#ifndef _ASM_GENERIC_RWSEM_H#define _ASM_GENERIC_RWSEM_H #ifndef _LINUX_RWSEM_H#error "Please don't include <asm/rwsem.h> directly, use <linux/rwsem.h> instead."#endif #ifdef __KERNEL__ /* * R/W semaphores originally for PPC using the stuff in lib/rwsem.c. * Adapted largely from include/asm-i386/rwsem.h * by Paul Mackerras <paulus@samba.org>. */ /* * the semaphore definition */#ifdef CONFIG_64BIT# define RWSEM_ACTIVE_MASK 0xffffffffL#else# define RWSEM_ACTIVE_MASK 0x0000ffffL#endif #define RWSEM_UNLOCKED_VALUE 0x00000000L#define RWSEM_ACTIVE_BIAS 0x00000001L#define RWSEM_WAITING_BIAS (-RWSEM_ACTIVE_MASK-1)#define RWSEM_ACTIVE_READ_BIAS RWSEM_ACTIVE_BIAS#define RWSEM_ACTIVE_WRITE_BIAS (RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS) /* * lock for reading */static inline void __down_read(struct rw_semaphore *sem){ if (unlikely(atomic_long_inc_return_acquire(&sem->count) <= 0)) rwsem_down_read_failed(sem);} static inline int __down_read_trylock(struct rw_semaphore *sem){ long tmp; while ((tmp = atomic_long_read(&sem->count)) >= 0) { if (tmp == atomic_long_cmpxchg_acquire(&sem->count, tmp, tmp + RWSEM_ACTIVE_READ_BIAS)) { return 1; } } return 0;} /* * lock for writing */static inline void __down_write(struct rw_semaphore *sem){ long tmp; tmp = atomic_long_add_return_acquire(RWSEM_ACTIVE_WRITE_BIAS, &sem->count); if (unlikely(tmp != RWSEM_ACTIVE_WRITE_BIAS)) rwsem_down_write_failed(sem);} static inline int __down_write_killable(struct rw_semaphore *sem){ long tmp; tmp = atomic_long_add_return_acquire(RWSEM_ACTIVE_WRITE_BIAS, &sem->count); if (unlikely(tmp != RWSEM_ACTIVE_WRITE_BIAS)) if (IS_ERR(rwsem_down_write_failed_killable(sem))) return -EINTR; return 0;} static inline int __down_write_trylock(struct rw_semaphore *sem){ long tmp; tmp = atomic_long_cmpxchg_acquire(&sem->count, RWSEM_UNLOCKED_VALUE, RWSEM_ACTIVE_WRITE_BIAS); return tmp == RWSEM_UNLOCKED_VALUE;} /* * unlock after reading */static inline void __up_read(struct rw_semaphore *sem){ long tmp; tmp = atomic_long_dec_return_release(&sem->count); if (unlikely(tmp < -1 && (tmp & RWSEM_ACTIVE_MASK) == 0)) rwsem_wake(sem);} /* * unlock after writing */static inline void __up_write(struct rw_semaphore *sem){ if (unlikely(atomic_long_sub_return_release(RWSEM_ACTIVE_WRITE_BIAS, &sem->count) < 0)) rwsem_wake(sem);} /* * downgrade write lock to read lock */static inline void __downgrade_write(struct rw_semaphore *sem){ long tmp; /* * When downgrading from exclusive to shared ownership, * anything inside the write-locked region cannot leak * into the read side. In contrast, anything in the * read-locked region is ok to be re-ordered into the * write side. As such, rely on RELEASE semantics. */ tmp = atomic_long_add_return_release(-RWSEM_WAITING_BIAS, &sem->count); if (tmp < 0) rwsem_downgrade_wake(sem);} #endif /* __KERNEL__ */#endif /* _ASM_GENERIC_RWSEM_H */
#ifndef _ASM_GENERIC_RWSEM_H
#define _ASM_GENERIC_RWSEM_H
#ifndef _LINUX_RWSEM_H
#error "Please don't include <asm/rwsem.h> directly, use <linux/rwsem.h> instead."
#endif
#ifdef __KERNEL__
/*
* R/W semaphores originally for PPC using the stuff in lib/rwsem.c.
* Adapted largely from include/asm-i386/rwsem.h
* by Paul Mackerras <paulus@samba.org>.
*/
/*
* the semaphore definition
*/
#ifdef CONFIG_64BIT
# define RWSEM_ACTIVE_MASK 0xffffffffL
#else
# define RWSEM_ACTIVE_MASK 0x0000ffffL
#endif
#define RWSEM_UNLOCKED_VALUE 0x00000000L
#define RWSEM_ACTIVE_BIAS 0x00000001L
#define RWSEM_WAITING_BIAS (-RWSEM_ACTIVE_MASK-1)
#define RWSEM_ACTIVE_READ_BIAS RWSEM_ACTIVE_BIAS
#define RWSEM_ACTIVE_WRITE_BIAS (RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)
/*
* lock for reading
*/
static inline void __down_read(struct rw_semaphore *sem)
{
if (unlikely(atomic_long_inc_return_acquire(&sem->count) <= 0))
rwsem_down_read_failed(sem);
}
static inline int __down_read_trylock(struct rw_semaphore *sem)
{
long tmp;
while ((tmp = atomic_long_read(&sem->count)) >= 0) {
if (tmp == atomic_long_cmpxchg_acquire(&sem->count, tmp,
tmp + RWSEM_ACTIVE_READ_BIAS)) {
return 1;
}
}
return 0;
}
/*
* lock for writing
*/
static inline void __down_write(struct rw_semaphore *sem)
{
long tmp;
tmp = atomic_long_add_return_acquire(RWSEM_ACTIVE_WRITE_BIAS,
&sem->count);
if (unlikely(tmp != RWSEM_ACTIVE_WRITE_BIAS))
rwsem_down_write_failed(sem);
}
static inline int __down_write_killable(struct rw_semaphore *sem)
{
long tmp;
tmp = atomic_long_add_return_acquire(RWSEM_ACTIVE_WRITE_BIAS,
&sem->count);
if (unlikely(tmp != RWSEM_ACTIVE_WRITE_BIAS))
if (IS_ERR(rwsem_down_write_failed_killable(sem)))
return -EINTR;
return 0;
}
static inline int __down_write_trylock(struct rw_semaphore *sem)
{
long tmp;
tmp = atomic_long_cmpxchg_acquire(&sem->count, RWSEM_UNLOCKED_VALUE,
RWSEM_ACTIVE_WRITE_BIAS);
return tmp == RWSEM_UNLOCKED_VALUE;
}
/*
* unlock after reading
*/
static inline void __up_read(struct rw_semaphore *sem)
{
long tmp;
tmp = atomic_long_dec_return_release(&sem->count);
if (unlikely(tmp < -1 && (tmp & RWSEM_ACTIVE_MASK) == 0))
rwsem_wake(sem);
}
/*
* unlock after writing
*/
static inline void __up_write(struct rw_semaphore *sem)
{
if (unlikely(atomic_long_sub_return_release(RWSEM_ACTIVE_WRITE_BIAS,
&sem->count) < 0))
rwsem_wake(sem);
}
/*
* downgrade write lock to read lock
*/
static inline void __downgrade_write(struct rw_semaphore *sem)
{
long tmp;
/*
* When downgrading from exclusive to shared ownership,
* anything inside the write-locked region cannot leak
* into the read side. In contrast, anything in the
* read-locked region is ok to be re-ordered into the
* write side. As such, rely on RELEASE semantics.
*/
tmp = atomic_long_add_return_release(-RWSEM_WAITING_BIAS, &sem->count);
if (tmp < 0)
rwsem_downgrade_wake(sem);
}
#endif /* __KERNEL__ */
#endif /* _ASM_GENERIC_RWSEM_H */