1898108 - Intermittent SUMMARY: ThreadSanitizer: data race /builds/worker/workspace/obj-build/dist/include/nsTArray.h:2694:23 in AppendElementInternal<nsTArrayInfallibleAllocator, mozilla::dom::WorkerRunnable *const &>

Status: RESOLVED FIXED

(Core :: DOM: Workers, defect)

Description

Filed by: nfay [at] mozilla.com
Parsed log: https://treeherder.mozilla.org/logviewer?job_id=459081084&repo=autoland
Full log: https://firefox-ci-tc.services.mozilla.com/api/queue/v1/task/WrQxWxyLS-m8zf5GZDUfrg/runs/0/artifacts/public/logs/live_backing.log

---

TEST-START | devtools/client/webconsole/test/browser/browser_console_webconsole_private_browsing.js
...
GECKO(18176) | WARNING: ThreadSanitizer: data race (pid=18176)
GECKO(18176) |   Write of size 4 at 0x726c0024a860 by main thread (mutexes: write M0):
GECKO(18176) |     #0 AppendElementInternal<nsTArrayInfallibleAllocator, mozilla::dom::WorkerRunnable *const &> /builds/worker/workspace/obj-build/dist/include/nsTArray.h:2694:23 (libxul.so+0x7737c3c) (BuildId: d66feaf756a054140232f420cf187b11369c938e)
GECKO(18176) |     #1 AppendElement<mozilla::dom::WorkerRunnable *const &> /builds/worker/workspace/obj-build/dist/include/nsTArray.h:2832:24 (libxul.so+0x7737c3c)
GECKO(18176) |     #2 Push /builds/worker/workspace/obj-build/dist/include/mozilla/dom/workerinternals/Queue.h:37:14 (libxul.so+0x7737c3c)
GECKO(18176) |     #3 Push /builds/worker/workspace/obj-build/dist/include/mozilla/dom/workerinternals/Queue.h:116:5 (libxul.so+0x7737c3c)
GECKO(18176) |     #4 mozilla::dom::WorkerPrivate::DispatchDebuggerRunnable(already_AddRefed<mozilla::dom::WorkerRunnable>) /builds/worker/checkouts/gecko/dom/workers/WorkerPrivate.cpp:1770:18 (libxul.so+0x7737c3c)
...
GECKO(18176) |   Previous read of size 4 at 0x726c0024a860 by thread T398:
GECKO(18176) |     #0 Length /builds/worker/workspace/obj-build/dist/include/nsTArray.h:397:43 (libxul.so+0x774645d) (BuildId: d66feaf756a054140232f420cf187b11369c938e)
GECKO(18176) |     #1 IsEmpty /builds/worker/workspace/obj-build/dist/include/nsTArray.h:400:33 (libxul.so+0x774645d)
GECKO(18176) |     #2 IsEmpty /builds/worker/workspace/obj-build/dist/include/mozilla/dom/workerinternals/Queue.h:33:23 (libxul.so+0x774645d)
GECKO(18176) |     #3 IsEmpty /builds/worker/workspace/obj-build/dist/include/mozilla/dom/workerinternals/Queue.h:111:47 (libxul.so+0x774645d)
GECKO(18176) |     #4 mozilla::dom::WorkerPrivate::InterruptCallback(JSContext*) /builds/worker/checkouts/gecko/dom/workers/WorkerPrivate.cpp:3976:34 (libxul.so+0x774645d)
GECKO(18176) |     #5 mozilla::dom::workerinternals::(anonymous namespace)::InterruptCallback(JSContext*) /builds/worker/checkouts/gecko/dom/workers/RuntimeService.cpp:473:33 (libxul.so+0x772879c) (BuildId: d66feaf756a054140232f420cf187b11369c938e)

Comment 1

[Andrew McCreight [:mccr8]]

Attachment: full TSan report

Here's the full TSan log. It looks like this is a race on WorkerPrivate::mDebuggerQueue.

Comment 2

[Andrew McCreight [:mccr8]]

This looks at least in the ballpark of bug 1821250, which landed recently.

Comment 3

[Alexandre Poirot [:ochameau]]

This is about:

• mDebuggerQueue.IsEmpty() done from WorkerPrivate::InterruptCallback
  which isn't guarded by any mutex
  https://searchfox.org/mozilla-central/rev/55944eaee1e358b5443eaedc8adcd37e3fd23fd3/dom/workers/WorkerPrivate.cpp#3976

versus

• mDebuggerQueue.Push(runnable.forget().take()); done from WorkerPrivate::DispatchDebuggerRunnable
  which is quarded by mMutex
  https://searchfox.org/mozilla-central/rev/55944eaee1e358b5443eaedc8adcd37e3fd23fd3/dom/workers/WorkerPrivate.cpp#1770

Should we simply guard the isEmpty call behind mMutex?

Comment 4

[Eden Chuang[:edenchuang]]

Attachment: Bug 1898108 - Making WorkerPrivate::mDebuggerQueue accesses protected by WorkerPrivate::mMutex. r=#dom-worker-reviewers

Comment 5

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/06aacf2f4ea6
Making WorkerPrivate::mDebuggerQueue accesses protected by WorkerPrivate::mMutex. r=dom-worker-reviewers,asuth

Comment 6

[Donal Meehan [:dmeehan]]

https://hg.mozilla.org/mozilla-central/rev/06aacf2f4ea6