From: Zhi Jin zhi.jin@intel.com

There is a bug in the channel allocation logic that leads to an endless loop when looking for a contiguous range of channels in a range with a mixture of free and occupied channels. For example, opening three consequtive channels, closing the first two and requesting 4 channels in a row will trigger this soft lockup. The bug is that the search loop forgets to skip over the range once it detects that one channel in that range is occupied.

Restore the original intent to the logic by fixing the omission.

Signed-off-by: Zhi Jin zhi.jin@intel.com Signed-off-by: Alexander Shishkin alexander.shishkin@linux.intel.com Fixes: 7bd1d4093c2f ("stm class: Introduce an abstraction for System Trace Module devices") CC: stable@vger.kernel.org # v4.4+ --- drivers/hwtracing/stm/core.c | 3 +++ 1 file changed, 3 insertions(+)

diff --git a/drivers/hwtracing/stm/core.c b/drivers/hwtracing/stm/core.c index 93ce3aa740a9..c80b064224f6 100644 --- a/drivers/hwtracing/stm/core.c +++ b/drivers/hwtracing/stm/core.c @@ -244,6 +244,9 @@ static int find_free_channels(unsigned long *bitmap, unsigned int start, ; if (i == width) return pos; + + /* step over [pos..pos+i) to continue search */ + pos += i; }

return -1;