linux-kernel - Re: [tip:core/urgent] rcu: avoid pointless blocked-task warnings

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Date:	Sat, 15 Jan 2011 15:28:57 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	linux-kernel@...r.kernel.org, mingo@...hat.com, hpa@...or.com,
	paul.mckenney@...aro.org, rmk+kernel@....linux.org.uk,
	weber@...science.de, paulmck@...ux.vnet.ibm.com, tglx@...utronix.de
Cc:	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:core/urgent] rcu: avoid pointless blocked-task warnings


* tip-bot for Paul E. McKenney <paul.mckenney@...aro.org> wrote:

> Commit-ID:  b24efdfdf679cf9b05947c531971905fc727dd40
> Gitweb:     http://git.kernel.org/tip/b24efdfdf679cf9b05947c531971905fc727dd40
> Author:     Paul E. McKenney <paul.mckenney@...aro.org>
> AuthorDate: Wed, 12 Jan 2011 14:18:11 -0800
> Committer:  Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
> CommitDate: Fri, 14 Jan 2011 04:58:08 -0800
> 
> rcu: avoid pointless blocked-task warnings
> 
> If the RCU callback-processing kthread has nothing to do, it parks in
> a wait_event().  If RCU remains idle for more than two minutes, the
> kernel complains about this.  This commit changes from wait_event()
> to wait_event_interruptible() to prevent the kernel from complaining
> just because RCU is idle.

Btw., a sidenote, it's not just about the blocked-tasks lockup detector warning, 
uninterruptible sleeps will also artificially inflate the load average of the box, 
+1.0 per such task. So it's definitely a bug to sleep for a very long time 
uninterruptible.

Thanks,

	Ingo
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