Merge branch 'ppp-replace-per-cpu-recursion-counter-with-lock-owner-field'

Sebastian Andrzej Siewior says:

====================
ppp: Replace per-CPU recursion counter with lock-owner field

This is another approach to avoid relying on local_bh_disable() for
locking of per-CPU in ppp.

I redid it with the per-CPU lock and local_lock_nested_bh() as discussed
in v1. The xmit_recursion counter has been removed since it served the
same purpose as the owner field. Both were updated and checked.

The xmit_recursion looks like a counter in ppp_channel_push() but at
this point, the counter should always be 0 so it always serves as a
boolean. Therefore I removed it.

I do admit that this looks easier to review.

v2 https://lore.kernel.org/all/20250710162403.402739-1-bigeasy@linutronix.de/
v1 https://lore.kernel.org/all/20250627105013.Qtv54bEk@linutronix.de/
====================

Link: https://patch.msgid.link/20250715150806.700536-1-bigeasy@linutronix.de
Signed-off-by: Paolo Abeni <pabeni@redhat.com>