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

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Message-Id: <20250116202434.3783613-10-paulmck@kernel.org>
Date: Thu, 16 Jan 2025 12:24:33 -0800
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,
	"Paul E. McKenney" <paulmck@...nel.org>
Subject: [PATCH rcu 10/11] srcu: Add FORCE_NEED_SRCU_NMI_SAFE Kconfig for testing

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>
---
 kernel/rcu/Kconfig | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/kernel/rcu/Kconfig b/kernel/rcu/Kconfig
index 80242957fa417..aa42de4d27684 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

-- 
2.40.1