linux-kernel - [PATCH v2 1/4] locking/mutex: implement mutex_trylock

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Message-Id: <20250409014136.2816971-2-mlevitsk@redhat.com>
Date: Tue,  8 Apr 2025 21:41:33 -0400
From: Maxim Levitsky <mlevitsk@...hat.com>
To: kvm@...r.kernel.org
Cc: Alexander Potapenko <glider@...gle.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Suzuki K Poulose <suzuki.poulose@....com>,
	kvm-riscv@...ts.infradead.org,
	Oliver Upton <oliver.upton@...ux.dev>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Jing Zhang <jingzhangos@...gle.com>,
	Waiman Long <longman@...hat.com>,
	x86@...nel.org,
	Kunkun Jiang <jiangkunkun@...wei.com>,
	Boqun Feng <boqun.feng@...il.com>,
	Anup Patel <anup@...infault.org>,
	Albert Ou <aou@...s.berkeley.edu>,
	kvmarm@...ts.linux.dev,
	linux-kernel@...r.kernel.org,
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	Alexandre Ghiti <alex@...ti.fr>,
	Keisuke Nishimura <keisuke.nishimura@...ia.fr>,
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	linux-riscv@...ts.infradead.org,
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	Thomas Gleixner <tglx@...utronix.de>,
	Sean Christopherson <seanjc@...gle.com>,
	Catalin Marinas <catalin.marinas@....com>,
	Maxim Levitsky <mlevitsk@...hat.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>
Subject: [PATCH v2 1/4] locking/mutex: implement mutex_trylock_nested

Allow to specify the lockdep subclass in mutex_trylock
instead of hardcoding it to 0.

Signed-off-by: Maxim Levitsky <mlevitsk@...hat.com>
---
 include/linux/mutex.h  |  8 ++++++++
 kernel/locking/mutex.c | 14 +++++++++++---
 2 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/include/linux/mutex.h b/include/linux/mutex.h
index 2143d05116be..ea568d6c4c68 100644
--- a/include/linux/mutex.h
+++ b/include/linux/mutex.h
@@ -193,7 +193,15 @@ extern void mutex_lock_io(struct mutex *lock);
  *
  * Returns 1 if the mutex has been acquired successfully, and 0 on contention.
  */
+
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+extern int mutex_trylock_nested(struct mutex *lock, unsigned int subclass);
+#define mutex_trylock(lock) mutex_trylock_nested(lock, 0)
+#else
 extern int mutex_trylock(struct mutex *lock);
+#define mutex_trylock_nested(lock, subclass) mutex_trylock(lock)
+#endif
+
 extern void mutex_unlock(struct mutex *lock);
 
 extern int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock);
diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c
index 555e2b3a665a..5e3078865f2b 100644
--- a/kernel/locking/mutex.c
+++ b/kernel/locking/mutex.c
@@ -1062,6 +1062,7 @@ __ww_mutex_lock_interruptible_slowpath(struct ww_mutex *lock,
 
 #endif
 
+#ifndef CONFIG_DEBUG_LOCK_ALLOC
 /**
  * mutex_trylock - try to acquire the mutex, without waiting
  * @lock: the mutex to be acquired
@@ -1077,18 +1078,25 @@ __ww_mutex_lock_interruptible_slowpath(struct ww_mutex *lock,
  * mutex must be released by the same task that acquired it.
  */
 int __sched mutex_trylock(struct mutex *lock)
+{
+	MUTEX_WARN_ON(lock->magic != lock);
+	return __mutex_trylock(lock);
+}
+EXPORT_SYMBOL(mutex_trylock);
+#else
+int __sched mutex_trylock_nested(struct mutex *lock, unsigned int subclass)
 {
 	bool locked;
 
 	MUTEX_WARN_ON(lock->magic != lock);
-
 	locked = __mutex_trylock(lock);
 	if (locked)
-		mutex_acquire(&lock->dep_map, 0, 1, _RET_IP_);
+		mutex_acquire(&lock->dep_map, subclass, 1, _RET_IP_);
 
 	return locked;
 }
-EXPORT_SYMBOL(mutex_trylock);
+EXPORT_SYMBOL(mutex_trylock_nested);
+#endif
 
 #ifndef CONFIG_DEBUG_LOCK_ALLOC
 int __sched
-- 
2.26.3