diff options
| -rw-r--r-- | base/message_loop.cc | 18 | ||||
| -rw-r--r-- | base/message_loop.h | 29 | ||||
| -rw-r--r-- | base/object_watcher.cc | 13 | ||||
| -rw-r--r-- | base/object_watcher.h | 7 | ||||
| -rw-r--r-- | base/object_watcher_unittest.cc | 33 |
5 files changed, 94 insertions, 6 deletions
diff --git a/base/message_loop.cc b/base/message_loop.cc index 7d2fbff..78f820c 100644 --- a/base/message_loop.cc +++ b/base/message_loop.cc @@ -140,9 +140,17 @@ MessageLoop::MessageLoop() : message_hwnd_(NULL), MessageLoop::~MessageLoop() { DCHECK(this == current()); + + // Let interested parties have one last shot at accessing this. + FOR_EACH_OBSERVER(DestructionObserver, destruction_observers_, + WillDestroyCurrentMessageLoop()); + + // OK, now make it so that no one can find us. ThreadLocalStorage::Set(tls_index_, NULL); + DCHECK(!dispatcher_); DCHECK(!quit_received_ && !quit_now_); + // Most tasks that have not been Run() are deleted in the |timer_manager_| // destructor after we remove our tls index. We delete the tasks in our // queues here so their destuction is similar to the tasks in the @@ -158,6 +166,16 @@ void MessageLoop::SetThreadName(const std::string& thread_name) { StartHistogrammer(); } +void MessageLoop::AddDestructionObserver(DestructionObserver *obs) { + DCHECK(this == current()); + destruction_observers_.AddObserver(obs); +} + +void MessageLoop::RemoveDestructionObserver(DestructionObserver *obs) { + DCHECK(this == current()); + destruction_observers_.RemoveObserver(obs); +} + void MessageLoop::AddObserver(Observer *obs) { DCHECK(this == current()); observers_.AddObserver(obs); diff --git a/base/message_loop.h b/base/message_loop.h index 1610d07..cd7b1c5 100644 --- a/base/message_loop.h +++ b/base/message_loop.h @@ -150,6 +150,10 @@ class MessageLoop { virtual void OnObjectSignaled(HANDLE object) = 0; }; + // Have the current thread's message loop watch for a signaled object. + // Pass a null watcher to stop watching the object. + bool WatchObject(HANDLE, Watcher*); + // Dispatcher is used during a nested invocation of Run to dispatch events. // If Run is invoked with a non-NULL Dispatcher, MessageLoop does not // dispatch events (or invoke TranslateMessage), rather every message is @@ -172,9 +176,27 @@ class MessageLoop { virtual bool Dispatch(const MSG& msg) = 0; }; - // Have the current thread's message loop watch for a signaled object. - // Pass a null watcher to stop watching the object. - bool WatchObject(HANDLE, Watcher*); + // A DestructionObserver is notified when the current MessageLoop is being + // destroyed. These obsevers are notified prior to MessageLoop::current() + // being changed to return NULL. This gives interested parties the chance to + // do final cleanup that depends on the MessageLoop. + // + // NOTE: Any tasks posted to the MessageLoop during this notification will + // not be run. Instead, they will be deleted. + // + class DestructionObserver { + public: + virtual ~DestructionObserver() {} + virtual void WillDestroyCurrentMessageLoop() = 0; + }; + + // Add a DestructionObserver, which will start receiving notifications + // immediately. + void AddDestructionObserver(DestructionObserver* destruction_observer); + + // Remove a DestructionObserver. It is safe to call this method while a + // DestructionObserver is receiving a notification callback. + void RemoveDestructionObserver(DestructionObserver* destruction_observer); // An Observer is an object that receives global notifications from the // MessageLoop. @@ -577,6 +599,7 @@ class MessageLoop { std::vector<Watcher*> watchers_; ObserverList<Observer> observers_; + ObserverList<DestructionObserver> destruction_observers_; HWND message_hwnd_; IDMap<Task> timed_tasks_; // A recursion block that prevents accidentally running additonal tasks when diff --git a/base/object_watcher.cc b/base/object_watcher.cc index 5e8c27b..9872a4c 100644 --- a/base/object_watcher.cc +++ b/base/object_watcher.cc @@ -29,7 +29,6 @@ #include "base/object_watcher.h" -#include "base/message_loop.h" #include "base/logging.h" namespace base { @@ -91,6 +90,10 @@ bool ObjectWatcher::StartWatching(HANDLE object, Delegate* delegate) { } watch_ = watch; + + // We need to know if the current message loop is going away so we can + // prevent the wait thread from trying to access a dead message loop. + MessageLoop::current()->AddDestructionObserver(this); return true; } @@ -124,6 +127,8 @@ bool ObjectWatcher::StopWatching() { delete watch_; watch_ = NULL; + + MessageLoop::current()->RemoveDestructionObserver(this); return true; } @@ -142,4 +147,10 @@ void CALLBACK ObjectWatcher::DoneWaiting(void* param, BOOLEAN timed_out) { watch->origin_loop->PostTask(FROM_HERE, watch); } +void ObjectWatcher::WillDestroyCurrentMessageLoop() { + // Need to shutdown the watch so that we don't try to access the MessageLoop + // after this point. + StopWatching(); +} + } // namespace base diff --git a/base/object_watcher.h b/base/object_watcher.h index de4816a..9058ab4 100644 --- a/base/object_watcher.h +++ b/base/object_watcher.h @@ -32,7 +32,7 @@ #include <windows.h> -#include "base/basictypes.h" +#include "base/message_loop.h" namespace base { @@ -64,7 +64,7 @@ namespace base { // scope, the watcher_ will be destroyed, and there is no need to worry about // OnObjectSignaled being called on a deleted MyClass pointer. Easy! // -class ObjectWatcher { +class ObjectWatcher : public MessageLoop::DestructionObserver { public: class Delegate { public: @@ -97,6 +97,9 @@ class ObjectWatcher { // Called on a background thread when done waiting. static void CALLBACK DoneWaiting(void* param, BOOLEAN timed_out); + // MessageLoop::DestructionObserver implementation: + virtual void WillDestroyCurrentMessageLoop(); + // Internal state. struct Watch; Watch* watch_; diff --git a/base/object_watcher_unittest.cc b/base/object_watcher_unittest.cc index 51ed968..6c3fcce 100644 --- a/base/object_watcher_unittest.cc +++ b/base/object_watcher_unittest.cc @@ -27,6 +27,8 @@ // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. +#include <process.h> + #include "base/message_loop.h" #include "base/object_watcher.h" #include "testing/gtest/include/gtest/gtest.h" @@ -113,3 +115,34 @@ TEST(ObjectWatcherTest, CancelAfterSet) { CloseHandle(event); } + +// Used so we can simulate a MessageLoop that dies before an ObjectWatcher. +// This ordinarily doesn't happen when people use the Thread class, but it can +// happen when people use the Singleton pattern or atexit. +static unsigned __stdcall ThreadFunc(void* param) { + HANDLE event = CreateEvent(NULL, TRUE, FALSE, NULL); // not signaled + { + base::ObjectWatcher watcher; + { + MessageLoop message_loop; + + QuitDelegate delegate; + watcher.StartWatching(event, &delegate); + } + } + CloseHandle(event); + return 0; +} + +TEST(ObjectWatcherTest, OutlivesMessageLoop) { + unsigned int thread_id; + HANDLE thread = reinterpret_cast<HANDLE>( + _beginthreadex(NULL, + 0, + ThreadFunc, + NULL, + 0, + &thread_id)); + WaitForSingleObject(thread, INFINITE); + CloseHandle(thread); +} |