I wrote a buggy patch that crashed JP, but these just showed up as timeouts in TBPL, which is deceptive, and makes the machine sit there for 5 minutes waiting for the timeout: https://tbpl.mozilla.org/?tree=Try&rev=f3122d33c773 Run locally, it shows this in the log: 0:08.41 Hit MOZ_CRASH() at /home/amccreight/icc/memory/mozjemalloc/jemalloc.c:1572 0:08.41 0:08.41 Program ./dist/bin/firefox-bin (pid = 12946) received signal 11. 0:08.41 Stack: ... (the stack isn't fully symbolicated, but that's probably a separate bug...) 0:08.41 Sleeping for 300 seconds. 0:08.41 Type 'gdb ./dist/bin/firefox-bin 12946' to attach your debugger to this thread.