[PATCH] Default enable RCU list lockdep debugging with PROVE_RCU

From: madhuparnabhowmik10@gmail.com
To: paulmck@kernel.org, josh@joshtriplett.org, rostedt@goodmis.org,
	mathieu.desnoyers@efficios.com, jiangshanlai@gmail.com,
	joel@joelfernandes.org
Cc: linux-kernel@vger.kernel.org,
	Madhuparna Bhowmik <madhuparnabhowmik10@gmail.com>,
	Amol Grover <frextrite@gmail.com>
Subject: [PATCH] Default enable RCU list lockdep debugging with PROVE_RCU
Date: Fri, 28 Feb 2020 14:54:51 +0530	[thread overview]
Message-ID: <20200228092451.10455-1-madhuparnabhowmik10@gmail.com> (raw)

From: Madhuparna Bhowmik <madhuparnabhowmik10@gmail.com>

This patch default enables CONFIG_PROVE_RCU_LIST option with
CONFIG_PROVE_RCU for RCU list lockdep debugging.

With this change, RCU list lockdep debugging will be default
enabled in CONFIG_PROVE_RCU=y kernels.

Most of the RCU users (in core kernel/, drivers/, and net/
subsystem) have already been modified to include lockdep
expressions hence RCU list debugging can be enabled by
default.

However, there are still chances of enountering
false-positive lockdep splats because not everything is converted,
in case RCU list primitives are used in non-RCU read-side critical
section but under the protection of a lock. It would be okay to
have a few false-positives, as long as bugs are identified, since this
patch only affects debugging kernels.

Co-developed-by: Amol Grover <frextrite@gmail.com>
Signed-off-by: Amol Grover <frextrite@gmail.com>
Signed-off-by: Madhuparna Bhowmik <madhuparnabhowmik10@gmail.com>
---
 kernel/rcu/Kconfig.debug | 11 +++--------
 1 file changed, 3 insertions(+), 8 deletions(-)

diff --git a/kernel/rcu/Kconfig.debug b/kernel/rcu/Kconfig.debug
index 4aa02eee8f6c..ec4bb6c09048 100644
--- a/kernel/rcu/Kconfig.debug
+++ b/kernel/rcu/Kconfig.debug
@@ -9,15 +9,10 @@ config PROVE_RCU
 	def_bool PROVE_LOCKING
 
 config PROVE_RCU_LIST
-	bool "RCU list lockdep debugging"
-	depends on PROVE_RCU && RCU_EXPERT
-	default n
+	def_bool PROVE_RCU
 	help
-	  Enable RCU lockdep checking for list usages. By default it is
-	  turned off since there are several list RCU users that still
-	  need to be converted to pass a lockdep expression. To prevent
-	  false-positive splats, we keep it default disabled but once all
-	  users are converted, we can remove this config option.
+	  Enable RCU lockdep checking for list usages. It is default
+	  enabled with CONFIG_PROVE_RCU.
 
 config TORTURE_TEST
 	tristate
-- 
2.17.1

