linux-kernel - Re: [PATCH v2 3/8] mm/vmstat: Use preempt_[dis|en]able

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Date:   Thu, 1 Sep 2022 16:41:09 +0200
From:   Michal Hocko <mhocko@...e.com>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:     linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Matthew Wilcox <willy@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org
Subject: Re: [PATCH v2 3/8] mm/vmstat: Use preempt_[dis|en]able_nested()

On Thu 25-08-22 18:41:26, Sebastian Andrzej Siewior wrote:
> From: Thomas Gleixner <tglx@...utronix.de>
> 
> Replace the open coded CONFIG_PREEMPT_RT conditional
> preempt_enable/disable() pairs with the new helper functions which hide
> the underlying implementation details.
> 
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: linux-mm@...ck.org
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
> Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>

Acked-by: Michal Hocko <mhocko@...e.com>
Thanks!

> ---
>  mm/vmstat.c | 36 ++++++++++++------------------------
>  1 file changed, 12 insertions(+), 24 deletions(-)
> 
> diff --git a/mm/vmstat.c b/mm/vmstat.c
> index 373d2730fcf21..d514fe7f90af0 100644
> --- a/mm/vmstat.c
> +++ b/mm/vmstat.c
> @@ -355,8 +355,7 @@ void __mod_zone_page_state(struct zone *zone, enum zone_stat_item item,
>  	 * CPU migrations and preemption potentially corrupts a counter so
>  	 * disable preemption.
>  	 */
> -	if (IS_ENABLED(CONFIG_PREEMPT_RT))
> -		preempt_disable();
> +	preempt_disable_nested();
>  
>  	x = delta + __this_cpu_read(*p);
>  
> @@ -368,8 +367,7 @@ void __mod_zone_page_state(struct zone *zone, enum zone_stat_item item,
>  	}
>  	__this_cpu_write(*p, x);
>  
> -	if (IS_ENABLED(CONFIG_PREEMPT_RT))
> -		preempt_enable();
> +	preempt_enable_nested();
>  }
>  EXPORT_SYMBOL(__mod_zone_page_state);
>  
> @@ -393,8 +391,7 @@ void __mod_node_page_state(struct pglist_data *pgdat, enum node_stat_item item,
>  	}
>  
>  	/* See __mod_node_page_state */
> -	if (IS_ENABLED(CONFIG_PREEMPT_RT))
> -		preempt_disable();
> +	preempt_disable_nested();
>  
>  	x = delta + __this_cpu_read(*p);
>  
> @@ -406,8 +403,7 @@ void __mod_node_page_state(struct pglist_data *pgdat, enum node_stat_item item,
>  	}
>  	__this_cpu_write(*p, x);
>  
> -	if (IS_ENABLED(CONFIG_PREEMPT_RT))
> -		preempt_enable();
> +	preempt_enable_nested();
>  }
>  EXPORT_SYMBOL(__mod_node_page_state);
>  
> @@ -441,8 +437,7 @@ void __inc_zone_state(struct zone *zone, enum zone_stat_item item)
>  	s8 v, t;
>  
>  	/* See __mod_node_page_state */
> -	if (IS_ENABLED(CONFIG_PREEMPT_RT))
> -		preempt_disable();
> +	preempt_disable_nested();
>  
>  	v = __this_cpu_inc_return(*p);
>  	t = __this_cpu_read(pcp->stat_threshold);
> @@ -453,8 +448,7 @@ void __inc_zone_state(struct zone *zone, enum zone_stat_item item)
>  		__this_cpu_write(*p, -overstep);
>  	}
>  
> -	if (IS_ENABLED(CONFIG_PREEMPT_RT))
> -		preempt_enable();
> +	preempt_enable_nested();
>  }
>  
>  void __inc_node_state(struct pglist_data *pgdat, enum node_stat_item item)
> @@ -466,8 +460,7 @@ void __inc_node_state(struct pglist_data *pgdat, enum node_stat_item item)
>  	VM_WARN_ON_ONCE(vmstat_item_in_bytes(item));
>  
>  	/* See __mod_node_page_state */
> -	if (IS_ENABLED(CONFIG_PREEMPT_RT))
> -		preempt_disable();
> +	preempt_disable_nested();
>  
>  	v = __this_cpu_inc_return(*p);
>  	t = __this_cpu_read(pcp->stat_threshold);
> @@ -478,8 +471,7 @@ void __inc_node_state(struct pglist_data *pgdat, enum node_stat_item item)
>  		__this_cpu_write(*p, -overstep);
>  	}
>  
> -	if (IS_ENABLED(CONFIG_PREEMPT_RT))
> -		preempt_enable();
> +	preempt_enable_nested();
>  }
>  
>  void __inc_zone_page_state(struct page *page, enum zone_stat_item item)
> @@ -501,8 +493,7 @@ void __dec_zone_state(struct zone *zone, enum zone_stat_item item)
>  	s8 v, t;
>  
>  	/* See __mod_node_page_state */
> -	if (IS_ENABLED(CONFIG_PREEMPT_RT))
> -		preempt_disable();
> +	preempt_disable_nested();
>  
>  	v = __this_cpu_dec_return(*p);
>  	t = __this_cpu_read(pcp->stat_threshold);
> @@ -513,8 +504,7 @@ void __dec_zone_state(struct zone *zone, enum zone_stat_item item)
>  		__this_cpu_write(*p, overstep);
>  	}
>  
> -	if (IS_ENABLED(CONFIG_PREEMPT_RT))
> -		preempt_enable();
> +	preempt_enable_nested();
>  }
>  
>  void __dec_node_state(struct pglist_data *pgdat, enum node_stat_item item)
> @@ -526,8 +516,7 @@ void __dec_node_state(struct pglist_data *pgdat, enum node_stat_item item)
>  	VM_WARN_ON_ONCE(vmstat_item_in_bytes(item));
>  
>  	/* See __mod_node_page_state */
> -	if (IS_ENABLED(CONFIG_PREEMPT_RT))
> -		preempt_disable();
> +	preempt_disable_nested();
>  
>  	v = __this_cpu_dec_return(*p);
>  	t = __this_cpu_read(pcp->stat_threshold);
> @@ -538,8 +527,7 @@ void __dec_node_state(struct pglist_data *pgdat, enum node_stat_item item)
>  		__this_cpu_write(*p, overstep);
>  	}
>  
> -	if (IS_ENABLED(CONFIG_PREEMPT_RT))
> -		preempt_enable();
> +	preempt_enable_nested();
>  }
>  
>  void __dec_zone_page_state(struct page *page, enum zone_stat_item item)
> -- 
> 2.37.2

-- 
Michal Hocko
SUSE Labs