linux-kernel - Re: [PATCH RFC] mm: slub: fix flush_cpu_slab()/__free

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Date:   Tue, 30 Aug 2022 21:03:11 +0200
From:   Maurizio Lombardi <mlombard@...hat.com>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:     Vlastimil Babka <vbabka@...e.cz>, linux-mm <linux-mm@...ck.org>,
        David Rientjes <rientjes@...gle.com>,
        Pekka Enberg <penberg@...nel.org>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>, tglx@...utronix.de
Subject: Re: [PATCH RFC] mm: slub: fix flush_cpu_slab()/__free_slab()
 invocations in task context.

út 30. 8. 2022 v 20:59 odesílatel Sebastian Andrzej Siewior
<bigeasy@...utronix.de> napsal:
>
> On 2022-08-30 17:48:06 [+0200], Maurizio Lombardi wrote:
> > Hmm, this is not good indeed. I guess I should have used for_each_online_cpu()
> > instead of on_each_cpu_cond().
>
> But you must not invoked that function cross-CPU since the code expects
> to access the per-CPU variables always from the local-CPU.

Ok, thanks for the clarification.

>
> > >
> > > Couldn't we instead use a workqueue with that WQ_MEM_RECLAIM bit? It may
> > > reclaim memory after all ;)
> >
> > That should also fix it, do you think it would be ok to allocate a workqueue in
> > in kmem_cache_init() ?
>
> I guess so. There is probably none that is already available.
>

Will test it and submit a patch soon.

Thanks,
Maurizio