linux-kernel - Re: [RFC PATCH 09/10] memcg: trylock stock for objcg

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Message-ID: <20250314114700.TiLB4FH0@linutronix.de>
Date: Fri, 14 Mar 2025 12:47:00 +0100
From: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To: Shakeel Butt <shakeel.butt@...ux.dev>
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>,
	Vlastimil Babka <vbabka@...e.cz>, linux-mm@...ck.org,
	cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
	Meta kernel team <kernel-team@...a.com>
Subject: Re: [RFC PATCH 09/10] memcg: trylock stock for objcg

On 2025-03-13 23:15:10 [-0700], Shakeel Butt wrote:
> To make objcg stock functions work without disabling irq, we need to
> convert those function to use localtry_trylock_irqsave() instead of
> localtry_lock_irqsave(). This patch for now just does the conversion and
> later patch will eliminate the irq disabling code.
> 
> Signed-off-by: Shakeel Butt <shakeel.butt@...ux.dev>
> ---
>  mm/memcontrol.c | 14 +++++++++++---
>  1 file changed, 11 insertions(+), 3 deletions(-)
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index c803d2f5e322..ba5d004049d3 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -2764,7 +2764,11 @@ static void mod_objcg_state(struct obj_cgroup *objcg, struct pglist_data *pgdat,
>  	unsigned long flags;
>  	int *bytes;
>  
> -	localtry_lock_irqsave(&memcg_stock.stock_lock, flags);
> +	if (!localtry_trylock_irqsave(&memcg_stock.stock_lock, flags)) {

Don't you need to change the of memcg_stock.stock_lock? Didn't we
introduce an explicit different type for this trylock feature?

> +		__mod_objcg_mlstate(objcg, pgdat, idx, nr);
> +		return;
> +	}
> +
>  	stock = this_cpu_ptr(&memcg_stock);
>  
>  	/*

Sebastian