linux-kernel - Re: [PATCH v12 2/6] mm/vmstat: Use vmstat_dirty to track CPU-specific vmstat discrepancies

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Date:   Fri, 30 Dec 2022 14:21:32 +0100
From:   Frederic Weisbecker <frederic@...nel.org>
To:     Marcelo Tosatti <mtosatti@...hat.com>
Cc:     atomlin@...mlin.com, cl@...ux.com, tglx@...utronix.de,
        mingo@...nel.org, peterz@...radead.org, pauld@...hat.com,
        neelx@...hat.com, oleksandr@...alenko.name,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH v12 2/6] mm/vmstat: Use vmstat_dirty to track
 CPU-specific vmstat discrepancies

On Tue, Dec 27, 2022 at 09:11:39AM -0300, Marcelo Tosatti wrote:
> @@ -606,6 +608,7 @@ static inline void mod_zone_state(struct
>  
>  	if (z)
>  		zone_page_state_add(z, zone, item);
> +	vmstat_mark_dirty();
>  }
>  
>  void mod_zone_page_state(struct zone *zone, enum zone_stat_item item,
> @@ -674,6 +677,7 @@ static inline void mod_node_state(struct
>  
>  	if (z)
>  		node_page_state_add(z, pgdat, item);
> +	vmstat_mark_dirty();

Looking at this further, about the two above chunks, there is a risk to
mark the wrong CPU dirty because those functions are preemptible and rely
on this_cpu_cmpxchg() to deal with preemption.

Thanks.