linux-kernel - [PATCH v7 20/23] locking/spinlock: Introduce spin_lock_init

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Date:   Thu, 14 Feb 2019 15:00:55 -0800
From:   Bart Van Assche <bvanassche@....org>
To:     peterz@...radead.org
Cc:     mingo@...hat.com, will.deacon@....com, tj@...nel.org,
        longman@...hat.com, johannes.berg@...el.com,
        linux-kernel@...r.kernel.org, Bart Van Assche <bvanassche@....org>,
        Ingo Molnar <mingo@...nel.org>
Subject: [PATCH v7 20/23] locking/spinlock: Introduce spin_lock_init_key()

Some code uses nested locking of different spinlocks that share a
lock class. That results in false positives because spin_lock_init()
forces these instances to share a lock class. Make it possible to
avoid these false positives by allowing spinlock users to specify
the lock class at runtime.

Cc: Ingo Molnar <mingo@...nel.org>
Cc: Will Deacon <will.deacon@....com>
Signed-off-by: Bart Van Assche <bvanassche@....org>
---
 include/linux/spinlock.h | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/include/linux/spinlock.h b/include/linux/spinlock.h
index e089157dcf97..09b3e27ed21d 100644
--- a/include/linux/spinlock.h
+++ b/include/linux/spinlock.h
@@ -99,10 +99,19 @@ do {								\
 								\
 	__raw_spin_lock_init((lock), #lock, &__key);		\
 } while (0)
+#define raw_spin_lock_init_key(lock, key)			\
+	__raw_spin_lock_init((lock), #lock, key)
 
 #else
+
 # define raw_spin_lock_init(lock)				\
 	do { *(lock) = __RAW_SPIN_LOCK_UNLOCKED(lock); } while (0)
+static inline void raw_spin_lock_init_key(struct raw_spinlock *lock,
+					  struct lock_class_key *key)
+{
+	*(lock) = __RAW_SPIN_LOCK_UNLOCKED(lock);
+}
+
 #endif
 
 #define raw_spin_is_locked(lock)	arch_spin_is_locked(&(lock)->raw_lock)
@@ -324,6 +333,12 @@ do {							\
 	raw_spin_lock_init(&(_lock)->rlock);		\
 } while (0)
 
+#define spin_lock_init_key(_lock, _key)			\
+do {							\
+	spinlock_check(_lock);				\
+	raw_spin_lock_init_key(&(_lock)->rlock, _key);	\
+} while (0)
+
 static __always_inline void spin_lock(spinlock_t *lock)
 {
 	raw_spin_lock(&lock->rlock);
-- 
2.21.0.rc0.258.g878e2cd30e-goog