jack2/posix/JackPosixSemaphore.cpp

/*
Copyright (C) 2004-2008 Grame

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 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 Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.

*/

#include "JackPosixSemaphore.h"
#include "JackTools.h"
#include "JackConstants.h"
#include "JackError.h"
#include "JackPosixCommon.h"
#include <fcntl.h>
#include <stdio.h>
#include <ctype.h>
#include <sys/time.h>
#ifdef __linux__
#include "promiscuous.h"
#endif

#if defined(__FreeBSD__) || defined(__FreeBSD_kernel__)
#define JACK_SEM_PREFIX "/jack_sem"
#define SEM_DEFAULT_O 0
#else
#define JACK_SEM_PREFIX "jack_sem"
#define SEM_DEFAULT_O O_RDWR
#endif

namespace Jack
{

JackPosixSemaphore::JackPosixSemaphore() : JackSynchro(), fSemaphore(NULL)
{
    const char* promiscuous = getenv("JACK_PROMISCUOUS_SERVER");
    fPromiscuous = (promiscuous != NULL);
#ifdef __linux__
    fPromiscuousGid = jack_group2gid(promiscuous);
#endif
}

void JackPosixSemaphore::BuildName(const char* client_name, const char* server_name, char* res, int size)
{
    char ext_client_name[SYNC_MAX_NAME_SIZE + 1];
    JackTools::RewriteName(client_name, ext_client_name);
#if __APPLE__  // POSIX semaphore names are limited to 32 characters...
    snprintf(res, 32, "js_%s", ext_client_name);
#else
    if (fPromiscuous) {
        snprintf(res, size, JACK_SEM_PREFIX ".%s_%s", server_name, ext_client_name);
    } else {
        snprintf(res, size, JACK_SEM_PREFIX ".%d_%s_%s", JackTools::GetUID(), server_name, ext_client_name);
    }
#endif
}

bool JackPosixSemaphore::Signal()
{
    int res;

    if (!fSemaphore) {
        jack_error("JackPosixSemaphore::Signal name = %s already deallocated!!", fName);
        return false;
    }

    if (fFlush) {
        return true;
    }

    if ((res = sem_post(fSemaphore)) != 0) {
        jack_error("JackPosixSemaphore::Signal name = %s err = %s", fName, strerror(errno));
    }
    return (res == 0);
}

bool JackPosixSemaphore::SignalAll()
{
    int res;

    if (!fSemaphore) {
        jack_error("JackPosixSemaphore::SignalAll name = %s already deallocated!!", fName);
        return false;
    }

    if (fFlush) {
        return true;
    }

    if ((res = sem_post(fSemaphore)) != 0) {
        jack_error("JackPosixSemaphore::SignalAll name = %s err = %s", fName, strerror(errno));
    }
    return (res == 0);
}

bool JackPosixSemaphore::Wait()
{
    int res;

    if (!fSemaphore) {
        jack_error("JackPosixSemaphore::Wait name = %s already deallocated!!", fName);
        return false;
    }

    while ((res = sem_wait(fSemaphore) < 0)) {
        jack_error("JackPosixSemaphore::Wait name = %s err = %s", fName, strerror(errno));
        if (errno != EINTR) {
            break;
        }
    }
    return (res == 0);
}

bool JackPosixSemaphore::TimedWait(long usec)
{
    int res;
    struct timespec rel_timeout, now_mono, end_mono, now_real, end_real;
    struct timespec diff_mono;

	if (!fSemaphore) {
		jack_error("JackPosixSemaphore::TimedWait name = %s already deallocated!!", fName);
		return false;
	}

    /* Convert usec argument to timespec */
    rel_timeout.tv_sec = usec / 1000000;
    rel_timeout.tv_nsec = (usec % 1000000) * 1000;

    /* Calculate absolute monotonic timeout */
    res = clock_gettime(CLOCK_MONOTONIC, &now_mono);
    if (res != 0) {
        /* CLOCK_MONOTONIC is not supported, do not check for time skips. */
        res = clock_gettime(CLOCK_REALTIME, &now_real);
        assert(res == 0);
        JackPosixTools::TimespecAdd(&now_real, &rel_timeout, &end_real);
        while ((res = sem_timedwait(fSemaphore, &end_real)) < 0) {
            if (errno != EINTR) {
                break;
            }
        }
        if (res == 0) {
            return true;
        } else {
            goto err;
        }
    }
    JackPosixTools::TimespecAdd(&now_mono, &rel_timeout, &end_mono);

    /* sem_timedwait() is affected by abrupt time jumps, i.e. when the system
     * time is changed. To protect against this, measure the time difference
     * between and after the sem_timedwait() call and if it suggests that there
     * has been a time jump, restart the call. */
    for (;;) {
        /* Calculate absolute realtime timeout, assuming no steps */
        res = clock_gettime(CLOCK_REALTIME, &now_real);
        assert(res == 0);
        JackPosixTools::TimespecSub(&end_mono, &now_mono, &diff_mono);
        JackPosixTools::TimespecAdd(&now_real, &diff_mono, &end_real);

        while ((res = sem_timedwait(fSemaphore, &end_real)) < 0) {
            if (errno != EINTR) {
                break;
            }
        }
        if (res == 0) {
            return true;
        }
        if (errno != ETIMEDOUT) {
            goto err;
        }

        /* Compare with monotonic timeout, in case a step happened */
        int old_errno = errno;
        res = clock_gettime(CLOCK_MONOTONIC, &now_mono);
        assert(res == 0);
        errno = old_errno;
        if (JackPosixTools::TimespecCmp(&now_mono, &end_mono) >= 0) {
            goto err;
        }
    }
    return true;

err:
    jack_error("JackPosixSemaphore::TimedWait err = %s", strerror(errno));
    jack_log("JackPosixSemaphore::TimedWait now : %ld %ld ", now_real.tv_sec,
        now_real.tv_nsec / 1000);
    jack_log("JackPosixSemaphore::TimedWait next : %ld %ld ", end_real.tv_sec,
        end_real.tv_nsec / 1000);
    return false;
}

// Server side : publish the semaphore in the global namespace
bool JackPosixSemaphore::Allocate(const char* name, const char* server_name, int value)
{
    BuildName(name, server_name, fName, sizeof(fName));
    jack_log("JackPosixSemaphore::Allocate name = %s val = %ld", fName, value);

    if ((fSemaphore = sem_open(fName, O_CREAT | SEM_DEFAULT_O, 0777, value)) == (sem_t*)SEM_FAILED) {
        jack_error("Allocate: can't check in named semaphore name = %s err = %s", fName, strerror(errno));
        return false;
    } else {
#ifdef __linux__
        if (fPromiscuous) {
            char sempath[SYNC_MAX_NAME_SIZE+13];
            snprintf(sempath, sizeof(sempath), "/dev/shm/sem.%s", fName);
            if (jack_promiscuous_perms(-1, sempath, fPromiscuousGid) < 0)
                return false;
        }
#endif
        return true;
    }
}

// Client side : get the published semaphore from server
bool JackPosixSemaphore::ConnectInput(const char* name, const char* server_name)
{
    BuildName(name, server_name, fName, sizeof(fName));
    jack_log("JackPosixSemaphore::Connect name = %s", fName);

    // Temporary...
    if (fSemaphore) {
        jack_log("Already connected name = %s", name);
        return true;
    }

    if ((fSemaphore = sem_open(fName, SEM_DEFAULT_O)) == (sem_t*)SEM_FAILED) {
        jack_error("Connect: can't connect named semaphore name = %s err = %s", fName, strerror(errno));
        return false;
    } else if (fSemaphore) {
        int val = 0;
        sem_getvalue(fSemaphore, &val);
        jack_log("JackPosixSemaphore::Connect sem_getvalue %ld", val);
        return true;
    } else {
        jack_error("Connect: fSemaphore not initialized!");
        return false;
    }
}

bool JackPosixSemaphore::Connect(const char* name, const char* server_name)
{
    return ConnectInput(name, server_name);
}

bool JackPosixSemaphore::ConnectOutput(const char* name, const char* server_name)
{
    return ConnectInput(name, server_name);
}

bool JackPosixSemaphore::Disconnect()
{
    if (fSemaphore) {
        jack_log("JackPosixSemaphore::Disconnect name = %s", fName);
        if (sem_close(fSemaphore) != 0) {
            jack_error("Disconnect: can't disconnect named semaphore name = %s err = %s", fName, strerror(errno));
            return false;
        } else {
            fSemaphore = NULL;
            return true;
        }
    } else {
        return true;
    }
}

// Server side : destroy the semaphore
void JackPosixSemaphore::Destroy()
{
    if (fSemaphore != NULL) {
        jack_log("JackPosixSemaphore::Destroy name = %s", fName);
        sem_unlink(fName);
        if (sem_close(fSemaphore) != 0) {
            jack_error("Destroy: can't destroy semaphore name = %s err = %s", fName, strerror(errno));
        }
        fSemaphore = NULL;
    } else {
        jack_error("JackPosixSemaphore::Destroy semaphore == NULL");
    }
}

} // end of namespace