linux-kernel - Re: [PATCH 17/18] drm/radeon: make radeon_mn_get wait for mmap

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Message-ID: <56E2E3D7.2060404@suse.cz>
Date:	Fri, 11 Mar 2016 16:27:19 +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 17/18] drm/radeon: make radeon_mn_get wait for mmap_sem
 killable

On 02/29/2016 02:26 PM, Michal Hocko wrote:
> From: Michal Hocko <mhocko@...e.com>
>
> radeon_mn_get which is called during ioct path relies 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: Alex Deucher <alexander.deucher@....com>
> Cc: "Christian König" <christian.koenig@....com>
> Cc: David Airlie <airlied@...ux.ie>
> Signed-off-by: Michal Hocko <mhocko@...e.com>

Acked-by: Vlastimil Babka <vbabka@...e.cz>

> ---
>   drivers/gpu/drm/radeon/radeon_mn.c | 4 +++-
>   1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/radeon/radeon_mn.c b/drivers/gpu/drm/radeon/radeon_mn.c
> index eef006c48584..896f2cf51e4e 100644
> --- a/drivers/gpu/drm/radeon/radeon_mn.c
> +++ b/drivers/gpu/drm/radeon/radeon_mn.c
> @@ -186,7 +186,9 @@ static struct radeon_mn *radeon_mn_get(struct radeon_device *rdev)
>   	struct radeon_mn *rmn;
>   	int r;
>
> -	down_write(&mm->mmap_sem);
> +	if (down_write_killable(&mm->mmap_sem))
> +		return ERR_PTR(-EINTR);
> +
>   	mutex_lock(&rdev->mn_lock);
>
>   	hash_for_each_possible(rdev->mn_hash, rmn, node, (unsigned long)mm)
>