From: Dmitry Vyukov <dvyukov@google.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Hillf Danton <hdanton@sina.com>,
syzbot <syzbot+0e964fad69a9c462bc1e@syzkaller.appspotmail.com>,
linux-kernel@vger.kernel.org, paulmck@kernel.org,
syzkaller-bugs@googlegroups.com,
Peter Zijlstra <peterz@infradead.org>,
kasan-dev <kasan-dev@googlegroups.com>,
Johannes Berg <johannes.berg@intel.com>,
Kalle Valo <kvalo@codeaurora.org>,
linux-wireless@vger.kernel.org
Subject: Re: [syzbot] INFO: rcu detected stall in syscall_exit_to_user_mode
Date: Thu, 16 Sep 2021 11:24:33 +0200 [thread overview]
Message-ID: <CACT4Y+ZCRiwobf0rGUoMiUEi=6Eoxvvgxxv-c+AhH=7U6M3LXQ@mail.gmail.com> (raw)
In-Reply-To: <87k0jib2wd.ffs@tglx>
On Wed, 15 Sept 2021 at 11:32, Thomas Gleixner <tglx@linutronix.de> wrote:
>
> On Wed, Sep 15 2021 at 11:14, Dmitry Vyukov wrote:
> > On Wed, 15 Sept 2021 at 10:57, Thomas Gleixner <tglx@linutronix.de> wrote:
> >> That made me actually look at that mac80211_hwsim callback again.
> >>
> >> hrtimer_forward(&data->beacon_timer, hrtimer_get_expires(timer),
> >> ns_to_ktime(bcn_int * NSEC_PER_USEC));
> >>
> >> So what this does is really wrong because it tries to schedule the timer
> >> on the theoretical periodic timeline. Which goes really south once the
> >> timer is late or the callback execution took longer than the
> >> period. Hypervisors scheduling out a VCPU at the wrong place will do
> >> that for you nicely.
> >
> > Nice!
> >
> > You mentioned that hrtimer_run_queues() may not return. Does it mean
> > that it can just loop executing the same re-armed callback again and
> > again? Maybe then the debug check condition should be that
> > hrtimer_run_queues() runs the same callback more than N times w/o
> > returning?
>
> Something like that.
I've filed https://bugzilla.kernel.org/show_bug.cgi?id=214429 so that
it's not lost. Thanks.
prev parent reply other threads:[~2021-09-16 9:25 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-28 4:52 [syzbot] INFO: rcu detected stall in syscall_exit_to_user_mode syzbot
2021-08-30 10:58 ` Dmitry Vyukov
[not found] ` <20210831074532.2255-1-hdanton@sina.com>
2021-09-13 10:28 ` Thomas Gleixner
[not found] ` <20210914123726.4219-1-hdanton@sina.com>
2021-09-14 14:58 ` Thomas Gleixner
2021-09-14 18:00 ` Dmitry Vyukov
2021-09-14 18:31 ` Paul E. McKenney
2021-09-15 9:36 ` Thomas Gleixner
2021-09-15 8:57 ` Thomas Gleixner
2021-09-15 9:14 ` Dmitry Vyukov
2021-09-15 9:32 ` Thomas Gleixner
2021-09-16 9:24 ` Dmitry Vyukov [this message]
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