linux-kernel - Re: [PATCH 09/18] ipc, shm: make shmem attach/detach wait for mmap

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Date:	Wed, 9 Mar 2016 11:16:52 +0100
From:	Michal Hocko <mhocko@...nel.org>
To:	Davidlohr Bueso <dave@...olabs.net>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	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 K?nig <christian.koenig@....com>,
	Daniel Vetter <daniel.vetter@...el.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	David Airlie <airlied@...ux.ie>,
	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>
Subject: Re: [PATCH 09/18] ipc, shm: make shmem attach/detach wait for
 mmap_sem killable

On Tue 08-03-16 11:15:50, Davidlohr Bueso wrote:
> On Mon, 29 Feb 2016, Michal Hocko wrote:
> 
> >From: Michal Hocko <mhocko@...e.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@...olabs.net>
> >Cc: Hugh Dickins <hughd@...gle.com>
> >Signed-off-by: Michal Hocko <mhocko@...e.com>
> 
> I have no objection to this perse, just one comment below.
> 
> Acked-by: Davidlohr Bueso <dave@...olabs.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