linux-kernel - Re: ppoll() stuck on POLLIN while TCP peer is sending

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Message-ID: <20130109084247.GA6545@dcvr.yhbt.net>
Date:	Wed, 9 Jan 2013 08:42:47 +0000
From:	Eric Wong <normalperson@...t.net>
To:	Eric Dumazet <erdnetdev@...il.com>
Cc:	Mel Gorman <mgorman@...e.de>, linux-mm@...ck.org,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	Rik van Riel <riel@...hat.com>,
	Minchan Kim <minchan@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: ppoll() stuck on POLLIN while TCP peer is sending

Eric Wong <normalperson@...t.net> wrote:
> Eric Dumazet <erdnetdev@...il.com> wrote:
> > On Tue, 2013-01-08 at 18:32 -0800, Eric Dumazet wrote:
> > > Hmm, it seems sk_filter() can return -ENOMEM because skb has the
> > > pfmemalloc() set.
> > 
> > > 
> > > One TCP socket keeps retransmitting an SKB via loopback, and TCP stack 
> > > drops the packet again and again.
> > 
> > sock_init_data() sets sk->sk_allocation to GFP_KERNEL
> > 
> > Shouldnt it use (GFP_KERNEL | __GFP_NOMEMALLOC) instead ?
> 
> Thanks, things are running good after ~35 minutes so far.
> Will report back if things break (hopefully I don't run out
> of laptop battery power :x).

Oops, I had to restart my test :x.  However, I was able to reproduce the
issue very quickly again with your patch.  I've double-checked I'm
booting into the correct kernel, but I do have more load on this
laptop host now, so maybe that made it happen more quickly...
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