linux-kernel - Re: [feature] automatically detect hung TASK

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Message-ID: <20071202222040.GA31707@elte.hu>
Date:	Sun, 2 Dec 2007 23:20:40 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	Arjan van de Ven <arjan@...radead.org>,
	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [feature] automatically detect hung TASK_UNINTERRUPTIBLE tasks


* Andi Kleen <andi@...stfloor.org> wrote:

> > Until now users had little direct recourse to get such problems 
> > fixed. (we had sysrq-t, but that included no real metric of how long 
> > a task was
> 
> Actually task delay accounting can measure this now.  iirc someone had 
> a latencytop based on it already.

Delay accounting (or the /proc/<PID>/sched fields that i added recently) 
only get updated once a task has finished its unreasonably long delay 
and has scheduled. So lockups or extremely long delays _wont be 
detected_ this way. This is a debugging facility that clearly belongs 
into the kernel. Your arguments just make no objective sense.

	Ingo
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