linux-kernel - Re: [PATCH 14/18] prctl: make PR_SET_THP_DISABLE wait for mmap

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Date:	Fri, 11 Mar 2016 13:54:10 +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 14/18] prctl: make PR_SET_THP_DISABLE wait for mmap_sem
 killable

On 02/29/2016 02:26 PM, Michal Hocko wrote:
> From: Michal Hocko <mhocko@...e.com>
>
> PR_SET_THP_DISABLE requires 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 Thorlton <athorlton@....com>
> Signed-off-by: Michal Hocko <mhocko@...e.com>

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

> ---
>   kernel/sys.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/sys.c b/kernel/sys.c
> index cf8ba545c7d3..89d5be418157 100644
> --- a/kernel/sys.c
> +++ b/kernel/sys.c
> @@ -2246,7 +2246,8 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3,
>   	case PR_SET_THP_DISABLE:
>   		if (arg3 || arg4 || arg5)
>   			return -EINVAL;
> -		down_write(&me->mm->mmap_sem);
> +		if (down_write_killable(&me->mm->mmap_sem))
> +			return -EINTR;
>   		if (arg2)
>   			me->mm->def_flags |= VM_NOHUGEPAGE;
>   		else
>