netdev - [PATCH net-next v3 0/1] ppp: Replace per-CPU recursion counter with lock-owner field

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Message-ID: <20250715150806.700536-1-bigeasy@linutronix.de>
Date: Tue, 15 Jul 2025 17:08:05 +0200
From: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To: netdev@...r.kernel.org,
	linux-rt-devel@...ts.linux.dev,
	linux-ppp@...r.kernel.org
Cc: "David S. Miller" <davem@...emloft.net>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	Clark Williams <clrkwllms@...nel.org>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	Simon Horman <horms@...nel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Guillaume Nault <gnault@...hat.com>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Subject: [PATCH net-next v3 0/1] 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…v3 https://lore.kernel.org/all/20250710162403.402739-1-bigeasy@linutronix.de/
  - rebase on top of net-next
  - replace "ppp channel" with "ppp unit" in the patch description

v1…v2 https://lore.kernel.org/all/20250627105013.Qtv54bEk@linutronix.de/
  - Instead of rewriting the sequence and adding two owner fields to
    the two variables that may recurse it now adds a per-CPU variable
    for locking and keeping mostly the old code flow.  

Sebastian Andrzej Siewior (1):
  ppp: Replace per-CPU recursion counter with lock-owner field

 drivers/net/ppp/ppp_generic.c | 38 ++++++++++++++++++++++++++---------
 1 file changed, 29 insertions(+), 9 deletions(-)

-- 
2.50.0