Messages in this thread | | | Date | Thu, 19 Jul 2012 16:22:07 -0700 | From | Darren Hart <> | Subject | Re: 3.5-rc6 futex_wait_requeue_pi oops. |
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On 07/13/2012 11:54 AM, Dave Jones wrote: > On Fri, Jul 13, 2012 at 08:47:38PM +0200, Thomas Gleixner wrote: > > On Fri, 13 Jul 2012, Dave Jones wrote: > > > > > Looks like calling futex() with garbage makes things unhappy. > > > > WARN_ON(!&q.pi_state); > > pi_mutex = &q.pi_state->pi_mutex; > > ret = rt_mutex_finish_proxy_lock(pi_mutex, to, &rt_waiter, 1); > > debug_rt_mutex_free_waiter(&rt_waiter); > > > > So there is some weird way which causes q.pi_state = NULL. Dave, did > > you see the warning before the oops happened ? > > No, that didn't seem to trigger.
Well I don't have a fix yet, but I can explain this not triggering.
q is on the stack, so the ADDRESS for q.pi_state is never going to be NULL. However, properly instrumented, we do see this:
[ 23.621501] ---[ end trace 20bdfb44db182a17 ]--- [ 23.622425] q.pi_state @ (null) [ 23.623272] &q.pi_state @ ffff880185e2dca8 [ 23.624119] ------------[ cut here ]------------
Duh.
I'll add a fix to that WARN_ON in my futex-fixes branch along with the fix for the bug Dan found.
-- Darren Hart Intel Open Source Technology Center Yocto Project - Linux Kernel
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