1204043 - TSan: data race netwerk/base/nsSocketTransportService2.cpp:880 Run (race on mServeMultipleEventsPerPollIter)

Status: RESOLVED FIXED

(Core :: Networking, defect)

Description

[Nathan Froyd [:froydnj]]

Attachment: TSan stack trace

The attached logfile shows a thread/data race detected by TSan (ThreadSanitizer).

* Specific information about this bug

Like bug 1204042, this is another race where we're reading something on the socket thread but that is getting written on the main thread.

It looks like this pref was added in bug 1131557; I assume the pref was there in case we needed to quickly back out the new behavior.  But the new behavior has had multiple releases of bake time...can we just remove the pref entirely?

If we can't remove the pref, I guess we could make this an Atomic<> member...

* General information about TSan, data races, etc.

Typically, races reported by TSan are not false positives, but it is possible that the race is benign. Even in this case though, we should try to come up with a fix unless this would cause unacceptable performance issues. Also note that seemingly benign races can possibly be harmful (also depending on the compiler and the architecture) [1][2].

If the bug cannot be fixed, then this bug should be used to either make a compile-time annotation for blacklisting or add an entry to the runtime blacklist.

[1] http://software.intel.com/en-us/blogs/2013/01/06/benign-data-races-what-could-possibly-go-wrong
[2] _How to miscompile programs with "benign" data races_: https://www.usenix.org/legacy/events/hotpar11/tech/final_files/Boehm.pdf

Comment 1

[Patrick McManus [:mcmanus]]

I think this can probably be removed now. to dragana for comment and patch.

Comment 2

[Dragana Damjanovic [:dragana]]

We can remove the pref.

Comment 3

[Dragana Damjanovic [:dragana]]

https://treeherder.mozilla.org/#/jobs?repo=try&revision=c60235ca2af9

Comment 4

[Dragana Damjanovic [:dragana]]

Attachment: bug_1204043.patch

Comment 5

[Carsten Book [:Tomcat]]

Hi, this failed to apply:

renamed 1204043 -> bug_1204043.patch
applying bug_1204043.patch
patching file netwerk/base/nsSocketTransportService2.h
Hunk #1 FAILED at 230
1 out of 1 hunks FAILED -- saving rejects to file netwerk/base/nsSocketTransportService2.h.rej
patch failed, unable to continue (try -v)
patch failed, rejects left in working directory
errors during apply, please fix and refresh bug_1204043.patch

maybe this needs a rebase ?

Comment 6

[Dragana Damjanovic [:dragana]]

Attachment: bug_1204043.patch

rebased

Comment 7

[Pulsebot]

https://hg.mozilla.org/integration/mozilla-inbound/rev/689f55b551e6

Comment 8

[Wes Kocher (:KWierso) (Not reading bugmail; email directly if needed)]

https://hg.mozilla.org/mozilla-central/rev/689f55b551e6