Messages in this thread | | | Subject | 2.6.16-rt11 and low-latency audio xruns (interrupt latency problem?) | From | "Valin, Jean-Marc (ICT Centre, Marsfield)" <> | Date | Thu, 30 Mar 2006 16:13:58 +1100 |
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Hi,
I'm getting xruns while trying to do low-latency capture/playback of audio. After enabling the alsa debug options, I'm seeing errors like these in my logs:
[66205.003000] Unexpected hw_pointer value [1] (stream = 0, delta: -3, max jitter = 16): wrong interrupt acknowledge? [66205.003000] [<f0ae2ec1>] snd_pcm_period_elapsed+0x136/0x27a [snd_pcm] (8) [66205.003000] [<f0af7780>] snd_intel8x0_interrupt+0x18d/0x1e5 [snd_intel8x0] (20) [66205.003000] [<b013495b>] handle_IRQ_event+0x4e/0xb6 (44) [66205.003000] [<b0135443>] thread_edge_irq+0x6f/0xc4 (48) [66205.003000] [<b0135519>] do_irqd+0x0/0x8a (16) [66205.003000] [<b01354d8>] do_hardirq+0x40/0x81 (4) [66205.003000] [<b0135575>] do_irqd+0x5c/0x8a (16) [66205.003000] [<b01261f6>] kthread+0x79/0xa3 (16) [66205.003000] [<b012617d>] kthread+0x0/0xa3 (24) [66205.003000] [<b0101319>] kernel_thread_helper+0x5/0xb (16) [66205.004000] XRUN: pcmC0D0p [66205.004000] [<f0ae2f72>] snd_pcm_period_elapsed+0x1e7/0x27a [snd_pcm] (8) [66205.004000] [<f0af7780>] snd_intel8x0_interrupt+0x18d/0x1e5 [snd_intel8x0] (24) [66205.004000] [<b013495b>] handle_IRQ_event+0x4e/0xb6 (44) [66205.004000] [<b0135443>] thread_edge_irq+0x6f/0xc4 (48) [66205.004000] [<b0135519>] do_irqd+0x0/0x8a (16) [66205.004000] [<b01354d8>] do_hardirq+0x40/0x81 (4) [66205.004000] [<b0135575>] do_irqd+0x5c/0x8a (16) [66205.004000] [<b01261f6>] kthread+0x79/0xa3 (16) [66205.004000] [<b012617d>] kthread+0x0/0xa3 (24) [66205.004000] [<b0101319>] kernel_thread_helper+0x5/0xb (16)
The only info I could get after searching for a while is that the "Unexpected hw_pointer value" *could* be related to the audio interrupt being serviced too late (http://www.ussg.iu.edu/hypermail/linux/kernel/0407.1/1613.html). However, I'm running the audio IRQ (IRQ 16) at priority 99 and my app at 98 (I also tried the opposite and get the same result). In this case, I'm running with two periods of 16 samples each (48 kHz), but I've seen that error occur with periods up to 64 samples.
Any idea how to fix/further investigate that? My machine is a Dell D600 laptop with a Pentium-M 2.13 GHz, which I'm running at full-speed (performance governor). Kernel is stock 2.6.16 + rt11 patch. Distro is Ubuntu 5.10, kernel is not tainted.
Thanks,
Jean-Marc
P.S. Please include me in CC since I'm not subscribed to lkml.
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