From: Thomas Gleixner <tglx@linutronix.de>
To: Dmitry Vyukov <dvyukov@google.com>
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: Wed, 15 Sep 2021 11:32:02 +0200 [thread overview]
Message-ID: <87k0jib2wd.ffs@tglx> (raw)
In-Reply-To: <CACT4Y+avKp8LCS8vBdaFLXFNcNiCq3vF-8K59o7c1oy86v-ADA@mail.gmail.com>
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.
next prev parent reply other threads:[~2021-09-15 9:32 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 [this message]
2021-09-16 9:24 ` Dmitry Vyukov
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