"Browse..." file dialog leads to mutex-related deadlock

[Daniel Richard G.]

Binary package hint: firefox-3.0

This concerns firefox-3.0 3.0.13+nobinonly-0ubuntu0.9.04.1 in Jaunty.

I hit the "Attach file" button in a Web-mail page, which brings up a file-selection dialog. Normally, this works fine, but here, the window comes up, everything but the actual file list is painted, and then... the CPU is at 100%, and the browser sits unresponsive, not even repainting the window.

After a minute or two, I checked out what Firefox was doing by attaching with strace(1), and saw a flurry of futex() calls flying past. I captured a few seconds' worth of strace(1) output in a file (the log grew very fast), and figured I would "compress" it by running it through "uniq -c". The result is attached.

This bug is very difficult to reproduce---I've never run into it before, and I've attached a lot of files in that Web-mail client---and likely represents an unanticipated corner case.