releases/2.6.32.17/alsa-echoaudio-fix-guru-meditation-00000005.48454c50.patch

   1 From b721e68bdc5b39c51bf6a1469f8d3663fbe03243 Mon Sep 17 00:00:00 2001
   2 From: Giuliano Pochini <pochini@shiny.it>
   3 Date: Wed, 17 Feb 2010 00:57:44 +0100
   4 Subject: ALSA: Echoaudio, fix Guru Meditation #00000005.48454C50
   5
   6 From: Giuliano Pochini <pochini@shiny.it>
   7
   8 commit b721e68bdc5b39c51bf6a1469f8d3663fbe03243 upstream.
   9
  10 This patch fixes a division by zero error in the irq handler.
  11
  12 There is a small window between the hw_params() callback and when
  13 runtime->frame_bits is set by ALSA middle layer. When another substream is
  14 already running, if an interrupt is delivered during that window the irq
  15 handler calls pcm_pointer() which does a division by zero. The patch below
  16 makes the irq handler skip substreams that are initialized but not started
  17 yet. Cc to Clemens Ladisch because he proposed an alternate fix.
  18
  19 For more information, please read the original thread in the linux-kernel
  20 mailing list: http://lkml.org/lkml/2010/2/2/187
  21
  22 Signed-off-by: Giuliano Pochini <pochini@shiny.it>
  23 Signed-off-by: Takashi Iwai <tiwai@suse.de>
  24 Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
  25
  26 ---
  27  sound/pci/echoaudio/echoaudio.c |    4 +++-
  28  1 file changed, 3 insertions(+), 1 deletion(-)
  29
  30 --- a/sound/pci/echoaudio/echoaudio.c
  31 +++ b/sound/pci/echoaudio/echoaudio.c
  32 @@ -1821,7 +1821,9 @@ static irqreturn_t snd_echo_interrupt(in
  33         /* The hardware doesn't tell us which substream caused the irq,
  34         thus we have to check all running substreams. */
  35         for (ss = 0; ss < DSP_MAXPIPES; ss++) {
  36 -               if ((substream = chip->substream[ss])) {
  37 +               substream = chip->substream[ss];
  38 +               if (substream && ((struct audiopipe *)substream->runtime->
  39 +                               private_data)->state == PIPE_STATE_STARTED) {
  40                         period = pcm_pointer(substream) /
  41                                 substream->runtime->period_size;
  42                         if (period != chip->last_period[ss]) {