linux-kernel - Re: [PATCH 1/7] memcg: memcg_rstat_updated re-entrant safe against irqs

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Message-ID: <bnofgbnkkcgvybob7dt2bzti3bfsxwcaur5iobttyzxtfb7iue@oo6sj5pfjgud>
Date: Wed, 14 May 2025 09:39:15 -0700
From: Shakeel Butt <shakeel.butt@...ux.dev>
To: Vlastimil Babka <vbabka@...e.cz>
Cc: Andrew Morton <akpm@...ux-foundation.org>, 
	Johannes Weiner <hannes@...xchg.org>, Michal Hocko <mhocko@...nel.org>, 
	Roman Gushchin <roman.gushchin@...ux.dev>, Muchun Song <muchun.song@...ux.dev>, 
	Alexei Starovoitov <ast@...nel.org>, Sebastian Andrzej Siewior <bigeasy@...utronix.de>, 
	Harry Yoo <harry.yoo@...cle.com>, Yosry Ahmed <yosry.ahmed@...ux.dev>, bpf@...r.kernel.org, 
	linux-mm@...ck.org, cgroups@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Meta kernel team <kernel-team@...a.com>
Subject: Re: [PATCH 1/7] memcg: memcg_rstat_updated re-entrant safe against
 irqs

On Wed, May 14, 2025 at 11:50:16AM +0200, Vlastimil Babka wrote:
> On 5/14/25 07:08, Shakeel Butt wrote:
> > The function memcg_rstat_updated() is used to track the memcg stats
> > updates for optimizing the flushes. At the moment, it is not re-entrant
> > safe and the callers disabled irqs before calling. However to achieve
> > the goal of updating memcg stats without irqs, memcg_rstat_updated()
> > needs to be re-entrant safe against irqs.
> > 
> > This patch makes memcg_rstat_updated() re-entrant safe using this_cpu_*
> > ops. On archs with CONFIG_ARCH_HAS_NMI_SAFE_THIS_CPU_OPS, this patch is
> > also making memcg_rstat_updated() nmi safe.
> > 
> > Signed-off-by: Shakeel Butt <shakeel.butt@...ux.dev>
> 
> Reviewed-by: Vlastimil Babka <vbabka@...e.cz>
> 
> Some nits:
> 

Thanks Vlastimil. I will address your comments in v2 and Andrew asked me
to rebase over mm-new instead of next which I will do as well.