Zhi Jin <zhi....@intel.com> writes: > 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.
The description is slightly confusing, but the patch looks correct and the original code is clearly wrong. Thank you for finding this! Basically, if you request 1 channel 3 times, release the first two and then request 4 channels, you'll be stuck, right? Thanks, -- Alex
