1157392 - TSan: data race dom/plugins/ipc/PluginModuleParent.cpp:499 PluginModuleChromeParent::LoadModule

Status: RESOLVED WONTFIX

(Core Graveyard :: Plug-ins, defect)

Description

[Nathan Froyd [:froydnj]]

Attachment: plugin-race.txt

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

* Specific information about this bug

These stacks look very strange.  There's no UniquePtr accesses on the lines given in PluginModuleParent.cpp, so I *think* we must be complaining about something related to the PluginProcessParent::Launch call around here:

http://mxr.mozilla.org/mozilla-central/source/dom/plugins/ipc/PluginModuleParent.cpp#486

But that doesn't explain to me how TSan thinks we're racing on UniquePtr instances, which really shouldn't be shared across threads.

* 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

[Kris Wright :KrisWright]

Plugin code will be removed in bug 1677160.