From: Mel Gorman <mgorman@suse.de>
To: Weijie Yang <weijie.yang@samsung.com>
Cc: 'Andrew Morton' <akpm@linux-foundation.org>,
'Johannes Weiner' <hannes@cmpxchg.org>,
'Rik van Riel' <riel@redhat.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
'Weijie Yang' <weijie.yang.kh@gmail.com>
Subject: Re: [PATCH] mm: page_alloc: place zone id check before VM_BUG_ON_PAGE check
Date: Tue, 9 Dec 2014 09:59:22 +0000 [thread overview]
Message-ID: <20141209095922.GB21903@suse.de> (raw)
In-Reply-To: <000001d01383$8e0f1120$aa2d3360$%yang@samsung.com>
On Tue, Dec 09, 2014 at 03:40:35PM +0800, Weijie Yang wrote:
> If the free page and its buddy has different zone id, the current
> zone->lock cann't prevent buddy page getting allocated, this could
> trigger VM_BUG_ON_PAGE in a very tiny chance:
>
Under what circumstances can a buddy page be allocated without the
zone->lock? Any parallel allocation from that zone that takes place will
be from the per-cpu allocator and should not be affected by this. Have
you actually hit this race?
--
Mel Gorman
SUSE Labs
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WARNING: multiple messages have this Message-ID (diff)
From: Mel Gorman <mgorman@suse.de>
To: Weijie Yang <weijie.yang@samsung.com>
Cc: "'Andrew Morton'" <akpm@linux-foundation.org>,
"'Johannes Weiner'" <hannes@cmpxchg.org>,
"'Rik van Riel'" <riel@redhat.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
"'Weijie Yang'" <weijie.yang.kh@gmail.com>
Subject: Re: [PATCH] mm: page_alloc: place zone id check before VM_BUG_ON_PAGE check
Date: Tue, 9 Dec 2014 09:59:22 +0000 [thread overview]
Message-ID: <20141209095922.GB21903@suse.de> (raw)
In-Reply-To: <000001d01383$8e0f1120$aa2d3360$%yang@samsung.com>
On Tue, Dec 09, 2014 at 03:40:35PM +0800, Weijie Yang wrote:
> If the free page and its buddy has different zone id, the current
> zone->lock cann't prevent buddy page getting allocated, this could
> trigger VM_BUG_ON_PAGE in a very tiny chance:
>
Under what circumstances can a buddy page be allocated without the
zone->lock? Any parallel allocation from that zone that takes place will
be from the per-cpu allocator and should not be affected by this. Have
you actually hit this race?
--
Mel Gorman
SUSE Labs
next prev parent reply other threads:[~2014-12-09 9:59 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-12-09 7:40 [PATCH] mm: page_alloc: place zone id check before VM_BUG_ON_PAGE check Weijie Yang
2014-12-09 7:40 ` Weijie Yang
2014-12-09 9:59 ` Mel Gorman [this message]
2014-12-09 9:59 ` Mel Gorman
2014-12-10 13:38 ` Weijie Yang
2014-12-10 13:38 ` Weijie Yang
2014-12-10 14:03 ` Mel Gorman
2014-12-10 14:03 ` Mel Gorman
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