#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((atomic_long_t *)&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,
				     (atomic_long_t *)&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,
				     (atomic_long_t *)&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((atomic_long_t *)&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,
				 (atomic_long_t *)&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,
				     (atomic_long_t *)&sem->count);
	if (tmp < 0)
		rwsem_downgrade_wake(sem);
}

#endif	/* __KERNEL__ */
#endif	/* _ASM_GENERIC_RWSEM_H */
remove&amp;id=b4c4ebcf3ca22bf9b04fa9c6ccfbfdfe0a256d07'>net</a>/<a href='/cgit.cgi/linux/net-next.git/log/include/net/sock.h?h=nds-private-remove&amp;id=b4c4ebcf3ca22bf9b04fa9c6ccfbfdfe0a256d07'>sock.h</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/cgit.cgi/linux/net-next.git/log/include/net/sock.h?h=nds-private-remove&amp;id=b4c4ebcf3ca22bf9b04fa9c6ccfbfdfe0a256d07&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th><th class='left'>Files</th><th class='left'>Lines</th></tr>
<tr><td><span title='2017-02-07 16:29:30 -0500'>2017-02-07</span></td><td><a href='/cgit.cgi/linux/net-next.git/commit/include/net/sock.h?h=nds-private-remove&amp;id=3efa70d78f218e4c9276b0bac0545e5184c1c47b'>Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net</a></td><td>David S. Miller