linux-kernel - Re: [PATCH 1/4] mm/vmalloc: allow to call vfree() in atomic context

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Date:   Tue, 4 Apr 2017 11:41:48 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Andrey Ryabinin <aryabinin@...tuozzo.com>
Cc:     Thomas Hellstrom <thellstrom@...are.com>,
        akpm@...ux-foundation.org, penguin-kernel@...ove.SAKURA.ne.jp,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org, hpa@...or.com,
        chris@...is-wilson.co.uk, hch@....de, mingo@...e.hu,
        jszhang@...vell.com, joelaf@...gle.com, joaodias@...gle.com,
        willy@...radead.org, tglx@...utronix.de, stable@...r.kernel.org
Subject: Re: [PATCH 1/4] mm/vmalloc: allow to call vfree() in atomic context

On Thu 30-03-17 17:48:39, Andrey Ryabinin wrote:
> From: Andrey Ryabinin <aryabinin@...tuozzo.com>
> Subject: mm/vmalloc: allow to call vfree() in atomic context fix
> 
> Don't spawn worker if we already purging.
> 
> Signed-off-by: Andrey Ryabinin <aryabinin@...tuozzo.com>

I would rather put this into a separate patch. Ideally with some numners
as this is an optimization...

> ---
>  mm/vmalloc.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index ea1b4ab..88168b8 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -737,7 +737,8 @@ static void free_vmap_area_noflush(struct vmap_area *va)
>  	/* After this point, we may free va at any time */
>  	llist_add(&va->purge_list, &vmap_purge_list);
>  
> -	if (unlikely(nr_lazy > lazy_max_pages()))
> +	if (unlikely(nr_lazy > lazy_max_pages()) &&
> +	    !mutex_is_locked(&vmap_purge_lock))
>  		schedule_work(&purge_vmap_work);
>  }
>  
> -- 
> 2.10.2
> 

-- 
Michal Hocko
SUSE Labs