601557 - imgRequestProxy requests in async_load_tests.js are too susceptible to garbage collection

Status: RESOLVED FIXED

(Core :: Graphics: ImageLib, defect)

Description

[Josh Matthews [:jdm]]

Applying the httpd.js GC patch from bug 508128 has exposed a problem in the tests in async_load_tests.js.  Since imgRequests only hold weak references to the proxies, the only strong ref comes from the |var req = loader.loadImageWithChannel(...)| lines.  With the 508128 patch, there's a race which httpd.js can win which initiates a GC before the various necko events occur.  Since the req variable is out of scope at this point, the proxy is destroyed and triggers the |NS_PRECONDITION(!mListener, "Someone forgot to properly cancel this request!");| assertion.  The attached testcase easily demonstrates this with 508128 applied - for me it consistently asserts in check-interactive and passes in check-one.

Comment 1

[Josh Matthews [:jdm]]

Attachment: Reduced testcase

Comment 2

[Josh Matthews [:jdm]]

The easiest fix is just to push each request onto a global array which retains them until the end of time.  I don't know if it's worth trying to find a more elegant solution.

Comment 3

[Josh Matthews [:jdm]]

Attachment: Retain requests to avoid early GC.

Like so.

Comment 4

[(no longer active)]

http://hg.mozilla.org/mozilla-central/rev/56e77ab3cb8d