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

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Message-ID: <20130104002635.GA6693@dcvr.yhbt.net>
Date:	Fri, 4 Jan 2013 00:26:35 +0000
From:	Eric Wong <normalperson@...t.net>
To:	Eric Dumazet <eric.dumazet@...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:
> I think this requires frequent dirtying/cycling of pages to reproduce.
> (from copying large files around) to interact with compaction.
> I'll see if I can reproduce the issue with read-only FS activity.

Still successfully running the read-only test on my main machine, will
provide another update in a few hours or so if it's still successful
(it usually takes <1 hour to hit).

I also fired up a VM on my laptop (still running v3.7) and was able to
get stuck with only 2 cores and 512M on the VM (x86_64).  On the small
VM with little disk space, it doesn't need much dirty data to trigger.
I just did this:

    find $45G_NFS_MOUNT -type f -print0 | \
       xargs -0 -n1 -P4 sh -c 'cat "$1" >> tmp; > tmp' --

...while running two instances of toosleepy (one got stuck and aborted).
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