base/threading/thread_collision_warner.cc

   1 // Copyright (c) 2010 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "base/threading/thread_collision_warner.h"
   6
   7 #include "base/logging.h"
   8 #include "base/threading/platform_thread.h"
   9
  10 namespace base {
  11
  12 void DCheckAsserter::warn() {
  13   NOTREACHED() << "Thread Collision";
  14 }
  15
  16 static subtle::Atomic32 CurrentThread() {
  17   const PlatformThreadId current_thread_id = PlatformThread::CurrentId();
  18   // We need to get the thread id into an atomic data type. This might be a
  19   // truncating conversion, but any loss-of-information just increases the
  20   // chance of a fault negative, not a false positive.
  21   const subtle::Atomic32 atomic_thread_id =
  22       static_cast<subtle::Atomic32>(current_thread_id);
  23
  24   return atomic_thread_id;
  25 }
  26
  27 void ThreadCollisionWarner::EnterSelf() {
  28   // If the active thread is 0 then I'll write the current thread ID
  29   // if two or more threads arrive here only one will succeed to
  30   // write on valid_thread_id_ the current thread ID.
  31   subtle::Atomic32 current_thread_id = CurrentThread();
  32
  33   int previous_value = subtle::NoBarrier_CompareAndSwap(&valid_thread_id_,
  34                                                         0,
  35                                                         current_thread_id);
  36   if (previous_value != 0 && previous_value != current_thread_id) {
  37     // gotcha! a thread is trying to use the same class and that is
  38     // not current thread.
  39     asserter_->warn();
  40   }
  41
  42   subtle::NoBarrier_AtomicIncrement(&counter_, 1);
  43 }
  44
  45 void ThreadCollisionWarner::Enter() {
  46   subtle::Atomic32 current_thread_id = CurrentThread();
  47
  48   if (subtle::NoBarrier_CompareAndSwap(&valid_thread_id_,
  49                                        0,
  50                                        current_thread_id) != 0) {
  51     // gotcha! another thread is trying to use the same class.
  52     asserter_->warn();
  53   }
  54
  55   subtle::NoBarrier_AtomicIncrement(&counter_, 1);
  56 }
  57
  58 void ThreadCollisionWarner::Leave() {
  59   if (subtle::Barrier_AtomicIncrement(&counter_, -1) == 0) {
  60     subtle::NoBarrier_Store(&valid_thread_id_, 0);
  61   }
  62 }
  63
  64 }  // namespace base