Messages in this thread | | | Date | Tue, 10 Dec 2013 11:55:06 -0800 | Subject | Re: process 'stuck' at exit. | From | Linus Torvalds <> |
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On Tue, Dec 10, 2013 at 11:18 AM, Thomas Gleixner <tglx@linutronix.de> wrote: > > So this is pretty unlikely. The retry requires: > > get_futex_value_locked() == EFAULT; > > Now we drop the hash bucket locks and do: > > get_user(); > > And if that get_user() faults again, we bail out.
I think you need to look closer.
We have at least also that "futex_proxy_trylock_atomic() returns -EAGAIN" case. Which triggers at some exit condition. Another thread in the same group, perhaps never completing the exit because it's waiting for this one? I dunno, I didn't look any closer (but this does make me think "Hey, we should add Oleg to the Cc too", since PF_EXITING is involved).. So maybe there is some situation where that EAGAIN will keep happening, forever..
Now, I'm *not* saying that that is it. It's quite possible/likely some other loop, but I do have to say that it sure isn't _obvious_. And that whole EAGAIN return case is quite deep and special, so ...
Linus
PS: Oleg - the whole thread is on lkml. Ping me if you need more context.
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