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From: Thomas Gleixner <tglx@linutronix.de>
To: Marco Elver <elver@google.com>,
	Naresh Kamboju <naresh.kamboju@linaro.org>
Cc: open list <linux-kernel@vger.kernel.org>,
	kasan-dev <kasan-dev@googlegroups.com>,
	rcu@vger.kernel.org, lkft-triage@lists.linaro.org,
	Peter Zijlstra <peterz@infradead.org>,
	"Paul E. McKenney" <paulmck@kernel.org>,
	Ingo Molnar <mingo@kernel.org>,
	fweisbec@gmail.com, Arnd Bergmann <arnd@arndb.de>
Subject: Re: BUG: KCSAN: data-race in tick_nohz_next_event / tick_nohz_stop_tick
Date: Sun, 06 Dec 2020 00:47:13 +0100	[thread overview]
Message-ID: <87eek395oe.fsf@nanos.tec.linutronix.de> (raw)
In-Reply-To: <87wnxw86bv.fsf@nanos.tec.linutronix.de>

On Sat, Dec 05 2020 at 19:18, Thomas Gleixner wrote:
> On Fri, Dec 04 2020 at 20:53, Marco Elver wrote:
> It might be useful to find the actual variable, data member or whatever
> which is involved in the various reports and if there is a match then
> the reports could be aggregated. The 3 patterns here are not even the
> complete possible picture.
>
> So if you sum them up: 58 + 148 + 205 instances then their weight
> becomes more significant as well.

I just looked into the moderation queue and picked stuff which I'm
familiar with from the subject line.

There are quite some reports which have a different trigger scenario,
but are all related to the same issue.

  https://syzkaller.appspot.com/bug?id=f5a5ed5b2b6c3e92bc1a9dadc934c44ee3ba4ec5
  https://syzkaller.appspot.com/bug?id=36fc4ad4cac8b8fc8a40713f38818488faa9e9f4

are just variations of the same problem timer_base->running_timer being
set to NULL without holding the base lock. Safe, but insanely hard to
explain why :)

Next:

  https://syzkaller.appspot.com/bug?id=e613fc2458de1c8a544738baf46286a99e8e7460
  https://syzkaller.appspot.com/bug?id=55bc81ed3b2f620f64fa6209000f40ace4469bc0
  https://syzkaller.appspot.com/bug?id=972894de81731fc8f62b8220e7cd5153d3e0d383
  .....

That's just the ones which caught my eye and all are related to
task->flags usage. There are tons more judging from the subject
lines.

So you really want to look at them as classes of problems and not as
individual scenarios.

Thanks,

        tglx



  reply	other threads:[~2020-12-05 23:48 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-12-04 19:03 Naresh Kamboju
2020-12-04 19:53 ` Marco Elver
2020-12-05 18:18   ` Thomas Gleixner
2020-12-05 23:47     ` Thomas Gleixner [this message]
2020-12-07 12:23       ` Marco Elver

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