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Subject: Re: [rfc/patch] mm/slub: restore/expand unfreeze_partials() local
 exclusion scope
To:     Mike Galbraith <efault@gmx.de>,
        Thomas Gleixner <tglx@linutronix.de>,
        LKML <linux-kernel@vger.kernel.org>
Cc:     linux-rt-users@vger.kernel.org,
        Mel Gorman <mgorman@techsingularity.net>,
        Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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From:   Vlastimil Babka <vbabka@suse.cz>
Message-ID: <ea7694ef-f3b5-a075-8c65-f211515e2716@suse.cz>
Date:   Thu, 29 Jul 2021 11:51:10 +0200
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On 7/29/21 6:51 AM, Mike Galbraith wrote:
> On Wed, 2021-07-28 at 18:59 +0200, Vlastimil Babka wrote:
>> On 7/27/21 6:09 AM, Mike Galbraith wrote:
>> > On Mon, 2021-07-26 at 23:26 +0200, Vlastimil Babka wrote:
>> > > On 7/26/21 7:00 PM, Mike Galbraith wrote:
>> > > >
>> > > > Why not do something like the below?...
>> > >
>> > > Yep, sounds like a good approach, thanks. Percpu partial is not *the*
>> > > SLUB fast path, so it should be sufficient without the lockless cmpxchg
>> > > tricks. Will incorporate in updated series.
>>
>> The updated series incorporating hopefully all fixes from Mike and
>> bigeasy, and rebased to 5.14-rc3 (Thomas told me RT is moving to it), is
>> here:
>>
>> https://git.kernel.org/pub/scm/linux/kernel/git/vbabka/linux.git/log/?h=slub-local-lock-v3r0
> 
> I had to resurrect the hunk below to build with lockdep, but modulo
> dinky speedbump, the same RT testdrive that previously exploded was as
> entertainment free as such testing is supposed to be.

Ah forgot about that, I'll include it too. Thanks for testing!

> ---
>  mm/slub.c |    4 ++++
>  1 file changed, 4 insertions(+)
> 
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -2890,7 +2890,11 @@ static void *___slab_alloc(struct kmem_c
> 
>  load_freelist:
> 
> +#ifdef CONFIG_PREEMPT_RT
> +	lockdep_assert_held(this_cpu_ptr(&s->cpu_slab->lock.lock));
> +#else
>  	lockdep_assert_held(this_cpu_ptr(&s->cpu_slab->lock));
> +#endif
> 
>  	/*
>  	 * freelist is pointing to the list of objects to be used.
> 
>