platform: fix semaphore on mac os

src/platform-macos.cc

Index: src/platform-macos.cc
diff --git a/src/platform-macos.cc b/src/platform-macos.cc
index a937ed3a5c12c580a2c26e36611e6070aa2ee2dc..50f909888ff7ef2d3d5d1d732a2d6859c3544161 100644
--- a/src/platform-macos.cc
+++ b/src/platform-macos.cc
@@ -682,17 +682,28 @@ Mutex* OS::CreateMutex() {
 class MacOSSemaphore : public Semaphore {
  public:
   explicit MacOSSemaphore(int count) {
-    semaphore_create(mach_task_self(), &semaphore_, SYNC_POLICY_FIFO, count);
+    int r;
+    r = semaphore_create(mach_task_self(),
+                         &semaphore_,
+                         SYNC_POLICY_FIFO,
+                         count);
+    ASSERT(r == KERN_SUCCESS);
   }
 
   ~MacOSSemaphore() {
-    semaphore_destroy(mach_task_self(), semaphore_);
+    int r;
+    r = semaphore_destroy(mach_task_self(), semaphore_);
+    ASSERT(r == KERN_SUCCESS);
   }
 
-  // The MacOS mach semaphore documentation claims it does not have spurious
-  // wakeups, the way pthreads semaphores do.  So the code from the linux
-  // platform is not needed here.
-  void Wait() { semaphore_wait(semaphore_); }
+  void Wait() {
+    int r;
+    do {
+      r = semaphore_wait(semaphore_);
+    } while (r == KERN_ABORTED);
+
+    ASSERT(r == KERN_SUCCESS);

[Erik Corry, 2012/08/23 09:23:39]

I will move this up into the loop and assert that it is either SUCCESS or
ABORTED.  That way it doesn't loop if the assumption is wrong.

+  }
 
   bool Wait(int timeout);