queue-4.14/stm-class-fix-an-endless-loop-in-channel-allocation.patch

   1 From a1d75dad3a2c689e70a1c4e0214cca9de741d0aa Mon Sep 17 00:00:00 2001
   2 From: Zhi Jin <zhi.jin@intel.com>
   3 Date: Thu, 6 Sep 2018 15:22:10 +0800
   4 Subject: stm class: Fix an endless loop in channel allocation
   5
   6 From: Zhi Jin <zhi.jin@intel.com>
   7
   8 commit a1d75dad3a2c689e70a1c4e0214cca9de741d0aa upstream.
   9
  10 There is a bug in the channel allocation logic that leads to an endless
  11 loop when looking for a contiguous range of channels in a range with a
  12 mixture of free and occupied channels. For example, opening three
  13 consequtive channels, closing the first two and requesting 4 channels in
  14 a row will trigger this soft lockup. The bug is that the search loop
  15 forgets to skip over the range once it detects that one channel in that
  16 range is occupied.
  17
  18 Restore the original intent to the logic by fixing the omission.
  19
  20 Signed-off-by: Zhi Jin <zhi.jin@intel.com>
  21 Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
  22 Fixes: 7bd1d4093c2f ("stm class: Introduce an abstraction for System Trace Module devices")
  23 CC: stable@vger.kernel.org # v4.4+
  24 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  25
  26 ---
  27  drivers/hwtracing/stm/core.c |    3 +++
  28  1 file changed, 3 insertions(+)
  29
  30 --- a/drivers/hwtracing/stm/core.c
  31 +++ b/drivers/hwtracing/stm/core.c
  32 @@ -252,6 +252,9 @@ static int find_free_channels(unsigned l
  33                         ;
  34                 if (i == width)
  35                         return pos;
  36 +
  37 +               /* step over [pos..pos+i) to continue search */
  38 +               pos += i;
  39         }
  40
  41         return -1;