linux-kernel - Re: Random process lockup on ARM board: alsa-lib-1.0.25, FUTEX_WAIT

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Date:	Wed, 07 Mar 2012 21:22:48 +0000
From:	Jonathan Andrews <jon@...shouse.co.uk>
To:	Darren Hart <dvhart@...ux.intel.com>
Cc:	Huang Shijie <shijie8@...il.com>, linux-kernel@...r.kernel.org
Subject: Re: Random process lockup on ARM board: alsa-lib-1.0.25,
 FUTEX_WAIT_PRIVATE

On Wed, 2012-03-07 at 12:07 -0800, Darren Hart wrote:
> 
> On 02/29/2012 01:12 AM, Huang Shijie wrote:
> > Hi ,
> > 
> > I meet a similar problem with the latest futex code.
> > 
> > I play the video and the processes will hang at the futex.
> 
> Are either of you able to bisect the kernel?
I'm not a kernel hacker what do you mean ?

>  At the very least can you
> find two kernels where it works and where it does not?
> 
> Hanging on FUTEX_WAIT_PRIVATE can be the symptom for higher level
> problems including userspace locking issues and race conditions.

My workload is UDP network audio.  I have compiled my code with and
without ALSA support. The version without ALSA seems to run forever, the
version with ALSA works on ARM for between a few minutes and a few
hours. On Intel the same futex stall problem occurs, but it may take
runtime of days.

I have two processes running. One RX process that takes UDP packets from
the network mixes them and presents them to ALSA as an audio stream, the
second process takes audio from the sound device and transmits it as a
UDP audio stream.  The two processes are independent. 

My workload is atypical as I need to both transmit and receive audio via
UDP on a 27/7 basis.

So far I have experienced the problem on 3 kernels, but I have tried
only 3 kernels it may be all 2.6 kernels that suffer.

My development PC is "Linux jonspc 2.6.32.26-175.fc12.i686 #1 SMP Wed
Dec 1 21:52:04 UTC 2010 i686 athlon i386 GNU/Linux"

My ARM board target:
ARM / # uname -a
Linux (none) 3.2.5 #2 Wed Feb 22 17:11:52 GMT 2012 armv4tl GNU/Linux

And my ARM target running its older kernel was (2.6.36).

I have an strace of the process running and stalling on the PC.
The file is 2GB, its not a fast link sorry.

http://www.jonshouse.co.uk/download/a_stop.txt

Many thanks,
Jon

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