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Subject: Re: [PATCH 10/10] oom: Make find_lock_task_mm() sparse-aware
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: Anton Vorontsov <anton.vorontsov@linaro.org>
Date: Sat, 24 Mar 2012 17:43:27 +0100
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Cc: Mike Frysinger <vapier@gentoo.org>,
 user-mode-linux-devel@lists.sourceforge.net, linux-sh@vger.kernel.org,
 Richard Weinberger <richard@nod.at>, linuxppc-dev@lists.ozlabs.org,
 Oleg Nesterov <oleg@redhat.com>,
 Linus Torvalds <torvalds@linux-foundation.org>, linux-kernel@vger.kernel.org,
 linux-mm@kvack.org, Paul Mundt <lethal@linux-sh.org>,
 John Stultz <john.stultz@linaro.org>,
 KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
 Russell King <linux@arm.linux.org.uk>,
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On Sat, 2012-03-24 at 20:21 +0400, Anton Vorontsov wrote:

> Just wonder how do you see the feature implemented?
>=20
> Something like this?
>=20
> #define __ret_cond_locked(l, c)	__attribute__((ret_cond_locked(l, c)))
> #define __ret_value		__attribute__((ret_value))
> #define __ret_locked_nonnull(l)	__ret_cond_locked(l, __ret_value);
>=20
> extern struct task_struct *find_lock_task_mm(struct task_struct *p)
> 	__ret_locked_nonnull(&__ret_value->alloc_lock);

Yeah, see the email I just CC'ed you on to linux-sparse.

Basically extend __attribute__((context())) to allow things similar to
what you proposed.