1137002 - Fix data races in ImageLib related to off-main-thread OnDataAvailable

Status: RESOLVED FIXED

(Core :: Graphics: ImageLib, defect)

Description

[Seth Fowler [:seth] [:s2h]]

We're seeing multiple TSan bugs (which are blocked by this bug) that suggest that we're accessing imgRequest fields from multiple threads in an unsynchronized way. The current bug reports involve mImage and mProgressTracker, but I want to be sure that everything we're doing is safe (especially since we have some crashes in this area of the code that are currently unexplained).

As far as I'm aware, imgRequest::OnDataAvailable is the only method we're calling off-main-thread. (Well, that and the methods that it calls transitively.) So this bug boils down to making sure that all the state that OnDataAvailable touches is threadsafe.

I think there are really a few different sub-issues here, so let's treat this as a metabug.

Comment 1

[Seth Fowler [:seth] [:s2h]]

This should be ready to resolve, but I'd like to wait for verification that ASAN doesn't report any more warnings in this code.

Comment 2

[Seth Fowler [:seth] [:s2h]]

OK, I think we're finally ready to resolve this. Nathan, please reopen (or file a new bug) if you hit any further TSan issues in this area of the code.