mirror of https://gitee.com/openkylin/linux.git
135 lines
3.7 KiB
C
135 lines
3.7 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
|
|
#ifndef _LINUX_PERCPU_RWSEM_H
|
|
#define _LINUX_PERCPU_RWSEM_H
|
|
|
|
#include <linux/atomic.h>
|
|
#include <linux/rwsem.h>
|
|
#include <linux/percpu.h>
|
|
#include <linux/rcuwait.h>
|
|
#include <linux/rcu_sync.h>
|
|
#include <linux/lockdep.h>
|
|
|
|
struct percpu_rw_semaphore {
|
|
struct rcu_sync rss;
|
|
unsigned int __percpu *read_count;
|
|
struct rw_semaphore rw_sem; /* slowpath */
|
|
struct rcuwait writer; /* blocked writer */
|
|
int readers_block;
|
|
};
|
|
|
|
#define DEFINE_STATIC_PERCPU_RWSEM(name) \
|
|
static DEFINE_PER_CPU(unsigned int, __percpu_rwsem_rc_##name); \
|
|
static struct percpu_rw_semaphore name = { \
|
|
.rss = __RCU_SYNC_INITIALIZER(name.rss, RCU_SCHED_SYNC), \
|
|
.read_count = &__percpu_rwsem_rc_##name, \
|
|
.rw_sem = __RWSEM_INITIALIZER(name.rw_sem), \
|
|
.writer = __RCUWAIT_INITIALIZER(name.writer), \
|
|
}
|
|
|
|
extern int __percpu_down_read(struct percpu_rw_semaphore *, int);
|
|
extern void __percpu_up_read(struct percpu_rw_semaphore *);
|
|
|
|
static inline void percpu_down_read(struct percpu_rw_semaphore *sem)
|
|
{
|
|
might_sleep();
|
|
|
|
rwsem_acquire_read(&sem->rw_sem.dep_map, 0, 0, _RET_IP_);
|
|
|
|
preempt_disable();
|
|
/*
|
|
* We are in an RCU-sched read-side critical section, so the writer
|
|
* cannot both change sem->state from readers_fast and start checking
|
|
* counters while we are here. So if we see !sem->state, we know that
|
|
* the writer won't be checking until we're past the preempt_enable()
|
|
* and that once the synchronize_rcu() is done, the writer will see
|
|
* anything we did within this RCU-sched read-size critical section.
|
|
*/
|
|
__this_cpu_inc(*sem->read_count);
|
|
if (unlikely(!rcu_sync_is_idle(&sem->rss)))
|
|
__percpu_down_read(sem, false); /* Unconditional memory barrier */
|
|
/*
|
|
* The preempt_enable() prevents the compiler from
|
|
* bleeding the critical section out.
|
|
*/
|
|
preempt_enable();
|
|
}
|
|
|
|
static inline int percpu_down_read_trylock(struct percpu_rw_semaphore *sem)
|
|
{
|
|
int ret = 1;
|
|
|
|
preempt_disable();
|
|
/*
|
|
* Same as in percpu_down_read().
|
|
*/
|
|
__this_cpu_inc(*sem->read_count);
|
|
if (unlikely(!rcu_sync_is_idle(&sem->rss)))
|
|
ret = __percpu_down_read(sem, true); /* Unconditional memory barrier */
|
|
preempt_enable();
|
|
/*
|
|
* The barrier() from preempt_enable() prevents the compiler from
|
|
* bleeding the critical section out.
|
|
*/
|
|
|
|
if (ret)
|
|
rwsem_acquire_read(&sem->rw_sem.dep_map, 0, 1, _RET_IP_);
|
|
|
|
return ret;
|
|
}
|
|
|
|
static inline void percpu_up_read(struct percpu_rw_semaphore *sem)
|
|
{
|
|
preempt_disable();
|
|
/*
|
|
* Same as in percpu_down_read().
|
|
*/
|
|
if (likely(rcu_sync_is_idle(&sem->rss)))
|
|
__this_cpu_dec(*sem->read_count);
|
|
else
|
|
__percpu_up_read(sem); /* Unconditional memory barrier */
|
|
preempt_enable();
|
|
|
|
rwsem_release(&sem->rw_sem.dep_map, 1, _RET_IP_);
|
|
}
|
|
|
|
extern void percpu_down_write(struct percpu_rw_semaphore *);
|
|
extern void percpu_up_write(struct percpu_rw_semaphore *);
|
|
|
|
extern int __percpu_init_rwsem(struct percpu_rw_semaphore *,
|
|
const char *, struct lock_class_key *);
|
|
|
|
extern void percpu_free_rwsem(struct percpu_rw_semaphore *);
|
|
|
|
#define percpu_init_rwsem(sem) \
|
|
({ \
|
|
static struct lock_class_key rwsem_key; \
|
|
__percpu_init_rwsem(sem, #sem, &rwsem_key); \
|
|
})
|
|
|
|
#define percpu_rwsem_is_held(sem) lockdep_is_held(&(sem)->rw_sem)
|
|
|
|
#define percpu_rwsem_assert_held(sem) \
|
|
lockdep_assert_held(&(sem)->rw_sem)
|
|
|
|
static inline void percpu_rwsem_release(struct percpu_rw_semaphore *sem,
|
|
bool read, unsigned long ip)
|
|
{
|
|
lock_release(&sem->rw_sem.dep_map, 1, ip);
|
|
#ifdef CONFIG_RWSEM_SPIN_ON_OWNER
|
|
if (!read)
|
|
sem->rw_sem.owner = RWSEM_OWNER_UNKNOWN;
|
|
#endif
|
|
}
|
|
|
|
static inline void percpu_rwsem_acquire(struct percpu_rw_semaphore *sem,
|
|
bool read, unsigned long ip)
|
|
{
|
|
lock_acquire(&sem->rw_sem.dep_map, 0, 1, read, 1, NULL, ip);
|
|
#ifdef CONFIG_RWSEM_SPIN_ON_OWNER
|
|
if (!read)
|
|
sem->rw_sem.owner = current;
|
|
#endif
|
|
}
|
|
|
|
#endif
|