Messages in this thread Patch in this message | | | From | Sasha Levin <> | Subject | [PATCH AUTOSEL 5.15 03/36] rcu: Make RCU_LOCKDEP_WARN() avoid early lockdep checks | Date | Sun, 26 Feb 2023 09:48:11 -0500 |
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From: "Paul E. McKenney" <paulmck@kernel.org>
[ 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 <rostedt@goodmis.org> Reported-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> Reported-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Boqun Feng <boqun.feng@gmail.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Sasha Levin <sashal@kernel.org> --- 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 434d12fe2d4f5..c8703fb3bfe44 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -311,11 +311,18 @@ 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); \ } \ -- 2.39.0
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