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

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Message-ID: <alpine.DEB.0.9999.0712011036340.10996@chino.kir.corp.google.com>
Date:	Sat, 1 Dec 2007 10:42:57 -0800 (PST)
From:	David Rientjes <rientjes@...gle.com>
To:	Ingo Molnar <mingo@...e.hu>
cc:	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Arjan van de Ven <arjan@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [feature] automatically detect hung TASK_UNINTERRUPTIBLE tasks

On Sat, 1 Dec 2007, Ingo Molnar wrote:

> this patch extends the soft-lockup detector to automatically
> detect hung TASK_UNINTERRUPTIBLE tasks. Such hung tasks are
> printed the following way:
> 

Wouldn't a natural extension of this feature be to mark these hung 
TASK_UNINTERRUPTIBLE tasks with a new thread flag such as TIF_HUNG for the 
purposes of the OOM killer?

Right now, the OOM killer will become a no-op when any candidate task that 
it scans through is found to have the TIF_MEMDIE flag when selecting a 
task to kill.  So any hung task in this state could cause the OOM killer 
to infinitely loop.

If lockdep could set_tsk_thread_flag(g, TIF_HUNG), this could be detected 
in the OOM killer and not only could we prevent the infinite looping but 
we could also clear TIF_MEMDIE and reduce the increased timeslice that the 
OOM killer gives to the tasks it kills.

		David
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