linux-kernel - Re: [PATCH] prctl: return MCE process flags through pointer

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Message-Id: <20091223021807.abbd993e.akpm@linux-foundation.org>
Date:	Wed, 23 Dec 2009 02:18:07 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	"Smith, GeoffX" <geoffx.smith@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Michael Stone <michael@...top.org>,
	Arjan van de Ven <arjan@...radead.org>
Subject: Re: [PATCH] prctl: return MCE process flags through pointer

On Wed, 23 Dec 2009 10:52:23 +0100 Andi Kleen <andi@...stfloor.org> wrote:

> On Tue, Dec 22, 2009 at 05:34:24PM -0800, Andrew Morton wrote:
> > On Wed, 23 Dec 2009 02:14:51 +0100 Andi Kleen <andi@...stfloor.org> wrote:
> > 
> > > "Smith, GeoffX" <geoffx.smith@...el.com> writes:
> > > 
> > > > This patch fixes the semantics of prctl() option PR_MCE_KILL_GET 
> > > > to pass the return value through *arg2.
> > > >
> > > > With this change, the option now follows the same conventions as the
> > > > other "get" options added since 2.6.0, and also brings it into
> > > > conformance with the advice in chapter 16 of Documentation/CodingStyle.
> > > >
> > > > This prctl() option was only added within the last month, so there are
> > > > not any production applications to break.  This patch applies cleanly
> > > > to mainline and to 2.6.32.2 for backporting.
> > > 
> > > It breaks the test suite, the man pages, qemu and one slide deck at least.
> > > 
> > 
> > Should've got it right the first time.
> 
> To be honest it's not fully clear to me what is "wrong" with returning
> the return value with "return".

Just a convention thing.

> If there was a security bug or something maybe such a radical step
> as changing a published API would be justified, but for this I'm sceptical.

hm, OK, shrug.

Regarding "prctl: return timerslack through pointer": are there any
known users of PR_GET_TIMERSLACK yet?

Why are task_struct.timer_slack_ns and
task_struct.default_timer_slack_ns unsigned long, btw?  AFACIT we could
make them unsigned ints.

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