Re: [patch] futex: PI state locking fix

[Chuck Ebbert]

Ingo Molnar wrote:
> Subject: [patch] futex: PI state locking fix
> From: Ingo Molnar <mingo@xxxxxxx>
> 
> testing of -rt by IBM uncovered a locking bug in wake_futex_pi(): the PI 
> state needs to be locked before we access it.
> 
> this patch has been tested in -rt. Must-have for v2.6.21.
> 

Does that fix this:

https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=224262

[<c043f3d7>] rt_mutex_next_owner+0x2f/0x40
    kernel/rt_mutex_common.c:rt_mutex_top_waiter():74:
        BUG_ON(w->lock != lock);
[<c043ecfc>] do_futex+0x94d/0xbe3
     inlined: futex_unlock_pi()
     inlined: wake_futex_pi()
     kernel/futex.c:wake_futex_pi():569:
        new_owner = rt_mutex_next_owner(&pi_state->pi_mutex);
[<c043f0af>] sys_futex+0x11d/0x130
[<c040404b>] syscall_call+0x7/0xb


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