This bug was filed from the Socorro interface and is report bp-bce93404-ea89-4166-a0b5-53f842170413. ============================================================= Seen while looking at nightly crash data - crashes started using 20170413030227 build: http://bit.ly/2pbBhxo Possible regression window based on Build ID: https://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=f40e24f40b4c4556944c762d4764eace261297f5&tochange=819a666afddc804b6099ee1b3cff3a0fdf35ec15 Bug 1349699? ni on billm
Any chance you could look at this David? It's an assertion where the compositor thread shuts down before the PCompositorBridgeParent protocol has closed (I had to click on the raw JSON file to find the ProtocolName field). I guess this user doesn't have a GPU process.
This is now the top browser crash on Nightly.
Created attachment 8859373 [details] [diff] [review] make DEBUG-only For now let's make this DEBUG-only. There's no reason to crash everybody.
Pushed by email@example.com: https://hg.mozilla.org/integration/mozilla-inbound/rev/edda32a96d46 Make MessageChannel::WillDestroyCurrentMessageLoop assertion DEBUG-only (r=mccr8)
Created attachment 8859919 [details] [diff] [review] fix Milan managed to accidentally reproduce this on try by enabling the GPU process in more places, and I think this is the likely cause. VideoBridgeParent and VsyncBridgeParent both run on the compositor thread, but don't retain a reference to CompositorThreadHolder. As long the holder is alive, the compositor thread will spin an event loop to wait for other threads to receive ActorDestroys. The fix is to just hold a ref in both of these actors.
If this is the problem, why would the protocol be reported as PCompositorBridgeParent?
Probably we're seeing two different bugs, then. By xpcom-shutdown time, it's too late to report crash metadata in the GPU process, so I had to guess the protocol by looking at the stack. This does appear to fix the issue Milan saw on try.
Pushed by firstname.lastname@example.org: https://hg.mozilla.org/integration/mozilla-inbound/rev/9fd7a385411f Fix a race condition between VideoBridge and Compositor thread shutdown. (bug 1356365, r=mattwoodrow)
No crashes after 20170418030220 so far, which doesn't really line up to when this landed. But the crash rate dropped quite a bit after 4/21.
I disabled the assertion on the 18th, so we need to re-enable it to see what was fixed.