gpu: nvgpu: hold ch ref when getting ch from fd

Fix a race condition in gk20a_get_channel_from_file() that returns a
channel pointer from an fd: take a reference to the channel before
putting the file ref back. Now the caller is responsible of releasing
the channel reference eventually.

Also document why dbg_session_channel_data has to hold a ref to the
channel file instead of just the channel: that might deadlock if the fds
were closed in "wrong" order.

Change-Id: I8e91b809f5f7b1cb0c1487bd955ad6d643727a53
Signed-off-by: Konsta Holtta <kholtta@nvidia.com>
Reviewed-on: https://git-master.nvidia.com/r/1549290
Reviewed-by: mobile promotions <svcmobile_promotions@nvidia.com>
Tested-by: mobile promotions <svcmobile_promotions@nvidia.com>

0 files changed, 0 insertions, 0 deletions