New lock implementation for mac

webrtc/base/criticalsection.h

Index: webrtc/base/criticalsection.h
diff --git a/webrtc/base/criticalsection.h b/webrtc/base/criticalsection.h
index 5b3eaf56840cd1698701ac1669ccca9b3763c0b4..ddbf2bfd4aeb1c73c5faf39a6022b728506e30b4 100644
--- a/webrtc/base/criticalsection.h
+++ b/webrtc/base/criticalsection.h
@@ -29,6 +29,10 @@
 #include <pthread.h>
 #endif
 
+#if defined(WEBRTC_MAC)
+#include <dispatch/dispatch.h>
+#endif
+
 #if (!defined(NDEBUG) || defined(DCHECK_ALWAYS_ON))
 #define CS_DEBUG_CHECKS 1
 #endif
@@ -59,7 +63,21 @@ class LOCKABLE CriticalSection {
 #if defined(WEBRTC_WIN)
   CRITICAL_SECTION crit_;
 #elif defined(WEBRTC_POSIX)
+#if defined(WEBRTC_MAC)
+  // Number of times the lock has been locked + number of threads waiting.
+  // TODO(tommi): We could use this number and subtract the recursion count
+  // to find places where we have multiple threads contending on the same lock.
+  volatile int lock_queue_;
+  // |recursion_| represents the recursion count + 1 for the thread that owns
+  // the lock. Only modified by the thread that owns the lock.
+  int recursion_;
+  // Used to signal a single waiting thread when the lock becomes available.
+  dispatch_semaphore_t semaphore_;
+  // The thread that currently holds the lock. Required to handle recursion.
+  pthread_t owning_thread_;
+#else
   pthread_mutex_t mutex_;
+#endif
   CS_DEBUG_CODE(pthread_t thread_);
   CS_DEBUG_CODE(int recursion_count_);
 #endif