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Subject: Re: [PATCH 11/18] coredump: make coredump_wait wait for mma_sem for
 write killable
To: Michal Hocko <mhocko@kernel.org>, LKML <linux-kernel@vger.kernel.org>
References: <1456752417-9626-1-git-send-email-mhocko@kernel.org>
 <1456752417-9626-12-git-send-email-mhocko@kernel.org>
 <56E2ACE7.50008@suse.cz>
Cc: Andrew Morton <akpm@linux-foundation.org>, linux-mm@kvack.org,
        Alex Deucher <alexander.deucher@amd.com>,
        Alex Thorlton <athorlton@sgi.com>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Andy Lutomirski <luto@amacapital.net>,
        Benjamin LaHaise <bcrl@kvack.org>,
        =?UTF-8?Q?Christian_K=c3=b6nig?= <christian.koenig@amd.com>,
        Daniel Vetter <daniel.vetter@intel.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        David Airlie <airlied@linux.ie>, Davidlohr Bueso <dave@stgolabs.net>,
        David Rientjes <rientjes@google.com>,
        "H . Peter Anvin" <hpa@zytor.com>, Hugh Dickins <hughd@google.com>,
        Ingo Molnar <mingo@kernel.org>, Johannes Weiner <hannes@cmpxchg.org>,
        "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
        Konstantin Khlebnikov <koct9i@gmail.com>, linux-arch@vger.kernel.org,
        Mel Gorman <mgorman@suse.de>, Oleg Nesterov <oleg@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Petr Cermak <petrcermak@chromium.org>,
        Thomas Gleixner <tglx@linutronix.de>, Michal Hocko <mhocko@suse.com>
From: Vlastimil Babka <vbabka@suse.cz>
Message-ID: <56E2B1E9.90201@suse.cz>
Date: Fri, 11 Mar 2016 12:54:17 +0100
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On 03/11/2016 12:32 PM, Vlastimil Babka wrote:
> On 02/29/2016 02:26 PM, Michal Hocko wrote:
>> From: Michal Hocko <mhocko@suse.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@redhat.com>
>> Signed-off-by: Michal Hocko <mhocko@suse.com>
>
> Acked-by: Vlastimil Babka <vbabka@suse.cz>

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