linux-kernel - Re: [PATCH] CIFS: make cifsd (more)

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Date:	Sat, 30 Jun 2007 09:42:09 +0100
From:	Christoph Hellwig <hch@...radead.org>
To:	Steve French <smfrench@...il.com>
Cc:	linux-fsdevel@...r.kernel.org, jlayton@...hat.com,
	linux-kernel@...r.kernel.org, linux-cifs-client@...ts.samba.org,
	netdev@...r.kernel.org
Subject: Re: [PATCH] CIFS: make cifsd (more)

On Mon, Jun 25, 2007 at 05:25:00PM -0500, Steve French wrote:
> Jeff,
> Not seeing any objections to your revised approach (to not allowing
> signals for cifsd kernel thread), I just merged something similar to
> your patch to the cifs-2.6.git tree (also fixed some nearby lines that
> went past 80 columns).

Ok, I'm back to this.

As I said mixing force_sig with the kthread infrastructure is a bad idea.
The proper short-term (aka 2.6.22) fix is to revert the kthread conversion
for this particular thread.  Just go back to what worked before.

Now the right fix is a lot more complicated and involved:

	Stop using blocking recvmsg (or read) in kernel threads!

If you look at what the other consumers of networking reads from kernel
threads do is they either use tcp_read_sock and hooks into the sk_ callbacks
which would be nice for high performance reads in cifs aswell, but probably
not the demultiplexer thread, or they use MSG_DONTWAIT to avoid this problems
and deal with the blocking behaviour on a higher level.
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