caps);
		return -1;
	}
	cap_free (caps);
	return 0;
}

static int
jack_set_client_capabilities (jack_engine_t *engine, pid_t cap_pid)
{
	int ret = -1;

	/* before sending this request the client has
	   already checked that the engine has
	   realtime capabilities, that it is running
	   realtime and that the pid is defined
	 */

	if ((ret = give_capabilities (engine, cap_pid)) != 0) {
		jack_error ("could not give capabilities to "
			    "process %d",
			    cap_pid);
	} else {
		VERBOSE (engine, "gave capabilities to"
			 " process %d",
			 cap_pid);
	}

	return ret;
}

#endif /* USE_CAPABILITIES */

/* perform internal or external client request
 *
 * reply_fd is NULL for internal requests
 */
static void
do_request (jack_engine_t *engine, jack_request_t *req, int *reply_fd)
{
	/* The request_lock serializes internal requests (from any
	 * thread in the server) with external requests (always from "the"
	 * server thread).
	 */
	pthread_mutex_lock (&engine->request_lock);

	DEBUG ("got a request of type %d (%s)", req->type, jack_event_type_name (req->type));

	switch (req->type) {
	case RegisterPort:
		req->status = jack_port_do_register (engine, req, reply_fd ? FALSE : TRUE);
		break;

	case UnRegisterPort:
		req->status = jack_port_do_unregister (engine, req);
		break;

	case ConnectPorts:
		req->status = jack_port_do_connect
				      (engine, req->x.connect.source_port,
				      req->x.connect.destination_port);
		break;

	case DisconnectPort:
		req->status = jack_port_do_disconnect_all
				      (engine, req->x.port_info.port_id);
		break;

	case DisconnectPorts:
		req->status = jack_port_do_disconnect
				      (engine, req->x.connect.source_port,
				      req->x.connect.destination_port);
		break;

	case ActivateClient:
		req->status = jack_client_activate (engine, req->x.client_id);
		break;

	case DeactivateClient:
		req->status = jack_client_deactivate (engine, req->x.client_id);
		break;

	case SetTimeBaseClient:
		req->status = jack_timebase_set (engine,
						 req->x.timebase.client_id,
						 req->x.timebase.conditional);
		break;

	case ResetTimeBaseClient:
		req->status = jack_timebase_reset (engine, req->x.client_id);
		break;

	case SetSyncClient:
		req->status =
			jack_transport_client_set_sync (engine,
							req->x.client_id);
		break;

	case ResetSyncClient:
		req->status =
			jack_transport_client_reset_sync (engine,
							  req->x.client_id);
		break;

	case SetSyncTimeout:
		req->status = jack_transport_set_sync_timeout (engine,
							       req->x.timeout);
		break;

#ifdef USE_CAPABILITIES
	case SetClientCapabilities:
		req->status = jack_set_client_capabilities (engine,
							    req->x.cap_pid);
		break;
#endif          /* USE_CAPABILITIES */

	case GetPortConnections:
	case GetPortNConnections:
		//JOQ bug: reply_fd may be NULL if internal request
		if ((req->status =
			     jack_do_get_port_connections (engine, req, *reply_fd))
		    == 0) {
			/* we have already replied, don't do it again */
			*reply_fd = -1;
		}
		break;

	case FreeWheel:
		req->status = jack_start_freewheeling (engine, req->x.client_id);
		break;

	case StopFreeWheel:
		req->status = jack_stop_freewheeling (engine, 0);
		break;

	case SetBufferSize:
		req->status = jack_set_buffer_size_request (engine, req->x.nframes);
		jack_lock_graph (engine);
		jack_compute_new_latency (engine);
		jack_unlock_graph (engine);
		break;

	case IntClientHandle:
		jack_intclient_handle_request (engine, req);
		break;

	case IntClientLoad:
		jack_intclient_load_request (engine, req);
		break;

	case IntClientName:
		jack_intclient_name_request (engine, req);
		break;

	case IntClientUnload:
		jack_intclient_unload_request (engine, req);
		break;

	case RecomputeTotalLatencies:
		jack_lock_graph (engine);
		jack_compute_all_port_total_latencies (engine);
		jack_compute_new_latency (engine);
		jack_unlock_graph (engine);
		req->status = 0;
		break;

	case RecomputeTotalLatency:
		jack_lock_graph (engine);
		jack_compute_port_total_latency (engine, &engine->control->ports[req->x.port_info.port_id]);
		jack_unlock_graph (engine);
		req->status = 0;
		break;

	case GetClientByUUID:
		jack_rdlock_graph (engine);
		jack_do_get_client_by_uuid (engine, req);
		jack_unlock_graph (engine);
		break;
	case GetUUIDByClientName:
		jack_rdlock_graph (engine);
		jack_do_get_uuid_by_client_name (engine, req);
		jack_unlock_graph (engine);
		break;
	case ReserveName:
		jack_rdlock_graph (engine);
		jack_do_reserve_name (engine, req);
		jack_unlock_graph (engine);
		break;
	case SessionReply:
		jack_rdlock_graph (engine);
		jack_do_session_reply (engine, req);
		jack_unlock_graph (engine);
		break;
	case SessionNotify:
		jack_rdlock_graph (engine);
		if ((req->status =
			     jack_do_session_notify (engine, req, *reply_fd))
		    >= 0) {
			/* we have already replied, don't do it again */
			*reply_fd = -1;
		}
		jack_unlock_graph (engine);
		break;
	case SessionHasCallback:
		jack_rdlock_graph (engine);
		req->status = jack_do_has_session_cb (engine, req);
		jack_unlock_graph (engine);
		break;
	case PropertyChangeNotify:
		jack_property_change_notify (engine, req->x.property.change, req->x.property.uuid, req->x.property.key);
		break;

	case PortNameChanged:
		jack_rdlock_graph (engine);
		jack_port_rename_notify (engine, req->x.connect.source_port, req->x.connect.destination_port);
		jack_unlock_graph (engine);
		break;

	default:
		/* some requests are handled entirely on the client
		 * side, by adjusting the shared memory area(s) */
		break;
	}

	pthread_mutex_unlock (&engine->request_lock);

	DEBUG ("status of request: %d", req->status);
}

int
internal_client_request (void* ptr, jack_request_t *request)
{
	do_request ((jack_engine_t*)ptr, request, NULL);
	return request->status;
}

static int
handle_external_client_request (jack_engine_t *engine, int fd)
{
	/* CALLER holds read lock on graph */

	jack_request_t req;
	jack_client_internal_t *client = 0;
	int reply_fd;
	JSList *node;
	ssize_t r;

	for (node = engine->clients; node; node = jack_slist_next (node)) {
		if (((jack_client_internal_t*)node->data)->request_fd == fd) {
			client = (jack_client_internal_t*)node->data;
			break;
		}
	}

	if (client == NULL) {
		jack_error ("client input on unknown fd %d!", fd);
		return -1;
	}

	if ((r = read (client->request_fd, &req, sizeof(req)))
	    < (ssize_t)sizeof(req)) {
		if (r == 0) {
#ifdef JACK_USE_MACH_THREADS
			/* poll is implemented using
			   select (see the macosx/fakepoll
			   code). When the socket is closed
			   select does not return any error,
			   POLLIN is true and the next read
			   will return 0 bytes. This
			   behaviour is diffrent from the
			   Linux poll behaviour. Thus we use
			   this condition as a socket error
			   and remove the client.
			 */
			jack_mark_client_socket_error (engine, fd);
#endif                  /* JACK_USE_MACH_THREADS */
			return 1;
		} else {
			jack_error ("cannot read request from client (%d/%d/%s)",
				    r, sizeof(req), strerror (errno));
			// XXX: shouldnt we mark this client as error now ?

			return -1;
		}
	}

	if (req.type == PropertyChangeNotify) {
		if (req.x.property.keylen) {
			req.x.property.key = (char*)malloc (req.x.property.keylen);
			if ((r = read (client->request_fd, (char*)req.x.property.key, req.x.property.keylen)) != req.x.property.keylen) {
				jack_error ("cannot read property key from client (%d/%d/%s)",
					    r, sizeof(req), strerror (errno));
				return -1;
			}
		} else {
			req.x.property.key = 0;
		}
	}

	reply_fd = client->request_fd;

	jack_unlock_graph (engine);
	do_request (engine, &req, &reply_fd);
	jack_lock_graph (engine);

	if (req.type == PropertyChangeNotify && req.x.property.key) {
		free ((char*)req.x.property.key);
	}

	if (reply_fd >= 0) {
		DEBUG ("replying to client");
		if (write (reply_fd, &req, sizeof(req))
		    < (ssize_t)sizeof(req)) {
			jack_error ("cannot write request result to client");
			return -1;
		}
	} else {
		DEBUG ("*not* replying to client");
	}

	return 0;
}

static int
handle_client_ack_connection (jack_engine_t *engine, int client_fd)
{
	jack_client_internal_t *client;
	jack_client_connect_ack_request_t req;
	jack_client_connect_ack_result_t res;

	if (read (client_fd, &req, sizeof(req)) != sizeof(req)) {
		jack_error ("cannot read ACK connection request from client");
		return -1;
	}

	if ((client = jack_client_internal_by_id (engine, req.client_id))
	    == NULL) {
		jack_error ("unknown client ID in ACK connection request");
		return -1;
	}

	client->event_fd = client_fd;
	VERBOSE (engine, "new client %s using %d for events", client->control->name,
		 client->event_fd);

	res.status = 0;

	if (write (client->event_fd, &res, sizeof(res)) != sizeof(res)) {
		jack_error ("cannot write ACK connection response to client");
		return -1;
	}

	return 0;
}


static void *
jack_server_thread (void *arg)

{
	jack_engine_t *engine = (jack_engine_t*)arg;
	struct sockaddr_un client_addr;
	socklen_t client_addrlen;
	int problemsProblemsPROBLEMS = 0;
	int client_socket;
	int done = 0;
	int i;
	const int fixed_fd_cnt = 3;
	int stop_freewheeling;

	while (!done) {
		JSList* node;
		int clients;

		jack_rdlock_graph (engine);

		clients = jack_slist_length (engine->clients);

		if (engine->pfd_size < fixed_fd_cnt + clients) {
			if (engine->pfd) {
				free (engine->pfd);
			}

			engine->pfd = (struct pollfd*)malloc (sizeof(struct pollfd) *
							      (fixed_fd_cnt + clients));

			if (engine->pfd == NULL) {
				/*
				 * this can happen if limits.conf was changed
				 * but the user hasn't logged out and back in yet
				 */
				if (errno == EAGAIN) {
					jack_error ("malloc failed (%s) - make"
						    "sure you log out and back"
						    "in after changing limits"
						    ".conf!", strerror (errno));
				} else {
					jack_error ("malloc failed (%s)", strerror (errno));
				}

				break;
			}
		}

		engine->pfd[0].fd = engine->fds[0];
		engine->pfd[0].events = POLLIN | POLLERR;
		engine->pfd[1].fd = engine->fds[1];
		engine->pfd[1].events = POLLIN | POLLERR;
		engine->pfd[2].fd = engine->cleanup_fifo[0];
		engine->pfd[2].events = POLLIN | POLLERR;
		engine->pfd_max = fixed_fd_cnt;

		for (node = engine->clients; node; node = node->next) {

			jack_client_internal_t* client = (jack_client_internal_t*)(node->data);

			if (client->request_fd < 0 || client->error >= JACK_ERROR_WITH_SOCKETS) {
				continue;
			}
			if ( client->control->dead ) {
				engine->pfd[engine->pfd_max].fd = client->request_fd;
				engine->pfd[engine->pfd_max].events = POLLHUP | POLLNVAL;
				engine->pfd_max++;
				continue;
			}
			engine->pfd[engine->pfd_max].fd = client->request_fd;
			engine->pfd[engine->pfd_max].events = POLLIN | POLLPRI | POLLERR | POLLHUP | POLLNVAL;
			engine->pfd_max++;
		}

		jack_unlock_graph (engine);

		VERBOSE (engine, "start poll on %d fd's", engine->pfd_max);

		/* go to sleep for a long, long time, or until a request
		   arrives, or until a communication channel is broken
		 */

		if (poll (engine->pfd, engine->pfd_max, -1) < 0) {
			if (errno == EINTR) {
				continue;
			}
			jack_error ("poll failed (%s)", strerror (errno));
			break;
		}

		VERBOSE (engine, "server thread back from poll");

		/* Stephane Letz: letz@grame.fr : has to be added
		 * otherwise pthread_cancel() does not work on MacOSX */
		pthread_testcancel ();


		/* empty cleanup FIFO if necessary */

		if (engine->pfd[2].revents & ~POLLIN) {
			/* time to die */
			break;
		}

		if (engine->pfd[2].revents & POLLIN) {
			char c;
			while (read (engine->cleanup_fifo[0], &c, 1) == 1) ;
		}

		/* check each client socket before handling other request*/

		jack_rdlock_graph (engine);

		for (i = fixed_fd_cnt; i < engine->pfd_max; i++) {

			if (engine->pfd[i].fd < 0) {
				continue;
			}

			if (engine->pfd[i].revents & ~POLLIN) {

				jack_mark_client_socket_error (engine, engine->pfd[i].fd);
				jack_engine_signal_problems (engine);
				VERBOSE (engine, "non-POLLIN events on fd %d", engine->pfd[i].fd);
			} else if (engine->pfd[i].revents & POLLIN) {

				if (handle_external_client_request (engine, engine->pfd[i].fd)) {
					jack_error ("could not handle external"
						    " client request");
					jack_engine_signal_problems (engine);
				}
			}
		}

		problemsProblemsPROBLEMS = engine->problems;

		jack_unlock_graph (engine);

		/* need to take write lock since we may/will rip out some clients,
		   and reset engine->problems
		 */

		stop_freewheeling = 0;

		while (problemsProblemsPROBLEMS) {

			VERBOSE (engine, "trying to lock graph to remove %d problems", problemsProblemsPROBLEMS);
			jack_lock_graph (engine);
			VERBOSE (engine, "we have problem clients (problems = %d", problemsProblemsPROBLEMS);
			jack_remove_clients (engine, &stop_freewheeling);
			if (stop_freewheeling) {
				VERBOSE (engine, "need to stop freewheeling once problems are cleared");
			}
			jack_unlock_graph (engine);

			jack_lock_problems (engine);
			engine->problems -= problemsProblemsPROBLEMS;
			problemsProblemsPROBLEMS = engine->problems;
			jack_unlock_problems (engine);

			VERBOSE (engine, "after removing clients, problems = %d", problemsProblemsPROBLEMS);
		}

		if (engine->freewheeling && stop_freewheeling) {
			jack_stop_freewheeling (engine, 0);
		}

		/* check the master server socket */

		if (engine->pfd[0].revents & POLLERR) {
			jack_error ("error on server socket");
			break;
		}

		if (engine->control->engine_ok && engine->pfd[0].revents & POLLIN) {
			DEBUG ("pfd[0].revents & POLLIN");

			memset (&client_addr, 0, sizeof(client_addr));
			client_addrlen = sizeof(client_addr);

			if ((client_socket =
				     accept (engine->fds[0],
					     (struct sockaddr*)&client_addr,
					     &client_addrlen)) < 0) {
				jack_error ("cannot accept new connection (%s)",
					    strerror (errno));
			} else if (!engine->new_clients_allowed || jack_client_create (engine, client_socket) < 0) {
				jack_error ("cannot complete client "
					    "connection process");
				close (client_socket);
			}
		}

		/* check the ACK server socket */

		if (engine->pfd[1].revents & POLLERR) {
			jack_error ("error on server ACK socket");
			break;
		}

		if (engine->control->engine_ok && engine->pfd[1].revents & POLLIN) {
			DEBUG ("pfd[1].revents & POLLIN");

			memset (&client_addr, 0, sizeof(client_addr));
			client_addrlen = sizeof(client_addr);

			if ((client_socket =
				     accept (engine->fds[1],
					     (struct sockaddr*)&client_addr,
					     &client_addrlen)) < 0) {
				jack_error ("cannot accept new ACK connection"
					    " (%s)", strerror (errno));
			} else if (handle_client_ack_connection
					   (engine, client_socket)) {
				jack_error ("cannot complete client ACK "
					    "connection process");
				close (client_socket);
			}
		}
	}

	return 0;
}

jack_engine_t *
jack_engine_new (int realtime, int rtpriority, int do_mlock, int do_unlock,
		 const char *server_name, int temporary, int verbose,
		 int client_timeout, unsigned int port_max, pid_t wait_pid,
		 jack_nframes_t frame_time_offset, int nozombies, int timeout_count_threshold, JSList *drivers)
{
	jack_engine_t *engine;
	unsigned int i;
	char server_dir[PATH_MAX + 1] = "";

#ifdef USE_CAPABILITIES
	uid_t uid = getuid ();
	uid_t euid = geteuid ();
#endif  /* USE_CAPABILITIES */

	/* before we start allocating resources, make sure that if realtime was requested that we can
	   actually do it.
	 */

	if (realtime) {
		if (jack_acquire_real_time_scheduling (pthread_self (), 10) != 0) {
			/* can't run realtime - time to bomb */
			return NULL;
		}

		jack_drop_real_time_scheduling (pthread_self ());

#ifdef USE_MLOCK

		if (do_mlock && (mlockall (MCL_CURRENT | MCL_FUTURE) != 0)) {
			jack_error ("cannot lock down memory for jackd (%s)",
				    strerror (errno));
#ifdef ENSURE_MLOCK
			return NULL;
#endif  /* ENSURE_MLOCK */
		}
#endif  /* USE_MLOCK */
	}

	/* start a thread to display messages from realtime threads */
	jack_messagebuffer_init ();

	jack_init_time ();

	/* allocate the engine, zero the structure to ease debugging */
	engine = (jack_engine_t*)calloc (1, sizeof(jack_engine_t));

	engine->drivers = drivers;
	engine->driver = NULL;
	engine->driver_desc = NULL;
	engine->driver_params = NULL;

	engine->slave_drivers = NULL;

	engine->set_sample_rate = jack_set_sample_rate;
	engine->set_buffer_size = jack_driver_buffer_size;
	engine->run_cycle = jack_run_cycle;
	engine->delay = jack_engine_delay;
	engine->driver_exit = jack_engine_driver_exit;
	engine->transport_cycle_start = jack_transport_cycle_start;
	engine->client_timeout_msecs = client_timeout;
	engine->timeout_count = 0;
	engine->problems = 0;

	engine->port_max = port_max;
	engine->server_thread = 0;
	engine->rtpriority = rtpriority;
	engine->silent_buffer = 0;
	engine->verbose = verbose;
	engine->server_name = server_name;
	engine->temporary = temporary;
	engine->freewheeling = 0;
	engine->stop_freewheeling = 0;
	jack_uuid_clear (&engine->fwclient);
	engine->feedbackcount = 0;
	engine->wait_pid = wait_pid;
	engine->nozombies = nozombies;
	engine->timeout_count_threshold = timeout_count_threshold;
	engine->removing_clients = 0;
	engine->new_clients_allowed = 1;

	engine->session_reply_fd = -1;
	engine->session_pending_replies = 0;

	engine->audio_out_cnt = 0;
	engine->audio_in_cnt = 0;
	engine->midi_out_cnt = 0;
	engine->midi_in_cnt = 0;

	jack_engine_reset_rolling_usecs (engine);
	engine->max_usecs = 0.0f;

	pthread_rwlock_init (&engine->client_lock, 0);
	pthread_mutex_init (&engine->port_lock, 0);
	pthread_mutex_init (&engine->request_lock, 0);
	pthread_mutex_init (&engine->problem_lock, 0);

	engine->clients = 0;
	engine->reserved_client_names = 0;

	/* Added new double-linked list of clients in execution order.
	 * FA 08/2015
	 */
	engine->execlist_head = 0;
	engine->execlist_tail = 0;
	engine->execlist_request = 0;

	engine->pfd_size = 0;
	engine->pfd_max = 0;
	engine->pfd = 0;

	engine->fifo_size = 16;
	engine->fifo = (int*)malloc (sizeof(int) * engine->fifo_size);
	for (i = 0; i < engine->fifo_size; i++)
		engine->fifo[i] = -1;

	if (pipe (engine->cleanup_fifo)) {
		jack_error ("cannot create cleanup FIFOs (%s)", strerror (errno));
		return NULL;
	}

	if (fcntl (engine->cleanup_fifo[0], F_SETFL, O_NONBLOCK)) {
		jack_error ("cannot set O_NONBLOCK on cleanup read FIFO (%s)", strerror (errno));
		return NULL;
	}

	if (fcntl (engine->cleanup_fifo[1], F_SETFL, O_NONBLOCK)) {
		jack_error ("cannot set O_NONBLOCK on cleanup write FIFO (%s)", strerror (errno));
		return NULL;
	}

	engine->external_client_cnt = 0;

	srandom (time ((time_t*)0));

	if (jack_shmalloc (sizeof(jack_control_t)
			   + ((sizeof(jack_port_shared_t) * engine->port_max)),
			   &engine->control_shm)) {
		jack_error ("cannot create engine control shared memory "
			    "segment (%s)", strerror (errno));
		return NULL;
	}

	if (jack_attach_shm (&engine->control_shm)) {
		jack_error ("cannot attach to engine control shared memory"
			    " (%s)", strerror (errno));
		jack_destroy_shm (&engine->control_shm);
		return NULL;
	}

	engine->control = (jack_control_t*)
			  jack_shm_addr (&engine->control_shm);

	/* Setup port type information from builtins. buffer space is
	 * allocated when the driver calls jack_driver_buffer_size().
	 */
	for (i = 0; jack_builtin_port_types[i].type_name[0]; ++i) {

		memcpy (&engine->control->port_types[i],
			&jack_builtin_port_types[i],
			sizeof(jack_port_type_info_t));

		VERBOSE (engine, "registered builtin port type %s",
			 engine->control->port_types[i].type_name);

		/* the port type id is index into port_types array */
		engine->control->port_types[i].ptype_id = i;

		/* be sure to initialize mutex correctly */
		pthread_mutex_init (&engine->port_buffers[i].lock, NULL);

		/* set buffer list info correctly */
		engine->port_buffers[i].freelist = NULL;
		engine->port_buffers[i].info = NULL;

		/* mark each port segment as not allocated */
		engine->port_segment[i].index = -1;
		engine->port_segment[i].attached_at = 0;
	}

	engine->control->n_port_types = i;

	/* Mark all ports as available */

	for (i = 0; i < engine->port_max; i++) {
		engine->control->ports[i].in_use = 0;
		engine->control->ports[i].id = i;
		engine->control->ports[i].alias1[0] = '\0';
		engine->control->ports[i].alias2[0] = '\0';
	}

	/* allocate internal port structures so that we can keep track
	 * of port connections.
	 */
	engine->internal_ports = (jack_port_internal_t*)
				 malloc (sizeof(jack_port_internal_t) * engine->port_max);

	for (i = 0; i < engine->port_max; i++)
		engine->internal_ports[i].connections = 0;

	if (make_sockets (engine->server_name, engine->fds) < 0) {
		jack_error ("cannot create server sockets");
		return NULL;
	}

	engine->control->port_max = engine->port_max;
	engine->control->real_time = realtime;

	/* leave some headroom for other client threads to run
	   with priority higher than the regular client threads
	   but less than the server. see thread.h for
	   jack_client_real_time_priority() and jack_client_max_real_time_priority()
	   which are affected by this.
	 */

	engine->control->client_priority = (realtime
					    ? engine->rtpriority - 5
					    : 0);
	engine->control->max_client_priority = (realtime
						? engine->rtpriority - 1
						: 0);
	engine->control->do_mlock = do_mlock;
	engine->control->do_munlock = do_unlock;
	engine->control->cpu_load = 0;
	engine->control->xrun_delayed_usecs = 0;
	engine->control->max_delayed_usecs = 0;

	jack_set_clock_source (clock_source);
	engine->control->clock_source = clock_source;
	engine->get_microseconds = jack_get_microseconds_pointer ();

	VERBOSE (engine, "clock source = %s", jack_clock_source_name (clock_source));

	engine->control->frame_timer.frames = frame_time_offset;
	engine->control->frame_timer.reset_pending = 0;
	engine->control->frame_timer.current_wakeup = 0;
	engine->control->frame_timer.next_wakeup = 0;
	engine->control->frame_timer.initialized = 0;
	engine->control->frame_timer.filter_omega = 0;  /* Initialised later */
	engine->control->frame_timer.period_usecs = 0;  /* Initialised later */

	engine->first_wakeup = 1;

	engine->control->buffer_size = 0;
	jack_transport_init (engine);
	jack_set_sample_rate (engine, 0);
	engine->control->internal = 0;

	engine->control->has_capabilities = 0;

#ifdef JACK_USE_MACH_THREADS
	/* specific resources for server/client real-time thread
	 * communication */
	engine->servertask = mach_task_self ();
	if (task_get_bootstrap_port (engine->servertask, &engine->bp)) {
		jack_error ("Jackd: Can't find bootstrap mach port");
		return NULL;
	}
	engine->portnum = 0;
#endif  /* JACK_USE_MACH_THREADS */


#ifdef USE_CAPABILITIES
	if (uid == 0 || euid == 0) {
		VERBOSE (engine, "running with uid=%d and euid=%d, "
			 "will not try to use capabilites",
			 uid, euid);
	} else {
		/* only try to use capabilities if not running as root */
		engine->control->has_capabilities = check_capabilities (engine);
		if (engine->control->has_capabilities == 0) {
			VERBOSE (engine, "required capabilities not "
				 "available");
		}
		if (engine->verbose) {
			size_t size;
			cap_t cap = cap_init ();
			capgetp (0, cap);
			VERBOSE (engine, "capabilities: %s",
				 cap_to_text (cap, &size));
		}
	}
#endif  /* USE_CAPABILITIES */

	engine->control->engine_ok = 1;

	snprintf (engine->fifo_prefix, sizeof(engine->fifo_prefix),
		  "%s/jack-ack-fifo-%d",
		  jack_server_dir (engine->server_name, server_dir), getpid ());

	(void)jack_get_fifo_fd (engine, 0);

	jack_client_create_thread (NULL, &engine->server_thread, 0, FALSE,
				   &jack_server_thread, engine);

	return engine;
}

static void
jack_engine_delay (jack_engine_t *engine, float delayed_usecs)
{
	jack_event_t event;

	engine->control->frame_timer.reset_pending = 1;

	engine->control->xrun_delayed_usecs = delayed_usecs;

	if (delayed_usecs > engine->control->max_delayed_usecs) {
		engine->control->max_delayed_usecs = delayed_usecs;
	}

	event.type = XRun;

	jack_deliver_event_to_all (engine, &event);
}

static void*
jack_engine_freewheel (void *arg)
{
	jack_engine_t* engine = (jack_engine_t*)arg;
	jack_client_internal_t* client;

	VERBOSE (engine, "freewheel thread starting ...");

	/* we should not be running SCHED_FIFO, so we don't
	   have to do anything about scheduling.
	 */

	client = jack_client_internal_by_id (engine, engine->fwclient);

	while (!engine->stop_freewheeling) {

		jack_run_one_cycle (engine, engine->control->buffer_size, 0.0f);

		if (client && client->error) {
			/* run one cycle() will already have told the server thread
			   about issues, and the server thread will clean up.
			   however, its time for us to depart this world ...
			 */
			break;
		}
	}

	VERBOSE (engine, "freewheel came to an end, naturally");
	return 0;
}

static void
jack_slave_driver_remove (jack_engine_t *engine, jack_driver_t *sdriver)
{
	sdriver->detach (sdriver, engine);
	engine->slave_drivers = jack_slist_remove (engine->slave_drivers, sdriver);

	jack_driver_unload (sdriver);
}
int
jack_drivers_start (jack_engine_t *engine)
{
	JSList *node;
	JSList *failed_drivers = NULL;

	/* first start the slave drivers */
	for (node = engine->slave_drivers; node; node = jack_slist_next (node)) {
		jack_driver_t *sdriver = node->data;
		if (sdriver->start (sdriver)) {
			failed_drivers = jack_slist_append (failed_drivers, sdriver);
		}
	}

	// Clean up drivers which failed to start.
	for (node = failed_drivers; node; node = jack_slist_next (node)) {
		jack_driver_t *sdriver = node->data;
		jack_error ( "slave driver %s failed to start, removing it", sdriver->internal_client->control->name );
		jack_slave_driver_remove (engine, sdriver);
	}

	/* now the master driver is started */
	return engine->driver->start (engine->driver);
}

static int
jack_drivers_stop (jack_engine_t *engine)
{
	JSList *node;
	/* first stop the master driver */
	int retval = engine->driver->stop (engine->driver);

	/* now the slave drivers are stopped */
	for (node = engine->slave_drivers; node; node = jack_slist_next (node)) {
		jack_driver_t *sdriver = node->data;
		sdriver->stop ( sdriver );
	}

	return retval;
}

static int
jack_drivers_read (jack_engine_t *engine, jack_nframes_t nframes)
{
	JSList *node;

	/* first read the slave drivers */
	for (node = engine->slave_drivers; node; node = jack_slist_next (node)) {
		jack_driver_t *sdriver = node->data;
		sdriver->read (sdriver, nframes);
	}

	/* now the master driver is read */
	return engine->driver->read (engine->driver, nframes);
}

static int
jack_drivers_write (jack_engine_t *engine, jack_nframes_t nframes)
{
	JSList *node;

	/* first start the slave drivers */
	for (node = engine->slave_drivers; node; node = jack_slist_next (node)) {
		jack_driver_t *sdriver = node->data;
		sdriver->write (sdriver, nframes);
	}

	/* now the master driver is written */
	return engine->driver->write (engine->driver, nframes);
}
static int
jack_start_freewheeling (jack_engine_t* engine, jack_uuid_t client_id)
{
	jack_event_t event;
	jack_client_internal_t *client;

	if (engine->freewheeling) {
		return 0;
	}

	if (engine->driver == NULL) {
		jack_error ("cannot start freewheeling without a driver!");
		return -1;
	}

	/* stop driver before telling anyone about it so
	   there are no more process() calls being handled.
	 */

	if (jack_drivers_stop (engine)) {
		jack_error ("could not stop driver for freewheeling");
		return -1;
	}

	client = jack_client_internal_by_id (engine, client_id);

	if (client->control->process_cbset || client->control->thread_cb_cbset) {
		jack_uuid_copy (&engine->fwclient, client_id);
	}

	engine->freewheeling = 1;
	engine->stop_freewheeling = 0;

	event.type = StartFreewheel;
	jack_deliver_event_to_all (engine, &event);

	if (jack_client_create_thread (NULL, &engine->freewheel_thread, 0, FALSE,
				       jack_engine_freewheel, engine)) {
		jack_error ("could not start create freewheel thread");
		return -1;
	}

	return 0;
}

int
jack_stop_freewheeling (jack_engine_t* engine, int engine_exiting)
{
	jack_event_t event;
	void *ftstatus;

	if (!engine->freewheeling) {
		return 0;
	}

	if (engine->driver == NULL) {
		jack_error ("cannot start freewheeling without a driver!");
		return -1;
	}

	if (!engine->freewheeling) {
		VERBOSE (engine, "stop freewheel when not freewheeling");
		return 0;
	}

	/* tell the freewheel thread to stop, and wait for it
	   to exit.
	 */

	engine->stop_freewheeling = 1;

	VERBOSE (engine, "freewheeling stopped, waiting for thread");
	pthread_join (engine->freewheel_thread, &ftstatus);
	VERBOSE (engine, "freewheel thread has returned");

	jack_uuid_clear (&engine->fwclient);
	engine->freewheeling = 0;
	engine->control->frame_timer.reset_pending = 1;

	if (!engine_exiting) {
		/* tell everyone we've stopped */

		event.type = StopFreewheel;
		jack_deliver_event_to_all (engine, &event);

		/* restart the driver */

		if (jack_drivers_start (engine)) {
			jack_error ("could not restart driver after freewheeling");
			return -1;
		}
	}

	return 0;
}

static int
jack_check_client_status (jack_engine_t* engine)
{
	JSList *node;
	int err = 0;

	/* we are already late, or something else went wrong,
	   so it can't hurt to check the existence of all
	   clients.
	 */

	for (node = engine->clients; node;
	     node = jack_slist_next (node)) {
		jack_client_internal_t *client =
			(jack_client_internal_t*)node->data;

		if (client->control->type == ClientExternal) {
			if (kill (client->control->pid, 0)) {
				VERBOSE (engine,
					 "client %s has died/exited",
					 client->control->name);
				client->error++;
				err++;
			}
			if (client->control->last_status != 0) {
				VERBOSE (engine,
					 "client %s has nonzero process callback status (%d)\n",
					 client->control->name, client->control->last_status);
				client->error++;
				err++;
			}
		}

		DEBUG ("client %s errors = %d", client->control->name,
		       client->error);
	}

	return err;
}

static int
jack_run_one_cycle (jack_engine_t *engine, jack_nframes_t nframes,
		    float delayed_usecs)
{
	jack_driver_t* driver = engine->driver;
	int ret = -1;
	static int consecutive_excessive_delays = 0;

#define WORK_SCALE 1.0f

	if (!engine->freewheeling &&
	    engine->control->real_time &&
	    engine->spare_usecs &&
	    ((WORK_SCALE * engine->spare_usecs) <= delayed_usecs)) {

		MESSAGE ("delay of %.3f usecs exceeds estimated spare"
			 " time of %.3f; restart ...\n",
			 delayed_usecs, WORK_SCALE * engine->spare_usecs);

		if (++consecutive_excessive_delays > 10) {
			jack_error ("too many consecutive interrupt delays "
				    "... engine pausing");
			return -1;      /* will exit the thread loop */
		}

		jack_engine_delay (engine, delayed_usecs);

		return 0;

	} else {
		consecutive_excessive_delays = 0;
	}

	DEBUG ("trying to acquire read lock (FW = %d)", engine->freewheeling);
	if (jack_try_rdlock_graph (engine)) {
		VERBOSE (engine, "lock-driven null cycle");
		if (!engine->freewheeling) {
			driver->null_cycle (driver, nframes);
		} else {
			/* don't return too fast */
			usleep (1000);
		}
		return 0;
	}

	if (jack_trylock_problems (engine)) {
		VERBOSE (engine, "problem-lock-driven null cycle");
		jack_unlock_graph (engine);
		if (!engine->freewheeling) {
			driver->null_cycle (driver, nframes);
		} else {
			/* don't return too fast */
			usleep (1000);
		}
		return 0;
	}

	if (engine->problems || (engine->timeout_count_threshold && (engine->timeout_count > (1 + engine->timeout_count_threshold * 1000 / engine->driver->period_usecs) ))) {
		VERBOSE (engine, "problem-driven null cycle problems=%d", engine->problems);
		jack_unlock_problems (engine);
		jack_unlock_graph (engine);
		if (!engine->freewheeling) {
			driver->null_cycle (driver, nframes);
		} else {
			/* don't return too fast */
			usleep (1000);
		}
		return 0;
	}

	jack_unlock_problems (engine);

	if (!engine->freewheeling) {
		DEBUG ("waiting for driver read\n");
		if (jack_drivers_read (engine, nframes)) {
			goto unlock;
		}
	}

	DEBUG ("run process\n");

	if (jack_engine_process (engine, nframes) != 0) {
		DEBUG ("engine process cycle failed");
		jack_check_client_status (engine);
	}

	if (!engine->freewheeling) {
		if (jack_drivers_write (engine, nframes)) {
			goto unlock;
		}
	}

	jack_engine_post_process (engine);

	if (delayed_usecs > engine->control->max_delayed_usecs) {
		engine->control->max_delayed_usecs = delayed_usecs;
	}

	ret = 0;

unlock:
	jack_unlock_graph (engine);
	DEBUG ("cycle finished, status = %d", ret);

	return ret;
}

static void
jack_engine_driver_exit (jack_engine_t* engine)
{
	jack_driver_t* driver = engine->driver;

	VERBOSE (engine, "stopping driver");
	driver->stop (driver);
	VERBOSE (engine, "detaching driver");
	driver->detach (driver, engine);

	/* tell anyone waiting that the driver exited. */
	kill (engine->wait_pid, SIGUSR2);

	engine->driver = NULL;
}

static int
jack_run_cycle (jack_engine_t *engine, jack_nframes_t nframes,
		float delayed_usecs)
{
	jack_time_t now = engine->driver->last_wait_ust;
	jack_time_t dus = 0;
	jack_time_t p_usecs = engine->driver->period_usecs;
	jack_nframes_t b_size = engine->control->buffer_size;
	jack_nframes_t left;
	jack_frame_timer_t* timer = &engine->control->frame_timer;

	if (engine->verbose) {
		if (nframes != b_size) {
			VERBOSE (engine,
				 "late driver wakeup: nframes to process = %"
				 PRIu32 ".", nframes);
		}
	}

	/* Run as many cycles as it takes to consume nframes */

	for (left = nframes; left >= b_size; left -= b_size) {
		/* Change: the DLL code is now inside this loop which ensures
		   that more than one period is run if more than a buffer size
		   of frames is available. This is a very unlikely event, but
		   it is possible and now handled correctly.
		   FA 25/06/2014
		 */
		/* Change: 'first_wakeup' now means only the very first wakeup
		   after the engine was created. In that case frame time is not
		   modified, it stays at the initialised value.
		   OTOH 'reset_pending' is  used after freewheeling or an xrun.
		   In those cases frame time is adjusted by using the difference
		   in usecs time between the end of the previous period and the
		   start of the current one. This way, a client monitoring the
		   frame time for the start of each period will have a correct
		   idea of the number of frames that were skipped.
		   FA 25/06/2014
		 */
		/* Change: in contrast to previous versions, the DLL is *not*
		   run if any of the two conditions above is true, it is just
		   initialised correctly for the current period. Previously it
		   was initialised and then run, which meant that the requred
		   initialisation was rather counter-intiutive.
		   FA 25/06/2014
		 */
		/* Added initialisation of timer->period_usecs, required
		   due to the modified implementation of the DLL itself.
		   OTOH, this should maybe not be repeated after e.g.
		   freewheeling or an xrun, as the current value would be
		   more accurate than the nominal one. But it doesn't really
		   harm either.
		   FA 13/02/2012
		 */
		/* Added initialisation of timer->filter_omega. This makes
		   the DLL bandwidth independent of the actual period time.
		   The bandwidth is now 1/8 Hz in all cases. The value of
		   timer->filter_omega is 2 * pi * BW * Tperiod.
		   FA 13/02/2012
		 */

		// maybe need a memory barrier here
		timer->guard1++;

		if (timer->reset_pending) {
			// Adjust frame time after a discontinuity.
			// The frames of the previous period.
			timer->frames += b_size;
			// The frames that were skipped.
			dus = now - timer->next_wakeup;
			timer->frames += (dus * b_size) / p_usecs;
		}
		if (engine->first_wakeup || timer->reset_pending) {
			// First wakeup or after discontinuity.
			// Initialiase the DLL.
			timer->current_wakeup = now;
			timer->next_wakeup = now + p_usecs;
			timer->period_usecs = (float)p_usecs;
			timer->filter_omega = timer->period_usecs * 7.854e-7f;
			timer->initialized = 1;

			// Reset both conditions.
			engine->first_wakeup = 0;
			timer->reset_pending = 0;
		} else {
			// Normal cycle. This code was originally in
			// jack_inc_frame_time() but only used here.
			// Moving it here means that now all code
			// related to timekeeping is close together
			// and easy to understand.
			float delta = (float)((int64_t)now - (int64_t)timer->next_wakeup);
			delta *= timer->filter_omega;
			timer->current_wakeup = timer->next_wakeup;
			timer->frames += b_size;
			timer->period_usecs += timer->filter_omega * delta;
			timer->next_wakeup += (int64_t)floorf (timer->period_usecs + 1.41f * delta + 0.5f);
		}

		// maybe need a memory barrier here
		timer->guard2++;

		if (jack_run_one_cycle (engine, b_size, delayed_usecs)) {
			jack_error ("cycle execution failure, exiting");
			return EIO;
		}
	}

	return 0;
}

void
jack_engine_delete (jack_engine_t *engine)
{
	int i;

	if (engine == NULL) {
		return;
	}

	VERBOSE (engine, "starting server engine shutdown");

	jack_stop_freewheeling (engine, 1);

	engine->control->engine_ok = 0; /* tell clients we're going away */

	/* this will wake the server thread and cause it to exit */

	close (engine->cleanup_fifo[0]);
	close (engine->cleanup_fifo[1]);

	/* shutdown master socket to prevent new clients arriving */
	shutdown (engine->fds[0], SHUT_RDWR);
	// close (engine->fds[0]);

	/* now really tell them we're going away */

	for (i = 0; i < engine->pfd_max; ++i)
		shutdown (engine->pfd[i].fd, SHUT_RDWR);

	if (engine->driver) {
		jack_driver_t* driver = engine->driver;

		VERBOSE (engine, "stopping driver");
		driver->stop (driver);
		// VERBOSE (engine, "detaching driver");
		// driver->detach (driver, engine);
		VERBOSE (engine, "unloading driver");
		jack_driver_unload (driver);
		engine->driver = NULL;
	}

	VERBOSE (engine, "freeing shared port segments");
	for (i = 0; i < engine->control->n_port_types; ++i) {
		jack_release_shm (&engine->port_segment[i]);
		jack_destroy_shm (&engine->port_segment[i]);
	}

	/* stop the other engine threads */
	VERBOSE (engine, "stopping server thread");

#if JACK_USE_MACH_THREADS
	// MacOSX pthread_cancel still not implemented correctly in Darwin
	mach_port_t machThread = pthread_mach_thread_np (engine->server_thread);
	thread_terminate (machThread);
#else
	pthread_cancel (engine->server_thread);
	pthread_join (engine->server_thread, NULL);
#endif


	VERBOSE (engine, "last xrun delay: %.3f usecs",
		 engine->control->xrun_delayed_usecs);
	VERBOSE (engine, "max delay reported by backend: %.3f usecs",
		 engine->control->max_delayed_usecs);

	/* free engine control shm segment */
	engine->control = NULL;
	VERBOSE (engine, "freeing engine shared memory");
	jack_release_shm (&engine->control_shm);
	jack_destroy_shm (&engine->control_shm);

	VERBOSE (engine, "max usecs: %.3f, engine deleted", engine->max_usecs);

	free (engine);

	jack_messagebuffer_exit ();
}

void
jack_port_clear_connections (jack_engine_t *engine,
			     jack_port_internal_t *port)
{
	JSList *node, *next;

	for (node = port->connections; node; ) {
		next = jack_slist_next (node);
		jack_port_disconnect_internal (
			engine, ((jack_connection_internal_t*)
				 node->data)->source,
			((jack_connection_internal_t*)
			 node->data)->destination);
		node = next;
	}

	jack_slist_free (port->connections);
	port->connections = 0;
}

static void
jack_deliver_event_to_all (jack_engine_t *engine, jack_event_t *event)
{
	JSList *node;

	jack_rdlock_graph (engine);
	for (node = engine->clients; node; node = jack_slist_next (node)) {
		jack_deliver_event (engine,
				    (jack_client_internal_t*)node->data,
				    event);
	}
	jack_unlock_graph (engine);
}

static void jack_do_get_client_by_uuid (jack_engine_t *engine, jack_request_t *req)
{
	JSList *node;

	req->status = -1;
	for (node = engine->clients; node; node = jack_slist_next (node)) {
		jack_client_internal_t* client = (jack_client_internal_t*)node->data;
		if (jack_uuid_compare (client->control->uuid, req->x.client_id) == 0) {
			snprintf ( req->x.port_info.name, sizeof(req->x.port_info.name), "%s", client->control->name );
			req->status = 0;
			return;
		}
	}
}

static void jack_do_get_uuid_by_client_name (jack_engine_t *engine, jack_request_t *req)
{
	JSList *node;

	req->status = -1;

	if (strcmp (req->x.name, "system") == 0) {
		/* request concerns the driver */
		if (engine->driver) {
			jack_uuid_copy (&req->x.client_id, engine->driver->internal_client->control->uuid);
			req->status = 0;
		}
		return;
	}

	for (node = engine->clients; node; node = jack_slist_next (node)) {
		jack_client_internal_t* client = (jack_client_internal_t*)node->data;
		if (strcmp (client->control->name, req->x.name) == 0) {
			jack_uuid_copy (&req->x.client_id, client->control->uuid);
			req->status = 0;
			return;
		}
	}
}

static void jack_do_reserve_name (jack_engine_t *engine, jack_request_t *req)
{
	jack_reserved_name_t *reservation;
	JSList *node;

	// check is name is free...
	for (node = engine->clients; node; node = jack_slist_next (node)) {
		jack_client_internal_t* client = (jack_client_internal_t*)node->data;
		if ( !strcmp ( (char*)client->control->name, req->x.reservename.name )) {
			req->status = -1;
			return;
		}
	}

	reservation = malloc (sizeof(jack_reserved_name_t));
	if (reservation == NULL) {
		req->status = -1;
		return;
	}

	snprintf (reservation->name, sizeof(reservation->name), "%s", req->x.reservename.name);
	jack_uuid_copy (&reservation->uuid, req->x.reservename.uuid);
	engine->reserved_client_names = jack_slist_append (engine->reserved_client_names, reservation);

	req->status = 0;
}

static int jack_send_session_reply ( jack_engine_t *engine, jack_client_internal_t *client )
{
	if (write (engine->session_reply_fd, (const void*)&client->control->uuid, sizeof(client->control->uuid))
	    < (ssize_t)sizeof(client->control->uuid)) {
		jack_error ("cannot write SessionNotify result "
			    "to client via fd = %d (%s)",
			    engine->session_reply_fd, strerror (errno));
		return -1;
	}
	if (write (engine->session_reply_fd, (const void*)client->control->name, sizeof(client->control->name))
	    < (ssize_t)sizeof(client->control->name)) {
		jack_error ("cannot write SessionNotify result "
			    "to client via fd = %d (%s)",
			    engine->session_reply_fd, strerror (errno));
		return -1;
	}
	if (write (engine->session_reply_fd, (const void*)client->control->session_command,
		   sizeof(client->control->session_command))
	    < (ssize_t)sizeof(client->control->session_command)) {
		jack_error ("cannot write SessionNotify result "
			    "to client via fd = %d (%s)",
			    engine->session_reply_fd, strerror (errno));
		return -1;
	}
	if (write (engine->session_reply_fd, (const void*)( &client->control->session_flags ),
		   sizeof(client->control->session_flags))
	    < (ssize_t)sizeof(client->control->session_flags)) {
		jack_error ("cannot write SessionNotify result "
			    "to client via fd = %d (%s)",
			    engine->session_reply_fd, strerror (errno));
		return -1;
	}

	return 0;
}

static int
jack_do_session_notify (jack_engine_t *engine, jack_request_t *req, int reply_fd )
{
	JSList *node;
	jack_event_t event;

	int reply;
	jack_uuid_t finalizer;
	struct stat sbuf;

	jack_uuid_clear (&finalizer);

	if (engine->session_reply_fd != -1) {
		// we should have a notion of busy or somthing.
		// just sending empty reply now.
		goto send_final;
	}

	engine->session_reply_fd = reply_fd;
	engine->session_pending_replies = 0;

	event.type = SaveSession;
	event.y.n = req->x.session.type;

	/* GRAPH MUST BE LOCKED : see callers of jack_send_connection_notification()
	 */

	if (stat (req->x.session.path, &sbuf) != 0 || !S_ISDIR (sbuf.st_mode)) {
		jack_error ("session parent directory (%s) does not exist", req->x.session.path);
		goto send_final;
	}

	for (node = engine->clients; node; node = jack_slist_next (node)) {
		jack_client_internal_t* client = (jack_client_internal_t*)node->data;
		if (client->control->session_cbset) {

			// in case we only want to send to a special client.
			// uuid assign is still complete. not sure if thats necessary.
			if ( (req->x.session.target[0] != 0) && strcmp (req->x.session.target, (char*)client->control->name) ) {
				continue;
			}

			/* the caller of jack_session_notify() is required to have created the session dir
			 */

			if (req->x.session.path[strlen (req->x.session.path) - 1] == '/') {
				snprintf (event.x.name, sizeof(event.x.name), "%s%s/", req->x.session.path, client->control->name );
			} else {
				snprintf (event.x.name, sizeof(event.x.name), "%s/%s/", req->x.session.path, client->control->name );
			}
			if (mkdir (event.x.name, 0777) != 0) {
				jack_error ("cannot create session directory (%s) for client %s: %s",
					    event.x.name, client->control->name, strerror (errno));
				break;
			}

			reply = jack_deliver_event (engine, client, &event);
			if (reply == 1) {
				// delayed reply
				engine->session_pending_replies += 1;
				client->session_reply_pending = TRUE;
			} else if (reply == 2) {
				// immediate reply
				if (jack_send_session_reply (engine, client)) {
					goto error_out;
				}
			}
		}
	}

	if (engine->session_pending_replies != 0) {
		return 0;
	}

send_final:
	if (write (reply_fd, &finalizer, sizeof(finalizer))
	    < (ssize_t)sizeof(finalizer)) {
		jack_error ("cannot write SessionNotify result "
			    "to client via fd = %d (%s)",
			    reply_fd, strerror (errno));
		goto error_out;
	}

	engine->session_reply_fd = -1;
	return 0;
error_out:
	return -3;
}

static int
jack_do_has_session_cb (jack_engine_t *engine, jack_request_t *req)
{
	jack_client_internal_t *client;
	int retval = -1;

	client = jack_client_by_name (engine, req->x.name);
	if (client == NULL) {
		goto out;
	}

	retval = client->control->session_cbset ? 1 : 0;
out:
	return retval;
}

static void jack_do_session_reply (jack_engine_t *engine, jack_request_t *req )
{
	jack_uuid_t client_id;
	jack_client_internal_t *client;
	jack_uuid_t finalizer = JACK_UUID_EMPTY_INITIALIZER;

	jack_uuid_copy (&client_id, req->x.client_id);
	client = jack_client_internal_by_id (engine, client_id);
	jack_uuid_clear (&finalizer);

	req->status = 0;

	client->session_reply_pending = 0;

	if (engine->session_reply_fd == -1) {
		jack_error ("spurious Session Reply");
		return;
	}

	engine->session_pending_replies -= 1;

	if (jack_send_session_reply (engine, client)) {
		// maybe need to fix all client pendings.
		// but we will just get a set of spurious replies now.
		engine->session_reply_fd = -1;
		return;
	}

	if (engine->session_pending_replies == 0) {
		if (write (engine->session_reply_fd, &finalizer, sizeof(finalizer))
		    < (ssize_t)sizeof(finalizer)) {
			jack_error ("cannot write SessionNotify result "
				    "to client via fd = %d (%s)",
				    engine->session_reply_fd, strerror (errno));
			req->status = -1;
		}
		engine->session_reply_fd = -1;
	}
}

static void
jack_notify_all_port_interested_clients (jack_engine_t *engine, jack_uuid_t src, jack_uuid_t dst, jack_port_id_t a, jack_port_id_t b, int connected)
{
	JSList *node;
	jack_event_t event;

	event.type = (connected ? PortConnected : PortDisconnected);
	event.x.self_id = a;
	event.y.other_id = b;

	/* GRAPH MUST BE LOCKED : see callers of jack_send_connection_notification()
	 */

	jack_client_internal_t* src_client = jack_client_internal_by_id (engine, src);
	jack_client_internal_t* dst_client = jack_client_internal_by_id (engine, dst);

	for (node = engine->clients; node; node = jack_slist_next (node)) {
		jack_client_internal_t* client = (jack_client_internal_t*)node->data;
		if (src_client != client &&  dst_client  != client && client->control->port_connect_cbset != FALSE) {

			/* one of the ports belong to this client or it has a port connect callback */
			jack_deliver_event (engine, client, &event);
		}
	}
}

int
jack_deliver_event (jack_engine_t *engine, jack_client_internal_t *client,
		    const jack_event_t *event, ...)
{
	va_list ap;
	char status = 0;
	char* key = 0;
	size_t keylen = 0;

	va_start (ap, event);

	/* caller must hold the graph lock */

	DEBUG ("delivering event (type %s)", jack_event_type_name (event->type));

	/* we are not RT-constrained here, so use kill(2) to beef up
	   our check on a client's continued well-being
	 */

	if (client->control->dead || client->error >= JACK_ERROR_WITH_SOCKETS
	    || (client->control->type == ClientExternal && kill (client->control->pid, 0))) {
		DEBUG ("client %s is dead - no event sent",
		       client->control->name);
		va_end (ap);
		return 0;
	}

	DEBUG ("client %s is still alive", client->control->name);

	/* Check property change events for matching key_size and keys */

	if (event->type == PropertyChange) {
		key = va_arg (ap, char*);
		if (key && key[0] != '\0') {
			keylen = strlen (key) + 1;
			if (event->y.key_size != keylen) {
				jack_error ("property change key %s sent with wrong length (%d vs %d)", key, event->y.key_size, keylen);
				va_end (ap);
				return -1;
			}
		}
	}

	va_end (ap);

	if (jack_client_is_internal (client)) {

		switch (event->type) {
		case PortConnected:
		case PortDisconnected:
			jack_client_handle_port_connection
				(client->private_client, event);
			break;

		case BufferSizeChange:
			jack_client_fix_port_buffers (client->private_client);

			if (client->control->bufsize_cbset) {
				if (event->x.n < 16) {
					abort ();
				}
				client->private_client->bufsize
					(event->x.n, client->private_client->bufsize_arg);
			}
			break;

		case SampleRateChange:
			if (client->control->srate_cbset) {
				client->private_client->srate
					(event->x.n,
					client->private_client->srate_arg);
			}
			break;

		case GraphReordered:
			if (client->control->graph_order_cbset) {
				client->private_client->graph_order
					(client->private_client->graph_order_arg);
			}
			break;

		case XRun:
			if (client->control->xrun_cbset) {
				client->private_client->xrun
					(client->private_client->xrun_arg);
			}
			break;

		case PropertyChange:
			if (client->control->property_cbset) {
				client->private_client->property_cb
					(event->x.uuid, key, event->z.property_change, client->private_client->property_cb_arg);
			}
			break;

		case LatencyCallback:
			jack_client_handle_latency_callback (client->private_client, event, (client->control->type == ClientDriver));
			break;

		default:
			/* internal clients don't need to know */
			break;
		}

	} else {

		if (client->control->active) {

			/* there's a thread waiting for events, so
			 * it's worth telling the client */

			DEBUG ("engine writing on event fd");

			if (write (client->event_fd, event, sizeof(*event)) != sizeof(*event)) {
				jack_error ("cannot send event to client [%s] (%s)",
					    client->control->name,
					    strerror (errno));
				client->error += JACK_ERROR_WITH_SOCKETS;
				jack_engine_signal_problems (engine);
			}

			/* for property changes, deliver the extra data representing
			   the variable length "key" that has changed in some way.
			 */

			if (event->type == PropertyChange) {
				if (keylen) {
					if (write (client->event_fd, key, keylen) != keylen) {
						jack_error ("cannot send property change key to client [%s] (%s)",
							    client->control->name,
							    strerror (errno));
						client->error += JACK_ERROR_WITH_SOCKETS;
						jack_engine_signal_problems (engine);
					}
				}
			}

			if (client->error) {
				status = -1;
			} else {
				// then we check whether there really is an error.... :)

				struct pollfd pfd[1];
				pfd[0].fd = client->event_fd;
				pfd[0].events = POLLERR | POLLIN | POLLHUP | POLLNVAL;
				jack_time_t poll_timeout = JACKD_CLIENT_EVENT_TIMEOUT;
				int poll_ret;
				jack_time_t then = jack_get_microseconds ();
				jack_time_t now;

				/* if we're not running realtime and there is a client timeout set
				   that exceeds the default client event timeout (which is not
				   bound by RT limits, then use the larger timeout.
				 */

				if (!engine->control->real_time && (engine->client_timeout_msecs > poll_timeout)) {
					poll_timeout = engine->client_timeout_msecs;
				}

#ifdef __linux
again:
#endif
				VERBOSE (engine, "client event poll on %d for %s starts at %lld",
					 client->event_fd, client->control->name, then);
				if ((poll_ret = poll (pfd, 1, poll_timeout)) < 0) {
					DEBUG ("client event poll not ok! (-1) poll returned an error");
					jack_error ("poll on subgraph processing failed (%s)", strerror (errno));
					status = -1;
				} else {

					DEBUG ("\n\n\n\n\n back from client event poll, revents = 0x%x\n\n\n", pfd[0].revents);
					now = jack_get_microseconds ();
					VERBOSE (engine, "back from client event poll after %lld usecs", now - then);

					if (pfd[0].revents & ~POLLIN) {

						/* some kind of OOB socket event */

						DEBUG ("client event poll not ok! (-2), revents = %d\n", pfd[0].revents);
						jack_error ("subgraph starting at %s lost client", client->control->name);
						status = -2;

					} else if (pfd[0].revents & POLLIN) {

						/* client responded normally */

						DEBUG ("client event poll ok!");
						status = 0;

					} else if (poll_ret == 0) {

						/* no events, no errors, we woke up because poll()
						   decided that time was up ...
						 */

#ifdef __linux
						if (linux_poll_bug_encountered (engine, then, &poll_timeout)) {
							goto again;
						}

						if (poll_timeout < 200) {
							VERBOSE (engine, "FALSE WAKEUP skipped, remaining = %lld usec", poll_timeout);
							status = 0;
						} else {
#endif
						DEBUG ("client event poll not ok! (1 = poll timed out, revents = 0x%04x, poll_ret = %d)", pfd[0].revents, poll_ret);
						VERBOSE (engine, "client %s did not respond to event type %d in time"
							 "(fd=%d, revents = 0x%04x, timeout was %lld)",
							 client->control->name, event->type,
							 client->event_fd,
							 pfd[0].revents,
							 poll_timeout);
						status = -2;
#ifdef __linux
					}
#endif
					}
				}
			}

			if (status == 0) {
				if (read (client->event_fd, &status, sizeof(status)) != sizeof(status)) {
					jack_error ("cannot read event response from client [%s] (%s)",
						    client->control->name,
						    strerror (errno));
					status = -1;
				}

			} else {
				switch (status) {
				case -1:
					jack_error ("internal poll failure reading response from client %s to a %s event",
						    client->control->name,
						    jack_event_type_name (event->type));
					break;
				case -2:
					jack_error ("timeout waiting for client %s to handle a %s event",
						    client->control->name,
						    jack_event_type_name (event->type));
					break;
				default:
					jack_error ("bad status (%d) from client %s while handling a %s event",
						    (int)status,
						    client->control->name,
						    jack_event_type_name (event->type));
				}
			}

			if (status < 0) {
				client->error += JACK_ERROR_WITH_SOCKETS;
				jack_engine_signal_problems (engine);
			}
		}
	}
	DEBUG ("event delivered");

	return status;
}


/* Modified to use the new double-linked list of clients in execution order
 * FA 08/2015
 */
int
jack_rechain_graph (jack_engine_t *engine)
{
	jack_client_internal_t *client, *subgraph_client;
	jack_event_t event;
	int upstream_is_jackd;
	unsigned long n;


	VERBOSE (engine, "++ jack_rechain_graph():");
	VALGRIND_MEMSET (&event, 0, sizeof(event));

	jack_clear_fifos (engine);
	subgraph_client = 0;

	event.type = GraphReordered;

	n = 0;
	for (client = engine->execlist_head; client; client = client->execlist_next) {
		/* We are only interested in active clients that have a process callback */
		if (!client->control->active ||
		    (!client->control->process_cbset && !client->control->thread_cb_cbset)) {
			continue;
		}

		VERBOSE (engine, "+++ client is now %s", client->control->name);

			client->execution_order = n;

			if (jack_client_is_internal (client)) {
			/* Break the chain for the current subgraph. The server will
			 * wait for the chain on the nth FIFO, and will then execute
			 * this internal client. */
				if (subgraph_client) {
				subgraph_client->subgraph_wait_fd = jack_get_fifo_fd (engine, n);
				VERBOSE (engine, "client %s: wait_fd=%d execution_order=%lu.",
					 subgraph_client->control->name,
					 subgraph_client->subgraph_wait_fd, n);
					n++;
				}
			VERBOSE (engine, "client %s: internal client, execution_order=%lu.",
					 client->control->name, n);

			/* this does the right thing for internal clients too */
				jack_deliver_event (engine, client, &event);
				subgraph_client = 0;
			} else {
			if (subgraph_client) {
				/* continue current subgraph. */
					subgraph_client->subgraph_wait_fd = -1;
					upstream_is_jackd = 0;
				VERBOSE (engine, "client %s: in subgraph after %s, "
					 "execution_order=%lu.",
					 client->control->name,
					 subgraph_client->control->name, n);
			} else {
				/* start a new subgraph. The engine will start the chain
				 * by writing to the nth FIFO. */
				subgraph_client = client;
				subgraph_client->subgraph_start_fd = jack_get_fifo_fd (engine, n);
				upstream_is_jackd = 1;
				VERBOSE (engine, "client %s: start_fd=%d "
					 "execution_order=%lu.",
					 subgraph_client->control->name,
					 subgraph_client->subgraph_start_fd, n);
				}

			/* make sure fifo for 'n + 1' exists before issuing client reorder. */
			(void)jack_get_fifo_fd (engine, client->execution_order + 1);
				event.x.n = client->execution_order;
				event.y.n = upstream_is_jackd;
				jack_deliver_event (engine, client, &event);
				n++;
			}
		}

	if (subgraph_client) {
		/* finish current subgraph. */
		subgraph_client->subgraph_wait_fd = jack_get_fifo_fd (engine, n);
		VERBOSE (engine, "client %s: wait_fd=%d, "
			 "execution_order=%lu (last client).",
			 subgraph_client->control->name,
			 subgraph_client->subgraph_wait_fd, n);
	}

	VERBOSE (engine, "-- jack_rechain_graph()");
	return 0;
}


static jack_nframes_t
jack_get_port_total_latency (jack_engine_t *engine,
			     jack_port_internal_t *port, int hop_count,
			     int toward_port)
{
	JSList *node;
	jack_nframes_t latency;
	jack_nframes_t max_latency = 0;

#ifdef DEBUG_TOTAL_LATENCY_COMPUTATION
	char prefix[32];
	int i;

	for (i = 0; i < hop_count; ++i)
		prefix[i] = '\t';

	prefix[i] = '\0';
#endif

	/* call tree must hold engine->client_lock. */

	latency = port->shared->latency;

	/* we don't prevent cyclic graphs, so we have to do something
	   to bottom out in the event that they are created.
	 */

	if (hop_count > 8) {
		return latency;
	}

#ifdef DEBUG_TOTAL_LATENCY_COMPUTATION
	jack_info ("%sFor port %s (%s)", prefix, port->shared->name, (toward_port ? "toward" : "away"));
#endif

	for (node = port->connections; node; node = jack_slist_next (node)) {

		jack_nframes_t this_latency;
		jack_connection_internal_t *connection;

		connection = (jack_connection_internal_t*)node->data;


		if ((toward_port &&
		     (connection->source->shared == port->shared)) ||
		    (!toward_port &&
		     (connection->destination->shared == port->shared))) {

#ifdef DEBUG_TOTAL_LATENCY_COMPUTATION
			jack_info ("%s\tskip connection %s->%s",
				   prefix,
				   connection->source->shared->name,
				   connection->destination->shared->name);
#endif

			continue;
		}

#ifdef DEBUG_TOTAL_LATENCY_COMPUTATION
		jack_info ("%s\tconnection %s->%s ... ",
			   prefix,
			   connection->source->shared->name,
			   connection->destination->shared->name);
#endif
		/* if we're a destination in the connection, recurse
		   on the source to get its total latency
		 */

		if (connection->destination == port) {

			if (connection->source->shared->flags
			    & JackPortIsTerminal) {
				this_latency = connection->source->
					       shared->latency;
			} else {
				this_latency =
					jack_get_port_total_latency (
						engine, connection->source,
						hop_count + 1,
						toward_port);
			}

		} else {

			/* "port" is the source, so get the latency of
			 * the destination */
			if (connection->destination->shared->flags
			    & JackPortIsTerminal) {
				this_latency = connection->destination->
					       shared->latency;
			} else {
				this_latency =
					jack_get_port_total_latency (
						engine,
						connection->destination,
						hop_count + 1,
						toward_port);
			}
		}

		if (this_latency > max_latency) {
			max_latency = this_latency;
		}
	}

#ifdef DEBUG_TOTAL_LATENCY_COMPUTATION
	jack_info ("%s\treturn %lu + %lu = %lu", prefix, latency, max_latency, latency + max_latency);
#endif

	return latency + max_latency;
}

static void
jack_compute_port_total_latency (jack_engine_t* engine, jack_port_shared_t* port)
{
	if (port->in_use) {
		port->total_latency =
			jack_get_port_total_latency (
				engine, &engine->internal_ports[port->id],
				0, !(port->flags & JackPortIsOutput));
	}
}

static void
jack_compute_all_port_total_latencies (jack_engine_t *engine)
{
	jack_port_shared_t *shared = engine->control->ports;
	unsigned int i;
	int toward_port;

	for (i = 0; i < engine->control->port_max; i++) {
		if (shared[i].in_use) {
			if (shared[i].flags & JackPortIsOutput) {
				toward_port = FALSE;
			} else {
				toward_port = TRUE;
			}
			shared[i].total_latency =
				jack_get_port_total_latency (
					engine, &engine->internal_ports[i],
					0, toward_port);
		}
	}
}


/* Modified to use the new double-linked list of clients in execution order
 * FA 08/2015
 */
static void
jack_compute_new_latency (jack_engine_t *engine)
{
	jack_client_internal_t* client;
	jack_event_t event;

	VALGRIND_MEMSET (&event, 0, sizeof(event));
	event.type = LatencyCallback;

	/* iterate over all clients in graph order and emit capture latency callback. */
	event.x.n = 0;
	for (client = engine->execlist_head; client; client = client->execlist_next)
		jack_deliver_event (engine, client, &event);
	if (engine->driver) {
		jack_deliver_event (engine, engine->driver->internal_client, &event);
	}

	/* iterate over all clients in reverse order and emit playback latency callback. */
	event.x.n  = 1;
	for (client = engine->execlist_tail; client; client = client->execlist_prev)
		jack_deliver_event (engine, client, &event);
	if (engine->driver) {
		jack_deliver_event (engine, engine->driver->internal_client, &event);
	}
}


/* HOW THE SORT WORKS (new version)
 * FA 08/2015
 *
 * Each client has a linked list called 'feedlist' of other clients
 * directly depending on data from it. Element of the list are structs
 * of type jack_feedcounts_t, which contains:
 *
 *   .next      : pointer to the next list element (this is not a JSlist).
 *   .client    : pointer to the destination client depending on this one.
 *   .fwd_count : counter of forward direct connections.
 *   .rev_count : counter of reversed direct connections.
 *
 * The counters are incremented or decremented by port connect or disconnect
 * requests. At least one of them will be non-zero. Reversed dependencies
 * are those created by connections that create a cycle.
 *
 * As in the previous version, connections having the driver as destination
 * are ignored in order to avoid apparent cycles. Note: things just work
 * this way so this was not changed, but it would be cleaner to represent
 * the driver as two clients. This would allow to represent all dependencies
 * (which could be interesting for debugging) without creating fake cycles.
 *
 * In contrast to the previous version, there is no implicit dependency
 * of each client on the driver, this is created only when there is an
 * actual connection from the capture part. Other logic ensures that the
 * driver will run first anyway, even if no clients are connected to it
 * at all.
 *
 * Each client also has a counter 'depcount' indicating from how many
 * other clients it requires input. This is always equal to the number
 * of other clients having a feedlist element referring to this one.
 *
 * The algorithm that actually determines the execution order is run only
 * when an element is added or revomed from any of the 'feedlist' lists,
 * and when clients are activated or deactivated. It consists of two
 * parts, each of them controlled by a binary flag maintained in
 * engine->execlist_requestm and, if necessary, set by the port connect
 * and disconnect routines.
 *
 * First, if the EXECLIST_CYCLE flag is set, we test if any feedback
 * connections can be reverted to normal ones. If there are any, we
 * also set the EXECLIST_ORDER flag in case it was not already set.
 * Second, if the EXECLIST_ORDER flag is set, a double linked list
 * of clients in execution order is constructed. This list is then
 * used by all other routines that control running a cycle.
 *
 * The 'sorting' works as follows. Each client has a 'depcheck' field
 * which is originally set to its 'depcount' value. The list is reset,
 * and the driver is added to it. Then we loop over the engine->clients
 * JSlist, and add any clients which have their 'depcheck' equal to
 * zero to the new list.
 *
 * Whenever a client is added to the new list, its 'depcheck' is set to
 * -1 so that client won't be considered again, and we loop over its
 * 'feedlist' and decrement the 'depcheck' of each client on it. When
 * this decrements to zero, that client is added to the list recursively.
 *
 * The complexity of this algorithm is linear in the number of clients
 * plus the number of direct dependencies between them (i.e. the sum
 * of the lenghts of all feedlists). Multiple port connections between
 * the same clients count as a single dependency.
 *
 * Finally, the new double linked list is copied to the original
 * engine->clients JSlist. This ensures that in this list the driver
 * will always come before any active clients. It's not clear if this
 * is actually necessary, as all code related to running a cycle is
 * using the new list anyway (as far as I could verify), and all
 * other uses seem to be related to looking up client data only.
 *
 * Another open question is if jack_rechain_graph() needs to be
 * called if the order didn't change. If not, the call could be
 * moved to the place indicated in jack_check_execorder().
 */


/* Test if there is a direct dependency of client B on client A.
 * This may be because A feeds B directly, or because there is
 * a feedback connection from B to A.
 * Returns the jack_feedcounts_t for the dependency if it exists,
 * zero otherwise.
 */
static jack_feedcounts_t *
depends_direct (jack_client_internal_t *A, jack_client_internal_t *B)
{
	jack_feedcounts_t *F;

	for (F = A->feedlist; F; F = F->next)
		if (F->client == B) {
			return F;
	}
	return 0;
}

/* Test if client B depends on output from client A, either directly
 * or via other clients. Feedback connections are not considered in
 * this case. This is used to detect cycles.
 * Returns 1 if the dependency exists, 0 otherwise.
 */
static int
depends_closure (jack_client_internal_t *A, jack_client_internal_t *B)
{
	jack_feedcounts_t *F;

	for (F = A->feedlist; F; F = F->next) {
		if (F->fwd_count == 0) {
			continue;
	}
		if (F->client == B) {
			return 1;
		} else {              return depends_closure (F->client, B); }
		}
	return 0;
}

/* Create a new direct dependency of client B on client A.
 */
static void
add_depends (jack_client_internal_t *A, jack_client_internal_t *B, int fwd, int rev)
{
	jack_feedcounts_t *F;

	F = (jack_feedcounts_t*)malloc (sizeof(jack_feedcounts_t));
	F->client = B;
	F->fwd_count = fwd;
	F->rev_count = rev;
	F->next = A->feedlist;
	A->feedlist = F;
	B->depcount++;
	}

/* Delete a direct dependency of client B on client A.
 */
static void
rem_depends (jack_client_internal_t *A, jack_client_internal_t *B)
{
	jack_feedcounts_t *X, *Y;

	for (X = 0, Y = A->feedlist; Y; X = Y, Y = Y->next) {
		if (Y->client == B) {
			if (X) {
				X->next = Y->next;
			} else {                      A->feedlist = Y->next; }
			B->depcount--;
			free (Y);
			return;
		}
	}
}


/* Add client C at the tail of the execution order list, and then
 * recursively test if any others can be run after C has finished.
 */
static void
append_execlist (jack_engine_t *engine, jack_client_internal_t *C)
{
	jack_client_internal_t *D;
	jack_feedcounts_t *F;

	/* This client must not be considered again. */
	C->depcheck = -1;
	/* Append at end of list */
	C->execlist_next = 0;
	if (engine->execlist_tail) {
		C->execlist_prev = engine->execlist_tail;
		engine->execlist_tail->execlist_next = C;
	} else {
		C->execlist_prev = 0;
		engine->execlist_head = C;
				}
	engine->execlist_tail = C;
	/* Check if any others can be run after this one. */
	for (F = C->feedlist; F; F = F->next) {
		D = F->client;
		if (--(D->depcheck) == 0) {
			append_execlist (engine, D);
			}
		}
	}


/* Recreate the execution order client list if necessary.
 */
void
jack_check_execorder (jack_engine_t *engine)
{
	jack_client_internal_t *C, *D;
	jack_feedcounts_t *F;
	JSList *N;

	if (engine->execlist_request & EXECLIST_CYCLE) {
		/* Test if any feedback connections can be reverted
		 * to normal */
		for (C = engine->execlist_head; C; C = C->execlist_next) {
			for (F = C->feedlist; F; F = F->next) {
				int rev;
				D = F->client;
				if (F->rev_count == 0) {
					continue;
					}
				if (depends_closure (C, D)) {
					continue;
				}
				/* printf ("Reverting feedback %s -> %s\n", D->control->name, C->control->name); */
				rev = F->rev_count;
				rem_depends (C, D);
				add_depends (D, C, rev, 0);
				engine->execlist_request |= EXECLIST_ORDER;
			}
		}
	}
/*
        puts ("---------------------------------------------");
        printf ("Original client list:\n");
        for (N = engine->clients; N; N = jack_slist_next (N))
        {
                C = (jack_client_internal_t *) N->data;
                printf ("%-20s %d\n", C->control->name, C->depcount);
                for (F = C->feedlist; F; F = F->next)
                {
                        printf ("    %-20s %3d %3d\n", F->client->control->name, F->fwd_count, F->rev_count);
	}
}
        puts ("---------------------------------------------");
 */
	if (engine->execlist_request & EXECLIST_ORDER) {
/*
                puts ("Re-ordering...");
 */
		/* Put clients in correct execution order depending
		   on their dependencies. */
		D = 0;
		for (N = engine->clients; N; N = jack_slist_next (N)) {
			C = (jack_client_internal_t*)N->data;
			C->depcheck = C->depcount;
			if (C->control->type == ClientDriver) {
				D = C;
			}
		}
		/* Reset bidirectional linked list and build it again. */
		engine->execlist_head = 0;
		engine->execlist_tail = 0;
		/* The driver must be first even if nobody is using capture data. */
		if (D) {
			append_execlist (engine, D);
		}
		/* Then loop over all the other clients. */
		for (N = engine->clients; N; N = jack_slist_next (N)) {
			C = (jack_client_internal_t*)N->data;
			if (C->depcheck == 0) {
				append_execlist (engine, C);
			}
		}

		/* Copy execlist to engine->clients. Just overwrite the data pointers. */
		for (C = engine->execlist_head, N = engine->clients;
		     C && N;
		     C = C->execlist_next, N = N->next)
			N->data = C;

		/* ??? Maybe call jack_rechain_graph here instead of in jack_sort_graph() ??? */
	}
/*
        puts ("---------------------------------------------");
        printf ("Ordered client list:\n");
        for (C = engine->execlist_head; C; C = C->execlist_next)
        {
                printf ("   %-20s\n", C->control->name);
        }
        puts ("---------------------------------------------");
 */
	engine->execlist_request = 0;
}


/* Modified for new client execution order algorithm.
 * FA 08/2015
 */
void
jack_sort_graph (jack_engine_t *engine)
{
	/* caller, obviously, must hold engine->client_lock */
	VERBOSE (engine, "++ jack_sort_graph");
	jack_check_execorder (engine);
	jack_compute_all_port_total_latencies (engine);
	jack_compute_new_latency (engine);
	jack_rechain_graph (engine);
	engine->timeout_count = 0;
	VERBOSE (engine, "-- jack_sort_graph");
}


/**
 * Dumps current engine configuration.
 */
void jack_dump_configuration (jack_engine_t *engine, int take_lock)
{
	JSList *clientnode, *portnode, *connectionnode;
	jack_client_internal_t *client;
	jack_client_control_t *ctl;
	jack_port_internal_t *port;
	jack_connection_internal_t* connection;
	int n, m, o;

	jack_info ("engine.c: <-- dump begins -->");

	if (take_lock) {
		jack_rdlock_graph (engine);
	}

	for (n = 0, clientnode = engine->clients; clientnode;
	     clientnode = jack_slist_next (clientnode)) {
		client = (jack_client_internal_t*)clientnode->data;
		ctl = client->control;

		jack_info ("client #%d: %s (type: %d, process? %s, thread ? %s"
			   " start=%d wait=%d",
			   ++n,
			   ctl->name,
			   ctl->type,
			   ctl->process_cbset ? "yes" : "no",
			   ctl->thread_cb_cbset ? "yes" : "no",
			   client->subgraph_start_fd,
			   client->subgraph_wait_fd);

		for (m = 0, portnode = client->ports; portnode;
		     portnode = jack_slist_next (portnode)) {
			port = (jack_port_internal_t*)portnode->data;

			jack_info ("\t port #%d: %s", ++m,
				   port->shared->name);

			for (o = 0, connectionnode = port->connections;
			     connectionnode;
			     connectionnode = jack_slist_next (connectionnode)) {
				connection = (jack_connection_internal_t*)
					     connectionnode->data;

				jack_info ("\t\t connection #%d: %s %s",
					   ++o,
					   (port->shared->flags
					    & JackPortIsInput) ? "<-" : "->",
					   (port->shared->flags & JackPortIsInput) ?
					   connection->source->shared->name :
					   connection->destination->shared->name);
			}
		}
	}

	if (take_lock) {
		jack_unlock_graph (engine);
	}


	jack_info ("engine.c: <-- dump ends -->");
}



/* Modified for new client execution order algorithm.
 * FA 08/2015
 */
static int
jack_port_do_connect (jack_engine_t *engine,
		      const char *source_port,
		      const char *destination_port)
{
	jack_connection_internal_t *connection;
	jack_port_internal_t *srcport, *dstport;
	jack_port_id_t src_id, dst_id;
	jack_client_internal_t *srcclient, *dstclient;
	JSList *it;

	if ((srcport = jack_get_port_by_name (engine, source_port)) == NULL) {
		jack_error ("unknown source port in attempted connection [%s]",
			    source_port);
		return -1;
	}

	if ((dstport = jack_get_port_by_name (engine, destination_port))
	    == NULL) {
		jack_error ("unknown destination port in attempted connection"
			    " [%s]", destination_port);
		return -1;
	}

	if ((dstport->shared->flags & JackPortIsInput) == 0) {
		jack_error ("destination port in attempted connection of"
			    " %s and %s is not an input port",
			    source_port, destination_port);
		return -1;
	}

	if ((srcport->shared->flags & JackPortIsOutput) == 0) {
		jack_error ("source port in attempted connection of %s and"
			    " %s is not an output port",
			    source_port, destination_port);
		return -1;
	}

	if (srcport->shared->ptype_id != dstport->shared->ptype_id) {
		jack_error ("ports used in attemped connection are not of "
			    "the same data type");
		return -1;
	}

	if ((srcclient = jack_client_internal_by_id (engine,
						     srcport->shared->client_id))
	    == 0) {
		jack_error ("unknown client set as owner of port - "
			    "cannot connect");
		return -1;
	}

	if (!srcclient->control->active) {
		jack_error ("cannot connect ports owned by inactive clients;"
			    " \"%s\" is not active", srcclient->control->name);
		return -1;
	}

	if ((dstclient = jack_client_internal_by_id (engine,
						     dstport->shared->client_id))
	    == 0) {
		jack_error ("unknown client set as owner of port - cannot "
			    "connect");
		return -1;
	}

	if (!dstclient->control->active) {
		jack_error ("cannot connect ports owned by inactive clients;"
			    " \"%s\" is not active", dstclient->control->name);
		return -1;
	}

	for (it = srcport->connections; it; it = it->next) {
		if (((jack_connection_internal_t*)it->data)->destination
		    == dstport) {
			return EEXIST;
		}
	}

	if (dstport->connections && !dstport->shared->has_mixdown) {
		jack_port_type_info_t *port_type =
			jack_port_type_info (engine, dstport);
		jack_error ("cannot make multiple connections to a port of"
			    " type [%s]", port_type->type_name);
		return -1;
	}

	connection = (jack_connection_internal_t*)
		     malloc (sizeof(jack_connection_internal_t));
	connection->source = srcport;
	connection->destination = dstport;
	connection->srcclient = srcclient;
	connection->dstclient = dstclient;

	src_id = srcport->shared->id;
	dst_id = dstport->shared->id;
	jack_lock_graph (engine);

		if (dstclient->control->type == ClientDriver) {
			/* Ignore output connections to drivers for purposes
			   of sorting. Drivers are executed first in the sort
			   order anyway, and we don't want to treat graphs
			   such as driver -> client -> driver as containing
			   feedback */
			VERBOSE (engine,
				 "connect %s and %s (output)",
				 srcport->shared->name,
				 dstport->shared->name);
		} else if (srcclient != dstclient) {
		jack_feedcounts_t *F;
		int dir = 0;

		if ((F = depends_direct (srcclient, dstclient)) != 0) {
			/* We already have a direct dependency,
			   just increment the connection count. */
			F->fwd_count++;
			dir = 1;
		} else if ((F = depends_direct (dstclient, srcclient)) != 0) {
			/* We already have a reverse direct dependency,
			   just increment the reverse connection count. */
			F->rev_count++;
			dir = -1;
		} else if (depends_closure (dstclient, srcclient)) {
			/* We have an inverse dependency, this
			   connection must be a delayed one. */
			add_depends (dstclient, srcclient, 0, 1);
			engine->execlist_request = EXECLIST_ORDER;
			dir = -1;
		} else {
			/* First normal connection from source
			   to destination client. */
			add_depends (srcclient, dstclient, 1, 0);
			engine->execlist_request = EXECLIST_ORDER;
			dir = 1;
		}

		if (dir > 0) {
			VERBOSE (engine,
				 "connect %s and %s (forward)",
				 srcport->shared->name,
				 dstport->shared->name);
		} else {
				VERBOSE (engine,
					 "connect %s and %s (feedback)",
					 srcport->shared->name,
					 dstport->shared->name);
				engine->feedbackcount++;
				VERBOSE (engine,
					 "feedback count up to %d",
					 engine->feedbackcount);
			}
		} else {
			/* this is a connection to self */
			VERBOSE (engine,
				 "connect %s and %s (self)",
				 srcport->shared->name,
				 dstport->shared->name);

		}

		dstport->connections =
			jack_slist_prepend (dstport->connections, connection);
		srcport->connections =
			jack_slist_prepend (srcport->connections, connection);

		jack_send_connection_notification (engine,
						   srcport->shared->client_id,
						   src_id, dst_id, TRUE);
		jack_send_connection_notification (engine,
						   dstport->shared->client_id,
						   dst_id, src_id, TRUE);

	/* send a port connection notification just once to everyone who
	 * cares excluding clients involved in the connection */
	jack_notify_all_port_interested_clients (engine,
						 srcport->shared->client_id,
						 dstport->shared->client_id,
						 src_id, dst_id, 1);
		jack_sort_graph (engine);
	jack_unlock_graph (engine);
	return 0;
}


/* Modified for new client execution order algorithm.
 * FA 08/2015
 */
int
jack_port_disconnect_internal (jack_engine_t *engine,
			       jack_port_internal_t *srcport,
			       jack_port_internal_t *dstport )

{
	JSList *node;
	jack_connection_internal_t *connect;
	jack_client_internal_t *src, *dst;
	jack_port_id_t src_id, dst_id;
	int ret = -1;

	/* call tree **** MUST HOLD **** engine->client_lock. */
	for (node = srcport->connections; node; node = jack_slist_next (node)) {
		connect = (jack_connection_internal_t*)node->data;

		if (connect->source == srcport &&  connect->destination == dstport) {
			VERBOSE (engine, "DIS-connect %s and %s",
				 srcport->shared->name,
				 dstport->shared->name);

			srcport->connections =
				jack_slist_remove (srcport->connections,
						   connect);
			dstport->connections =
				jack_slist_remove (dstport->connections,
						   connect);
			free (connect);
			src_id = srcport->shared->id;
			dst_id = dstport->shared->id;

			/* this is a bit harsh, but it basically says
			   that if we actually do a disconnect, and
			   its the last one, then make sure that any
			   input monitoring is turned off on the
			   srcport. this isn't ideal for all
			   situations, but it works better for most of
			   them.
			 */
			if (srcport->connections == NULL) {
				srcport->shared->monitor_requests = 0;
			}

			jack_send_connection_notification (
				engine, srcport->shared->client_id, src_id,
				dst_id, FALSE);
			jack_send_connection_notification (
				engine, dstport->shared->client_id, dst_id,
				src_id, FALSE);

			/* send a port connection notification just once to everyone
			   who cares excluding clients involved in the connection */
			jack_notify_all_port_interested_clients (engine,
								 srcport->shared->client_id,
								 dstport->shared->client_id,
								 src_id, dst_id, 0);

			/* Update client dependencies */
			src = jack_client_internal_by_id (engine, srcport->shared->client_id);
			dst = jack_client_internal_by_id (engine, dstport->shared->client_id);
			/* Again we ignore connections if the destination is the driver. */
			if ((src != dst) && (dst->control->type != ClientDriver)) {
				jack_feedcounts_t *F;
				if ((F = depends_direct (src, dst)) != 0) {
					if (F->fwd_count > 0) {
						F->fwd_count--;
					}
					if (F->fwd_count == 0) {
						/* A direct forward dependency no longer exists.
						   This could break a cycle, so we'll test. */
						engine->execlist_request = EXECLIST_CYCLE;
						if (F->rev_count == 0) {
							/* A direct dependency no longer exists,
							   remove the corresponding list element. */
							rem_depends (src, dst);
							engine->execlist_request |= EXECLIST_ORDER;
						}
					}
				} else if ((F = depends_direct (dst, src)) != 0) {
					/* Removing a feedback connection. */
					if (F->rev_count > 0) {
						F->rev_count--;
					}
					if ((F->fwd_count | F->rev_count) == 0) {
						/* A direct dependency no longer exists,
						   remove the corresponding list element. */
						rem_depends (dst, src);
						engine->execlist_request = EXECLIST_ORDER;
					}
					engine->feedbackcount--;
					VERBOSE (engine,
						 "feedback count down to %d",
						 engine->feedbackcount);

				}
		}
			jack_sort_graph (engine);
			return 0;
	}
	}
	return -1;
}


static int
jack_port_do_disconnect_all (jack_engine_t *engine,
			     jack_port_id_t port_id)
{
	if (port_id >= engine->control->port_max) {
		jack_error ("illegal port ID in attempted disconnection [%"
			    PRIu32 "]", port_id);
		return -1;
	}

	VERBOSE (engine, "clear connections for %s",
		 engine->internal_ports[port_id].shared->name);

	jack_lock_graph (engine);
	jack_port_clear_connections (engine, &engine->internal_ports[port_id]);
	jack_sort_graph (engine);
	jack_unlock_graph (engine);

	return 0;
}

static int
jack_port_do_disconnect (jack_engine_t *engine,
			 const char *source_port,
			 const char *destination_port)
{
	jack_port_internal_t *srcport, *dstport;
	int ret = -1;

	if ((srcport = jack_get_port_by_name (engine, source_port)) == NULL) {
		jack_error ("unknown source port in attempted disconnection"
			    " [%s]", source_port);
		return -1;
	}

	if ((dstport = jack_get_port_by_name (engine, destination_port))
	    == NULL) {
		jack_error ("unknown destination port in attempted"
			    " disconnection [%s]", destination_port);
		return -1;
	}

	jack_lock_graph (engine);

	ret = jack_port_disconnect_internal (engine, srcport, dstport);

	jack_unlock_graph (engine);

	return ret;
}

int
jack_get_fifo_fd (jack_engine_t *engine, unsigned int which_fifo)
{
	/* caller must hold client_lock */
	char path[PATH_MAX + 1];
	struct stat statbuf;

	snprintf (path, sizeof(path), "%s-%d", engine->fifo_prefix,
		  which_fifo);

	DEBUG ("%s", path);

	if (stat (path, &statbuf)) {
		if (errno == ENOENT) {

			if (mkfifo (path, 0666) < 0) {
				jack_error ("cannot create inter-client FIFO"
					    " [%s] (%s)\n", path,
					    strerror (errno));
				return -1;
			}

		} else {
			jack_error ("cannot check on FIFO %d\n", which_fifo);
			return -1;
		}
	} else {
		if (!S_ISFIFO (statbuf.st_mode)) {
			jack_error ("FIFO %d (%s) already exists, but is not"
				    " a FIFO!\n", which_fifo, path);
			return -1;
		}
	}

	if (which_fifo >= engine->fifo_size) {
		unsigned int i;

		engine->fifo = (int*)
			       realloc (engine->fifo,
					sizeof(int) * (engine->fifo_size + 16));
		for (i = engine->fifo_size; i < engine->fifo_size + 16; i++)
			engine->fifo[i] = -1;
		engine->fifo_size += 16;
	}

	if (engine->fifo[which_fifo] < 0) {
		if ((engine->fifo[which_fifo] =
			     open (path, O_RDWR | O_CREAT | O_NONBLOCK, 0666)) < 0) {
			jack_error ("cannot open fifo [%s] (%s)", path,
				    strerror (errno));
			return -1;
		}
		DEBUG ("opened engine->fifo[%d] == %d (%s)",
		       which_fifo, engine->fifo[which_fifo], path);
	}

	return engine->fifo[which_fifo];
}

static void
jack_clear_fifos (jack_engine_t *engine)
{
	/* caller must hold client_lock */

	unsigned int i;
	char buf[16];

	/* this just drains the existing FIFO's of any data left in
	   them by aborted clients, etc. there is only ever going to
	   be 0, 1 or 2 bytes in them, but we'll allow for up to 16.
	 */
	for (i = 0; i < engine->fifo_size; i++) {
		if (engine->fifo[i] >= 0) {
			int nread = read (engine->fifo[i], buf, sizeof(buf));

			if (nread < 0 && errno != EAGAIN) {
				jack_error ("clear fifo[%d] error: %s",
					    i, strerror (errno));
			}
		}
	}
}

int
jack_use_driver (jack_engine_t *engine, jack_driver_t *driver)
{
	if (engine->driver) {
		engine->driver->detach (engine->driver, engine);
		engine->driver = 0;
	}

	if (driver) {
		engine->driver = driver;

		if (driver->attach (driver, engine)) {
			engine->driver = 0;
			return -1;
		}

		engine->rolling_interval =
			jack_rolling_interval (driver->period_usecs);
	}

	return 0;
}

int
jack_add_slave_driver (jack_engine_t *engine, jack_driver_t *driver)
{
	if (driver) {
		if (driver->attach (driver, engine)) {
			jack_info ("could not attach slave %s\n", driver->internal_client->control->name);
			return -1;
		}

		engine->slave_drivers = jack_slist_append (engine->slave_drivers, driver);
	}

	return 0;
}

/* PORT RELATED FUNCTIONS */


static jack_port_id_t
jack_get_free_port (jack_engine_t *engine)

{
	jack_port_id_t i;

	pthread_mutex_lock (&engine->port_lock);

	for (i = 0; i < engine->port_max; i++) {
		if (engine->control->ports[i].in_use == 0) {
			engine->control->ports[i].in_use = 1;
			break;
		}
	}

	pthread_mutex_unlock (&engine->port_lock);

	if (i == engine->port_max) {
		return (jack_port_id_t)-1;
	}

	return i;
}

void
jack_port_release (jack_engine_t *engine, jack_port_internal_t *port)
{
	char buf[JACK_UUID_STRING_SIZE];

	jack_uuid_unparse (port->shared->uuid, buf);
	if (jack_remove_properties (NULL, port->shared->uuid) > 0) {
		/* have to do the notification ourselves, since the client argument
		   to jack_remove_properties() was NULL
		 */
		jack_property_change_notify (engine, PropertyDeleted, port->shared->uuid, NULL);
	}


	pthread_mutex_lock (&engine->port_lock);
	port->shared->in_use = 0;
	port->shared->alias1[0] = '\0';
	port->shared->alias2[0] = '\0';

	if (port->buffer_info) {
		jack_port_buffer_list_t *blist =
			jack_port_buffer_list (engine, port);
		pthread_mutex_lock (&blist->lock);
		blist->freelist =
			jack_slist_prepend (blist->freelist,
					    port->buffer_info);
		port->buffer_info = NULL;
		pthread_mutex_unlock (&blist->lock);
	}
	pthread_mutex_unlock (&engine->port_lock);
}

jack_port_internal_t *
jack_get_port_internal_by_name (jack_engine_t *engine, const char *name)
{
	jack_port_id_t id;

	pthread_mutex_lock (&engine->port_lock);

	for (id = 0; id < engine->port_max; id++) {
		if (jack_port_name_equals (&engine->control->ports[id], name)) {
			break;
		}
	}

	pthread_mutex_unlock (&engine->port_lock);

	if (id != engine->port_max) {
		return &engine->internal_ports[id];
	} else {
		return NULL;
	}
}

int
jack_port_do_register (jack_engine_t *engine, jack_request_t *req, int internal)
{
	jack_port_id_t port_id;
	jack_port_shared_t *shared;
	jack_port_internal_t *port;
	jack_client_internal_t *client;
	unsigned long i;
	char *backend_client_name;
	size_t len;

	for (i = 0; i < engine->control->n_port_types; ++i) {
		if (strcmp (req->x.port_info.type,
			    engine->control->port_types[i].type_name) == 0) {
			break;
		}
	}

	if (i == engine->control->n_port_types) {
		jack_error ("cannot register a port of type \"%s\"",
			    req->x.port_info.type);
		return -1;
	}

	jack_lock_graph (engine);
	if ((client = jack_client_internal_by_id (engine,
						  req->x.port_info.client_id))
	    == NULL) {
		jack_error ("unknown client id in port registration request");
		jack_unlock_graph (engine);
		return -1;
	}

	if ((port = jack_get_port_by_name (engine, req->x.port_info.name)) != NULL) {
		jack_error ("duplicate port name (%s) in port registration request", req->x.port_info.name);
		jack_unlock_graph (engine);
		return -1;
	}

	if ((port_id = jack_get_free_port (engine)) == (jack_port_id_t)-1) {
		jack_error ("no ports available!");
		jack_unlock_graph (engine);
		return -1;
	}

	shared = &engine->control->ports[port_id];

	if (!internal || !engine->driver) {
		goto fallback;
	}

	/* if the port belongs to the backend client, do some magic with names
	 */

	backend_client_name = (char*)engine->driver->internal_client->control->name;
	len = strlen (backend_client_name);

	if (strncmp (req->x.port_info.name, backend_client_name, len) != 0) {
		goto fallback;
	}

	/* use backend's original as an alias, use predefined names */

	if (strcmp (req->x.port_info.type, JACK_DEFAULT_AUDIO_TYPE) == 0) {
		if ((req->x.port_info.flags & (JackPortIsPhysical | JackPortIsInput)) == (JackPortIsPhysical | JackPortIsInput)) {
			snprintf (shared->name, sizeof(shared->name), JACK_BACKEND_ALIAS ":playback_%d", ++engine->audio_out_cnt);
			strcpy (shared->alias1, req->x.port_info.name);
			goto next;
		} else if ((req->x.port_info.flags & (JackPortIsPhysical | JackPortIsOutput)) == (JackPortIsPhysical | JackPortIsOutput)) {
			snprintf (shared->name, sizeof(shared->name), JACK_BACKEND_ALIAS ":capture_%d", ++engine->audio_in_cnt);
			strcpy (shared->alias1, req->x.port_info.name);
			goto next;
		}
	}

#if 0   // do not do this for MIDI

	else if (strcmp (req->x.port_info.type, JACK_DEFAULT_MIDI_TYPE) == 0) {
		if ((req->x.port_info.flags & (JackPortIsPhysical | JackPortIsInput)) == (JackPortIsPhysical | JackPortIsInput)) {
			snprintf (shared->name, sizeof(shared->name), JACK_BACKEND_ALIAS ":midi_playback_%d", ++engine->midi_out_cnt);
			strcpy (shared->alias1, req->x.port_info.name);
			goto next;
		} else if ((req->x.port_info.flags & (JackPortIsPhysical | JackPortIsOutput)) == (JackPortIsPhysical | JackPortIsOutput)) {
			snprintf (shared->name, sizeof(shared->name), JACK_BACKEND_ALIAS ":midi_capture_%d", ++engine->midi_in_cnt);
			strcpy (shared->alias1, req->x.port_info.name);
			goto next;
		}
	}
#endif

fallback:
	strcpy (shared->name, req->x.port_info.name);

next:
	shared->ptype_id = engine->control->port_types[i].ptype_id;
	jack_uuid_copy (&shared->client_id, req->x.port_info.client_id);
	shared->uuid = jack_port_uuid_generate (port_id);
	shared->flags = req->x.port_info.flags;
	shared->latency = 0;
	shared->capture_latency.min = shared->capture_latency.max = 0;
	shared->playback_latency.min = shared->playback_latency.max = 0;
	shared->monitor_requests = 0;

	port = &engine->internal_ports[port_id];

	port->shared = shared;
	port->connections = 0;
	port->buffer_info = NULL;

	if (jack_port_assign_buffer (engine, port)) {
		jack_error ("cannot assign buffer for port");
		jack_port_release (engine, &engine->internal_ports[port_id]);
		jack_unlock_graph (engine);
		return -1;
	}

	client->ports = jack_slist_prepend (client->ports, port);
	if ( client->control->active ) {
		jack_port_registration_notify (engine, port_id, TRUE);
	}
	jack_unlock_graph (engine);

	VERBOSE (engine, "registered port %s, offset = %u",
		 shared->name, (unsigned int)shared->offset);

	req->x.port_info.port_id = port_id;

	return 0;
}

int
jack_port_do_unregister (jack_engine_t *engine, jack_request_t *req)
{
	jack_client_internal_t *client;
	jack_port_shared_t *shared;
	jack_port_internal_t *port;
	jack_uuid_t uuid;

	if (req->x.port_info.port_id < 0 ||
	    req->x.port_info.port_id > engine->port_max) {
		jack_error ("invalid port ID %" PRIu32
			    " in unregister request",
			    req->x.port_info.port_id);
		return -1;
	}

	shared = &engine->control->ports[req->x.port_info.port_id];

	if (jack_uuid_compare (shared->client_id, req->x.port_info.client_id) != 0) {
		char buf[JACK_UUID_STRING_SIZE];
		jack_uuid_unparse (req->x.port_info.client_id, buf);
		jack_error ("Client %s is not allowed to remove port %s",
			    buf, shared->name);
		return -1;
	}

	jack_uuid_copy (&uuid, shared->uuid);

	jack_lock_graph (engine);
	if ((client = jack_client_internal_by_id (engine, shared->client_id))
	    == NULL) {
		jack_error ("unknown client id in port registration request");
		jack_unlock_graph (engine);
		return -1;
	}

	port = &engine->internal_ports[req->x.port_info.port_id];

	jack_port_clear_connections (engine, port);
	jack_port_release (engine, &engine->internal_ports[req->x.port_info.port_id]);

	client->ports = jack_slist_remove (client->ports, port);
	jack_port_registration_notify (engine, req->x.port_info.port_id,
				       FALSE);
	jack_unlock_graph (engine);

	return 0;
}

int
jack_do_get_port_connections (jack_engine_t *engine, jack_request_t *req,
			      int reply_fd)
{
	jack_port_internal_t *port;
	JSList *node;
	unsigned int i;
	int ret = -1;
	int internal = FALSE;

	jack_rdlock_graph (engine);

	port = &engine->internal_ports[req->x.port_info.port_id];

	DEBUG ("Getting connections for port '%s'.", port->shared->name);

	req->x.port_connections.nports = jack_slist_length (port->connections);
	req->status = 0;

	/* figure out if this is an internal or external client */

	for (node = engine->clients; node; node = jack_slist_next (node)) {

		if (((jack_client_internal_t*)node->data)->request_fd
		    == reply_fd) {
			internal = jack_client_is_internal (
				(jack_client_internal_t*)node->data);
			break;
		}
	}

	if (!internal) {
		if (write (reply_fd, req, sizeof(*req))
		    < (ssize_t)sizeof(req)) {
			jack_error ("cannot write GetPortConnections result "
				    "to client via fd = %d (%s)",
				    reply_fd, strerror (errno));
			goto out;
		}
	} else {
		req->x.port_connections.ports = (const char**)
						malloc (sizeof(char *)
							* req->x.port_connections.nports);
	}

	if (req->type == GetPortConnections) {

		for (i = 0, node = port->connections; node;
		     node = jack_slist_next (node), ++i) {

			jack_port_id_t port_id;

			if (((jack_connection_internal_t*)node->data)->source
			    == port) {
				port_id = ((jack_connection_internal_t*)
					   node->data)->destination->shared->id;
			} else {
				port_id = ((jack_connection_internal_t*)
					   node->data)->source->shared->id;
			}

			if (internal) {

				/* internal client asking for
				 * names. store in malloc'ed space,
				 * client frees
				 */
				char **ports = (char**)req->x.port_connections.ports;

				ports[i] = engine->control->ports[port_id].name;

			} else {

				/* external client asking for
				 * names. we write the port id's to
				 * the reply fd.
				 */
				if (write (reply_fd, &port_id,
					   sizeof(port_id))
				    < (ssize_t)sizeof(port_id)) {
					jack_error ("cannot write port id "
						    "to client");
					goto out;
				}
			}
		}
	}

	ret = 0;

out:
	req->status = ret;
	jack_unlock_graph (engine);
	return ret;
}

void
jack_port_registration_notify (jack_engine_t *engine,
			       jack_port_id_t port_id, int yn)
{
	jack_event_t event;
	jack_client_internal_t *client;
	JSList *node;

	event.type = (yn ? PortRegistered : PortUnregistered);
	event.x.port_id = port_id;

	for (node = engine->clients; node; node = jack_slist_next (node)) {

		client = (jack_client_internal_t*)node->data;

		if (!client->control->active) {
			continue;
		}

		if (client->control->port_register_cbset) {
			if (jack_deliver_event (engine, client, &event)) {
				jack_error ("cannot send port registration"
					    " notification to %s (%s)",
					    client->control->name,
					    strerror (errno));
			}
		}
	}
}

static void
jack_port_rename_notify (jack_engine_t *engine,
			 const char* old_name,
			 const char* new_name)
{
	jack_event_t event;
	jack_client_internal_t *client;
	JSList *node;
	jack_port_internal_t* port;

	if ((port = jack_get_port_by_name (engine, new_name)) == NULL) {
		/* possible race condition: port renamed again
		   since this rename happened. Oh well.
		 */
		return;
	}

	event.type = PortRename;
	event.y.other_id = port->shared->id;
	snprintf (event.x.name, JACK_PORT_NAME_SIZE - 1, "%s", old_name);
	snprintf (event.z.other_name, JACK_PORT_NAME_SIZE - 1, "%s", new_name);

	for (node = engine->clients; node; node = jack_slist_next (node)) {

		client = (jack_client_internal_t*)node->data;

		if (!client->control->active) {
			continue;
		}

		if (client->control->port_rename_cbset) {
			if (jack_deliver_event (engine, client, &event)) {
				jack_error ("cannot send port registration"
					    " notification to %s (%s)",
					    client->control->name,
					    strerror (errno));
			}
		}
	}
}

void
jack_client_registration_notify (jack_engine_t *engine,
				 const char* name, int yn)
{
	jack_event_t event;
	jack_client_internal_t *client;
	JSList *node;

	event.type = (yn ? ClientRegistered : ClientUnregistered);
	snprintf (event.x.name, sizeof(event.x.name), "%s", name);

	for (node = engine->clients; node; node = jack_slist_next (node)) {

		client = (jack_client_internal_t*)node->data;

		if (!client->control->active) {
			continue;
		}

		if (strcmp ((char*)client->control->name, (char*)name) == 0) {
			/* do not notify client of its own registration */
			continue;
		}

		if (client->control->client_register_cbset) {
			if (jack_deliver_event (engine, client, &event)) {
				jack_error ("cannot send client registration"
					    " notification to %s (%s)",
					    client->control->name,
					    strerror (errno));
			}
		}
	}
}

void
jack_property_change_notify (jack_engine_t *engine,
			     jack_property_change_t change,
			     jack_uuid_t uuid,
			     const char* key)
{
	jack_event_t event;
	jack_client_internal_t *client;
	JSList *node;

	event.type = PropertyChange;
	event.z.property_change = change;
	jack_uuid_copy (&event.x.uuid, uuid);

	if (key) {
		event.y.key_size = strlen (key) + 1;
	} else {
		event.y.key_size = 0;
	}

	for (node = engine->clients; node; node = jack_slist_next (node)) {

		client = (jack_client_internal_t*)node->data;

		if (!client->control->active) {
			continue;
		}

		if (client->control->property_cbset) {
			if (jack_deliver_event (engine, client, &event, key)) {
				jack_error ("cannot send property change notification to %s (%s)",
					    client->control->name,
					    strerror (errno));
			}
		}
	}
}

int
jack_port_assign_buffer (jack_engine_t *engine, jack_port_internal_t *port)
{
	jack_port_buffer_list_t *blist =
		jack_port_buffer_list (engine, port);
	jack_port_buffer_info_t *bi;

	if (port->shared->flags & JackPortIsInput) {
		port->shared->offset = 0;
		return 0;
	}

	pthread_mutex_lock (&blist->lock);

	if (blist->freelist == NULL) {
		jack_port_type_info_t *port_type =
			jack_port_type_info (engine, port);
		jack_error ("all %s port buffers in use!",
			    port_type->type_name);
		pthread_mutex_unlock (&blist->lock);
		return -1;
	}

	bi = (jack_port_buffer_info_t*)blist->freelist->data;
	blist->freelist = jack_slist_remove (blist->freelist, bi);

	port->shared->offset = bi->offset;
	port->buffer_info = bi;

	pthread_mutex_unlock (&blist->lock);
	return 0;
}

static jack_port_internal_t *
jack_get_port_by_name (jack_engine_t *engine, const char *name)
{
	jack_port_id_t id;

	/* Note the potential race on "in_use". Other design
	   elements prevent this from being a problem.
	 */

	for (id = 0; id < engine->port_max; id++) {
		if (engine->control->ports[id].in_use &&
		    jack_port_name_equals (&engine->control->ports[id], name)) {
			return &engine->internal_ports[id];
		}
	}

	return NULL;
}

static int
jack_send_connection_notification (jack_engine_t *engine,
				   jack_uuid_t client_id,
				   jack_port_id_t self_id,
				   jack_port_id_t other_id, int connected)

{
	jack_client_internal_t *client;
	jack_event_t event;

	VALGRIND_MEMSET (&event, 0, sizeof(event));

	if ((client = jack_client_internal_by_id (engine, client_id)) == NULL) {
		jack_error ("no such client %" PRIu32
			    " during connection notification", client_id);
		return -1;
	}

	if (client->control->active) {
		event.type = (connected ? PortConnected : PortDisconnected);
		event.x.self_id = self_id;
		event.y.other_id = other_id;

		if (jack_deliver_event (engine, client, &event)) {
			jack_error ("cannot send port connection notification"
				    " to client %s (%s)",
				    client->control->name, strerror (errno));
			return -1;
		}
	}

	return 0;
}

static void
jack_wake_server_thread (jack_engine_t* engine)
{
	char c = 0;

	/* we don't actually care if this fails */
	VERBOSE (engine, "waking server thread");
	write (engine->cleanup_fifo[1], &c, 1);
}

void
jack_engine_signal_problems (jack_engine_t* engine)
{
	jack_lock_problems (engine);
	engine->problems++;
	jack_unlock_problems (engine);
	jack_wake_server_thread (engine);
}