From: Jack Miller <millerjo@us.ibm.com>
To: linux-kernel@vger.kernel.org
Cc: akpm@linux-foundation.org, davidlohr@hp.com, miltonm@us.ibm.com,
        anton@au1.ibm.com
Subject: [RESEND] shm: shm exit scalability fixes 
Date: Tue, 17 Jun 2014 12:27:44 -0500
Message-Id: <1403026067-14272-1-git-send-email-millerjo@us.ibm.com>
Sender: linux-kernel-owner@vger.kernel.org

[ RESEND note: Adding relevant CCs, fixed a couple of typos in commit message,
patches unchanged. Original intro follows. ]

All -

This is small set of patches our team has had kicking around for a few versions
internally that fixes tasks getting hung on shm_exit when there are many
threads hammering it at once.

Anton wrote a simple test to cause the issue:

http://ozlabs.org/~anton/junkcode/bust_shm_exit.c

Before applying this patchset, this test code will cause either hanging
tracebacks or pthread out of memory errors.

After this patchset, it will still produce output like:

root@somehost:~# ./bust_shm_exit 1024 160
...
INFO: rcu_sched detected stalls on CPUs/tasks: {} (detected by 116, t=2111
jiffies, g=241, c=240, q=7113)
INFO: Stall ended before state dump start
...
But the task will continue to run along happily, so we consider this an
improvement over hanging, even if it's a bit noisy.

I didn't author these patches, but I'd be happy to take any feedback and
address any issues.

- Jack

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/