From 4a501b4ef88170a860be55ad98efb4aab9e1bdfe Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Wed, 14 Dec 2022 11:41:44 -0800 Subject: [PATCH] rcu: Make RCU_LOCKDEP_WARN() avoid early lockdep checks [ Upstream commit 0cae5ded535c3a80aed94f119bbd4ee3ae284a65 ] Currently, RCU_LOCKDEP_WARN() checks the condition before checking to see if lockdep is still enabled. This is necessary to avoid the false-positive splats fixed by commit 3066820034b5dd ("rcu: Reject RCU_LOCKDEP_WARN() false positives"). However, the current state can result in false-positive splats during early boot before lockdep is fully initialized. This commit therefore checks debug_lockdep_rcu_enabled() both before and after checking the condition, thus avoiding both sets of false-positive error reports. Reported-by: Steven Rostedt Reported-by: Masami Hiramatsu (Google) Reported-by: Mathieu Desnoyers Signed-off-by: Paul E. McKenney Reviewed-by: Mathieu Desnoyers Cc: Boqun Feng Cc: Matthew Wilcox Cc: Thomas Gleixner Signed-off-by: Sasha Levin --- include/linux/rcupdate.h | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 4a3fd34..e9e61cd 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -350,11 +350,18 @@ static inline int rcu_read_lock_any_held(void) * RCU_LOCKDEP_WARN - emit lockdep splat if specified condition is met * @c: condition to check * @s: informative message + * + * This checks debug_lockdep_rcu_enabled() before checking (c) to + * prevent early boot splats due to lockdep not yet being initialized, + * and rechecks it after checking (c) to prevent false-positive splats + * due to races with lockdep being disabled. See commit 3066820034b5dd + * ("rcu: Reject RCU_LOCKDEP_WARN() false positives") for more detail. */ #define RCU_LOCKDEP_WARN(c, s) \ do { \ static bool __section(".data.unlikely") __warned; \ - if ((c) && debug_lockdep_rcu_enabled() && !__warned) { \ + if (debug_lockdep_rcu_enabled() && (c) && \ + debug_lockdep_rcu_enabled() && !__warned) { \ __warned = true; \ lockdep_rcu_suspicious(__FILE__, __LINE__, s); \ } \ -- 2.7.4