Replaced CondVar with a Semaphore in the new Signalling code.

This removes the race between releasing the bank semaphore and starting the
WaitCondVar (which was causing deadlocks in Windows)


git-svn-id: svn://svn.code.sf.net/p/sc2/code/trunk@529 8092fc87-c524-0410-9efc-e669fe64eaf9

sc2/ChangeLog

@@ -1,4 +1,5 @@
 Changes towards version 0.2:
+- Fixed deadlock races in new FlushGraphics method -PhracturedBlue
 - FlushGraphics now waits and notifies on a per-thread level
 - No longer using SHGetFolderPath on Windows - SvdB
 - Key repeat is now enabled when typing text, from slayne

sc2/src/sc2code/libs/graphics/sdl/3do_funcs.c

@@ -80,6 +80,8 @@ FlushGraphics (void)
 	TFB_BatchReset ();
 	DrawCommand.Type = TFB_DRAWCOMMANDTYPE_FLUSHGRAPHICS;
 	DrawCommand.image = 0;
+	// We need to lock the  mutex before quein the DC to prevent races 
+	LockSignalMutex ();
 	TFB_EnqueueDrawCommand(&DrawCommand);
 	WaitForSignal ();
 }

sc2/src/sc2code/libs/threadlib.h

@@ -104,11 +104,16 @@ typedef void *Semaphore;
 extern Semaphore CreateSemaphoreAux (DWORD initial, char *sem_name);
 #	define CreateSemaphore(initial,sem_name) \
 		CreateSemaphoreAux ((initial), (sem_name))
+extern void ResetSemaphoreOwnerAux (Semaphore sem);
+#	define ResetSemaphoreOwner(sem_name) \
+		ResetSemaphoreOwnerAux (sem_name)
 #else
 extern Semaphore CreateSemaphoreAux (DWORD initial);
 #	define CreateSemaphore(initial,sem_name) \
 		CreateSemaphoreAux ((initial))
+#	define ResetSemaphoreOwner(sem_name)
 #endif
+extern DWORD SemaphoreValue (Semaphore sem);
 extern void DestroySemaphore (Semaphore sem);
 extern int SetSemaphore (Semaphore sem);
 extern int TrySetSemaphore (Semaphore sem);
@@ -133,6 +138,7 @@ extern void BroadcastCondVar (CondVar);
 
 extern DWORD CurrentThreadID (void);
 
+extern void LockSignalMutex(void);
 extern void WaitForSignal (void);
 extern void SignalThread (DWORD);
 

sc2/src/sc2code/libs/threads/condbank.c

@@ -29,10 +29,11 @@
 
 #define CONDVAR_BANK_SIZE 10
 
-static Semaphore bank_sem;
+static Mutex bank_mutex;
+static int wait = 0, signal = 0;
 
 static struct {
-	CondVar var;
+	Semaphore var;
 	DWORD   id;
 	int     used;
 } bank[CONDVAR_BANK_SIZE];
@@ -41,10 +42,12 @@ void
 init_cond_bank ()
 {
 	int i;
-	bank_sem = CreateSemaphore (1, "CondVar Bank Semaphore");
+	bank_mutex = CreateMutex ();
 	for (i = 0; i < CONDVAR_BANK_SIZE; i++)
 	{
-		bank[i].var = CreateCondVar ();
+		char str[20];
+		sprintf (str, "bank sem %d", i);
+		bank[i].var = CreateSemaphore (0, str); 
 		bank[i].id = bank[i].used = 0;
 	}
 }
@@ -57,16 +60,20 @@ uninit_cond_bank ()
 	{
 		DestroyCondVar (bank[i].var);
 	}
-	DestroySemaphore (bank_sem);
+	DestroyMutex (bank_mutex);
 }
 
+void
+LockSignalMutex ()
+{
+	LockMutex (bank_mutex);
+}
 void
 WaitForSignal ()
 {
 	int i;
 	int index = -1;
 	DWORD me = CurrentThreadID ();
-	SetSemaphore (bank_sem);
 	for (i = 0; i < CONDVAR_BANK_SIZE; i++)
 	{
 		if (!bank[i].used)
@@ -79,15 +86,19 @@ WaitForSignal ()
 	{
 		/* The bank is full! */
 		fprintf(stderr, "Condvar bank is full, %ul is waiting on DCQ.", me);
-		ClearSemaphore (bank_sem);
+		UnlockMutex (bank_mutex);
 		WaitCondVar (RenderingCond);
 	}
 	else
 	{
 		bank[i].used = 1;
 		bank[i].id = me;
-		ClearSemaphore (bank_sem);
-		WaitCondVar (bank[i].var);
+		// Initialize the Semaphore to a value of '0' in case it isn't already
+		while (SemaphoreValue (bank[i].var))
+			SetSemaphore (bank[i].var);
+		UnlockMutex (bank_mutex);
+		// Block on Semaphore until it is cleared by the Signal
+		SetSemaphore (bank[i].var);
 	}
 }
 
@@ -95,16 +106,19 @@ void
 SignalThread (DWORD id)
 {
 	int i;
-	SetSemaphore (bank_sem);
+	LockMutex (bank_mutex);
 	for (i = 0; i < CONDVAR_BANK_SIZE; i++)
 	{
 		if (bank[i].used && bank[i].id == id)
 		{
 			bank[i].id = bank[i].used = 0;
-			SignalCondVar (bank[i].var);
+			ResetSemaphoreOwner (bank[i].var);
+			ClearSemaphore (bank[i].var);
 			break;
 		}
 	}
-	ClearSemaphore (bank_sem);
+	if (i == CONDVAR_BANK_SIZE)
+		fprintf (stderr, "Warning: Couldn't find thread to signal!\n");
+	UnlockMutex (bank_mutex);
 }
 

sc2/src/sc2code/libs/threads/sdl/sdlthreads.h

@@ -87,6 +87,7 @@ typedef SDL_cond *NativeCondVar;
 		SDL_CreateCond ()
 #define NativeDestroyCondVar(condvar) \
 		SDL_DestroyCond ((condvar))
+extern void SDLWrapper_WaitCondVar (CondVar candvar);
 #define NativeWaitCondVar(condvar) \
 		SDLWrapper_WaitCondVar ((condvar))
 #define NativeSignalCondVar(condvar) \

sc2/src/sc2code/libs/threads/thrcommon.c

@@ -518,6 +518,27 @@ TimeoutSetSemaphore (Semaphore sem, TimePeriod timeout)
 	return (i);
 }
 
+DWORD
+SemaphoreValue (Semaphore sem)
+{
+	return NativeSemValue (sem);
+}
+
+#ifdef DEBUG_TRACK_SEM
+// Use this function to prevent messages when it  is known that
+// a semaphore will be cleared by a different thread than set it
+void 
+ResetSemaphoreOwnerAux (Semaphore sem)
+{
+	int i;
+	for (i = 0; i < numSems; i++)
+		if (SemMon[i].Sem == sem)
+		{
+			SemMon[i].Thread = 0;
+			break;
+		}
+}
+#endif
 void
 ClearSemaphore (Semaphore sem)
 {