linux-kernel - Re: [PATCH] audit: wait_for_auditd() should use TASK

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Message-Id: <20130529145933.6e02f8379cf20b9c7ef30977@linux-foundation.org>
Date:	Wed, 29 May 2013 14:59:33 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Al Viro <viro@...iv.linux.org.uk>,
	Guy Streeter <streeter@...hat.com>,
	Eric Paris <eparis@...hat.com>,
	David Woodhouse <dwmw2@...radead.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] audit: wait_for_auditd() should use
 TASK_UNINTERRUPTIBLE

On Fri, 24 May 2013 19:39:25 +0200 Oleg Nesterov <oleg@...hat.com> wrote:

> audit_log_start() does wait_for_auditd() in a loop until
> audit_backlog_wait_time passes or audit_skb_queue has a room.
> 
> If signal_pending() is true this becomes a busy-wait loop,
> schedule() in TASK_INTERRUPTIBLE won't block.

And that's game over for a uniprocessor non-preempt machine, yes?

> Reported-by: Guy Streeter <streeter@...hat.com>

And what did Guy report?  "that looks screwy"?  "my machine locked up"?

> @@ -1056,7 +1056,7 @@ static inline void audit_get_stamp(struc
>  static void wait_for_auditd(unsigned long sleep_time)
>  {
>  	DECLARE_WAITQUEUE(wait, current);
> -	set_current_state(TASK_INTERRUPTIBLE);
> +	set_current_state(TASK_UNINTERRUPTIBLE);
>  	add_wait_queue(&audit_backlog_wait, &wait);
>  
>  	if (audit_backlog_limit &&
--
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