On Thu, Jun 24, 2021 at 3:26 AM SeongJae Park [off-list ref] wrote:

[...]

quoted

The high level comment I have for this patch is the layering of pid
reference counting. The dbgfs should treat the targets as abstract
objects and vaddr should handle the reference counting of pids. More
specifically move find_get_pid from dbgfs to vaddr and to add an
interface to the primitive for set_targets.

At the moment, the pid reference is taken in dbgfs and put in vaddr.
This will be the source of bugs in future.

Good point, and agreed on the problem.  But, I'd like to move 'put_pid()' to
dbgfs, because I think that would let extending the dbgfs user interface to
pidfd a little bit simpler.  Also, I think that would be easier to use for
in-kernel programming interface usages.  If you disagree, please feel free to
let me know.

I was thinking of removing targetid_is_pid() checks. Anyways this is
not something we can not change later, so I will let you decide which
direction you want to take.