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

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Date:   Mon, 29 Mar 2021 16:24:07 -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>,
        "Peter Zijlstra (Intel)" <peterz@...radead.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:     c2c360ed7f28fd6b7eb7e39e70af2d2ae405f466
Gitweb:        https://git.kernel.org/tip/c2c360ed7f28fd6b7eb7e39e70af2d2ae405f466
Author:        Thomas Gleixner <tglx@...utronix.de>
AuthorDate:    Fri, 26 Mar 2021 16:29:43 +01:00
Committer:     Ingo Molnar <mingo@...nel.org>
CommitterDate: Mon, 29 Mar 2021 15:57:04 +02:00

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>
Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Link: https://lore.kernel.org/r/20210326153944.436565064@linutronix.de
---
 kernel/locking/rtmutex.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c
index 512b400..c68542d 100644
--- a/kernel/locking/rtmutex.c
+++ b/kernel/locking/rtmutex.c
@@ -1456,7 +1456,7 @@ 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_DEBUG_RT_MUTEXES) && WARN_ON_ONCE(!in_task()))
 		return 0;
 
 	/*