Messages in this thread | | | Date | Fri, 14 Apr 2017 16:23:00 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH] futex: Fix hrtimer oops in futex_lock_pi() |
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On Fri, Apr 14, 2017 at 07:08:19AM -0700, Tony Lindgren wrote: > Commit cfafcd117da0 ("futex: Rework futex_lock_pi() to use > rt_mutex_*_proxy_lock()") caused a regression where things would > occasionally randomly oops when restarting X: > > Unable to handle kernel NULL pointer dereference at virtual address 00000000 > ... > Internal error: Oops: 80000005 [#1] SMP ARM > ... > PC is at 0x0 > LR is at __hrtimer_run_queues+0x138/0x58c > pc : [<00000000>] lr : [<c01c7884>] psr: 20000193 > ... > [<c01c7884>] (__hrtimer_run_queues) from [<c01c7f4c>] > (hrtimer_interrupt+0xbc/0x210) > [<c01c7f4c>] (hrtimer_interrupt) from [<c010fcfc>] > ... > > When this happens, the hrtimer is not properly initialized and it's > function is NULL. This happens because we now call hrtimer_start_expires() > in futex_lock_pi() for the timer initialized with hrtimer_init_on_stack(). > > To fix it, let's pair the hrtimer_start_expires() with hrtimer_cancel() > in the same function.
Already fixed:
https://lkml.kernel.org/r/tip-97181f9bd57405b879403763284537e27d46963d@git.kernel.org
Thanks for the patch though.
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