linux-kernel - Re: [rfc/patch] mm/slub: restore/expand unfreeze

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Message-ID: <76dedfc3-0497-1776-d006-486b9bfd88da@suse.cz>
Date:   Sun, 25 Jul 2021 16:16:42 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Mike Galbraith <efault@....de>,
        Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>
Cc:     linux-rt-users@...r.kernel.org,
        Mel Gorman <mgorman@...hsingularity.net>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Subject: Re: [rfc/patch] mm/slub: restore/expand unfreeze_partials() local
 exclusion scope

On 7/25/21 4:09 PM, Mike Galbraith wrote:
> On Sat, 2021-07-24 at 00:39 +0200, Vlastimil Babka wrote:
>>
>> If not, then I would expect this to work (I don't think they ever nest
>> in the opposite order, also lockdep should tell us instead of
>> -ENOBOOT?), but might be missing something...
> 
> Yeah, like #ifndef CONFIG_PREMPT_RT at the bottom of the loop that our
> useless damn eyeballs auto-correct instead of reporting :)

Well doh, good catch. Hope fixing that helps then?
I've so far convinced myself that the full patch will be needed - in my
theory the ->partial cmpxchg in put_cpu_partial() itself can race with
assignment in ___slab_alloc() in a way that will not cause crashes, but
will leak slab pages.

> 	-Mike
>