Re: OMAP1 realtime patch

[Kevin Hilman <khilman@mvista.com>]

On Sun, 2007-02-11 at 18:01 +0100, Dirk Behme wrote:
> Dirk Behme wrote:
> > Kevin Hilman wrote:
> > 
> >> Here is a patch which leaves out the raw_spinlock conversions.  It goes
> >> on the OMAP git tree on top of -rt5 (ignoring conflicts.)  I've left out
> >> all the raw_spinlock conversions.  This has been tested on an
> >> OMAP1623/H2 platform.
> > 
> > Update of Kevins update. Tested on OSK.
> > 
> > Changes:
> > 
> > - Remove kernel/printk.c "+    zap_rt_locks();". It's already in -rt5.
> > 
> > - Re-add HRTIMER conversion to ads7846.c
> > 
> > With this patch I get Oops below after playing mp3 via NFS. Add 
> > raw_spinlock_t to sound/arm/omap/omap-alsa-dma.c like in my original 
> > patch doesn't seem to help.
> 
> Re-adding raw_spinlock_t to omap-alsa.h helps against this Oops.

My guess the oops you sent is that you saw this crash when doing a
Ctrl-C or otherwise stopping the playback, correct?

This oops is triggered by the same thread trying to take the same
spinlock (now an rt_mutex under PREEMPT_RT.)  The following patch
fixes the nested spinlocks,  and removes the raw_spinlock.  It applies
on top of your latest patch.

On my OSK, I do notice however that using -rt (with and without this
fix) mp3 playback has some audible noise under PREEMPT_RT.  Do you hear
this too?

Kevin