Messages in this thread |  | | Date | Sun, 26 Oct 2014 15:29:06 +0100 (CET) | From | Thomas Gleixner <> | Subject | Re: [PATCH] futex: fix a race condition between REQUEUE_PI and task death |
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On Sat, 25 Oct 2014, Brian Silverman wrote: > On Sat, 25 Oct 2014, Thomas Gleixner wrote: > > > > pi_state_free and exit_pi_state_list both clean up futex_pi_state's. > > > exit_pi_state_list takes the hb lock first, and most callers of > > > pi_state_free do too. requeue_pi didn't, which causes lots of problems. > > > > "causes lots of problems" is not really a good explanation of the root > > cause. That wants a proper description of the race, i.e. > > > > CPU 0 CPU 1 > > ... .... > > > > I'm surely someone who is familiar with that code, but it took me > > quite some time to understand whats going on. The casual reader will > > just go into brain spiral mode and give up. > > Thinking about it again, I'm no longer so sure that exit_pi_state_list is the > only place that it can race against. However, I did catch that one with a > particularly lucky crashdump, so I know it _can_ happen there. Is just > giving an example for that good?
Sure. That immediately makes clear whats going on.
Thanks,
tglx
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