linux-kernel - Re: [PATCH] Introduce ActivePid: in /proc/self/status (v2, was Vpid:)

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Message-ID: <20110616131821.GA21230@redhat.com>
Date:	Thu, 16 Jun 2011 15:18:21 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Greg Kurz <gkurz@...ibm.com>
Cc:	Louis Rilling <Louis.Rilling@...labs.com>,
	linux-kernel@...r.kernel.org, ebiederm@...ssion.com,
	containers@...ts.osdl.org, akpm@...ux-foundation.org,
	xemul@...nvz.org
Subject: Re: [PATCH] Introduce ActivePid: in /proc/self/status (v2, was
	Vpid:)

On 06/16, Greg Kurz wrote:
>
> Ok. You're right, the RCU grace period is just what I need to ensure I
> won't dereference a stale pointer. So I don't even have to bother with
> ->siglock and just check pid_alive() before peeking into pid->numbers.

Yes, but you don't really need pid_alive(). Just read ->pids[].pid and
check it is !NULL before dereferencing. Also, we already have 2 pid_alive()
checks, this is ugly. You can consolidate this code.

Oleg.

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