From: "Paul E. McKenney" <paulmck@kernel.org>
To: rcu@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, kernel-team@meta.com,
rostedt@goodmis.org, "Paul E. McKenney" <paulmck@kernel.org>,
Masami Hiramatsu <mhiramat@kernel.org>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
Boqun Feng <boqun.feng@gmail.com>,
Matthew Wilcox <willy@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>
Subject: [PATCH rcu 05/10] rcu: Make RCU_LOCKDEP_WARN() avoid early lockdep checks
Date: Wed, 4 Jan 2023 16:23:00 -0800 [thread overview]
Message-ID: <20230105002305.1768591-5-paulmck@kernel.org> (raw)
In-Reply-To: <20230105002257.GA1768487@paulmck-ThinkPad-P17-Gen-1>
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>
---
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 03abf883a281b..aa86de01aab6d 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -374,11 +374,18 @@ static inline int debug_lockdep_rcu_enabled(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); \
} \
--
2.31.1.189.g2e36527f23
next prev parent reply other threads:[~2023-01-05 0:23 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-05 0:22 [PATCH rcu 0/10] Miscellaneous fixes for v6.3 Paul E. McKenney
2023-01-05 0:22 ` [PATCH rcu 01/10] rcu: Use hlist_nulls_next_rcu() in hlist_nulls_add_tail_rcu() Paul E. McKenney
2023-01-05 0:22 ` [PATCH rcu 02/10] rcu: Consolidate initialization and CPU-hotplug code Paul E. McKenney
2023-01-05 0:22 ` [PATCH rcu 03/10] rcu: Throttle callback invocation based on number of ready callbacks Paul E. McKenney
2023-01-05 0:22 ` [PATCH rcu 04/10] rcu: Upgrade header comment for poll_state_synchronize_rcu() Paul E. McKenney
2023-01-05 0:23 ` Paul E. McKenney [this message]
2023-01-05 0:23 ` [PATCH rcu 06/10] rcu: Suppress smp_processor_id() complaint in synchronize_rcu_expedited_wait() Paul E. McKenney
2023-01-05 0:23 ` [PATCH rcu 07/10] rcu: Make rcu_blocking_is_gp() stop early-boot might_sleep() Paul E. McKenney
2023-01-05 0:23 ` [PATCH rcu 08/10] rcu: Test synchronous RCU grace periods at the end of rcu_init() Paul E. McKenney
2023-01-05 0:23 ` [PATCH rcu 09/10] rcu: Allow expedited RCU CPU stall warnings to dump task stacks Paul E. McKenney
2023-01-05 0:23 ` [PATCH rcu 10/10] rcu: Remove redundant call to rcu_boost_kthread_setaffinity() Paul E. McKenney
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