linux-kernel - Re: [PATCH v5 6/9] slub: Delay freezing of partial slabs

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Message-ID: <ZVwIFNdABN1b+qWC@finisterre.sirena.org.uk>
Date:   Tue, 21 Nov 2023 01:29:56 +0000
From:   Mark Brown <broonie@...nel.org>
To:     Chengming Zhou <chengming.zhou@...ux.dev>
Cc:     vbabka@...e.cz, cl@...ux.com, penberg@...nel.org,
        rientjes@...gle.com, iamjoonsoo.kim@....com,
        akpm@...ux-foundation.org, roman.gushchin@...ux.dev,
        42.hyeyoo@...il.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        Chengming Zhou <zhouchengming@...edance.com>
Subject: Re: [PATCH v5 6/9] slub: Delay freezing of partial slabs

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@...ux.dev wrote:

> > 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=def4/1/0x40000000 softirq=1304/1304 fqs=951
> > [   46.467669] rcu: 	(detected by 0, t=2103 jiffies, g=1161, q=499 ncpus=4)
> > [   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:
> > 
> >    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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