commit bd93c3023ea2171bfcdf127d03a05d903ee7c9d8
author Brian Carlstrom <bdc@google.com> Mon Aug 27 16:58:28 2012 -0700
committer Brian Carlstrom <bdc@google.com> Mon Aug 27 16:58:28 2012 -0700
tree 8df67ff9be6b3af140260bf05abd145d398b70a2
parent 0ac41d58258a97c62d41c0137338a4c3b9ceb95d

Comment on use of 0 and -1 values in mutex implementation

Change-Id: I4834feb2aa78962086c39c1512483964a3a2a52a

src/mutex.cc

diff --git a/src/mutex.cc b/src/mutex.cc
index eef8bdc..2811843 100644
--- a/src/mutex.cc
+++ b/src/mutex.cc
@@ -278,6 +278,8 @@
 #elif defined(__APPLE__)
   const darwin_pthread_mutex_t* dpmutex = reinterpret_cast<const darwin_pthread_mutex_t*>(&mutex_);
   pthread_t owner = dpmutex->darwin_pthread_mutex_owner;
+  // 0 for unowned, -1 for PTHREAD_MTX_TID_SWITCHING
+  // TODO: should we make darwin_pthread_mutex_owner volatile and recheck until not -1?
   if ((owner == (pthread_t)0) || (owner == (pthread_t)-1)) {
     return 0;
   }