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Bug 1237690 - Fix possible deadlock in nsAppShell::SyncRunEvent; r=snorp

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In order to prevent the deadlock, we need to release sAppShellLock when
we start waiting in SyncRunEvent. However, we cannot simply unlock it
before the wait because that introduces an out-of-order unlocking wrt
mSyncRunMonitor, which can cause further deadlocks. So this patch
converts mSyncRunMoitor to a condvar and make it use sAppShellLock. That
then involves making aAppShellLock a Mutex instead of a StaticMutex. The
final result is having one lock (sAppShellLock), which supports any
other condvars that we have like mSyncRunFinished.
This commit is contained in:
Jim Chen 2016-01-13 14:35:27 -05:00
parent 019f175b5f
commit 85514b694a
2 changed files with 20 additions and 21 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

31
widget/android/nsAppShell.cpp
View File

@ -76,7 +76,7 @@ nsIGeolocationUpdate *gLocationCallback = nullptr;
nsAutoPtr<mozilla::AndroidGeckoEvent> gLastSizeChange;
nsAppShell* nsAppShell::sAppShell;
StaticMutex nsAppShell::sAppShellLock;
StaticAutoPtr<Mutex> nsAppShell::sAppShellLock;
NS_IMPL_ISUPPORTS_INHERITED(nsAppShell, nsBaseAppShell, nsIObserver)
@ -185,11 +185,12 @@ public:
};
nsAppShell::nsAppShell()
: mSyncRunMonitor("nsAppShell.SyncRun")
: mSyncRunFinished(*(sAppShellLock = new Mutex("nsAppShell")),
"nsAppShell.SyncRun")
, mSyncRunQuit(false)
{
{
StaticMutexAutoLock lock(sAppShellLock);
MutexAutoLock lock(*sAppShellLock);
sAppShell = this;
}
@ -220,7 +221,7 @@ nsAppShell::nsAppShell()
nsAppShell::~nsAppShell()
{
{
StaticMutexAutoLock lock(sAppShellLock);
MutexAutoLock lock(*sAppShellLock);
sAppShell = nullptr;
}
@ -286,9 +287,9 @@ nsAppShell::Observe(nsISupports* aSubject,
if (!strcmp(aTopic, "xpcom-shutdown")) {
{
// Release any thread waiting for a sync call to finish.
MonitorAutoLock runLock(mSyncRunMonitor);
mozilla::MutexAutoLock shellLock(*sAppShellLock);
mSyncRunQuit = true;
runLock.NotifyAll();
mSyncRunFinished.NotifyAll();
}
// We need to ensure no observers stick around after XPCOM shuts down
// or we'll see crashes, as the app shell outlives XPConnect.
@ -401,8 +402,9 @@ nsAppShell::SyncRunEvent(Event&& event,
// on the monitor on the current thread.
MOZ_ASSERT(!NS_IsMainThread());
// This is the lock to check that app shell is still alive.
mozilla::StaticMutexAutoLock shellLock(sAppShellLock);
// This is the lock to check that app shell is still alive,
// and to wait on for the sync call to complete.
mozilla::MutexAutoLock shellLock(*sAppShellLock);
nsAppShell* const appShell = sAppShell;
if (MOZ_UNLIKELY(!appShell)) {
@ -410,19 +412,16 @@ nsAppShell::SyncRunEvent(Event&& event,
return;
}
// This is the monitor that we will wait on for the call to complete.
mozilla::MonitorAutoLock runLock(appShell->mSyncRunMonitor);
bool finished = false;
auto runAndNotify = [&event, &finished] {
mozilla::MutexAutoLock shellLock(*sAppShellLock);
nsAppShell* const appShell = sAppShell;
if (MOZ_UNLIKELY(!appShell || appShell->mSyncRunQuit)) {
return;
}
event.Run();
mozilla::MonitorAutoLock runLock(appShell->mSyncRunMonitor);
finished = true;
runLock.NotifyAll();
appShell->mSyncRunFinished.NotifyAll();
};
UniquePtr<Event> runAndNotifyEvent = mozilla::MakeUnique<
@ -434,8 +433,8 @@ nsAppShell::SyncRunEvent(Event&& event,
appShell->mEventQueue.Post(mozilla::Move(runAndNotifyEvent));
while (!finished && MOZ_LIKELY(!appShell->mSyncRunQuit)) {
runLock.Wait();
while (!finished && MOZ_LIKELY(sAppShell && !sAppShell->mSyncRunQuit)) {
appShell->mSyncRunFinished.Wait();
}
}
@ -459,7 +458,7 @@ public:
void
nsAppShell::PostEvent(AndroidGeckoEvent* event)
{
mozilla::StaticMutexAutoLock lock(sAppShellLock);
mozilla::MutexAutoLock lock(*sAppShellLock);
if (!sAppShell) {
return;
}

10
widget/android/nsAppShell.h
View File

@ -10,7 +10,7 @@
#include "mozilla/LinkedList.h"
#include "mozilla/Monitor.h"
#include "mozilla/Move.h"
#include "mozilla/StaticMutex.h"
#include "mozilla/StaticPtr.h"
#include "mozilla/UniquePtr.h"
#include "mozilla/unused.h"
#include "mozilla/jni/Natives.h"
@ -112,7 +112,7 @@ public:
template<typename T, typename D>
static void PostEvent(mozilla::UniquePtr<T, D>&& event)
{
mozilla::StaticMutexAutoLock lock(sAppShellLock);
mozilla::MutexAutoLock lock(*sAppShellLock);
if (!sAppShell) {
return;
}
@ -124,7 +124,7 @@ public:
template<typename T>
static void PostEvent(T&& lambda)
{
mozilla::StaticMutexAutoLock lock(sAppShellLock);
mozilla::MutexAutoLock lock(*sAppShellLock);
if (!sAppShell) {
return;
}
@ -151,7 +151,7 @@ public:
protected:
static nsAppShell* sAppShell;
static mozilla::StaticMutex sAppShellLock;
static mozilla::StaticAutoPtr<mozilla::Mutex> sAppShellLock;
virtual ~nsAppShell();
@ -215,7 +215,7 @@ protected:
} mEventQueue;
mozilla::Monitor mSyncRunMonitor;
mozilla::CondVar mSyncRunFinished;
bool mSyncRunQuit;
bool mAllowCoalescingTouches;