linux-kernel - Re: [PATCH 7/9] memcg: use __mod_memcg_state in drain_obj

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Message-ID: <Z9jIxxllVwFSLYeL@google.com>
Date: Tue, 18 Mar 2025 01:13:43 +0000
From: Roman Gushchin <roman.gushchin@...ux.dev>
To: Shakeel Butt <shakeel.butt@...ux.dev>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
	Johannes Weiner <hannes@...xchg.org>,
	Michal Hocko <mhocko@...nel.org>,
	Muchun Song <muchun.song@...ux.dev>,
	Vlastimil Babka <vbabka@...e.cz>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	linux-mm@...ck.org, cgroups@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Meta kernel team <kernel-team@...a.com>
Subject: Re: [PATCH 7/9] memcg: use __mod_memcg_state in drain_obj_stock

On Sat, Mar 15, 2025 at 10:49:28AM -0700, Shakeel Butt wrote:
> For non-PREEMPT_RT kernels, drain_obj_stock() is always called with irq
> disabled, so we can use __mod_memcg_state() instead of
> mod_memcg_state(). For PREEMPT_RT, we need to add memcg_stats_[un]lock
> in __mod_memcg_state().
> 
> Signed-off-by: Shakeel Butt <shakeel.butt@...ux.dev>
> Reviewed-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
> ---
>  mm/memcontrol.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 3c4de384b5a0..dfe9c2eb7816 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -707,10 +707,12 @@ void __mod_memcg_state(struct mem_cgroup *memcg, enum memcg_stat_item idx,
>  	if (WARN_ONCE(BAD_STAT_IDX(i), "%s: missing stat item %d\n", __func__, idx))
>  		return;
>  
> +	memcg_stats_lock();
>  	__this_cpu_add(memcg->vmstats_percpu->state[i], val);
>  	val = memcg_state_val_in_pages(idx, val);
>  	memcg_rstat_updated(memcg, val);
>  	trace_mod_memcg_state(memcg, idx, val);
> +	memcg_stats_unlock();
>  }
>  
>  #ifdef CONFIG_MEMCG_V1
> @@ -2845,7 +2847,7 @@ static void drain_obj_stock(struct memcg_stock_pcp *stock)

VM_WARN_ON_IRQS_ENABLED() ?

Reviewed-by: Roman Gushchin <roman.gushchin@...ux.dev>