Messages in this thread | | | Date | Fri, 7 Apr 2023 16:49:09 +0200 | From | Frederic Weisbecker <> | Subject | Re: WARNING in timer_wait_running |
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On Fri, Apr 07, 2023 at 09:46:20PM +0800, Hillf Danton wrote: > On 5 Apr 2023 23:07:24 +0200 Marco Elver <elver@google.com> > > On Mon, Aug 31, 2020 at 10:07AM -0700, syzbot wrote: > > > Hello, > > > > > > syzbot found the following issue on: > > > > > > HEAD commit: 1127b219 Merge tag 'fallthrough-fixes-5.9-rc3' of git://gi.. > > > git tree: upstream > > > console output: https://syzkaller.appspot.com/x/log.txt?x=1501768e900000 > > > kernel config: https://syzkaller.appspot.com/x/.config?x=978db74cb30aa994 > > > dashboard link: https://syzkaller.appspot.com/bug?extid=3b14b2ed9b3d06dcaa07 > > > > Dashboard has recent reports (also below) and reproducer (also attached). > > My 2c, with PREEMPT_RT enabled it simply waits by taking timer->it_lock. > > --- upstream/kernel/time/posix-cpu-timers.c > +++ y/kernel/time/posix-cpu-timers.c > @@ -1613,6 +1613,21 @@ static int thread_cpu_timer_create(struc > return posix_cpu_timer_create(timer); > } > > +static void posix_cpu_timer_wait_running(struct k_itimer *timer) > +{ > +#ifdef CONFIG_PREEMPT_RT > + int stop = 0; > + > + while (!stop) { > + spin_lock(&timer->it_lock); > + stop = timer->it.cpu.firing == 0; > + spin_unlock(&timer->it_lock); > + }
No, because there is a whole lot of preemptible area with timer->it_lock not held between the time ctmr->firing is set to 1, and the actual handling of that timer that holds the lock.
So no priority inheritance in that case.
There has to be a lock between the time it is set to 1 and the handling of the timer.
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