From: Minchan Kim <minchan@kernel.org>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Mel Gorman <mgorman@techsingularity.net>,
Joonsoo Kim <iamjoonsoo.kim@lge.com>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
Sangseok Lee <sangseok.lee@lge.com>
Subject: Re: [PATCH 2/4] mm: prevent double decrease of nr_reserved_highatomic
Date: Fri, 7 Oct 2016 23:30:25 +0900 [thread overview]
Message-ID: <20161007143025.GB3060@bbox> (raw)
In-Reply-To: <6bcd7066-2748-8a96-4479-f85b18765948@suse.cz>
On Fri, Oct 07, 2016 at 02:44:15PM +0200, Vlastimil Babka wrote:
> On 10/07/2016 07:45 AM, Minchan Kim wrote:
> >There is race between page freeing and unreserved highatomic.
> >
> > CPU 0 CPU 1
> >
> > free_hot_cold_page
> > mt = get_pfnblock_migratetype
>
> so here mt == MIGRATE_HIGHATOMIC?
Yes.
>
> > set_pcppage_migratetype(page, mt)
> > unreserve_highatomic_pageblock
> > spin_lock_irqsave(&zone->lock)
> > move_freepages_block
> > set_pageblock_migratetype(page)
> > spin_unlock_irqrestore(&zone->lock)
> > free_pcppages_bulk
> > __free_one_page(mt) <- mt is stale
> >
> >By above race, a page on CPU 0 could go non-highorderatomic free list
> >since the pageblock's type is changed.
> >By that, unreserve logic of
> >highorderatomic can decrease reserved count on a same pageblock
> >several times and then it will make mismatch between
> >nr_reserved_highatomic and the number of reserved pageblock.
>
> Hmm I see.
>
> >So, this patch verifies whether the pageblock is highatomic or not
> >and decrease the count only if the pageblock is highatomic.
>
> Yeah I guess that's the easiest solution.
>
> >Signed-off-by: Minchan Kim <minchan@kernel.org>
>
> Acked-by: Vlastimil Babka <vbabka@suse.cz>
Thanks, Vlastimil.
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next prev parent reply other threads:[~2016-10-07 14:30 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-10-07 5:45 [PATCH 0/4] use up highorder free pages before OOM Minchan Kim
2016-10-07 5:45 ` [PATCH 1/4] mm: adjust reserved highatomic count Minchan Kim
2016-10-07 12:30 ` Vlastimil Babka
2016-10-07 14:29 ` Minchan Kim
2016-10-10 6:57 ` Vlastimil Babka
2016-10-11 4:19 ` Minchan Kim
2016-10-11 9:40 ` Vlastimil Babka
2016-10-12 5:36 ` Mel Gorman
2016-10-07 5:45 ` [PATCH 2/4] mm: prevent double decrease of nr_reserved_highatomic Minchan Kim
2016-10-07 12:44 ` Vlastimil Babka
2016-10-07 14:30 ` Minchan Kim [this message]
2016-10-12 5:36 ` Mel Gorman
2016-10-07 5:45 ` [PATCH 3/4] mm: unreserve highatomic free pages fully before OOM Minchan Kim
2016-10-07 9:09 ` Michal Hocko
2016-10-07 14:43 ` Minchan Kim
2016-10-10 7:41 ` Michal Hocko
2016-10-11 5:01 ` Minchan Kim
2016-10-11 6:50 ` Michal Hocko
2016-10-11 7:09 ` Minchan Kim
2016-10-11 7:26 ` Michal Hocko
2016-10-11 7:37 ` Minchan Kim
2016-10-11 8:01 ` Michal Hocko
2016-10-07 5:45 ` [PATCH 4/4] mm: skip to reserve pageblock crossed zone boundary for HIGHATOMIC Minchan Kim
2016-10-07 9:16 ` [PATCH 0/4] use up highorder free pages before OOM Michal Hocko
2016-10-07 15:04 ` Minchan Kim
2016-10-10 7:47 ` Michal Hocko
2016-10-11 5:06 ` Minchan Kim
2016-10-11 6:53 ` Michal Hocko
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