Bug 243456

Summary: AX ITM: Avoid dispatching AXIsolatedObject methods to the main thread when it is busy updating the isolated tree.
Product: WebKit Reporter: Andres Gonzalez <andresg_22>
Component: AccessibilityAssignee: Andres Gonzalez <andresg_22>
Status: NEW    
Severity: Normal CC: aboxhall, andresg_22, apinheiro, cfleizach, darin, dmazzoni, ews-watchlist, jcraig, jdiggs, samuel_white, webkit-bug-importer
Priority: P2 Keywords: InRadar
Version: WebKit Nightly Build   
Hardware: All   
OS: All   
Attachments:
Description Flags
Patch
none
Patch andresg_22: review?, ews-feeder: commit-queue-

Andres Gonzalez
Reported 2022-08-02 08:29:43 PDT
This causes VoiceOver to become irresponsive.
Attachments
Patch (13.48 KB, patch)
2022-08-02 08:38 PDT, Andres Gonzalez 		no flags
DetailsFormatted DiffDiff
Patch (29.65 KB, patch)
2022-08-12 06:53 PDT, Andres Gonzalez 		andresg_22: review?
ews-feeder: commit-queue-
DetailsFormatted DiffDiff
Show Obsolete (1) View All Add attachment proposed patch, testcase, etc.
Radar WebKit Bug Importer
Comment 1 2022-08-02 08:29:55 PDT
<rdar://problem/97982075>
Andres Gonzalez
Comment 2 2022-08-02 08:38:56 PDT
Created attachment 461361 [details] Patch
Darin Adler
Comment 3 2022-08-03 12:39:59 PDT
Comment on attachment 461361 [details] Patch View in context: https://bugs.webkit.org/attachment.cgi?id=461361&action=review I didn’t get a chance to review the whole thing, but a couple comments. > Source/WebCore/accessibility/AccessibilityObjectInterface.h:1695 > +T retrieveValueFromMainThreadWithTimeout(U&& function, Seconds&& timeout) Since Seconds is a class wrapping a double, we can just use Seconds, we don’t need to use Seconds&&. > Source/WebCore/accessibility/AccessibilityObjectInterface.h:1708 > + while (!done && !hasElapsed(elapseTime)) { } This kind of loop is not an efficient way to have one thread wait on another. Surely there is a better idiom for such things using locks, mutexes, or semaphores of some kind.
Andres Gonzalez
Comment 4 2022-08-12 06:53:25 PDT
Created attachment 461559 [details] Patch Extended the check for whether to dispatch to the main thread to all AXIsolatedObject methods that were using Accessibility::retrieveValueFromMainThread.
Andres Gonzalez
Comment 5 2022-08-12 06:59:48 PDT
(In reply to Darin Adler from comment #3) > Comment on attachment 461361 [details] > Patch > > View in context: > https://bugs.webkit.org/attachment.cgi?id=461361&action=review > > I didn’t get a chance to review the whole thing, but a couple comments. > > > Source/WebCore/accessibility/AccessibilityObjectInterface.h:1695 > > +T retrieveValueFromMainThreadWithTimeout(U&& function, Seconds&& timeout) > > Since Seconds is a class wrapping a double, we can just use Seconds, we > don’t need to use Seconds&&. Fixed. > > > Source/WebCore/accessibility/AccessibilityObjectInterface.h:1708 > > + while (!done && !hasElapsed(elapseTime)) { } > > This kind of loop is not an efficient way to have one thread wait on > another. Surely there is a better idiom for such things using locks, > mutexes, or semaphores of some kind. Yes, still working on that. I'm getting deadlocks using BinarySemaphore that I'm still debugging. I'm keeping this for now so that it is testable but not the final version yet. Thanks!
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