Proposed fix for [ba44e415a0]: "Use of mutexLock causes problem with reactive event handling in AndroWish".

This basically undoes the retry mechamism in Tcl_MutexLock, introduced in [9f8b7bea53]. Does this retry mechamism hurt more than it helps? Feedback requested.

2 files changed, 10 insertions, 78 deletions

diff --git a/unix/tclUnixThrd.c b/unix/tclUnixThrd.c
index ae81c5f..0e8070d 100644
--- a/unix/tclUnixThrd.c
+++ b/unix/tclUnixThrd.c
@@ -22,19 +22,6 @@ typedef struct ThreadSpecificData {
 static Tcl_ThreadDataKey dataKey;
 
 /*
- * This is the number of milliseconds to wait between internal retries in
- * the Tcl_MutexLock function.  This value must be greater than zero and
- * should be a suitable value for the given platform.
- *
- * TODO: This may need to be dynamically determined, based on the relative
- *       performance of the running process.
- */
-
-#ifndef TCL_MUTEX_LOCK_SLEEP_TIME
-#  define TCL_MUTEX_LOCK_SLEEP_TIME	(25)
-#endif
-
-/*
  * masterLock is used to serialize creation of mutexes, condition variables,
  * and thread local storage. This is the only place that can count on the
  * ability to statically initialize the mutex.
@@ -58,13 +45,6 @@ static pthread_mutex_t allocLock = PTHREAD_MUTEX_INITIALIZER;
 static pthread_mutex_t *allocLockPtr = &allocLock;
 
 /*
- * The mutexLock serializes Tcl_MutexLock. This is necessary to prevent
- * races when finalizing a mutex that some other thread may want to lock.
- */
-
-static pthread_mutex_t mutexLock = PTHREAD_MUTEX_INITIALIZER;
-
-/*
  * These are for the critical sections inside this file.
  */
 
@@ -380,7 +360,6 @@ TclpMasterUnlock(void)
     pthread_mutex_unlock(&masterLock);
 #endif
 }
-
 
 /*
  *----------------------------------------------------------------------
@@ -457,32 +436,12 @@ retry:
 	}
 	MASTER_UNLOCK;
     }
-    while (1) {
-	pthread_mutex_lock(&mutexLock);
-	pmutexPtr = *((pthread_mutex_t **)mutexPtr);
-	if (pmutexPtr == NULL) {
-	    pthread_mutex_unlock(&mutexLock);
-	    goto retry;
-	}
-	if (pthread_mutex_trylock(pmutexPtr) == 0) {
-	    pthread_mutex_unlock(&mutexLock);
-	    return;
-	}
-	pthread_mutex_unlock(&mutexLock);
-	/*
-	 * BUGBUG: All core and Thread package tests pass when usleep()
-	 *         is used; however, the Thread package tests hang at
-	 *         various places when Tcl_Sleep() is used, typically
-	 *         while running test "thread-17.8", "thread-17.9", or
-	 *         "thread-17.11a".  Really, what we want here is just
-	 *         to yield to other threads for a while.
-	 */
-#ifdef HAVE_USLEEP
-	usleep(TCL_MUTEX_LOCK_SLEEP_TIME * 1000);
-#else
-	Tcl_Sleep(TCL_MUTEX_LOCK_SLEEP_TIME);
-#endif
+
+    pmutexPtr = *((pthread_mutex_t **)mutexPtr);
+    if (pmutexPtr == NULL) {
+	goto retry;
     }
+    pthread_mutex_lock(pmutexPtr);
 }
 
 /*
diff --git a/win/tclWinThrd.c b/win/tclWinThrd.c
index ae7ce80..927e115 100644
--- a/win/tclWinThrd.c
+++ b/win/tclWinThrd.c
@@ -24,16 +24,6 @@ _CRTIMP unsigned int __cdecl _controlfp (unsigned int unNew, unsigned int unMask
 #endif
 
 /*
- * This is the number of milliseconds to wait between internal retries in
- * the Tcl_MutexLock function.  This value must be greater than or equal
- * to zero and should be a suitable value for the given platform.
- */
-
-#ifndef TCL_MUTEX_LOCK_SLEEP_TIME
-#  define TCL_MUTEX_LOCK_SLEEP_TIME	(0)
-#endif
-
-/*
  * This is the master lock used to serialize access to other serialization
  * data structures.
  */
@@ -67,13 +57,6 @@ static int allocOnce = 0;
 #endif /* TCL_THREADS */
 
 /*
- * The mutexLock serializes Tcl_MutexLock. This is necessary to prevent
- * races when finalizing a mutex that some other thread may want to lock.
- */
-
-static CRITICAL_SECTION mutexLock;
-
-/*
  * The joinLock serializes Create- and ExitThread. This is necessary to
  * prevent a race where a new joinable thread exits before the creating thread
  * had the time to create the necessary data structures in the emulation
@@ -386,7 +369,6 @@ TclpInitLock(void)
 	 */
 
 	init = 1;
-	InitializeCriticalSection(&mutexLock);
 	InitializeCriticalSection(&joinLock);
 	InitializeCriticalSection(&initLock);
 	InitializeCriticalSection(&masterLock);
@@ -534,7 +516,6 @@ void
 TclFinalizeLock(void)
 {
     MASTER_LOCK;
-    DeleteCriticalSection(&mutexLock);
     DeleteCriticalSection(&joinLock);
 
     /*
@@ -605,20 +586,12 @@ retry:
 	}
 	MASTER_UNLOCK;
     }
-    while (1) {
-	EnterCriticalSection(&mutexLock);
-	csPtr = *((CRITICAL_SECTION **)mutexPtr);
-	if (csPtr == NULL) {
-	    LeaveCriticalSection(&mutexLock);
-	    goto retry;
-	}
-	if (TryEnterCriticalSection(csPtr)) {
-	    LeaveCriticalSection(&mutexLock);
-	    return;
-	}
-	LeaveCriticalSection(&mutexLock);
-	Tcl_Sleep(TCL_MUTEX_LOCK_SLEEP_TIME);
+
+    csPtr = *((CRITICAL_SECTION **)mutexPtr);
+    if (csPtr == NULL) {
+	goto retry;
     }
+    EnterCriticalSection(csPtr);
 }
 
 /*