releases/2.6.25.8/b43-fix-noise-calculation-warn_on.patch

   1 From stable-bounces@linux.kernel.org Sat Jun 14 14:48:30 2008
   2 From: Michael Buesch <mb@bu3sch.de>
   3 Date: Sat, 14 Jun 2008 23:00:14 +0200
   4 Subject: b43: Fix noise calculation WARN_ON
   5 To: stable@kernel.org
   6 Cc: linux-wireless@vger.kernel.org, bcm43xx-dev@lists.berlios.de
   7 Message-ID: <200806142300.15391.mb@bu3sch.de>
   8 Content-Disposition: inline
   9
  10 From: Michael Buesch <mb@bu3sch.de>
  11
  12 commit 98a3b2fe435ae76170936c14f5c9e6a87548e3ef upstream.
  13
  14 This removes a WARN_ON that is responsible for the following koops:
  15 http://www.kerneloops.org/searchweek.php?search=b43_generate_noise_sample
  16
  17 The comment in the patch describes why it's safe to simply remove
  18 the check.
  19
  20 Signed-off-by: Michael Buesch <mb@bu3sch.de>
  21 Signed-off-by: John W. Linville <linville@tuxdriver.com>
  22 Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
  23
  24
  25 ---
  26  drivers/net/wireless/b43/b43.h  |    1 -
  27  drivers/net/wireless/b43/main.c |   16 ++++++++++------
  28  2 files changed, 10 insertions(+), 7 deletions(-)
  29
  30 --- a/drivers/net/wireless/b43/b43.h
  31 +++ b/drivers/net/wireless/b43/b43.h
  32 @@ -596,7 +596,6 @@ struct b43_dma {
  33
  34  /* Context information for a noise calculation (Link Quality). */
  35  struct b43_noise_calculation {
  36 -       u8 channel_at_start;
  37         bool calculation_running;
  38         u8 nr_samples;
  39         s8 samples[8][4];
  40 --- a/drivers/net/wireless/b43/main.c
  41 +++ b/drivers/net/wireless/b43/main.c
  42 @@ -1027,7 +1027,6 @@ static void b43_generate_noise_sample(st
  43         b43_jssi_write(dev, 0x7F7F7F7F);
  44         b43_write32(dev, B43_MMIO_MACCMD,
  45                     b43_read32(dev, B43_MMIO_MACCMD) | B43_MACCMD_BGNOISE);
  46 -       B43_WARN_ON(dev->noisecalc.channel_at_start != dev->phy.channel);
  47  }
  48
  49  static void b43_calculate_link_quality(struct b43_wldev *dev)
  50 @@ -1036,7 +1035,6 @@ static void b43_calculate_link_quality(s
  51
  52         if (dev->noisecalc.calculation_running)
  53                 return;
  54 -       dev->noisecalc.channel_at_start = dev->phy.channel;
  55         dev->noisecalc.calculation_running = 1;
  56         dev->noisecalc.nr_samples = 0;
  57
  58 @@ -1053,9 +1051,16 @@ static void handle_irq_noise(struct b43_
  59
  60         /* Bottom half of Link Quality calculation. */
  61
  62 +       /* Possible race condition: It might be possible that the user
  63 +        * changed to a different channel in the meantime since we
  64 +        * started the calculation. We ignore that fact, since it's
  65 +        * not really that much of a problem. The background noise is
  66 +        * an estimation only anyway. Slightly wrong results will get damped
  67 +        * by the averaging of the 8 sample rounds. Additionally the
  68 +        * value is shortlived. So it will be replaced by the next noise
  69 +        * calculation round soon. */
  70 +
  71         B43_WARN_ON(!dev->noisecalc.calculation_running);
  72 -       if (dev->noisecalc.channel_at_start != phy->channel)
  73 -               goto drop_calculation;
  74         *((__le32 *)noise) = cpu_to_le32(b43_jssi_read(dev));
  75         if (noise[0] == 0x7F || noise[1] == 0x7F ||
  76             noise[2] == 0x7F || noise[3] == 0x7F)
  77 @@ -1096,11 +1101,10 @@ static void handle_irq_noise(struct b43_
  78                         average -= 48;
  79
  80                 dev->stats.link_noise = average;
  81 -             drop_calculation:
  82                 dev->noisecalc.calculation_running = 0;
  83                 return;
  84         }
  85 -      generate_new:
  86 +generate_new:
  87         b43_generate_noise_sample(dev);
  88  }
  89