[0.99.21] add CHECK_PREEMPTION() macro to libjack

git-svn-id: svn+ssh://jackaudio.org/trunk/jack@818 0c269be4-1314-0410-8aa9-9f06e86f4224

configure.ac

@@ -15,7 +15,7 @@ dnl                 changes are made
 dnl ---
 JACK_MAJOR_VERSION=0
 JACK_MINOR_VERSION=99
-JACK_MICRO_VERSION=20
+JACK_MICRO_VERSION=21
 
 dnl ---
 dnl HOWTO: updating the jack protocol version
@@ -318,6 +318,17 @@ AC_ARG_ENABLE(timestamps,
         ]		
 )
 
+AC_ARG_ENABLE(preemption-check,
+	AC_HELP_STRING([--enable-preemption-check],
+		[check for inappropriate realtime preemption]),
+		[
+		  if test x$enable_preemption_check != xno ; then
+			echo checking for realtime preemption bugs
+			AC_DEFINE(DO_PREEMPTION_CHECKING,,
+				[check realtime preemption])
+		  fi
+		])
+
 USE_CAPABILITIES=false
 
 AC_ARG_ENABLE(capabilities,

jack/internal.h

@@ -60,6 +60,20 @@ extern void jack_error (const char *fmt, ...);
 #endif
 #endif
 
+/* Enable preemption checking for Linux Realtime Preemption kernels.
+ *
+ * This checks if any RT-safe code section does anything to cause
+ * possible CPU preemption.  Examples are sleep() or other system
+ * calls that block.  If a problem is detected, the kernel writes a
+ * syslog entry, and sends SIGUSR2 to the client.
+ */
+#ifdef DO_PREEMPTION_CHECKING
+#define CHECK_PREEMPTION(engine, onoff) \
+	if ((engine)->real_time) gettimeofday (1, (onoff))
+#else
+#define CHECK_PREEMPTION(engine, onoff)
+#endif
+
 #ifndef	FALSE
 #define	FALSE	(0)
 #endif

libjack/client.c

@@ -1235,6 +1235,9 @@ jack_client_thread (void *arg)
 
 			control->state = Running;
 
+			/* begin preemption checking */
+			CHECK_PREEMPTION (client->engine, TRUE);
+			
 			if (control->sync_cb)
 				jack_call_sync_client (client);
 
@@ -1251,6 +1254,9 @@ jack_client_thread (void *arg)
 			if (control->timebase_cb)
 				jack_call_timebase_master (client);
 
+			/* end preemption checking */
+			CHECK_PREEMPTION (client->engine, FALSE);
+
 			control->finished_at = jack_get_microseconds();
 
 #ifdef WITH_TIMESTAMPS