Message-Id: <200502212054.j1LKs3xi032658@turing-police.cc.vt.edu>
To: Anthony DiSante <theant@nodivisions.com>
Cc: linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: uninterruptible sleep lockups 
In-Reply-To: Your message of "Mon, 21 Feb 2005 15:24:21 EST."
             <421A4375.9040108@nodivisions.com> 
From: Valdis.Kletnieks@vt.edu
References: <421A3414.2020508@nodivisions.com> <200502211945.j1LJjgbZ029643@turing-police.cc.vt.edu>
            <421A4375.9040108@nodivisions.com>
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On Mon, 21 Feb 2005 15:24:21 EST, Anthony DiSante said:
> Or maybe it SHOULD have killed your process, in some "proper" way that 
> prevents any outstanding I/O requests from coming in days later and breaking 
> things.  Again, I'm no kernel hacker, but if an I/O request takes *3 days*, 
> isn't that an indication of a bug or of faulty hardware perhaps?

Right.  And if you're an automated program trying to clean up after a *bug*,
what do you do?  It's quite likely that somebody's borked a lock - in which
case it may even be that the "hung" process is the victim rather than the
culprit, and breaking the lock will just make things worse.  Similar issues
apply to *all* of the resources the wedged process has attached to it.

When these things get posted on lkml, it almost always involves quite a bit
of code introspection and scratching of heads before we figure out how the
system *got* its figurative head wedged into that crevice.  Until you
figure out how it *got* there, a safe cleanup is in general impossible.  And
we haven't seen yet the automatic program that can introspect the code to that
detail - even the Stanford automated checker and sparse and the like are quite the
impressive pieces of work.

> > It's been covered before, look in the lkml archives for details.
> 
> Thanks, I'll do that.  But could you give me a more specific pointer? 

See the thread rooted here:
 
Date: Wed, 03 Nov 2004 07:51:39 -0500
From: Gene Heskett <gene.heskett@verizon.net>
Subject: is killing zombies possible w/o a reboot?
Sender: linux-kernel-owner@vger.kernel.org
To: linux-kernel@vger.kernel.org
Reply-to: gene.heskett@verizon.net
Message-id: <200411030751.39578.gene.heskett@verizon.net>


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