linux-kernel - Re: [PATCH 1/3] procfs: Export next

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Message-ID: <20120130204920.GA27812@oksana.dev.rtsoft.ru>
Date:	Tue, 31 Jan 2012 00:49:20 +0400
From:	Anton Vorontsov <anton.vorontsov@...aro.org>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Arve Hjønnevåg <arve@...roid.com>,
	KOSAKI Motohiro <kosaki.motohiro@...il.com>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	San Mehat <san@...gle.com>, Colin Cross <ccross@...roid.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	linux-kernel@...r.kernel.org, kernel-team@...roid.com,
	linaro-kernel@...ts.linaro.org
Subject: Re: [PATCH 1/3] procfs: Export next_tgid(), move it to kernel/pid.c

On Mon, Jan 30, 2012 at 02:43:12PM +0100, Oleg Nesterov wrote:
> On 01/30, Anton Vorontsov wrote:
> >
> > We'd like to use this function in the android low memory killer driver, so
> > let's export it.
> 
> I guess you mean 3/3.
> 
> If lowmem_shrink() can use next_tid() which is not really accurate,
> then why tou can't simply change it to use rcu_read_lock ?

Yes, in LMK driver we don't need to be accurate. I probably could use
rcu_read_lock, but the plan was in not holding any global locks (in
this case the rcu) at all, instead I'd like to hold just a reference
of the task, which the driver is analyzing at this time. Once we decide
(to kill or not to kill the task), we either send a signal (and drop
the reference) or just drop the reference.

Thanks,

-- 
Anton Vorontsov
Email: cbouatmailru@...il.com
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