Branch: refs/heads/main
Home: https://github.com/WebKit/WebKit
Commit: f4ce57789de592b5e4d90714e8d0e7c52e01dfa9
https://github.com/WebKit/WebKit/commit/f4ce57789de592b5e4d90714e8d0e7c52e01dfa9
Author: Ben Nham <[email protected]>
Date: 2024-02-06 (Tue, 06 Feb 2024)
Changed paths:
M Source/WebKit/UIProcess/RemoteLayerTree/RemoteLayerTreeDrawingAreaProxy.mm
Log Message:
-----------
hideContentUntilPendingUpdate async IPC call during backgrounding blocks
process suspension
https://bugs.webkit.org/show_bug.cgi?id=268799
rdar://121185956
Reviewed by Chris Dumez.
On iOS, when the UIProcess goes into the background, it eventually calls in to
hideContentUntilPendingUpdate through this call stack:
```
WebKit::RemoteLayerTreeDrawingAreaProxy::hideContentUntilPendingUpdate()
WebKit::WebPageProxy::applicationDidFinishSnapshottingAfterEnteringBackground()
WebKit::ApplicationStateTracker::didCompleteSnapshotSequence()
```
The problem is that we recently added an async
`DrawingArea::DispatchAfterEnsuringDrawing` IPC with
reply handler call to hideContentUntilPendingUpdate (see 269776@main,
270672@main, 271260@main). An
async IPC with a reply handler in the UIProcess implicitly takes out a
background activity which
prevents the WebContent process (and also the UIProcess) from suspending until
the reply handler
runs. Unfortunately, since the WebContent process is in the background,
presumably it doesn't
render, so the DispatchAfterEnsuringDrawing reply handler doesn't run, and the
background activity
also never completes. We basically end up blocking process suspension entirely
until the 15 second
timer in ProcessStateMonitor expires and forcefully invalidates all background
activities for all
processes.
We need to fix this by reworking the logic somehow or by making this
DispatchAfterEnsuringDrawing
IPC not create a background activity. Here I'm just trying to make the IPC call
not start a
background activity.
Note that there's also a DispatchAfterEnsuringDrawing call in WebPageProxy that
I didn't touch since
I don't have evidence that it's causing a background power regression, but I
wonder if that also
should avoid creating a background activity.
* Source/WebKit/UIProcess/RemoteLayerTree/RemoteLayerTreeDrawingAreaProxy.mm:
(WebKit::RemoteLayerTreeDrawingAreaProxy::hideContentUntilPendingUpdate):
Canonical link: https://commits.webkit.org/274157@main
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