On Tue, 02 Feb 2010 16:30:27 +0100 Clemens Ladisch clemens@ladisch.de wrote:
Frederick V Heitkamp wrote:
Repeatable Hard Crash. What else do I need to provide?
[ 5484.995249] WriteControlReg: not written, no change [ 5485.069621] divide error: 0000 [#1] pcm_hw_params ok [ 5485.070159] Prepare rate=44100 format=2 channels=2 [ 5485.070161] set_audio_format[14] = 5 [ 5485.070166] Prepare rate=44100 format=2 channels=2 [ 5485.070167] set_audio_format[14] = 5 [ 5485.070003] PREEMPT SMP ... [ 5485.070003] EIP is at pcm_pointer+0x37/0x70 [snd_echo3g] ... [ 5485.965788] [<c10041c0>] ? do_divide_error+0x0/0x90 [ 5485.980619] [<f87aa037>] ? pcm_pointer+0x37/0x70 [snd_echo3g] [ 5485.998047] [<c104764e>] ? run_timer_softirq+0x17e/0x2e0 [ 5486.014175] [<f87ac9bf>] ? snd_echo_interrupt+0x11f/0x240 [snd_echo3g] [ 5486.033940] [<c107a5d5>] ? handle_IRQ_event+0x45/0x190
bytes_to_frames() divides by runtime->frame_bits which is not set until after the hw_params callback has succeeded, but the corresponding chip->substream[] entry is set in that callback, by init_engine(). It should probably have been set in the prepare callback.
I've just had another look at my code. Although it never happened to me, it is indeed possible when hw_params() completes if another substream is already running. The reason is that the card delivers an irq when it executes an irq instruction in any of the running s-g lists. The irq handler cannot know which substream caused it, so it has to call the pointer() function for each of the configured substreams (ie. the ones which completed one of the pcm_*_hw_params() callbacks.
There is another possible fix. I tested it briefly. It looks ok wrt race conditions because pipe->state is set only in the trigger callback. I hope I didn't overlook anything again...
Signed-off-by: Giuliano Pochini pochini@shiny.it
--- alsa-driver-1.0.22.1/alsa-kernel/pci/echoaudio/echoaudio.c__orig 2010-02-02 22:37:33.000000000 +0100 +++ alsa-driver-1.0.22.1/alsa-kernel/pci/echoaudio/echoaudio.c 2010-02-02 22:44:03.000000000 +0100 @@ -1821,7 +1821,9 @@ static irqreturn_t snd_echo_interrupt(in /* The hardware doesn't tell us which substream caused the irq, thus we have to check all running substreams. */ for (ss = 0; ss < DSP_MAXPIPES; ss++) { - if ((substream = chip->substream[ss])) { + substream = chip->substream[ss]; + if (substream && ((struct audiopipe *)substream->runtime-> + private_data)->state == PIPE_STATE_STARTED) { period = pcm_pointer(substream) / substream->runtime->period_size; if (period != chip->last_period[ss]) {