linux-kernel - [PATCH 18/48] rcu: Make TINY_RCU depend on !PREEMPT

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Message-Id: <20240507093530.3043-19-urezki@gmail.com>
Date: Tue,  7 May 2024 11:35:00 +0200
From: "Uladzislau Rezki (Sony)" <urezki@...il.com>
To: "Paul E . McKenney" <paulmck@...nel.org>
Cc: RCU <rcu@...r.kernel.org>,
	Neeraj upadhyay <Neeraj.Upadhyay@....com>,
	Boqun Feng <boqun.feng@...il.com>,
	Hillf Danton <hdanton@...a.com>,
	Joel Fernandes <joel@...lfernandes.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Uladzislau Rezki <urezki@...il.com>,
	Oleksiy Avramchenko <oleksiy.avramchenko@...y.com>,
	Frederic Weisbecker <frederic@...nel.org>,
	Ankur Arora <ankur.a.arora@...cle.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH 18/48] rcu: Make TINY_RCU depend on !PREEMPT_RCU rather than !PREEMPTION

From: "Paul E. McKenney" <paulmck@...nel.org>

Right now, TINY_RCU depends on (!PREEMPTION && !SMP), which has served the
kernel well for many years due to the fact that PREEMPT_RCU is normally
a synonym for PREEMPTION.  But with the advent of lazy preemption,
it will be possible to have non-preemptible RCU in a preemptible kernel,
so that kernels could be built with PREEMPT_RCU=n and PREEMPTION=y.

This commit therefore makes TINY_RCU depend on (!PREEMPT_RCU && !SMP),
thus allowing for a non-preemptible RCU in preemptible kernels.

Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
Cc: Ankur Arora <ankur.a.arora@...cle.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Uladzislau Rezki (Sony) <urezki@...il.com>
---
 kernel/rcu/Kconfig | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/rcu/Kconfig b/kernel/rcu/Kconfig
index e7d2dd267593..7dca0138260c 100644
--- a/kernel/rcu/Kconfig
+++ b/kernel/rcu/Kconfig
@@ -31,7 +31,7 @@ config PREEMPT_RCU
 
 config TINY_RCU
 	bool
-	default y if !PREEMPTION && !SMP
+	default y if !PREEMPT_RCU && !SMP
 	help
 	  This option selects the RCU implementation that is
 	  designed for UP systems from which real-time response
-- 
2.39.2