linux-kernel - [tip: locking/core] locking/rtmutex: Restrict the trylock WARN

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Date:   Wed, 24 Mar 2021 07:22:27 -0000
From:   "tip-bot2 for Thomas Gleixner" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: locking/core] locking/rtmutex: Restrict the trylock WARN_ON() to debug

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

Commit-ID:     3ac7d0ecf0e18b44c2c7dc968ce5afc5beadf17c
Gitweb:        https://git.kernel.org/tip/3ac7d0ecf0e18b44c2c7dc968ce5afc5beadf17c
Author:        Thomas Gleixner <tglx@...utronix.de>
AuthorDate:    Tue, 23 Mar 2021 22:30:33 +01:00
Committer:     Ingo Molnar <mingo@...nel.org>
CommitterDate: Wed, 24 Mar 2021 08:08:16 +01:00

locking/rtmutex: Restrict the trylock WARN_ON() to debug

The warning as written is expensive and not really required for a
production kernel. Make it depend on rt mutex debugging and use !in_task()
for the condition which generates far better code and gives the same
answer.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Link: https://lore.kernel.org/r/20210323213708.908341972@linutronix.de
---
 kernel/locking/rtmutex.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c
index bece7aa..d584e32 100644
--- a/kernel/locking/rtmutex.c
+++ b/kernel/locking/rtmutex.c
@@ -1495,9 +1495,8 @@ int __sched __rt_mutex_futex_trylock(struct rt_mutex *lock)
  *
  * @lock:	the rt_mutex to be locked
  *
- * This function can only be called in thread context. It's safe to
- * call it from atomic regions, but not from hard interrupt or soft
- * interrupt context.
+ * This function can only be called in thread context. It's safe to call it
+ * from atomic regions, but not from hard or soft interrupt context.
  *
  * Returns 1 on success and 0 on contention
  */
@@ -1505,7 +1504,7 @@ int __sched rt_mutex_trylock(struct rt_mutex *lock)
 {
 	int ret;
 
-	if (WARN_ON_ONCE(in_irq() || in_nmi() || in_serving_softirq()))
+	if (IS_ENABLED(CONFIG_RT_MUTEX_DEBUG) && WARN_ON_ONCE(!in_task()))
 		return 0;
 
 	ret = rt_mutex_fasttrylock(lock, rt_mutex_slowtrylock);