Re: [feature] automatically detect hung TASK_UNINTERRUPTIBLE tasks

From: Ingo Molnar <mingo@elte.hu>
To: Andi Kleen <andi@firstfloor.org>
Cc: Radoslaw Szkodzinski <lkml@astralstorm.puszkin.org>,
	Arjan van de Ven <arjan@infradead.org>,
	linux-kernel@vger.kernel.org,
	Andrew Morton <akpm@linux-foundation.org>,
	Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [feature] automatically detect hung TASK_UNINTERRUPTIBLE tasks
Date: Mon, 3 Dec 2007 11:38:15 +0100	[thread overview]
Message-ID: <20071203103815.GA2707@elte.hu> (raw)
In-Reply-To: <20071203102715.GC28560@one.firstfloor.org>

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

> > Kernel waiting 2 minutes on TASK_UNINTERRUPTIBLE is certainly broken.
> 
> What should it do when the NFS server doesn't answer anymore or when 
> the network to the SAN RAID array located a few hundred KM away 
> develops some hickup?  [...]

maybe: if the user does a Ctrl-C (or a kill -9), the kernel should try 
to honor it, instead of staying there stuck for a very long time 
(possibly forever)?

I think you are somehow confusing two issues: this patch in no way 
declares that "long waits are bad" - if the user _choses_ to wait for 
the NFS server (after phoning IT quickly or whatever), he can wait an 
hour. This patch only declares that "long waits _that the user has no 
way to stop_ are quite likely bad".

Do you see the important distinction between the two cases? Please 
reconsider your position (or re-state it differently), it just makes no 
rational sense to me so far.

	Ingo