rwsem_rt.h
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#ifndef _LINUX_RWSEM_RT_H
#define _LINUX_RWSEM_RT_H
#ifndef _LINUX_RWSEM_H
#error "Include rwsem.h"
#endif
/*
* RW-semaphores are a spinlock plus a reader-depth count.
*
* Note that the semantics are different from the usual
* Linux rw-sems, in PREEMPT_RT mode we do not allow
* multiple readers to hold the lock at once, we only allow
* a read-lock owner to read-lock recursively. This is
* better for latency, makes the implementation inherently
* fair and makes it simpler as well.
*/
#include <linux/rtmutex.h>
struct rw_semaphore {
struct rt_mutex lock;
int read_depth;
#ifdef CONFIG_DEBUG_LOCK_ALLOC
struct lockdep_map dep_map;
#endif
};
#define __RWSEM_INITIALIZER(name) \
{ .lock = __RT_MUTEX_INITIALIZER(name.lock), \
RW_DEP_MAP_INIT(name) }
#define DECLARE_RWSEM(lockname) \
struct rw_semaphore lockname = __RWSEM_INITIALIZER(lockname)
extern void __rt_rwsem_init(struct rw_semaphore *rwsem, const char *name,
struct lock_class_key *key);
#define __rt_init_rwsem(sem, name, key) \
do { \
rt_mutex_init(&(sem)->lock); \
__rt_rwsem_init((sem), (name), (key));\
} while (0)
#define __init_rwsem(sem, name, key) __rt_init_rwsem(sem, name, key)
# define rt_init_rwsem(sem) \
do { \
static struct lock_class_key __key; \
\
__rt_init_rwsem((sem), #sem, &__key); \
} while (0)
extern void rt_down_write(struct rw_semaphore *rwsem);
extern void rt_down_read_nested(struct rw_semaphore *rwsem, int subclass);
extern void rt_down_write_nested(struct rw_semaphore *rwsem, int subclass);
extern void rt_down_write_nested_lock(struct rw_semaphore *rwsem,
struct lockdep_map *nest);
extern void rt__down_read(struct rw_semaphore *rwsem);
extern void rt_down_read(struct rw_semaphore *rwsem);
extern int rt_down_write_trylock(struct rw_semaphore *rwsem);
extern int rt__down_read_trylock(struct rw_semaphore *rwsem);
extern int rt_down_read_trylock(struct rw_semaphore *rwsem);
extern void __rt_up_read(struct rw_semaphore *rwsem);
extern void rt_up_read(struct rw_semaphore *rwsem);
extern void rt_up_write(struct rw_semaphore *rwsem);
extern void rt_downgrade_write(struct rw_semaphore *rwsem);
#define init_rwsem(sem) rt_init_rwsem(sem)
#define rwsem_is_locked(s) rt_mutex_is_locked(&(s)->lock)
static inline int rwsem_is_contended(struct rw_semaphore *sem)
{
/* rt_mutex_has_waiters() */
return !RB_EMPTY_ROOT(&sem->lock.waiters);
}
static inline void __down_read(struct rw_semaphore *sem)
{
rt__down_read(sem);
}
static inline void down_read(struct rw_semaphore *sem)
{
rt_down_read(sem);
}
static inline int __down_read_trylock(struct rw_semaphore *sem)
{
return rt__down_read_trylock(sem);
}
static inline int down_read_trylock(struct rw_semaphore *sem)
{
return rt_down_read_trylock(sem);
}
static inline void down_write(struct rw_semaphore *sem)
{
rt_down_write(sem);
}
static inline int down_write_trylock(struct rw_semaphore *sem)
{
return rt_down_write_trylock(sem);
}
static inline void __up_read(struct rw_semaphore *sem)
{
__rt_up_read(sem);
}
static inline void up_read(struct rw_semaphore *sem)
{
rt_up_read(sem);
}
static inline void up_write(struct rw_semaphore *sem)
{
rt_up_write(sem);
}
static inline void downgrade_write(struct rw_semaphore *sem)
{
rt_downgrade_write(sem);
}
static inline void down_read_nested(struct rw_semaphore *sem, int subclass)
{
return rt_down_read_nested(sem, subclass);
}
static inline void down_write_nested(struct rw_semaphore *sem, int subclass)
{
rt_down_write_nested(sem, subclass);
}
#ifdef CONFIG_DEBUG_LOCK_ALLOC
static inline void down_write_nest_lock(struct rw_semaphore *sem,
struct rw_semaphore *nest_lock)
{
rt_down_write_nested_lock(sem, &nest_lock->dep_map);
}
#else
static inline void down_write_nest_lock(struct rw_semaphore *sem,
struct rw_semaphore *nest_lock)
{
rt_down_write_nested_lock(sem, NULL);
}
#endif
#endif