[tsan] Add interceptors and sychronization for libdispatch semaphores on OS X

[kubamracek]

Summary

This patch adds release and acquire semantics for libdispatch semaphores and a test case.

compiler-rt/trunk/lib/tsan/rtl/tsan_libdispatch_mac.cc

 #include "tsan_interceptors.h"
 #include "tsan_platform.h"
 #include "tsan_rtl.h"
 
 #include <Block.h>
 #include <dispatch/dispatch.h>
 #include <pthread.h>
 
+typedef long long_t;  // NOLINT
+
 namespace __tsan {
 
 typedef struct {
   dispatch_queue_t queue;
   void *orig_context;
   dispatch_function_t orig_work;
 } tsan_block_context_t;
 

 TSAN_INTERCEPTOR(void, dispatch_once_f, dispatch_once_t *predicate,
                  void *context, dispatch_function_t function) {
   SCOPED_TSAN_INTERCEPTOR(dispatch_once_f, predicate, context, function);
   WRAP(dispatch_once)(predicate, ^(void) {
     function(context);
   });
 }
 
+TSAN_INTERCEPTOR(long_t, dispatch_semaphore_signal,
+                 dispatch_semaphore_t dsema) {
+  SCOPED_TSAN_INTERCEPTOR(dispatch_semaphore_signal, dsema);
+  Release(thr, pc, (uptr)dsema);
+  return REAL(dispatch_semaphore_signal)(dsema);
+}
+
+TSAN_INTERCEPTOR(long_t, dispatch_semaphore_wait, dispatch_semaphore_t dsema,
+                 dispatch_time_t timeout) {
+  SCOPED_TSAN_INTERCEPTOR(dispatch_semaphore_wait, dsema, timeout);
+  long_t result = REAL(dispatch_semaphore_wait)(dsema, timeout);
+  if (result == 0) Acquire(thr, pc, (uptr)dsema);
+  return result;
+}
+
 }  // namespace __tsan
 
 #endif  // SANITIZER_MAC

compiler-rt/trunk/test/tsan/Darwin/gcd-semaphore-norace.mm

+// RUN: %clang_tsan %s -o %t -framework Foundation
+// RUN: %run %t 2>&1
+
+#import <Foundation/Foundation.h>
+
+long global;
+
+int main() {
+    NSLog(@"Hello world.");
+
+    global = 42;
+    
+    dispatch_semaphore_t sem = dispatch_semaphore_create(0);
+    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
+        
+        global = 43;
+        dispatch_semaphore_signal(sem);
+    });
+    
+    dispatch_semaphore_wait(sem, DISPATCH_TIME_FOREVER);
+    global = 44;
+
+    NSLog(@"Done.");
+    return 0;
+}
+
+// CHECK: Hello world.
+// CHECK: Done.
+// CHECK-NOT: WARNING: ThreadSanitizer