I finally managed to catch this bug in debugger. After I closed Firefox window there were two threads consuming CPU so I printed their stacktraces. I won't stop process for one day so someone could gather more information by writing me commands to run. (I'm using Firefox 28)
** Attachment added: "firefox-log.txt" https://bugs.launchpad.net/ubuntu/+source/firefox/+bug/1266509/+attachment/4033911/+files/firefox-log.txt -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1266509 Title: Firefox takes all available CPU power occasionally, and can't quit To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/firefox/+bug/1266509/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs