gecko-dev/xpcom/threads/nsIDelayedRunnableObserver.h
Andreas Pehrson 9717c27492 Bug 1695580 - In xpcom, cancel pending DelayedRunnable timers on shutdown. r=KrisWright
Because DelayedRunnables are fire-and-forget, there is no way for a targeted
EventTarget to clean them up on shutdown. Thus if a timer fires after
EventTarget shutdown it will fail to dispatch the timer event, and avoid
releasing the timer callback because it's not on the targeted thread. This
causes a leak as there is a ref-cycle between nsTimerImpl::mCallback and
DelayedRunnable::mTimer.

This patch adds nsIDelayedRunnableObserver for a target to observe which
DelayedRunnables are relying on their timer to run them. This allows the target
to schedule a shutdown task to cancel those timers and release the runnables on
the target thread.

Supported DelayedRunnable targets with this patch are TaskQueues,
eventqueue-based nsThreads and XPCOMThreadWrappers that wrap a supported
nsThread.

An assertion makes sure at runtime that future new uses of DelayedRunnable
target nsIDelayedRunnableObserver-supported event targets.

Differential Revision: https://phabricator.services.mozilla.com/D109781
2021-04-06 20:15:11 +00:00

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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#ifndef XPCOM_THREADS_NSIDELAYEDRUNNABLEOBSERVER_H_
#define XPCOM_THREADS_NSIDELAYEDRUNNABLEOBSERVER_H_
#include "nsISupports.h"
namespace mozilla {
class DelayedRunnable;
}
#define NS_IDELAYEDRUNNABLEOBSERVER_IID \
{ \
0xd226bade, 0xac13, 0x46fe, { \
0x9f, 0xcc, 0xde, 0xe7, 0x48, 0x35, 0xcd, 0x82 \
} \
}
class NS_NO_VTABLE nsIDelayedRunnableObserver : public nsISupports {
public:
NS_DECLARE_STATIC_IID_ACCESSOR(NS_IDELAYEDRUNNABLEOBSERVER_IID)
/**
* Called by the DelayedRunnable after being created, on the dispatching
* thread. This allows for various lifetime checks and gives assertions a
* chance to provide useful stack traces.
*/
virtual void OnDelayedRunnableCreated(
mozilla::DelayedRunnable* aRunnable) = 0;
/**
* Called by the DelayedRunnable on its target thread when delegating the
* responsibility for being run to its underlying timer.
*/
virtual void OnDelayedRunnableScheduled(
mozilla::DelayedRunnable* aRunnable) = 0;
/**
* Called by the DelayedRunnable on its target thread after having been run by
* its underlying timer.
*/
virtual void OnDelayedRunnableRan(mozilla::DelayedRunnable* aRunnable) = 0;
};
NS_DEFINE_STATIC_IID_ACCESSOR(nsIDelayedRunnableObserver,
NS_IDELAYEDRUNNABLEOBSERVER_IID)
#endif