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Date: Wed, 9 Mar 2016 11:16:52 +0100
From: Michal Hocko <mhocko@kernel.org>
Subject: Re: [PATCH 09/18] ipc, shm: make shmem attach/detach wait for
 mmap_sem killable
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To: Davidlohr Bueso <dave@stgolabs.net>
Cc: LKML <linux-kernel@vger.kernel.org>, 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>, Christian K?nig <christian.koenig@amd.com>, Daniel Vetter <daniel.vetter@intel.com>, Dave Hansen <dave.hansen@linux.intel.com>, David Airlie <airlied@linux.ie>, 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>
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On Tue 08-03-16 11:15:50, Davidlohr Bueso wrote:
> On Mon, 29 Feb 2016, Michal Hocko wrote:
> 
> >From: Michal Hocko <mhocko@suse.com>
> >
> >shmat and shmdt rely on mmap_sem for write. If the waiting task
> >gets killed by the oom killer it would block oom_reaper from
> >asynchronous address space reclaim and reduce the chances of timely
> >OOM resolving. Wait for the lock in the killable mode and return with
> >EINTR if the task got killed while waiting.
> >
> >Cc: Davidlohr Bueso <dave@stgolabs.net>
> >Cc: Hugh Dickins <hughd@google.com>
> >Signed-off-by: Michal Hocko <mhocko@suse.com>
> 
> I have no objection to this perse, just one comment below.
> 
> Acked-by: Davidlohr Bueso <dave@stgolabs.net>

Thanks!

[...]
> >-	down_write(&current->mm->mmap_sem);
> >+	if (down_write_killable(&current->mm->mmap_sem)) {
> >+		err = -EINVAL;
> >+		goto out_fput;
> >+	}
> 
> This should be EINTR, no?

Of course. Thanks for catching that.
-- 
Michal Hocko
SUSE Labs