Added API and -Dd command line parameter to disable taking the global mutex when (un)locking a Mutex or Semaphore.

This provides better performance and reduces mutex contention on expense of some thread safety and ease of debugging.


git-svn-id: http://yate.null.ro/svn/yate/trunk@3801 acf43c95-373e-0410-b603-e72c3f656dc1

docs/man/yate.8

@@ -99,6 +99,9 @@ Abort (coredumps if allowed) if bugs are encountered
 .B \-Dm
 Attempt to debug mutex deadlocks by setting a maximum 10s limit, if repeated halves the limit
 .TP
+.B \-Dd
+Disable some locking debugging and safety features, improves performance instead
+.TP
 .B \-Dl
 Attempt to load modules without having their symbols globally visible
 .TP

engine/Engine.cpp

@@ -1490,6 +1490,7 @@ static void usage(bool client, FILE* f)
 "   -D[options]    Special debugging options\n"
 "     a            Abort if bugs are encountered\n"
 "     m            Attempt to debug mutex deadlocks\n"
+"     d            Disable locking debugging and safety features\n"
 #ifdef RTLD_GLOBAL
 "     l            Try to keep module symbols local\n"
 #endif
@@ -1745,6 +1746,9 @@ int Engine::main(int argc, const char** argv, const char** env, RunMode mode, bo
 					Lockable::wait(lockWait);
 				    }
 				    break;
+				case 'd':
+				    Lockable::disableSafety();
+				    break;
 #ifdef RTLD_GLOBAL
 				case 'l':
 				    s_localsymbol = true;

engine/Mutex.cpp

@@ -131,6 +131,7 @@ HMUTEX GlobalMutex::s_mutex;
 static GlobalMutex s_global;
 static unsigned long s_maxwait = 0;
 static bool s_unsafe = MUTEX_STATIC_UNSAFE;
+static bool s_safety = true;
 
 volatile int MutexPrivate::s_count = 0;
 volatile int MutexPrivate::s_locks = 0;
@@ -217,7 +218,8 @@ MutexPrivate::~MutexPrivate()
     if (m_locked) {
 	warn = true;
 	m_locked--;
-	s_locks--;
+	if (s_safety)
+	    s_locks--;
 #ifdef _WINDOWS
 	::ReleaseMutex(m_mutex);
 #else
@@ -248,13 +250,16 @@ bool MutexPrivate::lock(long maxwait)
 	maxwait = (long)s_maxwait;
 	warn = true;
     }
-    GlobalMutex::lock();
+    if (s_safety)
+	GlobalMutex::lock();
     ref();
-    m_waiting++;
     Thread* thr = Thread::current();
     if (thr)
 	thr->m_locking = true;
-    GlobalMutex::unlock();
+    if (s_safety) {
+	m_waiting++;
+	GlobalMutex::unlock();
+    }
 #ifdef _WINDOWS
     DWORD ms = 0;
     if (maxwait < 0)
@@ -295,12 +300,15 @@ bool MutexPrivate::lock(long maxwait)
 #endif // HAVE_TIMEDLOCK
     }
 #endif // _WINDOWS
-    GlobalMutex::lock();
+    if (s_safety) {
+	GlobalMutex::lock();
+	m_waiting--;
+    }
     if (thr)
 	thr->m_locking = false;
-    m_waiting--;
     if (rval) {
-	s_locks++;
+	if (s_safety)
+	    s_locks++;
 	m_locked++;
 	if (thr) {
 	    thr->m_locks++;
@@ -311,7 +319,8 @@ bool MutexPrivate::lock(long maxwait)
     }
     else
 	deref();
-    GlobalMutex::unlock();
+    if (s_safety)
+	GlobalMutex::unlock();
     if (warn && !rval)
 	Debug(DebugFail,"Thread '%s' could not lock mutex '%s' owned by '%s' waited by %u others for %lu usec!",
 	    Thread::currentName(),m_name,m_owner,m_waiting,maxwait);
@@ -322,7 +331,8 @@ bool MutexPrivate::unlock()
 {
     bool ok = false;
     // Hope we don't hit a bug related to the debug mutex!
-    GlobalMutex::lock();
+    if (s_safety)
+	GlobalMutex::lock();
     if (m_locked) {
 	Thread* thr = Thread::current();
 	if (thr)
@@ -334,12 +344,14 @@ bool MutexPrivate::unlock()
 		    m_name,tname,m_owner,this);
 	    m_owner = 0;
 	}
-	int locks = --s_locks;
-	if (locks < 0) {
-	    // this is very very bad - abort right now
-	    abortOnBug(true);
-	    s_locks = 0;
-	    Debug(DebugFail,"MutexPrivate::locks() is %d [%p]",locks,this);
+	if (s_safety) {
+	    int locks = --s_locks;
+	    if (locks < 0) {
+		// this is very very bad - abort right now
+		abortOnBug(true);
+		s_locks = 0;
+		Debug(DebugFail,"MutexPrivate::locks() is %d [%p]",locks,this);
+	    }
 	}
 	if (!s_unsafe)
 #ifdef _WINDOWS
@@ -352,7 +364,8 @@ bool MutexPrivate::unlock()
     }
     else
 	Debug(DebugFail,"MutexPrivate::unlock called on unlocked '%s' [%p]",m_name,this);
-    GlobalMutex::unlock();
+    if (s_safety)
+	GlobalMutex::unlock();
     return ok;
 }
 
@@ -395,14 +408,17 @@ bool SemaphorePrivate::lock(long maxwait)
 	maxwait = (long)s_maxwait;
 	warn = true;
     }
-    GlobalMutex::lock();
+    if (s_safety)
+	GlobalMutex::lock();
     ref();
-    s_locks++;
-    m_waiting++;
     Thread* thr = Thread::current();
     if (thr)
 	thr->m_locking = true;
-    GlobalMutex::unlock();
+    if (s_safety) {
+	s_locks++;
+	m_waiting++;
+	GlobalMutex::unlock();
+    }
 #ifdef _WINDOWS
     DWORD ms = 0;
     if (maxwait < 0)
@@ -443,19 +459,22 @@ bool SemaphorePrivate::lock(long maxwait)
 #endif // HAVE_TIMEDWAIT
     }
 #endif // _WINDOWS
-    GlobalMutex::lock();
-    m_waiting--;
-    int locks = --s_locks;
-    if (locks < 0) {
-	// this is very very bad - abort right now
-	abortOnBug(true);
-	s_locks = 0;
-	Debug(DebugFail,"SemaphorePrivate::locks() is %d [%p]",locks,this);
+    if (s_safety) {
+	GlobalMutex::lock();
+	int locks = --s_locks;
+	if (locks < 0) {
+	    // this is very very bad - abort right now
+	    abortOnBug(true);
+	    s_locks = 0;
+	    Debug(DebugFail,"SemaphorePrivate::locks() is %d [%p]",locks,this);
+	}
+	m_waiting--;
     }
     if (thr)
 	thr->m_locking = false;
     deref();
-    GlobalMutex::unlock();
+    if (s_safety)
+	GlobalMutex::unlock();
     if (warn && !rval)
 	Debug(DebugFail,"Thread '%s' could not lock semaphore '%s' waited by %u others for %lu usec!",
 	    Thread::currentName(),m_name,m_waiting,maxwait);
@@ -464,7 +483,8 @@ bool SemaphorePrivate::lock(long maxwait)
 
 bool SemaphorePrivate::unlock()
 {
-    GlobalMutex::lock();
+    if (s_safety)
+	GlobalMutex::lock();
     ref();
     if (!s_unsafe) {
 #ifdef _WINDOWS
@@ -476,7 +496,8 @@ bool SemaphorePrivate::unlock()
 #endif
     }
     deref();
-    GlobalMutex::unlock();
+    if (s_safety)
+	GlobalMutex::unlock();
     return true;
 }
 
@@ -508,6 +529,11 @@ void Lockable::startUsingNow()
     s_unsafe = false;
 }
 
+void Lockable::disableSafety()
+{
+    s_safety = false;
+}
+
 void Lockable::wait(unsigned long maxwait)
 {
     s_maxwait = maxwait;

yateclass.h

@@ -4259,6 +4259,13 @@ public:
      *  before creating any threads and without holding any object locked.
      */
     static void startUsingNow();
+
+    /**
+     * Disable some safety and sanity check features.
+     * This provides a performance improvement but makes the code less safe and
+     *  more difficult to debug locking issues.
+     */
+    static void disableSafety();
 };
 
 /**