Considering this case in find_free_channels():
bitmap:
+------------------+-+-+-+-+-+-+-+-+-+-+
| ...... |0|0|0|0|0|0|0|1|0|0|
+------------------+-+-+-+-+-+-+-+-+-+-+
1. Channel #2 has been occupied, so bit #2 is 1, and the others
are all 0.
2. Another thread tries to find 4 free channels from #0.
3. In the 1st loop, pos starts from 0, and then it checks if the
following 4 bits are all 0, but fails, as bit#2 is 1.
4. In the 2st loop, pos is not updated, and still starts from 0,
so nothing changes against loop #1.
5. Dead loop ...
This patch is to update the pos in step #3 to avoid the issue.
Fixes: 7bd1d4093c2f ("stm class: Introduce an abstraction for System Trace
Module devices")
Signed-off-by: Zhi Jin <zhi....@intel.com>
---
drivers/hwtracing/stm/core.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/drivers/hwtracing/stm/core.c b/drivers/hwtracing/stm/core.c
index 10bcb5d73f90..c86a979b9bd7 100644
--- a/drivers/hwtracing/stm/core.c
+++ b/drivers/hwtracing/stm/core.c
@@ -244,6 +244,8 @@ static int find_free_channels(unsigned long *bitmap,
unsigned int start,
;
if (i == width)
return pos;
+
+ pos += i;
}
return -1;
--
2.7.4
