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

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Message-ID: <a28cc48d-3d6f-b4dd-10c2-a75d2e83ef14@virtuozzo.com>
Date:   Thu, 30 Mar 2017 17:48:39 +0300
From:   Andrey Ryabinin <aryabinin@...tuozzo.com>
To:     Thomas Hellstrom <thellstrom@...are.com>,
        <akpm@...ux-foundation.org>
CC:     <penguin-kernel@...ove.SAKURA.ne.jp>,
        <linux-kernel@...r.kernel.org>, <mhocko@...nel.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 03/30/2017 03:00 PM, Thomas Hellstrom wrote:

>>  
>>  	if (unlikely(nr_lazy > lazy_max_pages()))
>> -		try_purge_vmap_area_lazy();
> 
> Perhaps a slight optimization would be to schedule work iff
> !mutex_locked(&vmap_purge_lock) below?
> 

Makes sense, we don't need to spawn workers if we already purging.



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>
---
 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