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

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Message-ID: <2b95af00-e4e6-4df7-7cd5-30b4f6980b09@vmware.com>
Date:   Tue, 4 Apr 2017 11:49:03 +0200
From:   Thomas Hellstrom <thellstrom@...are.com>
To:     Michal Hocko <mhocko@...nel.org>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>
CC:     <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 04/04/2017 11:41 AM, Michal Hocko wrote:
> 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...

Actually, this just mimics what the code was doing before, as it only
invoked
__purge_vmap_area_lazy() if the trylock succeeded.

/Thomas




>
>> ---
>>  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
>>