base: Enable lock dchecks with dchecks_always_on

base/synchronization/lock.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_H_
 #define BASE_SYNCHRONIZATION_LOCK_H_
 
 #include "base/base_export.h"
 #include "base/synchronization/lock_impl.h"
 #include "base/threading/platform_thread.h"
 
 namespace base {
 
 // A convenient wrapper for an OS specific critical section.  The only real
 // intelligence in this class is in debug mode for the support for the
 // AssertAcquired() method.
 class BASE_EXPORT Lock {
  public:
-#if defined(NDEBUG)             // Optimized wrapper implementation
+#if defined(NDEBUG) && !defined(DCHECK_ALWAYS_ON)
+   // Optimized wrapper implementation
   Lock() : lock_() {}
   ~Lock() {}
   void Acquire() { lock_.Lock(); }
   void Release() { lock_.Unlock(); }
 
   // If the lock is not held, take it and return true. If the lock is already
   // held by another thread, immediately return false. This must not be called
   // by a thread already holding the lock (what happens is undefined and an
   // assertion may fail).
   bool Try() { return lock_.Try(); }
@@ skipping 18 matching lines @@
 
   bool Try() {
     bool rv = lock_.Try();
     if (rv) {
       CheckUnheldAndMark();
     }
     return rv;
   }
 
   void AssertAcquired() const;
-#endif                          // NDEBUG
+#endif  // NDEBUG && !DCHECK_ALWAYS_ON
 
 #if defined(OS_POSIX)
   // The posix implementation of ConditionVariable needs to be able
   // to see our lock and tweak our debugging counters, as it releases
   // and acquires locks inside of pthread_cond_{timed,}wait.
   friend class ConditionVariable;

[boliu, 2014/07/21 18:23:11]

See comments on these friend statements about the "internal debug counter"
thing.

ConditionVariable need to update owning_thread_ref_ to make the DCHECKs on
owning_thread_ref_ hold, so the debug condition between Lock and
ConditionVariable must match.

Took me awhile to figure this out when I did not update ConditionVariable and
DCHECKs started failing that seemed to indidated lock stopped working...

 #elif defined(OS_WIN)
   // The Windows Vista implementation of ConditionVariable needs the
   // native handle of the critical section.
   friend class WinVistaCondVar;
 #endif
 
  private:
-#if !defined(NDEBUG)
+#if !defined(NDEBUG) || defined(DCHECK_ALWAYS_ON)
   // Members and routines taking care of locks assertions.
   // Note that this checks for recursive locks and allows them
   // if the variable is set.  This is allowed by the underlying implementation
   // on windows but not on Posix, so we're doing unneeded checks on Posix.
   // It's worth it to share the code.
   void CheckHeldAndUnmark();
   void CheckUnheldAndMark();
 
   // All private data is implicitly protected by lock_.
   // Be VERY careful to only access members under that lock.
   base::PlatformThreadRef owning_thread_ref_;
-#endif  // NDEBUG
+#endif  // !NDEBUG || DCHECK_ALWAYS_ON
 
   // Platform specific underlying lock implementation.
   internal::LockImpl lock_;
 
   DISALLOW_COPY_AND_ASSIGN(Lock);
 };
 
 // A helper class that acquires the given Lock while the AutoLock is in scope.
 class AutoLock {
  public:
@@ skipping 32 matching lines @@
   }
 
  private:
   Lock& lock_;
   DISALLOW_COPY_AND_ASSIGN(AutoUnlock);
 };
 
 }  // namespace base
 
 #endif  // BASE_SYNCHRONIZATION_LOCK_H_