linux-kernel - [PATCH rcu 10/11] srcu: Add FORCE_NEED_SRCU_NMI

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Message-Id: <20250219153938.24966-11-boqun.feng@gmail.com>
Date: Wed, 19 Feb 2025 07:39:37 -0800
From: Boqun Feng <boqun.feng@...il.com>
To: rcu@...r.kernel.org
Cc: Jonathan Corbet <corbet@....net>,	Steven Rostedt <rostedt@...dmis.org>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	"Paul E. McKenney" <paulmck@...nel.org>,
	Frederic Weisbecker <frederic@...nel.org>,
	Neeraj Upadhyay <neeraj.upadhyay@...nel.org>,
	Joel Fernandes <joel@...lfernandes.org>,
	Josh Triplett <josh@...htriplett.org>,	Boqun Feng <boqun.feng@...il.com>,
	Uladzislau Rezki <urezki@...il.com>,
	Lai Jiangshan <jiangshanlai@...il.com>,
	Zqiang <qiang.zhang1211@...il.com>,	Davidlohr Bueso <dave@...olabs.net>,
	Shuah Khan <shuah@...nel.org>,	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Huth <thuth@...hat.com>,	"Borislav Petkov (AMD)" <bp@...en8.de>,
	Ard Biesheuvel <ardb@...nel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Josh Poimboeuf <jpoimboe@...nel.org>,	Yury Norov <yury.norov@...il.com>,
	Valentin Schneider <vschneid@...hat.com>,	linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org,	linux-trace-kernel@...r.kernel.org,
	linux-kselftest@...r.kernel.org
Subject: [PATCH rcu 10/11] srcu: Add FORCE_NEED_SRCU_NMI_SAFE Kconfig for testing

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

The srcu_read_lock_nmisafe() and srcu_read_unlock_nmisafe() functions
map to __srcu_read_lock() and __srcu_read_unlock() on systems like x86
that have NMI-safe this_cpu_inc() operations.  This makes the underlying
__srcu_read_lock_nmisafe() and __srcu_read_unlock_nmisafe() functions
difficult to test on (for example) x86 systems, allowing bugs to creep in.

This commit therefore creates a FORCE_NEED_SRCU_NMI_SAFE Kconfig that
forces those underlying functions to be used even on systems where they
are not needed, thus providing better testing coverage.

Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
Signed-off-by: Boqun Feng <boqun.feng@...il.com>
---
 kernel/rcu/Kconfig | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/kernel/rcu/Kconfig b/kernel/rcu/Kconfig
index b9b6bc55185d..c8e540af3a35 100644
--- a/kernel/rcu/Kconfig
+++ b/kernel/rcu/Kconfig
@@ -65,6 +65,17 @@ config TREE_SRCU
 	help
 	  This option selects the full-fledged version of SRCU.
 
+config FORCE_NEED_SRCU_NMI_SAFE
+	bool "Force selection of NEED_SRCU_NMI_SAFE"
+	depends on !TINY_SRCU
+	select NEED_SRCU_NMI_SAFE
+	default n
+	help
+	  This option forces selection of the NEED_SRCU_NMI_SAFE
+	  Kconfig option, allowing testing of srcu_read_lock_nmisafe()
+	  and srcu_read_unlock_nmisafe() on architectures (like x86)
+	  that select the ARCH_HAS_NMI_SAFE_THIS_CPU_OPS Kconfig option.
+
 config NEED_SRCU_NMI_SAFE
 	def_bool HAVE_NMI && !ARCH_HAS_NMI_SAFE_THIS_CPU_OPS && !TINY_SRCU
 
-- 
2.39.5 (Apple Git-154)