tree 84d525b0045ed98581fdf1a523501c6519ee1311
parent edbcf7fb74cb1d88aae92099aee5ddcc49898e59
author cdumez@apple.com <cdumez@apple.com@268f45cc-cd09-0410-ab3c-d52691b4dbfc> 1557944980 +0000
committer cdumez@apple.com <cdumez@apple.com@268f45cc-cd09-0410-ab3c-d52691b4dbfc> 1557944980 +0000

[WK2][iOS] UIProcess may get killed because it is taking too long to release its background task after expiration
https://bugs.webkit.org/show_bug.cgi?id=197893
<rdar://problem/50234105>

Reviewed by Alex Christensen.

The UIProcess may get killed because it is taking too long to release its background task after its expiration handler
was called. The reason is that the background task's expiration handler was sequentially sending a ProcessWillSuspendImminently
synchronous IPC to each of its child processes and only then ends the background task. By the time we receive the response from
all child processes, it may be too late and we get killed.

To address the issue, we now:
1. Send the ProcessWillSuspendImminently asynchronously so that all processes can do their processing in parallel
2. After 2 seconds, the UIProcess releases the background task (We get killed after ~5 seconds)

Also, to make sure that the UIProcess supends promptly, we now make sure we never start a new background task *after*
the app has been backgrounded. The intention of our background task is too finish critical work (like releasing locked
files) after the app gets backgrounded, not to start new work and delay process suspension.

* NetworkProcess/NetworkProcess.cpp:
(WebKit::NetworkProcess::processWillSuspendImminently):
* NetworkProcess/NetworkProcess.h:
* NetworkProcess/NetworkProcess.messages.in:
* UIProcess/Network/NetworkProcessProxy.cpp:
(WebKit::NetworkProcessProxy::sendProcessWillSuspendImminently):
* UIProcess/WebProcessProxy.cpp:
(WebKit::WebProcessProxy::sendProcessWillSuspendImminently):
* UIProcess/ios/ProcessAssertionIOS.mm:
(-[WKProcessAssertionBackgroundTaskManager init]):
(-[WKProcessAssertionBackgroundTaskManager _scheduleReleaseTask]):
(-[WKProcessAssertionBackgroundTaskManager _cancelPendingReleaseTask]):
(-[WKProcessAssertionBackgroundTaskManager _updateBackgroundTask]):
* WebProcess/WebProcess.cpp:
(WebKit::WebProcess::didReceiveSyncMessage):
(WebKit::WebProcess::processWillSuspendImminently):
* WebProcess/WebProcess.h:
* WebProcess/WebProcess.messages.in:


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@245334 268f45cc-cd09-0410-ab3c-d52691b4dbfc