IPC::Semaphore doesn't get interrupted if it's waiting on a signal from a remote process that crashes. RemoteImageBufferProxy uses a 15 second timeout, per buffer, so we can end up waiting many minutes if we crash during a transaction with lots of layer changes.
For the case where we're waiting on the Semaphore on a background thread (normal painting), we could forward the 'GPU disconnected' message to each RemoteImageBufferProxy and manually notify the Semaphores. We might need a way to get notifications on a background thread (register with IPC::Connection for a notification from the IPC thread?), which we then use to invalidate Semaphore (by notifying them, and marking them as invalid).
<rdar://problem/114591255>
Pull request: https://github.com/WebKit/WebKit/pull/17526
Committed 268093@main (f2796edab116): <https://commits.webkit.org/268093@main> Reviewed commits have been landed. Closing PR #17526 and removing active labels.