From: Peter Zijlstra <peterz@infradead.org>
To: "Paul E. McKenney" <paulmck@kernel.org>
Cc: tglx@linutronix.de, linux-kernel@vger.kernel.org,
valentin.schneider@arm.com, bristot@redhat.com,
frederic@kernel.org
Subject: Re: lockdep splat in v5.11-rc1 involving console_sem and rq locks
Date: Wed, 6 Jan 2021 16:44:21 +0100 [thread overview]
Message-ID: <X/Xa1fwplnZIOm+U@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20210106144621.GJ17086@paulmck-ThinkPad-P72>
On Wed, Jan 06, 2021 at 06:46:21AM -0800, Paul E. McKenney wrote:
> Huh. The WARN does not always generate the lockdep complaint. But
> fair enough.
Any printk()/WARN/BUG with rq lock held ought to generate that splat,
sometimes we die before we splat. The printk rewrite should eventually
fix that.
> > https://lkml.kernel.org/r/20201226025117.2770-1-jiangshanlai@gmail.com
>
> Thomas pointed me at this one a couple of weeks ago. Here is an
> additional fix for rcutorture: f67e04bb0695 ("torture: Break affinity
> of kthreads last running on outgoing CPU"). I am still getting WARNs
> and lockdep splats with both applied.
That patch looks racy, what avoids the task being shuffled right back
before the CPU goes offline?
> What would break if I made the code dump out a few entries in the
> runqueue if the warning triggered?
There was a patch around that did that, Valentin might remember where
that was.
next prev parent reply other threads:[~2021-01-06 15:45 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-05 22:01 lockdep splat in v5.11-rc1 involving console_sem and rq locks Paul E. McKenney
2021-01-06 9:52 ` Peter Zijlstra
2021-01-06 14:46 ` Paul E. McKenney
2021-01-06 15:44 ` Peter Zijlstra [this message]
2021-01-06 15:49 ` Valentin Schneider
2021-01-06 17:52 ` Paul E. McKenney
2021-01-11 14:42 ` Peter Zijlstra
2021-01-11 15:11 ` Paul E. McKenney
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