linux-kernel - [PATCH] Enable RCU list lockdep debugging and drop CONFIG_PROVE_RCU

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Date:   Fri, 28 Feb 2020 01:53:55 +0530
From:   madhuparnabhowmik10@...il.com
To:     paulmck@...nel.org, josh@...htriplett.org, rostedt@...dmis.org,
        mathieu.desnoyers@...icios.com, jiangshanlai@...il.com,
        joel@...lfernandes.org
Cc:     linux-kernel@...r.kernel.org,
        Madhuparna Bhowmik <madhuparnabhowmik10@...il.com>,
        Amol Grover <frextrite@...il.com>
Subject: [PATCH] Enable RCU list lockdep debugging and drop CONFIG_PROVE_RCU_LIST

From: Madhuparna Bhowmik <madhuparnabhowmik10@...il.com>

This patch drops the CONFIG_PROVE_RCU_LIST option and instead
uses 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@...il.com>
Signed-off-by: Amol Grover <frextrite@...il.com>
Signed-off-by: Madhuparna Bhowmik <madhuparnabhowmik10@...il.com>
---
 include/linux/rculist.h  |  2 +-
 kernel/rcu/Kconfig.debug | 11 -----------
 2 files changed, 1 insertion(+), 12 deletions(-)

diff --git a/include/linux/rculist.h b/include/linux/rculist.h
index 63726577c6b8..f517eb421b5e 100644
--- a/include/linux/rculist.h
+++ b/include/linux/rculist.h
@@ -56,7 +56,7 @@ static inline void INIT_LIST_HEAD_RCU(struct list_head *list)
 
 #define check_arg_count_one(dummy)
 
-#ifdef CONFIG_PROVE_RCU_LIST
+#ifdef CONFIG_PROVE_RCU
 #define __list_check_rcu(dummy, cond, extra...)				\
 	({								\
 	check_arg_count_one(extra);					\
diff --git a/kernel/rcu/Kconfig.debug b/kernel/rcu/Kconfig.debug
index 4aa02eee8f6c..5ec3ea4028e2 100644
--- a/kernel/rcu/Kconfig.debug
+++ b/kernel/rcu/Kconfig.debug
@@ -8,17 +8,6 @@ menu "RCU Debugging"
 config PROVE_RCU
 	def_bool PROVE_LOCKING
 
-config PROVE_RCU_LIST
-	bool "RCU list lockdep debugging"
-	depends on PROVE_RCU && RCU_EXPERT
-	default n
-	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.
-
 config TORTURE_TEST
 	tristate
 	default n
-- 
2.17.1