linux-kernel - Re: [syzbot] INFO: rcu detected stall in syscall_exit_to_user

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Message-ID: <87mtogg475.ffs@tglx>
Date:   Mon, 13 Sep 2021 12:28:14 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Hillf Danton <hdanton@...a.com>, Dmitry Vyukov <dvyukov@...gle.com>
Cc:     syzbot <syzbot+0e964fad69a9c462bc1e@...kaller.appspotmail.com>,
        linux-kernel@...r.kernel.org, paulmck@...nel.org,
        syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] INFO: rcu detected stall in syscall_exit_to_user_mode

On Tue, Aug 31 2021 at 15:45, Hillf Danton wrote:
> On Mon, 30 Aug 2021 12:58:58 +0200 Dmitry Vyukov wrote:
>>>  ieee80211_iterate_active_interfaces_atomic+0x70/0x180 net/mac80211/util.c:829
>>>  mac80211_hwsim_beacon+0xd5/0x1a0 drivers/net/wireless/mac80211_hwsim.c:1861
>>>  __run_hrtimer kernel/time/hrtimer.c:1537 [inline]
>>>  __hrtimer_run_queues+0x609/0xe50 kernel/time/hrtimer.c:1601
>>>  hrtimer_run_softirq+0x17b/0x360 kernel/time/hrtimer.c:1618
>>>  __do_softirq+0x29b/0x9c2 kernel/softirq.c:558
>
> Add debug info only to help kasan catch the timer running longer than 2 ticks.
>
> Is it anything in the right direction, tglx?

Not really. As Dmitry pointed out this seems to be related to
mac80211_hwsim and if you look at the above stacktrace then how is
adding something to the timer wheel helpful?

Thanks,

        tglx