Patch #711835: Remove unnecessary lock operations. Will backport to 2.2.

Python/thread_pthread.h

@@ -497,27 +497,23 @@ PyThread_acquire_lock(PyThread_type_lock lock, int waitflag)
 	status = pthread_mutex_lock( &thelock->mut );
 	CHECK_STATUS("pthread_mutex_lock[1]");
 	success = thelock->locked == 0;
-	if (success) thelock->locked = 1;
-	status = pthread_mutex_unlock( &thelock->mut );
-	CHECK_STATUS("pthread_mutex_unlock[1]");
 
 	if ( !success && waitflag ) {
 		/* continue trying until we get the lock */
 
 		/* mut must be locked by me -- part of the condition
 		 * protocol */
-		status = pthread_mutex_lock( &thelock->mut );
-		CHECK_STATUS("pthread_mutex_lock[2]");
 		while ( thelock->locked ) {
 			status = pthread_cond_wait(&thelock->lock_released,
 						   &thelock->mut);
 			CHECK_STATUS("pthread_cond_wait");
 		}
-		thelock->locked = 1;
-		status = pthread_mutex_unlock( &thelock->mut );
-		CHECK_STATUS("pthread_mutex_unlock[2]");
 		success = 1;
 	}
+	if (success) thelock->locked = 1;
+	status = pthread_mutex_unlock( &thelock->mut );
+	CHECK_STATUS("pthread_mutex_unlock[1]");
+
 	if (error) success = 0;
 	dprintf(("PyThread_acquire_lock(%p, %d) -> %d\n", lock, waitflag, success));
 	return success;