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rcu: Make RCU_LOCKDEP_WARN() avoid early lockdep checks

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[ 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>
This commit is contained in:
Paul E. McKenney 2022-12-14 11:41:44 -08:00 committed by Greg Kroah-Hartman
parent d6ef66194b
commit f5657f3306
1 changed files with 8 additions and 1 deletions
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9
include/linux/rcupdate.h
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@ -308,11 +308,18 @@ static inline int rcu_read_lock_any_held(void)
* RCU_LOCKDEP_WARN - emit lockdep splat if specified condition is met * RCU_LOCKDEP_WARN - emit lockdep splat if specified condition is met
* @c: condition to check * @c: condition to check
* @s: informative message * @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) \ #define RCU_LOCKDEP_WARN(c, s) \
do { \ do { \
static bool __section(".data.unlikely") __warned; \ 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; \ __warned = true; \
lockdep_rcu_suspicious(__FILE__, __LINE__, s); \ lockdep_rcu_suspicious(__FILE__, __LINE__, s); \
} \ } \