Adds a helper class used to mark/define critical section in a class and then install controls to check that those critical sections are not violated.

This CL is due the thread posted on chromium-dev:
http://groups.google.com/group/chromium-dev/browse_frm/thread/30af0b63b6adb245.

From Gaetano Mendola <mendola bigfoot com>
Review URL: http://codereview.chromium.org/8621

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@7127 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 53 insertions, 0 deletions

diff --git a/base/thread_collision_warner.cc b/base/thread_collision_warner.cc
new file mode 100644
index 0000000..1c51a3e
--- /dev/null
+++ b/base/thread_collision_warner.cc
@@ -0,0 +1,53 @@
+// Copyright (c) 2006-2008 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.
+
+#include "base/thread_collision_warner.h"
+
+#include "base/atomicops.h"
+#include "base/logging.h"
+
+namespace base {
+
+void DCheckAsserter::warn() {
+  NOTREACHED() << "Thread Collision";
+}
+
+void ThreadCollisionWarner::EnterSelf() {
+  // If the active thread is 0 then I'll write the current thread ID
+  // if two or more threads arrive here only one will succeed to
+  // write on valid_thread_id_ the current thread ID.
+  const int current_thread_id = PlatformThread::CurrentId();
+
+  int previous_value = subtle::NoBarrier_CompareAndSwap(&valid_thread_id_,
+                                                        0,
+                                                        current_thread_id);
+  if (previous_value != 0 && previous_value != current_thread_id) {
+    // gotcha! a thread is trying to use the same class and that is
+    // not current thread.
+    asserter_->warn();
+  }
+
+  subtle::NoBarrier_AtomicIncrement(&counter_, 1);
+}
+
+void ThreadCollisionWarner::Enter() {
+  const int current_thread_id = PlatformThread::CurrentId();
+
+  if (subtle::NoBarrier_CompareAndSwap(&valid_thread_id_,
+                                       0,
+                                       current_thread_id) != 0) {
+    // gotcha! another thread is trying to use the same class.
+    asserter_->warn();
+  }
+
+  subtle::NoBarrier_AtomicIncrement(&counter_, 1);
+}
+
+void ThreadCollisionWarner::Leave() {
+  if (subtle::Barrier_AtomicIncrement(&counter_, -1) == 0) {
+    subtle::NoBarrier_Store(&valid_thread_id_, 0);
+  }
+}
+
+}  // namespace base