From: Corey Minyard <minyard@acm.org>
To: Juergen Gross <jgross@suse.com>
Cc: Ingo Molnar <mingo@kernel.org>,
"Paul E. McKenney" <paulmck@kernel.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: Possible reproduction of CSD locking issue
Date: Wed, 26 Jan 2022 09:31:17 -0600 [thread overview]
Message-ID: <20220126153117.GU34919@minyard.net> (raw)
In-Reply-To: <70245998-b99e-ebe7-e932-f8a1b46f6ac7@suse.com>
On Wed, Jan 26, 2022 at 03:51:36PM +0100, Juergen Gross wrote:
> On 26.01.22 14:56, Corey Minyard wrote:
> > On Wed, Jan 26, 2022 at 07:08:22AM +0100, Juergen Gross wrote:
snip..
> >
> > csd: cnt(63d8e1f): 0003->0037 queue
> > csd: cnt(63d8e20): 0003->0037 ipi
> > csd: cnt(63d8e21): 0003->0037 ping
> >
> > In __smp_call_single_queue_debug CPU 3 sends another message to
> > CPU 55 and sends an IPI. But there should be a pinged entry
> > after this.
> >
> > csd: cnt(63d8e22): 0003->0037 queue
> > csd: cnt(63d8e23): 0003->0037 noipi
>
> This is interesting. Those are 5 consecutive entries without any
> missing in between (see the counter values). Could it be that after
> the ping there was an interrupt and the code was re-entered for
> sending another IPI? This would clearly result in a hang as seen.
Since preempt is enabled, wouldn't it eventually come back to the first
thread and send the IPI? Unless CPU 3 is stuck in an interrupt or
interrupt storm.
-corey
next prev parent reply other threads:[~2022-01-26 15:31 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-25 18:27 Possible reproduction of CSD locking issue Corey Minyard
2022-01-25 18:53 ` Paul E. McKenney
2022-01-25 21:52 ` Corey Minyard
2022-01-25 22:51 ` Paul E. McKenney
2022-01-26 6:08 ` Juergen Gross
2022-01-26 13:56 ` Corey Minyard
2022-01-26 14:12 ` Corey Minyard
2022-01-26 14:51 ` Juergen Gross
2022-01-26 15:31 ` Corey Minyard [this message]
2022-01-26 15:34 ` Juergen Gross
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