[Webkit-unassigned] [Bug 237402] New: AX ITM: Updating m_pendingLoadingProgress can cause deadlock on AXIsolatedTree::m_changeLogLock

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=237402

            Bug ID: 237402
           Summary: AX ITM: Updating m_pendingLoadingProgress can cause
                    deadlock on AXIsolatedTree::m_changeLogLock
           Product: WebKit
           Version: WebKit Nightly Build
          Hardware: All
                OS: All
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: Accessibility
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: tyler_w at apple.com
                CC: andresg_22 at apple.com,
                    webkit-bug-importer at group.apple.com

AXIsolatedTree::m_pendingLoadingProgress is currently guarded by AXIsolatedTree::m_changeLogLock. Because loading can happen at any time, deadlocks can happen in this sequence:

1. AXIsolatedTree::updateLoadingProgress is called on the main thread while the secondary thread holds the lock
2. The secondary thread is holding the lock to service an AX request, and said AX request does something to call into the main thread (e.g. AXLOGs an isolated object, which causes a dispatch to the main thread as part of AXIsolatedObject::outerHTML)
3. Deadlock

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