linux-kernel - Re: [PATCH] mm: use in_atomic() in print_vma

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Date:   Thu, 2 Nov 2017 08:57:44 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Yang Shi <yang.s@...baba-inc.com>
Cc:     akpm@...ux-foundation.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: use in_atomic() in print_vma_addr()

On Thu 02-11-17 05:38:33, Yang Shi wrote:
> commit 3e51f3c4004c9b01f66da03214a3e206f5ed627b
> ("sched/preempt: Remove PREEMPT_ACTIVE unmasking off in_atomic()") makes
> in_atomic() just check the preempt count, so it is not necessary to use
> preempt_count() in print_vma_addr() any more. Replace preempt_count() to
> in_atomic() which is a generic API for checking atomic context.

But why? Is there some general work to get rid of the direct preempt_count
usage outside of the generic API?

> Signed-off-by: Yang Shi <yang.s@...baba-inc.com>
> ---
>  mm/memory.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/memory.c b/mm/memory.c
> index a728bed..19b684e 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -4460,7 +4460,7 @@ void print_vma_addr(char *prefix, unsigned long ip)
>  	 * Do not print if we are in atomic
>  	 * contexts (in exception stacks, etc.):
>  	 */
> -	if (preempt_count())
> +	if (in_atomic())
>  		return;
>  
>  	down_read(&mm->mmap_sem);
> -- 
> 1.8.3.1

-- 
Michal Hocko
SUSE Labs