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From: Hillf Danton <hdanton@sina.com>
To: Mel Gorman <mgorman@techsingularity.net>
Cc: Nicolas Saenz Julienne <nsaenzju@redhat.com>,
	Marcelo Tosatti <mtosatti@redhat.com>,
	Vlastimil Babka <vbabka@suse.cz>,
	Michal Hocko <mhocko@kernel.org>,
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	Linux-MM <linux-mm@kvack.org>
Subject: Re: [PATCH 5/6] mm/page_alloc: Protect PCP lists with a spinlock
Date: Wed, 20 Apr 2022 22:02:14 +0800
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On Wed, 20 Apr 2022 10:59:05 +0100 Mel Gorman wrote:
>  void drain_zone_pages(struct zone *zone, struct per_cpu_pages *pcp)
>  {
> -	unsigned long flags;
>  	int to_drain, batch;
>  
> -	local_lock_irqsave(&pagesets.lock, flags);
>  	batch = READ_ONCE(pcp->batch);
>  	to_drain = min(pcp->count, batch);
> -	if (to_drain > 0)
> +	if (to_drain > 0) {
> +		unsigned long flags;
> +
> +		/* free_pcppages_bulk expects IRQs disabled for zone->lock */
> +		local_irq_save(flags);
> +
> +		spin_lock(&pcp->lock);

Nit, spin_lock_irqsave() instead.

>  		free_pcppages_bulk(zone, to_drain, pcp, 0);
> -	local_unlock_irqrestore(&pagesets.lock, flags);
> +		spin_unlock(&pcp->lock);
> +
> +		local_irq_restore(flags);
> +	}
>  }
>  #endif

Hillf