linux-kernel - Re: [PATCH] TASK

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Date:	Fri, 28 Sep 2007 07:47:06 +1000
From:	Nick Piggin <nickpiggin@...oo.com.au>
To:	ric@....com, Andrea Arcangeli <andrea@...e.de>
Cc:	Chris Mason <chris.mason@...cle.com>, Mark Lord <mlord@...ox.com>,
	Valerie Henson <val.henson@...il.com>,
	Christoph Hellwig <hch@...radead.org>,
	Suparna Bhattacharya <suparna@...ibm.com>,
	Andreas Dilger <adilger@...sterfs.com>,
	Bob Bell <b_lkml@...bellsplace.com>,
	Matthew Wilcox <matthew@....cx>, trond@...app.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] TASK_KILLABLE version 2

On Wednesday 26 September 2007 21:57, Ric Wheeler wrote:
> Bob Bell wrote:
> > On Sat, Sep 01, 2007 at 08:43:49PM -0600, Matthew Wilcox wrote:
> >> Here's the second version of TASK_KILLABLE.  A few changes since
> >> version 1:
> >
> > <snip>
> >
> >> I obviously haven't covered every place that can result in a process
> >> sleeping uninterruptibly while attempting an operation.  But sync_page
> >> (patch 4/5) covers about 90% of the times I've attempted to kill cat,
> >> and I hope that by providing the two examples, I can help other people
> >> to fix the cases that they find interesting.
> >
> > I've been testing this patch on my systems.  It's working for me when
> > I read() a file.  Asynchronous write()s seem okay, too.  However,
> > synchronous writes (caused by either calling fsync() or fcntl() to
> > release a lock) prevent the process from being killed when the NFS
> > server goes down.
>
> After hearing again last month about how few people actually read every
> lkml thread, I  wanted to point you all at this thread explicitly since
> it seems that we are getting somewhat close to having a forced unmount
> that actually is usable by real applications, something that we seem to
> have been talking about for many years ;-)
>
> With Matthew's original TASK_KILLABLE patch, we have a solution for a
> task read, but still have some holes (fsync & fcntl, others?) that need
> fixed as well for NFS clients.
>
> Is this patch going in the right direction?

FWIW, I do think it seems like a good idea to work towards better
interruptibility in various potentially long-blocking paths like these.
I think Andrea's recent work to solve some oom killer deadlocks
probably has some requirements in common with this patch.
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