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

base/synchronization/lock_impl.h

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef BASE_SYNCHRONIZATION_LOCK_IMPL_H_
 #define BASE_SYNCHRONIZATION_LOCK_IMPL_H_
 #pragma once
 
 #include "build/build_config.h"
 
 #if defined(OS_WIN)
 #include <windows.h>
 #elif defined(OS_POSIX)
 #include <pthread.h>
 #endif
 
 #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 {
 
 // This class implements the underlying platform-specific spin-lock mechanism
 // used for the Lock class.  Most users should not use LockImpl directly, but
 // should instead use Lock.
 class BASE_EXPORT LockImpl {
  public:
 #if defined(OS_WIN)
   typedef CRITICAL_SECTION OSLockType;
@@ skipping 16 matching lines @@
   void Unlock();
 
   // Return the native underlying lock.  Not supported for Windows builds.
   // TODO(awalker): refactor lock and condition variables so that this is
   // unnecessary.
 #if !defined(OS_WIN)
   OSLockType* os_lock() { return &os_lock_; }
 #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);
 };
 
 }  // namespace internal
 }  // namespace base
 
 #endif  // BASE_SYNCHRONIZATION_LOCK_IMPL_H_