* Tony Lindgren <[email protected]> [170414 07:28]: > * Peter Zijlstra <[email protected]> [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/[email protected] > > > > 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
