/*-
 * Copyright (c) 2014-2016 MongoDB, Inc.
 * Copyright (c) 2008-2014 WiredTiger, Inc.
 *	All rights reserved.
 *
 * See the file LICENSE for redistribution information.
 */

/*
 * Spin locks:
 *
 * These used for cases where fast mutual exclusion is needed (where operations
 * done while holding the spin lock are expected to complete in a small number
 * of instructions.
 */

/*
 * __spin_init_internal --
 *      Initialize the WT portion of a spinlock.
 */
static inline void
__spin_init_internal(WT_SPINLOCK *t, const char *name)
{
	t->name = name;
	t->stat_count_off = t->stat_app_usecs_off = t->stat_int_usecs_off = -1;
	t->initialized = 1;
}

#if SPINLOCK_TYPE == SPINLOCK_GCC

/* Default to spinning 1000 times before yielding. */
#ifndef WT_SPIN_COUNT
#define	WT_SPIN_COUNT WT_THOUSAND
#endif

/*
 * __wt_spin_init --
 *      Initialize a spinlock.
 */
static inline int
__wt_spin_init(WT_SESSION_IMPL *session, WT_SPINLOCK *t, const char *name)
{
	WT_UNUSED(session);

	t->lock = 0;
	__spin_init_internal(t, name);
	return (0);
}

/*
 * __wt_spin_destroy --
 *      Destroy a spinlock.
 */
static inline void
__wt_spin_destroy(WT_SESSION_IMPL *session, WT_SPINLOCK *t)
{
	WT_UNUSED(session);

	t->lock = 0;
}

/*
 * __wt_spin_trylock --
 *      Try to lock a spinlock or fail immediately if it is busy.
 */
static inline int
__wt_spin_trylock(WT_SESSION_IMPL *session, WT_SPINLOCK *t)
{
	WT_UNUSED(session);

	return (__sync_lock_test_and_set(&t->lock, 1) == 0 ? 0 : EBUSY);
}

/*
 * __wt_spin_lock --
 *      Spin until the lock is acquired.
 */
static inline void
__wt_spin_lock(WT_SESSION_IMPL *session, WT_SPINLOCK *t)
{
	int i;

	WT_UNUSED(session);

	while (__sync_lock_test_and_set(&t->lock, 1)) {
		for (i = 0; t->lock && i < WT_SPIN_COUNT; i++)
			WT_PAUSE();
		if (t->lock)
			__wt_yield();
	}
}

/*
 * __wt_spin_unlock --
 *      Release the spinlock.
 */
static inline void
__wt_spin_unlock(WT_SESSION_IMPL *session, WT_SPINLOCK *t)
{
	WT_UNUSED(session);

	__sync_lock_release(&t->lock);
}

#elif SPINLOCK_TYPE == SPINLOCK_PTHREAD_MUTEX ||\
	SPINLOCK_TYPE == SPINLOCK_PTHREAD_MUTEX_ADAPTIVE

/*
 * __wt_spin_init --
 *      Initialize a spinlock.
 */
static inline int
__wt_spin_init(WT_SESSION_IMPL *session, WT_SPINLOCK *t, const char *name)
{
#if SPINLOCK_TYPE == SPINLOCK_PTHREAD_MUTEX_ADAPTIVE
	pthread_mutexattr_t attr;

	WT_RET(pthread_mutexattr_init(&attr));
	WT_RET(pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_ADAPTIVE_NP));
	WT_RET(pthread_mutex_init(&t->lock, &attr));
#else
	WT_RET(pthread_mutex_init(&t->lock, NULL));
#endif
	__spin_init_internal(t, name);

	WT_UNUSED(session);
	return (0);
}

/*
 * __wt_spin_destroy --
 *      Destroy a spinlock.
 */
static inline void
__wt_spin_destroy(WT_SESSION_IMPL *session, WT_SPINLOCK *t)
{
	WT_UNUSED(session);

	if (t->initialized) {
		(void)pthread_mutex_destroy(&t->lock);
		t->initialized = 0;
	}
}

#if SPINLOCK_TYPE == SPINLOCK_PTHREAD_MUTEX ||\
	SPINLOCK_TYPE == SPINLOCK_PTHREAD_MUTEX_ADAPTIVE

/*
 * __wt_spin_trylock --
 *      Try to lock a spinlock or fail immediately if it is busy.
 */
static inline int
__wt_spin_trylock(WT_SESSION_IMPL *session, WT_SPINLOCK *t)
{
	WT_UNUSED(session);

	return (pthread_mutex_trylock(&t->lock));
}

/*
 * __wt_spin_lock --
 *      Spin until the lock is acquired.
 */
static inline void
__wt_spin_lock(WT_SESSION_IMPL *session, WT_SPINLOCK *t)
{
	WT_DECL_RET;

	if ((ret = pthread_mutex_lock(&t->lock)) != 0)
		WT_PANIC_MSG(session, ret, "pthread_mutex_lock: %s", t->name);
}
#endif

/*
 * __wt_spin_unlock --
 *      Release the spinlock.
 */
static inline void
__wt_spin_unlock(WT_SESSION_IMPL *session, WT_SPINLOCK *t)
{
	WT_DECL_RET;

	if ((ret = pthread_mutex_unlock(&t->lock)) != 0)
		WT_PANIC_MSG(session, ret, "pthread_mutex_unlock: %s", t->name);
}

#elif SPINLOCK_TYPE == SPINLOCK_MSVC

/*
 * __wt_spin_init --
 *      Initialize a spinlock.
 */
static inline int
__wt_spin_init(WT_SESSION_IMPL *session, WT_SPINLOCK *t, const char *name)
{
	DWORD windows_error;

	if (InitializeCriticalSectionAndSpinCount(&t->lock, 4000) == 0) {
		windows_error = __wt_getlasterror();
		__wt_errx(session,
		    "%s: InitializeCriticalSectionAndSpinCount: %s",
		    name, __wt_formatmessage(session, windows_error));
		return (__wt_map_windows_error(windows_error));
	}

	__spin_init_internal(t, name);
	return (0);
}

/*
 * __wt_spin_destroy --
 *      Destroy a spinlock.
 */
static inline void
__wt_spin_destroy(WT_SESSION_IMPL *session, WT_SPINLOCK *t)
{
	WT_UNUSED(session);

	if (t->initialized) {
		DeleteCriticalSection(&t->lock);
		t->initialized = 0;
	}
}

/*
 * __wt_spin_trylock --
 *      Try to lock a spinlock or fail immediately if it is busy.
 */
static inline int
__wt_spin_trylock(WT_SESSION_IMPL *session, WT_SPINLOCK *t)
{
	WT_UNUSED(session);

	BOOL b = TryEnterCriticalSection(&t->lock);
	return (b == 0 ? EBUSY : 0);
}

/*
 * __wt_spin_lock --
 *      Spin until the lock is acquired.
 */
static inline void
__wt_spin_lock(WT_SESSION_IMPL *session, WT_SPINLOCK *t)
{
	WT_UNUSED(session);

	EnterCriticalSection(&t->lock);
}

/*
 * __wt_spin_unlock --
 *      Release the spinlock.
 */
static inline void
__wt_spin_unlock(WT_SESSION_IMPL *session, WT_SPINLOCK *t)
{
	WT_UNUSED(session);

	LeaveCriticalSection(&t->lock);
}

#else

#error Unknown spinlock type

#endif

/*
 * WT_SPIN_INIT_TRACKED --
 *	Spinlock initialization, with tracking.
 *
 * Implemented as a macro so we can pass in a statistics field and convert
 * it into a statistics structure array offset.
 */
#define	WT_SPIN_INIT_TRACKED(session, t, name) do {			\
	WT_RET(__wt_spin_init(session, t, #name));			\
	(t)->stat_count_off = (int16_t)WT_STATS_FIELD_TO_OFFSET(	\
	    S2C(session)->stats, lock_##name##_count);			\
	(t)->stat_app_usecs_off = (int16_t)WT_STATS_FIELD_TO_OFFSET(	\
	    S2C(session)->stats, lock_##name##_wait_application);	\
	(t)->stat_int_usecs_off = (int16_t)WT_STATS_FIELD_TO_OFFSET(	\
	    S2C(session)->stats, lock_##name##_wait_internal);		\
} while (0)

/*
 * __wt_spin_lock_track --
 *	Spinlock acquisition, with tracking.
 */
static inline void
__wt_spin_lock_track(WT_SESSION_IMPL *session, WT_SPINLOCK *t)
{
	struct timespec enter, leave;
	int64_t **stats;

	if (t->stat_count_off != -1 && WT_STAT_ENABLED(session)) {
		__wt_epoch(session, &enter);
		__wt_spin_lock(session, t);
		__wt_epoch(session, &leave);
		stats = (int64_t **)S2C(session)->stats;
		stats[session->stat_bucket][t->stat_count_off]++;
		if (F_ISSET(session, WT_SESSION_INTERNAL))
			stats[session->stat_bucket][t->stat_int_usecs_off] +=
			    (int64_t)WT_TIMEDIFF_US(leave, enter);
		else
			stats[session->stat_bucket][t->stat_app_usecs_off] +=
			    (int64_t)WT_TIMEDIFF_US(leave, enter);
	} else
		__wt_spin_lock(session, t);
}

/*
 * __wt_spin_trylock_track --
 *      Try to lock a spinlock or fail immediately if it is busy.
 *      Track if successful.
 */
static inline int
__wt_spin_trylock_track(WT_SESSION_IMPL *session, WT_SPINLOCK *t)
{
	int64_t **stats;

	if (t->stat_count_off != -1 && WT_STAT_ENABLED(session)) {
		WT_RET(__wt_spin_trylock(session, t));
		stats = (int64_t **)S2C(session)->stats;
		stats[session->stat_bucket][t->stat_count_off]++;
		return (0);
	}
	return (__wt_spin_trylock(session, t));
}