From: Thomas Gleixner <tglx@linutronix.de>
To: Hillf Danton <hdanton@sina.com>
Cc: syzbot <syzbot+ca740b95a16399ceb9a5@syzkaller.appspotmail.com>,
davem@davemloft.net, hchunhui@mail.ustc.edu.cn, hdanton@sina.com,
ja@ssi.bg, jmorris@namei.org, kuznet@ms2.inr.ac.ru,
linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
syzkaller-bugs@googlegroups.com, yoshfuji@linux-ipv6.org,
Johannes Berg <johannes.berg@intel.com>
Subject: Re: WARNING in hrtimer_forward
Date: Mon, 28 Sep 2020 20:35:58 +0200 [thread overview]
Message-ID: <87mu19kaup.fsf@nanos.tec.linutronix.de> (raw)
In-Reply-To: <20200928171137.16804-1-hdanton@sina.com>
On Tue, Sep 29 2020 at 01:11, Hillf Danton wrote:
> On Mon, 28 Sep 2020 18:13:42 +0200 Thomas Gleixner wrote:
>> So the timer was armed at some point and then the expiry which does the
>> forward races with the ioctl which starts the timer. Lack of
>> serialization or such ...
>
> To make syzbot happy, s/hrtimer_is_queued/hrtimer_active/ can close
> that race but this warning looks benign.
Why only make sysbot happy? It's clearly an issue and the warning is not
benign simply because forwarding a queued timer is an absolute NONO.
timers (both timer_list and hrtimer) need external synchronization.
> --- a/drivers/net/wireless/mac80211_hwsim.c
> +++ b/drivers/net/wireless/mac80211_hwsim.c
> @@ -1698,7 +1698,7 @@ static int mac80211_hwsim_config(struct
>
> if (!data->started || !data->beacon_int)
> hrtimer_cancel(&data->beacon_timer);
> - else if (!hrtimer_is_queued(&data->beacon_timer)) {
> + else if (!hrtimer_active(&data->beacon_timer)) {
> u64 tsf = mac80211_hwsim_get_tsf(hw, NULL);
> u32 bcn_int = data->beacon_int;
> u64 until_tbtt = bcn_int - do_div(tsf, bcn_int);
> @@ -1768,7 +1768,7 @@ static void mac80211_hwsim_bss_info_chan
> info->enable_beacon, info->beacon_int);
> vp->bcn_en = info->enable_beacon;
> if (data->started &&
> - !hrtimer_is_queued(&data->beacon_timer) &&
> + !hrtimer_active(&data->beacon_timer) &&
> info->enable_beacon) {
> u64 tsf, until_tbtt;
> u32 bcn_int;
Looks about right.
Thanks,
tglx
next prev parent reply other threads:[~2020-09-28 18:36 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-25 8:48 WARNING in hrtimer_forward syzbot
2020-09-27 0:38 ` syzbot
2020-09-27 14:29 ` syzbot
2020-09-28 16:13 ` Thomas Gleixner
[not found] ` <20200928171137.16804-1-hdanton@sina.com>
2020-09-28 18:35 ` Thomas Gleixner [this message]
2020-09-30 7:26 ` Dmitry Vyukov
[not found] ` <20200927080452.18340-1-hdanton@sina.com>
2020-09-28 14:18 ` Thomas Gleixner
2021-11-03 9:21 ` [syzbot] " syzbot
2021-12-04 10:19 ` Dmitry Vyukov
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