linux-kernel - Re: [PATCH 01/12] netvm: Prevent a stream-specific deadlock

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Message-ID: <20120620142127.GK4011@suse.de>
Date:	Wed, 20 Jun 2012 15:21:27 +0100
From:	Mel Gorman <mgorman@...e.de>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Linux-MM <linux-mm@...ck.org>,
	Linux-Netdev <netdev@...r.kernel.org>,
	Linux-NFS <linux-nfs@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	David Miller <davem@...emloft.net>,
	Trond Myklebust <Trond.Myklebust@...app.com>,
	Neil Brown <neilb@...e.de>,
	Christoph Hellwig <hch@...radead.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Mike Christie <michaelc@...wisc.edu>,
	Eric B Munson <emunson@...bm.net>
Subject: Re: [PATCH 01/12] netvm: Prevent a stream-specific deadlock

On Wed, Jun 20, 2012 at 10:37:50AM +0100, Mel Gorman wrote:
> It could happen that all !SOCK_MEMALLOC sockets have buffered so
> much data that we're over the global rmem limit. This will prevent
> SOCK_MEMALLOC buffers from receiving data, which will prevent userspace
> from running, which is needed to reduce the buffered data.
> 
> Fix this by exempting the SOCK_MEMALLOC sockets from the rmem limit.
> Once this change it applied, it is important that sockets that set
> SOCK_MEMALLOC do not clear the flag until the socket is being torn down.
> If this happens, a warning is generated and the tokens reclaimed to
> avoid accounting errors until the bug is fixed.
> 
> [davem@...emloft.net: Warning about clearing SOCK_MEMALLOC]
> Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> Signed-off-by: Mel Gorman <mgorman@...e.de>
> Acked-by: David S. Miller <davem@...emloft.net>

This patch introduced a new warning that I had previously missed. I'll
fix it up when rebasing this series on top of linux-next.

-- 
Mel Gorman
SUSE Labs
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