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/*-
* Copyright (c) 2008-2013 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.
*/
#if SPINLOCK_TYPE == SPINLOCK_GCC
#define WT_DECL_SPINLOCK_ID(i)
#define __wt_spin_trylock(session, lock, idp) \
__wt_spin_trylock_func(session, lock)
/* Default to spinning 1000 times before yielding. */
#ifndef WT_SPIN_COUNT
#define WT_SPIN_COUNT 1000
#endif
static inline int
__wt_spin_init(WT_SESSION_IMPL *session, WT_SPINLOCK *t, const char *name)
{
WT_UNUSED(session);
WT_UNUSED(name);
*(t) = 0;
return (0);
}
static inline void
__wt_spin_destroy(WT_SESSION_IMPL *session, WT_SPINLOCK *t)
{
WT_UNUSED(session);
*(t) = 0;
}
static inline int
__wt_spin_trylock_func(WT_SESSION_IMPL *session, WT_SPINLOCK *t)
{
WT_UNUSED(session);
return (__sync_lock_test_and_set(t, 1) == 0 ? 0 : EBUSY);
}
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, 1)) {
for (i = 0; *t && i < WT_SPIN_COUNT; i++)
WT_PAUSE();
if (*t)
__wt_yield();
}
}
static inline void
__wt_spin_unlock(WT_SESSION_IMPL *session, WT_SPINLOCK *t)
{
WT_UNUSED(session);
__sync_lock_release(t);
}
#elif SPINLOCK_TYPE == SPINLOCK_PTHREAD_MUTEX ||\
SPINLOCK_TYPE == SPINLOCK_PTHREAD_MUTEX_LOGGING
static inline int
__wt_spin_init(WT_SESSION_IMPL *session, WT_SPINLOCK *t, const char *name)
{
#ifdef HAVE_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
t->name = name;
t->initialized = 1;
#if SPINLOCK_TYPE == SPINLOCK_PTHREAD_MUTEX_LOGGING
WT_RET(__wt_spin_lock_register_lock(session, t));
#endif
WT_UNUSED(session);
return (0);
}
static inline void
__wt_spin_destroy(WT_SESSION_IMPL *session, WT_SPINLOCK *t)
{
WT_UNUSED(session);
#if SPINLOCK_TYPE == SPINLOCK_PTHREAD_MUTEX_LOGGING
__wt_spin_lock_unregister_lock(session, t);
#endif
if (t->initialized) {
(void)pthread_mutex_destroy(&t->lock);
t->initialized = 0;
}
}
#if SPINLOCK_TYPE == SPINLOCK_PTHREAD_MUTEX
#define WT_DECL_SPINLOCK_ID(i)
#define __wt_spin_trylock(session, lock, idp) \
__wt_spin_trylock_func(session, lock)
static inline int
__wt_spin_trylock_func(WT_SESSION_IMPL *session, WT_SPINLOCK *t)
{
WT_UNUSED(session);
return (pthread_mutex_trylock(&t->lock));
}
static inline void
__wt_spin_lock(WT_SESSION_IMPL *session, WT_SPINLOCK *t)
{
WT_UNUSED(session);
pthread_mutex_lock(&t->lock);
}
#endif
#if SPINLOCK_TYPE == SPINLOCK_PTHREAD_MUTEX_LOGGING
/*
* When logging statistics, we track which spinlocks block and why.
*/
#define WT_DECL_SPINLOCK_ID(i) \
static int i = WT_SPINLOCK_REGISTER
#define WT_SPINLOCK_REGISTER -1
#define WT_SPINLOCK_REGISTER_FAILED -2
#define __wt_spin_trylock(session, lock, idp) \
__wt_spin_trylock_func(session, lock, idp, __FILE__, __LINE__)
#define __wt_spin_lock(session, lock) do { \
WT_DECL_SPINLOCK_ID(__id); \
__wt_spin_lock_func(session, lock, &__id, __FILE__, __LINE__); \
} while (0)
static inline int
__wt_spin_trylock_func(WT_SESSION_IMPL *session,
WT_SPINLOCK *t, int *idp, const char *file, int line)
{
WT_CONNECTION_IMPL *conn;
WT_DECL_RET;
/* If we're not maintaining statistics, it's simple. */
if (session == NULL || !(conn = S2C(session))->stat_fast)
return (pthread_mutex_trylock(&t->lock));
/*
* If this caller hasn't yet registered, do so. The caller's location
* ID is a static offset into a per-connection structure, and that has
* problems: first, if there are multiple connections, we'll need to
* hold some kind of lock to avoid racing when setting that value, and
* second, if/when there are multiple connections and/or a single
* connection is closed and re-opened, the variable may be initialized
* and the underlying connection information may not. Check both.
*/
if (*idp == WT_SPINLOCK_REGISTER ||
conn->spinlock_block[*idp].name == NULL)
WT_RET(__wt_spin_lock_register_caller(
session, t->name, file, line, idp));
/*
* Try to acquire the mutex: on failure, update blocking statistics, on
* success, set our ID as the mutex holder.
*
* Note the race between acquiring the lock and setting our ID as the
* holder, this can appear in the output as mutexes blocking in ways
* that can't actually happen (although still an indicator of a mutex
* that's busier than we'd like).
*/
if ((ret = pthread_mutex_trylock(&t->lock)) == 0)
t->id = *idp;
else
if (*idp >= 0) {
++conn->spinlock_block[*idp].total;
if (t->id >= 0)
++conn->spinlock_block[*idp].blocked[t->id];
}
/* Update the mutex counter and flush to minimize the windows. */
++t->counter;
WT_FULL_BARRIER();
return (ret);
}
static inline void
__wt_spin_lock_func(WT_SESSION_IMPL *session,
WT_SPINLOCK *t, int *idp, const char *file, int line)
{
/* If we're not maintaining statistics, it's simple. */
if (session == NULL || !S2C(session)->stat_fast) {
pthread_mutex_lock(&t->lock);
return;
}
/* Try to acquire the mutex. */
if (__wt_spin_trylock_func(session, t, idp, file, line) == 0)
return;
/*
* On failure, wait on the mutex; once acquired, set our ID as the
* holder and flush to minimize the windows.
*/
pthread_mutex_lock(&t->lock);
t->id = *idp;
WT_FULL_BARRIER();
}
#endif
static inline void
__wt_spin_unlock(WT_SESSION_IMPL *session, WT_SPINLOCK *t)
{
WT_UNUSED(session);
pthread_mutex_unlock(&t->lock);
}
#else
#error Unknown spinlock type
#endif
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