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Date:   Tue, 21 Nov 2023 01:29:56 +0000
From:   Mark Brown <broonie@kernel.org>
To:     Chengming Zhou <chengming.zhou@linux.dev>
Cc:     vbabka@suse.cz, cl@linux.com, penberg@kernel.org,
        rientjes@google.com, iamjoonsoo.kim@lge.com,
        akpm@linux-foundation.org, roman.gushchin@linux.dev,
        42.hyeyoo@gmail.com, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org,
        Chengming Zhou <zhouchengming@bytedance.com>
Subject: Re: [PATCH v5 6/9] slub: Delay freezing of partial slabs
Message-ID: <ZVwIFNdABN1b+qWC@finisterre.sirena.org.uk>
References: <20231102032330.1036151-1-chengming.zhou@linux.dev>
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 <4f3bc1bd-ea87-465d-b58a-0ed57b15187b@sirena.org.uk>
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On Tue, Nov 21, 2023 at 08:58:40AM +0800, Chengming Zhou wrote:
> On 2023/11/21 02:49, Mark Brown wrote:
> > On Thu, Nov 02, 2023 at 03:23:27AM +0000, chengming.zhou@linux.dev wrot=
e:

> > When we see problems we see RCU stalls while logging in, for example:

> > [   46.453323] rcu: INFO: rcu_sched detected stalls on CPUs/tasks:
> > [   46.459361] rcu: 	3-...0: (1 GPs behind) idle=3Ddef4/1/0x40000000 so=
ftirq=3D1304/1304 fqs=3D951
> > [   46.467669] rcu: 	(detected by 0, t=3D2103 jiffies, g=3D1161, q=3D49=
9 ncpus=3D4)
> > [   46.474472] Sending NMI from CPU 0 to CPUs 3:

> IIUC, here should print the backtrace of CPU 3, right? It looks like CPU =
3 is the cause,
> but we couldn't see what it's doing from the log.

AIUI yes, but it looks like we've just completely lost the CPU - there's
more attempts to talk to it visible in the log:

> > A full log for that run can be seen at:
> >=20
> >    https://validation.linaro.org/scheduler/job/4017095

but none of them appear to cause CPU 3 to respond.  Note that 32 bit ARM
is just using a regular IPI rather than something that's actually a NMI
so this isn't hugely out of the ordinary, I'd guess it's stuck with
interrupts masked.

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