linux-kernel - Re: [PATCH 11/18] coredump: make coredump_wait wait for mma

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Message-ID: <56E2B1E9.90201@suse.cz>
Date:	Fri, 11 Mar 2016 12:54:17 +0100
From:	Vlastimil Babka <vbabka@...e.cz>
To:	Michal Hocko <mhocko@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	Alex Deucher <alexander.deucher@....com>,
	Alex Thorlton <athorlton@....com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Andy Lutomirski <luto@...capital.net>,
	Benjamin LaHaise <bcrl@...ck.org>,
	Christian König <christian.koenig@....com>,
	Daniel Vetter <daniel.vetter@...el.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	David Airlie <airlied@...ux.ie>,
	Davidlohr Bueso <dave@...olabs.net>,
	David Rientjes <rientjes@...gle.com>,
	"H . Peter Anvin" <hpa@...or.com>, Hugh Dickins <hughd@...gle.com>,
	Ingo Molnar <mingo@...nel.org>,
	Johannes Weiner <hannes@...xchg.org>,
	"Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
	Konstantin Khlebnikov <koct9i@...il.com>,
	linux-arch@...r.kernel.org, Mel Gorman <mgorman@...e.de>,
	Oleg Nesterov <oleg@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Petr Cermak <petrcermak@...omium.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Michal Hocko <mhocko@...e.com>
Subject: Re: [PATCH 11/18] coredump: make coredump_wait wait for mma_sem for
 write killable

On 03/11/2016 12:32 PM, Vlastimil Babka wrote:
> On 02/29/2016 02:26 PM, Michal Hocko wrote:
>> From: Michal Hocko <mhocko@...e.com>
>>
>> coredump_wait waits for mmap_sem for write currently which can
>> prevent oom_reaper to reclaim the oom victims address space
>> asynchronously because that requires mmap_sem for read. This might
>> happen if the oom victim is multi threaded and some thread(s) is
>> holding mmap_sem for read (e.g. page fault) and it is stuck in
>> the page allocator while other thread(s) reached coredump_wait
>> already.
>>
>> This patch simply uses down_write_killable and bails out with EINTR
>> if the lock got interrupted by the fatal signal. do_coredump will
>> return right away and do_group_exit will take care to zap the whole
>> thread group.
>>
>> Cc: Oleg Nesterov <oleg@...hat.com>
>> Signed-off-by: Michal Hocko <mhocko@...e.com>
>
> Acked-by: Vlastimil Babka <vbabka@...e.cz>

Forgot to point out typo in Subject which makes it hard to grep for mmap_sem