Temporary instrumentation to help understand lock errors on mac debug bots.

BUG=102161

Review URL: http://codereview.chromium.org/8414031

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@107835 0039d316-1c4b-4281-b951-d872f2087c98

base/synchronization/lock_impl.h

@@ -17,6 +17,18 @@
 #include "base/base_export.h"
 #include "base/basictypes.h"
 
+#if defined(OS_MACOSX) && !defined(NDEBUG)
+// For Mac debug builds, do some extra checks to make sure a LockImpl is not
+// used after it has been freed. This instrumentation is to help track down
+// spurious locking errors (EINVAL) which are happening on the bots.
+// In particular, I want to make sure they aren't a consequence of having
+// used a freed lock object (which can happen for instance when trying to
+// post tasks to a destroyed MessageLoop).
+// See http://crbug.com/102161 for more details. This instrumentation can be
+// removed once that bug has been identified.
+#define LOCK_IMPL_CHECK_LIVENESS
+#endif
+
 namespace base {
 namespace internal {
 
@@ -53,6 +65,17 @@ class BASE_EXPORT LockImpl {
 #endif
 
  private:
+#ifdef LOCK_IMPL_CHECK_LIVENESS
+  enum LivenessToken {
+    LT_ALIVE = 0xCa11ab1e,  // 3390155550
+    LT_DELETED = 0xDecea5ed,  // 3738084845
+  };
+
+  void CheckIsAlive();
+
+  LivenessToken liveness_token_;
+#endif  // LOCK_IMPL_CHECK_LIVENESS
+
   OSLockType os_lock_;
 
   DISALLOW_COPY_AND_ASSIGN(LockImpl);

base/synchronization/lock_impl_posix.cc

@@ -12,6 +12,10 @@ namespace base {
 namespace internal {
 
 LockImpl::LockImpl() {
+#ifdef LOCK_IMPL_CHECK_LIVENESS
+  liveness_token_ = LT_ALIVE;
+#endif
+
 #ifndef NDEBUG
   // In debug, setup attributes for lock error checking.
   pthread_mutexattr_t mta;
@@ -30,25 +34,45 @@ LockImpl::LockImpl() {
 }
 
 LockImpl::~LockImpl() {
+#ifdef LOCK_IMPL_CHECK_LIVENESS
+  CheckIsAlive();
+  liveness_token_ = LT_DELETED;
+#endif
   int rv = pthread_mutex_destroy(&os_lock_);
   DCHECK_EQ(rv, 0);
 }
 
 bool LockImpl::Try() {
+#ifdef LOCK_IMPL_CHECK_LIVENESS
+  CheckIsAlive();
+#endif
   int rv = pthread_mutex_trylock(&os_lock_);
   DCHECK(rv == 0 || rv == EBUSY);
   return rv == 0;
 }
 
 void LockImpl::Lock() {
+#ifdef LOCK_IMPL_CHECK_LIVENESS
+  CheckIsAlive();
+#endif
   int rv = pthread_mutex_lock(&os_lock_);
   DCHECK_EQ(rv, 0);
 }
 
 void LockImpl::Unlock() {
+#ifdef LOCK_IMPL_CHECK_LIVENESS
+  CheckIsAlive();
+#endif
   int rv = pthread_mutex_unlock(&os_lock_);
   DCHECK_EQ(rv, 0);
 }
 
+#ifdef LOCK_IMPL_CHECK_LIVENESS
+void LockImpl::CheckIsAlive() {
+  CHECK_EQ(LT_ALIVE, liveness_token_)
+      << "Lock was invalid. Please see: http://crbug.com/102161";
+}
+#endif
+
 }  // namespace internal
 }  // namespace base