Merge patch series "pidfs: ensure consistent ENOENT/ESRCH reporting"

Christian Brauner <brauner@kernel.org> says:

In a prior patch series we tried to cleanly differentiate between:

(1) The task has already been reaped.
(2) The caller requested a pidfd for a thread-group leader but the pid
actually references a struct pid that isn't used as a thread-group
leader.

as this was causing issues for non-threaded workloads.

But there's cases where the current simple logic is wrong. Specifically,
if the pid was a leader pid and the check races with __unhash_process().
Stabilize this by using the pidfd waitqueue lock.

* patches from https://lore.kernel.org/20250411-work-pidfs-enoent-v2-0-60b2d3bb545f@kernel.org:
  pidfs: ensure consistent ENOENT/ESRCH reporting
  exit: move wake_up_all() pidfd waiters into __unhash_process()

Link: https://lore.kernel.org/20250411-work-pidfs-enoent-v2-0-60b2d3bb545f@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>