Deepak Nibade 7c5404fa42 gpu: nvgpu: remove redundant busy()/idle() calls ...

gk20a_busy() call in channel_syncpt_incr() and corresponding
gk20a_idle() call in channel_update() are redundant since they
are already encapsulated inside another pair of busy/idle calls

This busy/idle pair will be called only from submit_gpfifo()
and submit_gpfifo() already has its own busy/idle which it
preserves for whole path and hence this redundant pair can be
removed

Also, this prevents a dead lock scenario while do_idle() is in
progress as follows :
- in submit_gpfifo() we call first gk20a_busy() which acquires
  busy read semaphore
- in do_idle() we acquire busy write semaphore and wait for
  current jobs to finish
- now submit_gpfifo() encounters second gk20a_busy() and requests
  busy read semaphore again
- this results in dead lock where do_idle() is waiting for
  submit_gpfifo() to complete and submit_gpfifo() is waiting for
  busy lock held by do_idle() and hence it cannot complete

bug 1529160

Change-Id: I96e4368352f693e93524f0f61689b4447e5331ea
Signed-off-by: Deepak Nibade <dnibade@nvidia.com>
Reviewed-on: http://git-master/r/434191
(cherry picked from commit c4315c6caa42bab72ba6017c7ded25f4e9363dec)
Reviewed-on: http://git-master/r/435132
Reviewed-by: Sachin Nikam <snikam@nvidia.com>
Tested-by: Sachin Nikam <snikam@nvidia.com>

2015-03-18 12:10:24 -07:00

..

nvgpu

gpu: nvgpu: remove redundant busy()/idle() calls

2015-03-18 12:10:24 -07:00