[linux-audio-dev] Re: [announce] [patch] Voluntary Kernel Preemption Patch

[Lee Revell]

On Mon, 2004-07-12 at 23:59, Andrew Morton wrote:
> Lee Revell <rlrevell at joe-job.com> wrote:
> >
> > Here are a few more:
> > 
> >  Jul 12 22:20:41 mindpipe kernel: ALSA /usr/src/alsa-cvs-1.0.5/alsa-driver/alsa-kernel/core/pcm_lib.c:169: XRUN: pcmC0D0p
> >  Jul 12 22:20:41 mindpipe kernel:  [__crc_totalram_pages+1387264/5353478] snd_pcm_period_elapsed+0x2ca/0x410 [snd_pcm]
> >  Jul 12 22:20:41 mindpipe kernel:  [__crc_totalram_pages+1455070/5353478] snd_emu10k1_interrupt+0x3c8/0x480 [snd_emu10k1]
> >  Jul 12 22:20:41 mindpipe kernel:  [handle_IRQ_event+49/96] handle_IRQ_event+0x31/0x60
> >  Jul 12 22:20:41 mindpipe kernel:  [do_IRQ+155/352] do_IRQ+0x9b/0x160
> >  Jul 12 22:20:41 mindpipe kernel:  [common_interrupt+24/32] common_interrupt+0x18/0x20
> >  Jul 12 22:20:41 mindpipe kernel:  [unix_stream_recvmsg+135/1088] unix_stream_recvmsg+0x87/0x440
> >  Jul 12 22:20:41 mindpipe kernel:  [avc_has_perm+72/96] avc_has_perm+0x48/0x60
> >  Jul 12 22:20:41 mindpipe kernel:  [sock_aio_read+155/176] sock_aio_read+0x9b/0xb0
> >  Jul 12 22:20:41 mindpipe kernel:  [do_sync_read+125/192] do_sync_read+0x7d/0xc0
> >  Jul 12 22:20:41 mindpipe kernel:  [do_select+435/752] do_select+0x1b3/0x2f0
> >  Jul 12 22:20:41 mindpipe kernel:  [vfs_read+223/256] vfs_read+0xdf/0x100
> >  Jul 12 22:20:42 mindpipe kernel:  [sys_read+45/80] sys_read+0x2d/0x50
> >  Jul 12 22:20:42 mindpipe kernel:  [syscall_call+7/11] syscall_call+0x7/0xb
> >  Jul 12 22:20:42 mindpipe kernel:
> >  Jul 12 22:20:44 mindpipe kernel: ALSA /usr/src/alsa-cvs-1.0.5/alsa-driver/alsa-kernel/core/pcm_lib.c:169: XRUN: pcmC0D0p
> >  Jul 12 22:20:44 mindpipe kernel:  [__crc_totalram_pages+1387264/5353478] snd_pcm_period_elapsed+0x2ca/0x410 [snd_pcm]
> >  Jul 12 22:20:44 mindpipe kernel:  [__crc_totalram_pages+1455070/5353478] snd_emu10k1_interrupt+0x3c8/0x480 [snd_emu10k1]
> >  Jul 12 22:20:44 mindpipe kernel:  [handle_IRQ_event+49/96] handle_IRQ_event+0x31/0x60
> >  Jul 12 22:20:44 mindpipe kernel:  [do_IRQ+155/352] do_IRQ+0x9b/0x160
> >  Jul 12 22:20:44 mindpipe kernel:  [common_interrupt+24/32] common_interrupt+0x18/0x20
> 
> Oh dear, these don't make much sense.
> 
> You'll have the best chance of getting decent traces with
> CONFIG_FRAME_POINTER=y and CONFIG_4KSTACKS=n, but I'm not sure that this
> will help a lot.  Are you sure that CONFIG_PREEMPT is enabled on that
> kernel?

Yes:

root at mindpipe:/home/rlrevell/kernel-source/kernel-source-2.6.7# grep . /proc/sys/kernel/*_preemption
/proc/sys/kernel/kernel_preemption:1
/proc/sys/kernel/voluntary_preemption:1

My testing also uncovered a possible bug in the emu10k1 driver, I am
looking into this.  I don't think it's related because the log entries
are spaced minutes apart.  Could this be a driver problem?  Hardware?

Just as a reference point, what do you think is the longest delay I
*should* be seeing?  I recall hearing that BEOS guaranteed that
interrupts are never disabled for more than 50 usecs.  This seems
achievable, as the average delay I am seeing is 15 usecs.

I will set CONFIG_FRAME_POINTER=Y and CONFIG_4KSTACKS=n and test some
more.

Lee