avoid pthread_mutex_timedlock in valgrind

stepmania/src/arch/Threads/Threads_Pthreads.cpp

@@ -135,9 +135,41 @@ MutexImpl_Pthreads::~MutexImpl_Pthreads()
 }
 
 
+#if defined(HAVE_PTHREAD_MUTEX_TIMEDLOCK) && defined(CRASH_HANDLER)
+static bool UseTimedlock()
+{
+#if defined(CPU_X86) && defined(__GNUC__)
+	/* Valgrind crashes and burns on pthread_mutex_timedlock. */
+        static int under_valgrind = -1;
+	if( under_valgrind == -1 )
+	{
+		unsigned int magic[8] = { 0x00001001, 0, 0, 0, 0, 0, 0, 0 };
+		asm(
+			"mov %1, %%eax\n"
+			"mov $0, %%edx\n"
+			"rol $29, %%eax\n"
+			"rol $3, %%eax\n"
+			"ror $27, %%eax\n"
+			"ror $5, %%eax\n"
+			"rol $13, %%eax\n"
+			"rol $19, %%eax\n"
+			"mov %%edx, %0\t"
+			: "=r" (under_valgrind): "r" (magic): "eax", "edx" );
+	}
+	
+	if( under_valgrind )
+		return false;
+#endif
+
+	return true;
+}
+#endif
+
 bool MutexImpl_Pthreads::Lock()
 {
 #if defined(HAVE_PTHREAD_MUTEX_TIMEDLOCK) && defined(CRASH_HANDLER)
+	if( UseTimedlock() )
+	{
 		int len = 10; /* seconds */
 		int tries = 2;
 
@@ -174,7 +206,9 @@ bool MutexImpl_Pthreads::Lock()
 		}
 
 		return false;
-#else
+	}
+#endif
+
 	int ret;
 	do
 	{
@@ -185,7 +219,6 @@ bool MutexImpl_Pthreads::Lock()
 	ASSERT_M( ret == 0, ssprintf("pthread_mutex_lock: %s", strerror(errno)) );
 
 	return true;
-#endif
 }
 
 bool MutexImpl_Pthreads::TryLock()