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/*-
* Copyright (c) 2014-present 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->stat_session_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 (!__atomic_test_and_set(&t->lock, __ATOMIC_ACQUIRE) ? 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 (__atomic_test_and_set(&t->lock, __ATOMIC_ACQUIRE)) {
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);
__atomic_clear(&t->lock, __ATOMIC_RELEASE);
}
#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
WT_DECL_RET;
pthread_mutexattr_t attr;
WT_RET(pthread_mutexattr_init(&attr));
ret = pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_ADAPTIVE_NP);
if (ret == 0)
ret = pthread_mutex_init(&t->lock, &attr);
WT_TRET(pthread_mutexattr_destroy(&attr));
WT_RET(ret);
#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_IGNORE_RET(__wt_panic(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_IGNORE_RET(__wt_panic(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, 4 * WT_THOUSAND) == 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)
#define WT_SPIN_INIT_SESSION_TRACKED(session, t, name) \
do { \
WT_SPIN_INIT_TRACKED(session, t, name); \
(t)->stat_session_usecs_off = \
(int16_t)WT_SESSION_STATS_FIELD_TO_OFFSET(&(session)->stats, lock_##name##_wait); \
} while (0)
/*
* __wt_spin_lock_track --
* Spinlock acquisition, with tracking.
*/
static inline void
__wt_spin_lock_track(WT_SESSION_IMPL *session, WT_SPINLOCK *t)
{
uint64_t time_diff, time_start, time_stop;
int64_t *session_stats, **stats;
if (t->stat_count_off != -1 && WT_STAT_ENABLED(session)) {
time_start = __wt_clock(session);
__wt_spin_lock(session, t);
time_stop = __wt_clock(session);
time_diff = WT_CLOCKDIFF_US(time_stop, time_start);
stats = (int64_t **)S2C(session)->stats;
session_stats = (int64_t *)&(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)time_diff;
else {
stats[session->stat_bucket][t->stat_app_usecs_off] += (int64_t)time_diff;
}
/*
* Not all spin locks increment session statistics. Check whether the offset is initialized
* to determine whether they are enabled.
*/
if (t->stat_session_usecs_off != -1)
session_stats[t->stat_session_usecs_off] += (int64_t)time_diff;
} 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));
}
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