linux-kernel - [tip: locking/core] lockdep: Don't disable interrupts on RT in disable_irq_nosync

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Message-ID: <174198383247.14745.4699313484562904011.tip-bot2@tip-bot2>
Date: Fri, 14 Mar 2025 20:23:52 -0000
From: "tip-bot2 for Sebastian Andrzej Siewior" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Guenter Roeck <linux@...ck-us.net>,
 "Steven Rostedt (Google)" <rostedt@...dmis.org>,
 Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
 "Peter Zijlstra (Intel)" <peterz@...radead.org>, x86@...nel.org,
 linux-kernel@...r.kernel.org
Subject: [tip: locking/core] lockdep: Don't disable interrupts on RT in
 disable_irq_nosync_lockdep.*()

The following commit has been merged into the locking/core branch of tip:

Commit-ID:     87886b32d669abc11c7be95ef44099215e4f5788
Gitweb:        https://git.kernel.org/tip/87886b32d669abc11c7be95ef44099215e4f5788
Author:        Sebastian Andrzej Siewior <bigeasy@...utronix.de>
AuthorDate:    Wed, 12 Feb 2025 11:36:18 +01:00
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Fri, 14 Mar 2025 21:13:20 +01:00

lockdep: Don't disable interrupts on RT in disable_irq_nosync_lockdep.*()

disable_irq_nosync_lockdep() disables interrupts with lockdep enabled to
avoid false positive reports by lockdep that a certain lock has not been
acquired with disabled interrupts. The user of this macros expects that
a lock can be acquried without disabling interrupts because the IRQ line
triggering the interrupt is disabled.

This triggers a warning on PREEMPT_RT because after
disable_irq_nosync_lockdep.*() the following spinlock_t now is acquired
with disabled interrupts.

On PREEMPT_RT there is no difference between spin_lock() and
spin_lock_irq() so avoiding disabling interrupts in this case works for
the two remaining callers as of today.

Don't disable interrupts on PREEMPT_RT in disable_irq_nosync_lockdep.*().

Closes: https://lore.kernel.org/760e34f9-6034-40e0-82a5-ee9becd24438@roeck-us.net
Fixes: e8106b941ceab ("[PATCH] lockdep: core, add enable/disable_irq_irqsave/irqrestore() APIs")
Reported-by: Guenter Roeck <linux@...ck-us.net>
Suggested-by: "Steven Rostedt (Google)" <rostedt@...dmis.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Tested-by: Guenter Roeck <linux@...ck-us.net>
Link: https://lore.kernel.org/r/20250212103619.2560503-2-bigeasy@linutronix.de
---
 include/linux/interrupt.h | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
index 8cd9327..a1b1be9 100644
--- a/include/linux/interrupt.h
+++ b/include/linux/interrupt.h
@@ -448,7 +448,7 @@ irq_calc_affinity_vectors(unsigned int minvec, unsigned int maxvec,
 static inline void disable_irq_nosync_lockdep(unsigned int irq)
 {
 	disable_irq_nosync(irq);
-#ifdef CONFIG_LOCKDEP
+#if defined(CONFIG_LOCKDEP) && !defined(CONFIG_PREEMPT_RT)
 	local_irq_disable();
 #endif
 }
@@ -456,7 +456,7 @@ static inline void disable_irq_nosync_lockdep(unsigned int irq)
 static inline void disable_irq_nosync_lockdep_irqsave(unsigned int irq, unsigned long *flags)
 {
 	disable_irq_nosync(irq);
-#ifdef CONFIG_LOCKDEP
+#if defined(CONFIG_LOCKDEP) && !defined(CONFIG_PREEMPT_RT)
 	local_irq_save(*flags);
 #endif
 }
@@ -471,7 +471,7 @@ static inline void disable_irq_lockdep(unsigned int irq)
 
 static inline void enable_irq_lockdep(unsigned int irq)
 {
-#ifdef CONFIG_LOCKDEP
+#if defined(CONFIG_LOCKDEP) && !defined(CONFIG_PREEMPT_RT)
 	local_irq_enable();
 #endif
 	enable_irq(irq);
@@ -479,7 +479,7 @@ static inline void enable_irq_lockdep(unsigned int irq)
 
 static inline void enable_irq_lockdep_irqrestore(unsigned int irq, unsigned long *flags)
 {
-#ifdef CONFIG_LOCKDEP
+#if defined(CONFIG_LOCKDEP) && !defined(CONFIG_PREEMPT_RT)
 	local_irq_restore(*flags);
 #endif
 	enable_irq(irq);