[PATCH bpf-next v2 3/6] locking/local_lock: Introduce local_trylock_irqsave()

[Alexei Starovoitov <alexei.starovoitov@gmail.com>]

From: Alexei Starovoitov <ast@kernel.org>

Similar to local_lock_irqsave() introduce local_trylock_irqsave().
It uses spin_trylock in PREEMPT_RT and always succeeds when !RT.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
---
 include/linux/local_lock.h          |  9 +++++++++
 include/linux/local_lock_internal.h | 23 +++++++++++++++++++++++
 2 files changed, 32 insertions(+)

diff --git a/include/linux/local_lock.h b/include/linux/local_lock.h
index 091dc0b6bdfb..6880c29b8b98 100644
--- a/include/linux/local_lock.h
+++ b/include/linux/local_lock.h
@@ -30,6 +30,15 @@
 #define local_lock_irqsave(lock, flags)				\
 	__local_lock_irqsave(lock, flags)
 
+/**
+ * local_trylock_irqsave - Try to acquire a per CPU local lock, save and disable
+ *			   interrupts. Always succeeds in !PREEMPT_RT.
+ * @lock:	The lock variable
+ * @flags:	Storage for interrupt flags
+ */
+#define local_trylock_irqsave(lock, flags)			\
+	__local_trylock_irqsave(lock, flags)
+
 /**
  * local_unlock - Release a per CPU local lock
  * @lock:	The lock variable
diff --git a/include/linux/local_lock_internal.h b/include/linux/local_lock_internal.h
index 8dd71fbbb6d2..2c0f8a49c2d0 100644
--- a/include/linux/local_lock_internal.h
+++ b/include/linux/local_lock_internal.h
@@ -31,6 +31,13 @@ static inline void local_lock_acquire(local_lock_t *l)
 	l->owner = current;
 }
 
+static inline void local_trylock_acquire(local_lock_t *l)
+{
+	lock_map_acquire_try(&l->dep_map);
+	DEBUG_LOCKS_WARN_ON(l->owner);
+	l->owner = current;
+}
+
 static inline void local_lock_release(local_lock_t *l)
 {
 	DEBUG_LOCKS_WARN_ON(l->owner != current);
@@ -45,6 +52,7 @@ static inline void local_lock_debug_init(local_lock_t *l)
 #else /* CONFIG_DEBUG_LOCK_ALLOC */
 # define LOCAL_LOCK_DEBUG_INIT(lockname)
 static inline void local_lock_acquire(local_lock_t *l) { }
+static inline void local_trylock_acquire(local_lock_t *l) { }
 static inline void local_lock_release(local_lock_t *l) { }
 static inline void local_lock_debug_init(local_lock_t *l) { }
 #endif /* !CONFIG_DEBUG_LOCK_ALLOC */
@@ -91,6 +99,13 @@ do {								\
 		local_lock_acquire(this_cpu_ptr(lock));		\
 	} while (0)
 
+#define __local_trylock_irqsave(lock, flags)			\
+	({							\
+		local_irq_save(flags);				\
+		local_trylock_acquire(this_cpu_ptr(lock));	\
+		1;						\
+	})
+
 #define __local_unlock(lock)					\
 	do {							\
 		local_lock_release(this_cpu_ptr(lock));		\
@@ -148,6 +163,14 @@ typedef spinlock_t local_lock_t;
 		__local_lock(lock);				\
 	} while (0)
 
+#define __local_trylock_irqsave(lock, flags)			\
+	({							\
+		typecheck(unsigned long, flags);		\
+		flags = 0;					\
+		migrate_disable();				\
+		spin_trylock(this_cpu_ptr((__lock)));		\
+	})
+
 #define __local_unlock(__lock)					\
 	do {							\
 		spin_unlock(this_cpu_ptr((__lock)));		\
-- 
2.43.5