linux-kernel - [PATCH v3 0/4] Switch __DECLARE_TRACE() to notrace variant of SRCU-fast

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Message-ID: <7387f0c2-75bc-420d-aa7e-3a9ac72d369c@paulmck-laptop>
Date: Mon, 21 Jul 2025 09:24:27 -0700
From: "Paul E. McKenney" <paulmck@...nel.org>
To: rcu@...r.kernel.org
Cc: linux-kernel@...r.kernel.org, kernel-team@...a.com, rostedt@...dmis.org
Subject: [PATCH v3 0/4] Switch __DECLARE_TRACE() to notrace variant of
 SRCU-fast

Hello!

This is version 3 of a patch series creating a new notrace variant of
SRCU-fast and introducing it to the __DECLARE_TRACE() in place of the
current preemption disabling.  This change enable preemption of BPF
programs attached to tracepoints, as is required for runtime use of BPF
in real-time systems.

1.	Move rcu_is_watching() checks to srcu_read_{,un}lock_fast().

2.	Add srcu_read_lock_fast_notrace() and
	srcu_read_unlock_fast_notrace().

3.	Add guards for notrace variants of SRCU-fast readers.

4.	Guard __DECLARE_TRACE() use of __DO_TRACE_CALL() with SRCU-fast.

Changes since v2:

o	Posting standalone as opposed to a reply.

	https://lore.kernel.org/all/3cecf6c9-b2ee-4f34-9d1b-ca4cfb8e56a7@paulmck-laptop/

Changes since RFC version:

o	RFC patch 6/4 has been pulled into the shared RCU tree:
	e88c632a8698 ("srcu: Add guards for SRCU-fast readers")

o	RFC patch 5/4 (which removed the now-unnecessary special boot-time
	avoidance of SRCU) has been folded into patch 4/4 shown above,
	as suggested by Steven Rostedt.

	https://lore.kernel.org/all/bb20a575-235b-499e-aa1d-70fe9e2c7617@paulmck-laptop/

						Thanx, Paul

------------------------------------------------------------------------

 b/include/linux/srcu.h       |    4 ++++
 b/include/linux/srcutree.h   |    2 --
 b/include/linux/tracepoint.h |    6 ++++--
 b/kernel/tracepoint.c        |   21 ++++++++++++++++++++-
 include/linux/srcu.h         |   30 ++++++++++++++++++++++++++++++
 5 files changed, 58 insertions(+), 5 deletions(-)