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Release 4.15 include/linux/percpu-rwsem.h

Directory: include/linux
/* 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_preempt_disable(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 one the synchronize_sched() 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 */ barrier(); /* * The barrier() prevents the compiler from * bleeding the critical section out. */ }

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Peter Zijlstra69100.00%2100.00%
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static inline void percpu_down_read(struct percpu_rw_semaphore *sem) { percpu_down_read_preempt_disable(sem); preempt_enable(); }

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Peter Zijlstra20100.00%2100.00%
Total20100.00%2100.00%


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; }

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Peter Zijlstra80100.00%1100.00%
Total80100.00%1100.00%


static inline void percpu_up_read_preempt_enable(struct percpu_rw_semaphore *sem) { /* * The barrier() prevents the compiler from * bleeding the critical section out. */ barrier(); /* * 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_); }

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Peter Zijlstra5690.32%266.67%
Mikulas Patocka69.68%133.33%
Total62100.00%3100.00%


static inline void percpu_up_read(struct percpu_rw_semaphore *sem) { preempt_disable(); percpu_up_read_preempt_enable(sem); }

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Peter Zijlstra20100.00%1100.00%
Total20100.00%1100.00%

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 = NULL; #endif }

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Oleg Nesterov51100.00%1100.00%
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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); }

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Oleg Nesterov41100.00%1100.00%
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#endif

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Peter Zijlstra27355.38%325.00%
Oleg Nesterov14930.22%650.00%
Mikulas Patocka6412.98%18.33%
Davidlohr Bueso A61.22%18.33%
Greg Kroah-Hartman10.20%18.33%
Total493100.00%12100.00%
Directory: include/linux
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