[<prev] [next>] [<thread-prev] [day] [month] [year] [list]
Message-ID: <55588D1C.5060900@gmail.com>
Date: Sun, 17 May 2015 20:44:12 +0800
From: yalin <yalin.wang2010@...il.com>
To: Vladimir Davydov <vdavydov@...allels.com>
CC: Rik van Riel <riel@...hat.com>, Hugh Dickins <hughd@...gle.com>,
Christoph Lameter <cl@...ux.com>,
"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
Peter Zijlstra <peterz@...radead.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Minchan Kim <minchan@...nel.org>,
Johannes Weiner <hannes@...xchg.org>,
Michal Hocko <mhocko@...e.cz>,
Greg Thelen <gthelen@...gle.com>,
Michel Lespinasse <walken@...gle.com>,
David Rientjes <rientjes@...gle.com>,
Pavel Emelyanov <xemul@...allels.com>,
Cyrill Gorcunov <gorcunov@...nvz.org>, linux-mm@...ck.org,
linux-kernel@...r.kernel.org
Subject: Re: [RFC] rmap: fix "race" between do_wp_page and shrink_active_list
> On Mon, May 11, 2015 at 04:59:27PM +0800, yalin wang wrote:
>> i am confused about your analysis ,
>> for the race stack:
>>
>> CPU0 CPU1
>>
>> ---- ----
>>
>> do_wp_page shrink_active_list
>>
>> lock_page page_referenced
>>
>> PageAnon->yes, so skip trylock_page
>>
>> page_move_anon_rmap
>>
>> page->mapping = anon_vma
>>
>> rmap_walk
>>
>> PageAnon->no
>>
>> rmap_walk_file
>>
>> BUG
>>
>> page->mapping += PAGE_MAPPING_ANON
>>
>> the page should must change from PageAnon() to !PageAnon() when crash happened.
>> but page_move_anon_rmap() is doing change a page from !PageAnon()
>> (swapcache page) to PageAnon() ,
> A swapcache page is not necessarily !PageAnon. In do_wp_page() old_page
> *is* PageAnon. It may or may not be on the swapcache though, which does
> not really matter.
>
>> how does this race condition crash happened ?
> It never happened. It might theoretically happen due to a compiler
> "optimization" I described above.
i see,
Thanks for your explanation!
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists