This bug is for crash report bp-23883d4d-e11d-4e68-afc2-69bc00191007.

Seen while looking at release crash stats: https://bit.ly/35bS0CQ. Primarily a Windows crash that doesn't appear to have been in 68. It appears to have started in 20190819184224, which was b15 and continued into RC and release. So far we have over 2800 crashes on the 69 release.

Bug 1521477 had some of the same stack, but seems to have SpinEventLoop in it. Not sure if this is a signature change from that bug?

Here is the changeset from B15: https://hg.mozilla.org/releases/mozilla-beta/pushloghtml?fromchange=FIREFOX_69_0b14_RELEASE&tochange=66a12ddcf77c6a1548989ced39edf39af78deb80&full=1

Top 10 frames of crashing thread:

0 ntdll.dll NtWaitForAlertByThreadId 
1 ntdll.dll RtlSleepConditionVariableSRW 
2 kernelbase.dll SleepConditionVariableSRW 
3 mozglue.dll mozilla::detail::ConditionVariableImpl::wait mozglue/misc/ConditionVariable_windows.cpp:50
4 xul.dll mozilla::ThreadEventQueue<mozilla::PrioritizedEventQueue>::GetEvent xpcom/threads/ThreadEventQueue.cpp:153
5 xul.dll nsThread::ProcessNextEvent xpcom/threads/nsThread.cpp:1134
6 xul.dll NS_ProcessNextEvent xpcom/threads/nsThreadUtils.cpp:486
7 xul.dll nsresult mozilla::dom::StorageObserver::Observe dom/storage/StorageObserver.cpp:409
8 xul.dll nsObserverService::NotifyObservers xpcom/ds/nsObserverService.cpp:291
9 xul.dll nsXREDirProvider::DoShutdown toolkit/xre/nsXREDirProvider.cpp:1097

This shows up again in crash stats because LSNG has been disabled in late 69 beta cycle. See bug 1570644.

(In reply to Jan Varga [:janv] from comment #1)

This shows up again in crash stats because LSNG has been disabled in late 69 beta cycle. See bug 1570644.

Jan, can you just clarify that it will be fixed in 70 when LSNG ships?

Yeah, it will be fixed in 70 when LSNG ships. Sorry for not being clear about that.

So to recap again what happens here is that we:

• spin the event loop here expecting the shutdownRunnable to be dispatched
• the dispatch is checked by MOZ_ALWAYS_SUCCEEDS based on MOZ_ALWAYS_TRUE which translates to a diagnostic assert in nightly and early beta but nothing in release builds
• we do not see any diagnostic assert for dispatch failures in crash-stats because in nightly and early beta LSNG is enabled which makes us return earlier here
• thus we can still expect this to be healed once LSNG lands for all, see bug 1599979.

Since the crash volume is low (less than 15 per week), the severity is downgraded to S3. Feel free to change it back if you think the bug is still critical.

For more information, please visit auto_nag documentation.

(In reply to Jan Varga [:janv] from comment #3)

Yeah, it will be fixed in 70 when LSNG ships. Sorry for not being clear about that.

OK, thanks.