Add PTHREAD_PRIO_INHERIT Locks for Mac

base/synchronization/lock_impl_posix.cc

Index: base/synchronization/lock_impl_posix.cc
diff --git a/base/synchronization/lock_impl_posix.cc b/base/synchronization/lock_impl_posix.cc
index 5619adaf5d829df72f93fd57b0687d551fb9390d..ed65aa69146c28baf53e2212830cc237a00f7e06 100644
--- a/base/synchronization/lock_impl_posix.cc
+++ b/base/synchronization/lock_impl_posix.cc
@@ -8,26 +8,30 @@
 #include <string.h>
 
 #include "base/logging.h"
+#include "base/synchronization/lock.h"
 
 namespace base {
 namespace internal {
 
 LockImpl::LockImpl() {
-#ifndef NDEBUG
-  // In debug, setup attributes for lock error checking.
   pthread_mutexattr_t mta;
   int rv = pthread_mutexattr_init(&mta);
   DCHECK_EQ(rv, 0) << ". " << strerror(rv);
+#if PRIORITY_INHERITANCE_LOCKS_POSSIBLE()
+  if (PriorityInheritanceAvailable()) {
+    rv = pthread_mutexattr_setprotocol(&mta, PTHREAD_PRIO_INHERIT);
+  }
+  DCHECK_EQ(rv, 0) << ". " << strerror(rv);
+#endif
+#ifndef NDEBUG
+  // In debug, setup attributes for lock error checking.
   rv = pthread_mutexattr_settype(&mta, PTHREAD_MUTEX_ERRORCHECK);
   DCHECK_EQ(rv, 0) << ". " << strerror(rv);
+#endif
   rv = pthread_mutex_init(&native_handle_, &mta);
   DCHECK_EQ(rv, 0) << ". " << strerror(rv);
   rv = pthread_mutexattr_destroy(&mta);
   DCHECK_EQ(rv, 0) << ". " << strerror(rv);
-#else
-  // In release, go with the default lock attributes.
-  pthread_mutex_init(&native_handle_, NULL);
-#endif
 }
 
 LockImpl::~LockImpl() {
@@ -51,5 +55,14 @@ void LockImpl::Unlock() {
   DCHECK_EQ(rv, 0) << ". " << strerror(rv);
 }
 
+// static
+bool LockImpl::PriorityInheritanceAvailable() {

[gab, 2016/07/22 20:07:31]

There's no longer anything run-time about this method? Why not just have a
single compile-time check?

[robliao, 2016/07/25 20:53:19]

This future-proofs lock against the known runtime checks we'll need to do
if/when we support Linux.

[gab, 2016/07/26 17:31:27]

Ok, can you add a TODO here then to indicate the intent of this method? (without
it, first thing I would do as a reader going through here is refactor them in
one call)

[gab, 2016/07/26 17:32:11]

Nvm, see you addressed this already with other comment, thanks!

+#if PRIORITY_INHERITANCE_LOCKS_POSSIBLE() && defined(OS_MACOSX)

[gab, 2016/07/22 20:07:31]

Please add a comment explaining why it doesn't work on Linux (it took you so
much effort to figure it out, we should at least encode the learnings in the
code somewhere -- or link to an @chromium.org doc if it's too complicated.

[robliao, 2016/07/25 20:53:19]

Done.

+  return true;
+#else
+  return false;
+#endif
+}
+
 }  // namespace internal
 }  // namespace base