Messages in this thread | | | Date | Fri, 14 Apr 2017 07:41:54 -0700 | From | Tony Lindgren <> | Subject | Re: [PATCH] futex: Fix hrtimer oops in futex_lock_pi() |
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* Tony Lindgren <tony@atomide.com> [170414 07:28]: > * Peter Zijlstra <peterz@infradead.org> [170414 07:25]: > > 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. > > Oh OK thanks. It seems to be missing in Linux next though.
Oh it was just committed, I see it now in tip after git fetch. So should be heading into nex soon.
Tony
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