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: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <000000000000eaacf005ca975d1a@google.com>
2021-08-30 10:58 ` [syzbot] INFO: rcu detected stall in syscall_exit_to_user_mode Dmitry Vyukov
[not found] ` <20210831074532.2255-1-hdanton@sina.com>
[not found] ` <20210914123726.4219-1-hdanton@sina.com>
[not found] ` <87v933b3wf.ffs@tglx>
[not found] ` <CACT4Y+Yd3pEfZhRUQS9ymW+sQZ4O58Dz714xSqoZvdKa_9s2oQ@mail.gmail.com>
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=87k0jib2wd.ffs@tglx \
--to=tglx@linutronix.de \
--cc=dvyukov@google.com \
--cc=hdanton@sina.com \
--cc=johannes.berg@intel.com \
--cc=kasan-dev@googlegroups.com \
--cc=kvalo@codeaurora.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-wireless@vger.kernel.org \
--cc=paulmck@kernel.org \
--cc=peterz@infradead.org \
--cc=syzbot+0e964fad69a9c462bc1e@syzkaller.appspotmail.com \
--cc=syzkaller-bugs@googlegroups.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox