Here's a link of a push : https://treeherder.mozilla.org/#/jobs?repo=try&revision=92b9646d31a6&filter-resultStatus=testfailed&filter-resultStatus=busted&filter-resultStatus=exception&filter-classifiedState=unclassified&filter-searchStr=xp These, failures were obtained while bisecting another directory, dom/media/test. 00:55:31 WARNING - TEST-UNEXPECTED-FAIL | dom/media/webaudio/test/test_waveShaperInvalidLengthCurve.html | application terminated with exit code 1 00:55:31 INFO - runtests.py | Application ran for: 0:01:24.374000 00:55:31 INFO - zombiecheck | Reading PID log: c:\docume~1\cltbld~1.t-x\locals~1\temp\tmpo0bntqpidlog 00:55:44 INFO - mozcrash Saved minidump as C:\slave\test\build\blobber_upload_dir\76f7f54f-aca8-489b-8551-dc250d1c9f30.dmp 00:55:44 INFO - mozcrash Saved app info as C:\slave\test\build\blobber_upload_dir\76f7f54f-aca8-489b-8551-dc250d1c9f30.extra 00:55:44 WARNING - PROCESS-CRASH | dom/media/webaudio/test/test_waveShaperInvalidLengthCurve.html | application crashed [@ mozilla::AssertNotAlreadyCached]

Don't really know what's going on here, maybe padenot who mentored me on this bug will. The interesting part of the log is the following: 00:55:30 INFO - Attempt to add a bool pref cache for preference 'dom.audiochannel.mutedByDefault' at address '06C6F630'was made. However, a pref was already cached at this address. 00:55:31 INFO - Assertion failure: false (Should not have an existing pref cache for this address), at c:/builds/moz2_slave/try-w32-d-00000000000000000000/build/src/modules/libpref/Preferences.cpp:216 00:55:31 INFO - #01: mozilla::Preferences::AddBoolVarCache(bool *,char const *,bool) [modules/libpref/Preferences.cpp:1745] 00:55:31 INFO - #02: mozilla::dom::AudioChannelService::AudioChannelService() [dom/audiochannel/AudioChannelService.cpp:227] 00:55:31 INFO - #03: mozilla::dom::AudioChannelService::GetOrCreate() [dom/audiochannel/AudioChannelService.cpp:170] 00:55:31 INFO - #04: mozilla::dom::AudioChannelAgent::NotifyStoppedPlaying(unsigned int) [dom/audiochannel/AudioChannelAgent.cpp:159] 00:55:31 INFO - #05: mozilla::dom::AudioDestinationNode::DestroyAudioChannelAgent() [dom/media/webaudio/AudioDestinationNode.cpp:391] 00:55:31 INFO - #06: mozilla::dom::AudioNode::cycleCollection::Unlink(void *) [dom/media/webaudio/AudioNode.cpp:25] 00:55:31 INFO - #07: mozilla::dom::AudioDestinationNode::cycleCollection::Unlink(void *) [dom/media/webaudio/AudioDestinationNode.cpp:313] 00:55:31 INFO - #08: nsCycleCollector::CollectWhite() [xpcom/base/nsCycleCollector.cpp:3276] 00:55:31 INFO - #09: nsCycleCollector::Collect(ccType,js::SliceBudget &,nsICycleCollectorListener *,bool) [xpcom/base/nsCycleCollector.cpp:3630] 00:55:31 INFO - #10: nsCycleCollector::ShutdownCollect() [xpcom/base/nsCycleCollector.cpp:3548] 00:55:31 INFO - #11: nsCycleCollector_shutdown() [xpcom/base/nsCycleCollector.cpp:4164] 00:55:31 INFO - #12: mozilla::ShutdownXPCOM(nsIServiceManager *) [xpcom/build/XPCOMInit.cpp:952] 00:55:31 INFO - #13: ScopedXPCOMStartup::~ScopedXPCOMStartup() [toolkit/xre/nsAppRunner.cpp:1498] 00:55:31 INFO - #14: mozilla::DefaultDelete<ScopedXPCOMStartup>::operator()(ScopedXPCOMStartup *) [mfbt/UniquePtr.h:490] 00:55:31 INFO - #15: XREMain::XRE_main(int,char * * const,nsXREAppData const *) [toolkit/xre/nsAppRunner.cpp:4416] 00:55:31 INFO - #16: XRE_main [toolkit/xre/nsAppRunner.cpp:4478] 00:55:31 INFO - #17: do_main [browser/app/nsBrowserApp.cpp:212] 00:55:31 INFO - #18: NS_internal_main(int,char * *) [browser/app/nsBrowserApp.cpp:399] 00:55:31 INFO - #19: wmain [toolkit/xre/nsWindowsWMain.cpp:138] 00:55:31 INFO - #20: __tmainCRTStartup [f:/dd/vctools/crt/crtw32/startup/crt0.c:255] 00:55:31 INFO - #21: kernel32 + 0x17067 00:55:31 INFO - TEST-INFO | Main app process: exit 1 see also https://dxr.mozilla.org/mozilla-central/source/dom/audiochannel/AudioChannelService.cpp#231-232

I'm not clear either, but some things to think about: I guess it is not desirable to create the AudioChannelService during shutdown. Not sure, but I wonder whether it would be practical to call DestroyAudioChannelAgent() earlier than Unlink(), because it wouldn't be unlinked if it were still playing.