Exemple #1
0
void
_thread_lock(struct thread *td)
#endif
{
	struct mtx *m;
	uintptr_t tid, v;

	tid = (uintptr_t)curthread;

	spinlock_enter();
	m = td->td_lock;
	thread_lock_validate(m, 0, file, line);
	v = MTX_READ_VALUE(m);
	if (__predict_true(v == MTX_UNOWNED)) {
		if (__predict_false(!_mtx_obtain_lock(m, tid)))
			goto slowpath_unlocked;
	} else if (v == tid) {
		m->mtx_recurse++;
	} else
		goto slowpath_unlocked;
	if (__predict_true(m == td->td_lock)) {
		WITNESS_LOCK(&m->lock_object, LOP_EXCLUSIVE, file, line);
		return;
	}
	if (m->mtx_recurse != 0)
		m->mtx_recurse--;
	else
		_mtx_release_lock_quick(m);
slowpath_unlocked:
	spinlock_exit();
	thread_lock_flags_(td, 0, 0, 0);
}
Exemple #2
0
/*
 * The important part of mtx_trylock{,_flags}()
 * Tries to acquire lock `m.'  If this function is called on a mutex that
 * is already owned, it will recursively acquire the lock.
 */
int
_mtx_trylock_flags_(volatile uintptr_t *c, int opts, const char *file, int line)
{
	struct mtx *m;
#ifdef LOCK_PROFILING
	uint64_t waittime = 0;
	int contested = 0;
#endif
	int rval;

	if (SCHEDULER_STOPPED())
		return (1);

	m = mtxlock2mtx(c);

	KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(curthread),
	    ("mtx_trylock() by idle thread %p on sleep mutex %s @ %s:%d",
	    curthread, m->lock_object.lo_name, file, line));
	KASSERT(m->mtx_lock != MTX_DESTROYED,
	    ("mtx_trylock() of destroyed mutex @ %s:%d", file, line));
	KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_sleep,
	    ("mtx_trylock() of spin mutex %s @ %s:%d", m->lock_object.lo_name,
	    file, line));

	if (mtx_owned(m) && ((m->lock_object.lo_flags & LO_RECURSABLE) != 0 ||
	    (opts & MTX_RECURSE) != 0)) {
		m->mtx_recurse++;
		atomic_set_ptr(&m->mtx_lock, MTX_RECURSED);
		rval = 1;
	} else
		rval = _mtx_obtain_lock(m, (uintptr_t)curthread);
	opts &= ~MTX_RECURSE;

	LOCK_LOG_TRY("LOCK", &m->lock_object, opts, rval, file, line);
	if (rval) {
		WITNESS_LOCK(&m->lock_object, opts | LOP_EXCLUSIVE | LOP_TRYLOCK,
		    file, line);
		TD_LOCKS_INC(curthread);
		if (m->mtx_recurse == 0)
			LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(adaptive__acquire,
			    m, contested, waittime, file, line);

	}

	return (rval);
}
Exemple #3
0
/*
 * _mtx_lock_spin: the tougher part of acquiring an MTX_SPIN lock.
 *
 * This is only called if we need to actually spin for the lock. Recursion
 * is handled inline.
 */
void
_mtx_lock_spin(struct mtx *m, uintptr_t tid, int opts, const char *file,
    int line)
{
	int i = 0;
#ifdef LOCK_PROFILING
	int contested = 0;
	uint64_t waittime = 0;
#endif

	if (LOCK_LOG_TEST(&m->lock_object, opts))
		CTR1(KTR_LOCK, "_mtx_lock_spin: %p spinning", m);

	lock_profile_obtain_lock_failed(&m->lock_object, &contested, &waittime);
	while (!_mtx_obtain_lock(m, tid)) {

		/* Give interrupts a chance while we spin. */
		spinlock_exit();
		while (m->mtx_lock != MTX_UNOWNED) {
			if (i++ < 10000000) {
				cpu_spinwait();
				continue;
			}
			if (i < 60000000 || kdb_active || panicstr != NULL)
				DELAY(1);
			else
				_mtx_lock_spin_failed(m);
			cpu_spinwait();
		}
		spinlock_enter();
	}

	if (LOCK_LOG_TEST(&m->lock_object, opts))
		CTR1(KTR_LOCK, "_mtx_lock_spin: %p spin done", m);

	LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(LS_MTX_SPIN_LOCK_ACQUIRE, m,
	    contested, waittime, (file), (line));
	LOCKSTAT_RECORD1(LS_MTX_SPIN_LOCK_SPIN, m, i);
}
Exemple #4
0
/*
 * The important part of mtx_trylock{,_flags}()
 * Tries to acquire lock `m.'  If this function is called on a mutex that
 * is already owned, it will recursively acquire the lock.
 */
int
_mtx_trylock(struct mtx *m, int opts, const char *file, int line)
{
#ifdef LOCK_PROFILING
	uint64_t waittime = 0;
	int contested = 0;
#endif
	int rval;

	MPASS(curthread != NULL);
	KASSERT(m->mtx_lock != MTX_DESTROYED,
	    ("mtx_trylock() of destroyed mutex @ %s:%d", file, line));
	KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_sleep,
	    ("mtx_trylock() of spin mutex %s @ %s:%d", m->lock_object.lo_name,
	    file, line));

	if (mtx_owned(m) && (m->lock_object.lo_flags & LO_RECURSABLE) != 0) {
		m->mtx_recurse++;
		atomic_set_ptr(&m->mtx_lock, MTX_RECURSED);
		rval = 1;
	} else
		rval = _mtx_obtain_lock(m, (uintptr_t)curthread);

	LOCK_LOG_TRY("LOCK", &m->lock_object, opts, rval, file, line);
	if (rval) {
		WITNESS_LOCK(&m->lock_object, opts | LOP_EXCLUSIVE | LOP_TRYLOCK,
		    file, line);
		curthread->td_locks++;
		if (m->mtx_recurse == 0)
			LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(LS_MTX_LOCK_ACQUIRE,
			    m, contested, waittime, file, line);

	}

	return (rval);
}
Exemple #5
0
void
_thread_lock_flags(struct thread *td, int opts, const char *file, int line)
{
	struct mtx *m;
	uintptr_t tid;
	int i;
#ifdef LOCK_PROFILING
	int contested = 0;
	uint64_t waittime = 0;
#endif
#ifdef KDTRACE_HOOKS
	uint64_t spin_cnt = 0;
#endif

	i = 0;
	tid = (uintptr_t)curthread;
	for (;;) {
retry:
		spinlock_enter();
		m = td->td_lock;
		KASSERT(m->mtx_lock != MTX_DESTROYED,
		    ("thread_lock() of destroyed mutex @ %s:%d", file, line));
		KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin,
		    ("thread_lock() of sleep mutex %s @ %s:%d",
		    m->lock_object.lo_name, file, line));
		if (mtx_owned(m))
			KASSERT((m->lock_object.lo_flags & LO_RECURSABLE) != 0,
	    ("thread_lock: recursed on non-recursive mutex %s @ %s:%d\n",
			    m->lock_object.lo_name, file, line));
		WITNESS_CHECKORDER(&m->lock_object,
		    opts | LOP_NEWORDER | LOP_EXCLUSIVE, file, line, NULL);
		while (!_mtx_obtain_lock(m, tid)) {
#ifdef KDTRACE_HOOKS
			spin_cnt++;
#endif
			if (m->mtx_lock == tid) {
				m->mtx_recurse++;
				break;
			}
			lock_profile_obtain_lock_failed(&m->lock_object,
			    &contested, &waittime);
			/* Give interrupts a chance while we spin. */
			spinlock_exit();
			while (m->mtx_lock != MTX_UNOWNED) {
				if (i++ < 10000000)
					cpu_spinwait();
				else if (i < 60000000 ||
				    kdb_active || panicstr != NULL)
					DELAY(1);
				else
					_mtx_lock_spin_failed(m);
				cpu_spinwait();
				if (m != td->td_lock)
					goto retry;
			}
			spinlock_enter();
		}
		if (m == td->td_lock)
			break;
		__mtx_unlock_spin(m);	/* does spinlock_exit() */
#ifdef KDTRACE_HOOKS
		spin_cnt++;
#endif
	}
	if (m->mtx_recurse == 0)
		LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(LS_MTX_SPIN_LOCK_ACQUIRE,
		    m, contested, waittime, (file), (line));
	LOCK_LOG_LOCK("LOCK", &m->lock_object, opts, m->mtx_recurse, file,
	    line);
	WITNESS_LOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line);
	LOCKSTAT_RECORD1(LS_THREAD_LOCK_SPIN, m, spin_cnt);
}
Exemple #6
0
/*
 * _mtx_lock_sleep: the tougher part of acquiring an MTX_DEF lock.
 *
 * We call this if the lock is either contested (i.e. we need to go to
 * sleep waiting for it), or if we need to recurse on it.
 */
void
_mtx_lock_sleep(struct mtx *m, uintptr_t tid, int opts, const char *file,
    int line)
{
	struct turnstile *ts;
	uintptr_t v;
#ifdef ADAPTIVE_MUTEXES
	volatile struct thread *owner;
#endif
#ifdef KTR
	int cont_logged = 0;
#endif
#ifdef LOCK_PROFILING
	int contested = 0;
	uint64_t waittime = 0;
#endif
#ifdef KDTRACE_HOOKS
	uint64_t spin_cnt = 0;
	uint64_t sleep_cnt = 0;
	int64_t sleep_time = 0;
#endif

	if (mtx_owned(m)) {
		KASSERT((m->lock_object.lo_flags & LO_RECURSABLE) != 0,
	    ("_mtx_lock_sleep: recursed on non-recursive mutex %s @ %s:%d\n",
		    m->lock_object.lo_name, file, line));
		m->mtx_recurse++;
		atomic_set_ptr(&m->mtx_lock, MTX_RECURSED);
		if (LOCK_LOG_TEST(&m->lock_object, opts))
			CTR1(KTR_LOCK, "_mtx_lock_sleep: %p recursing", m);
		return;
	}

	lock_profile_obtain_lock_failed(&m->lock_object,
		    &contested, &waittime);
	if (LOCK_LOG_TEST(&m->lock_object, opts))
		CTR4(KTR_LOCK,
		    "_mtx_lock_sleep: %s contested (lock=%p) at %s:%d",
		    m->lock_object.lo_name, (void *)m->mtx_lock, file, line);

	while (!_mtx_obtain_lock(m, tid)) {
#ifdef KDTRACE_HOOKS
		spin_cnt++;
#endif
#ifdef ADAPTIVE_MUTEXES
		/*
		 * If the owner is running on another CPU, spin until the
		 * owner stops running or the state of the lock changes.
		 */
		v = m->mtx_lock;
		if (v != MTX_UNOWNED) {
			owner = (struct thread *)(v & ~MTX_FLAGMASK);
			if (TD_IS_RUNNING(owner)) {
				if (LOCK_LOG_TEST(&m->lock_object, 0))
					CTR3(KTR_LOCK,
					    "%s: spinning on %p held by %p",
					    __func__, m, owner);
				while (mtx_owner(m) == owner &&
				    TD_IS_RUNNING(owner)) {
					cpu_spinwait();
#ifdef KDTRACE_HOOKS
					spin_cnt++;
#endif
				}
				continue;
			}
		}
#endif

		ts = turnstile_trywait(&m->lock_object);
		v = m->mtx_lock;

		/*
		 * Check if the lock has been released while spinning for
		 * the turnstile chain lock.
		 */
		if (v == MTX_UNOWNED) {
			turnstile_cancel(ts);
			continue;
		}

#ifdef ADAPTIVE_MUTEXES
		/*
		 * The current lock owner might have started executing
		 * on another CPU (or the lock could have changed
		 * owners) while we were waiting on the turnstile
		 * chain lock.  If so, drop the turnstile lock and try
		 * again.
		 */
		owner = (struct thread *)(v & ~MTX_FLAGMASK);
		if (TD_IS_RUNNING(owner)) {
			turnstile_cancel(ts);
			continue;
		}
#endif

		/*
		 * If the mutex isn't already contested and a failure occurs
		 * setting the contested bit, the mutex was either released
		 * or the state of the MTX_RECURSED bit changed.
		 */
		if ((v & MTX_CONTESTED) == 0 &&
		    !atomic_cmpset_ptr(&m->mtx_lock, v, v | MTX_CONTESTED)) {
			turnstile_cancel(ts);
			continue;
		}

		/*
		 * We definitely must sleep for this lock.
		 */
		mtx_assert(m, MA_NOTOWNED);

#ifdef KTR
		if (!cont_logged) {
			CTR6(KTR_CONTENTION,
			    "contention: %p at %s:%d wants %s, taken by %s:%d",
			    (void *)tid, file, line, m->lock_object.lo_name,
			    WITNESS_FILE(&m->lock_object),
			    WITNESS_LINE(&m->lock_object));
			cont_logged = 1;
		}
#endif

		/*
		 * Block on the turnstile.
		 */
#ifdef KDTRACE_HOOKS
		sleep_time -= lockstat_nsecs();
#endif
		turnstile_wait(ts, mtx_owner(m), TS_EXCLUSIVE_QUEUE);
#ifdef KDTRACE_HOOKS
		sleep_time += lockstat_nsecs();
		sleep_cnt++;
#endif
	}
#ifdef KTR
	if (cont_logged) {
		CTR4(KTR_CONTENTION,
		    "contention end: %s acquired by %p at %s:%d",
		    m->lock_object.lo_name, (void *)tid, file, line);
	}
#endif
	LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(LS_MTX_LOCK_ACQUIRE, m, contested,
	    waittime, file, line);
#ifdef KDTRACE_HOOKS
	if (sleep_time)
		LOCKSTAT_RECORD1(LS_MTX_LOCK_BLOCK, m, sleep_time);

	/*
	 * Only record the loops spinning and not sleeping. 
	 */
	if (spin_cnt > sleep_cnt)
		LOCKSTAT_RECORD1(LS_MTX_LOCK_SPIN, m, (spin_cnt - sleep_cnt));
#endif
}
Exemple #7
0
void
thread_lock_flags_(struct thread *td, int opts, const char *file, int line)
{
	struct mtx *m;
	uintptr_t tid;
	struct lock_delay_arg lda;
#ifdef LOCK_PROFILING
	int contested = 0;
	uint64_t waittime = 0;
#endif
#ifdef KDTRACE_HOOKS
	int64_t spin_time = 0;
#endif

	tid = (uintptr_t)curthread;

	if (SCHEDULER_STOPPED()) {
		/*
		 * Ensure that spinlock sections are balanced even when the
		 * scheduler is stopped, since we may otherwise inadvertently
		 * re-enable interrupts while dumping core.
		 */
		spinlock_enter();
		return;
	}

	lock_delay_arg_init(&lda, &mtx_spin_delay);

#ifdef KDTRACE_HOOKS
	spin_time -= lockstat_nsecs(&td->td_lock->lock_object);
#endif
	for (;;) {
retry:
		spinlock_enter();
		m = td->td_lock;
		KASSERT(m->mtx_lock != MTX_DESTROYED,
		    ("thread_lock() of destroyed mutex @ %s:%d", file, line));
		KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin,
		    ("thread_lock() of sleep mutex %s @ %s:%d",
		    m->lock_object.lo_name, file, line));
		if (mtx_owned(m))
			KASSERT((m->lock_object.lo_flags & LO_RECURSABLE) != 0,
	    ("thread_lock: recursed on non-recursive mutex %s @ %s:%d\n",
			    m->lock_object.lo_name, file, line));
		WITNESS_CHECKORDER(&m->lock_object,
		    opts | LOP_NEWORDER | LOP_EXCLUSIVE, file, line, NULL);
		for (;;) {
			if (m->mtx_lock == MTX_UNOWNED && _mtx_obtain_lock(m, tid))
				break;
			if (m->mtx_lock == tid) {
				m->mtx_recurse++;
				break;
			}
#ifdef HWPMC_HOOKS
			PMC_SOFT_CALL( , , lock, failed);
#endif
			lock_profile_obtain_lock_failed(&m->lock_object,
			    &contested, &waittime);
			/* Give interrupts a chance while we spin. */
			spinlock_exit();
			while (m->mtx_lock != MTX_UNOWNED) {
				if (lda.spin_cnt < 10000000) {
					lock_delay(&lda);
				} else {
					lda.spin_cnt++;
					if (lda.spin_cnt < 60000000 ||
					    kdb_active || panicstr != NULL)
						DELAY(1);
					else
						_mtx_lock_spin_failed(m);
					cpu_spinwait();
				}
				if (m != td->td_lock)
					goto retry;
			}
			spinlock_enter();
		}
		if (m == td->td_lock)
			break;
		__mtx_unlock_spin(m);	/* does spinlock_exit() */
	}
#ifdef KDTRACE_HOOKS
	spin_time += lockstat_nsecs(&m->lock_object);
#endif
	if (m->mtx_recurse == 0)
		LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(spin__acquire, m,
		    contested, waittime, file, line);
	LOCK_LOG_LOCK("LOCK", &m->lock_object, opts, m->mtx_recurse, file,
	    line);
	WITNESS_LOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line);
#ifdef KDTRACE_HOOKS
	if (spin_time != 0)
		LOCKSTAT_RECORD1(thread__spin, m, spin_time);
#endif
}
Exemple #8
0
/*
 * _mtx_lock_spin_cookie: the tougher part of acquiring an MTX_SPIN lock.
 *
 * This is only called if we need to actually spin for the lock. Recursion
 * is handled inline.
 */
void
_mtx_lock_spin_cookie(volatile uintptr_t *c, uintptr_t tid, int opts,
    const char *file, int line)
{
	struct mtx *m;
	struct lock_delay_arg lda;
#ifdef LOCK_PROFILING
	int contested = 0;
	uint64_t waittime = 0;
#endif
#ifdef KDTRACE_HOOKS
	int64_t spin_time = 0;
#endif

	if (SCHEDULER_STOPPED())
		return;

	lock_delay_arg_init(&lda, &mtx_spin_delay);
	m = mtxlock2mtx(c);

	if (LOCK_LOG_TEST(&m->lock_object, opts))
		CTR1(KTR_LOCK, "_mtx_lock_spin: %p spinning", m);
	KTR_STATE1(KTR_SCHED, "thread", sched_tdname((struct thread *)tid),
	    "spinning", "lockname:\"%s\"", m->lock_object.lo_name);

#ifdef HWPMC_HOOKS
	PMC_SOFT_CALL( , , lock, failed);
#endif
	lock_profile_obtain_lock_failed(&m->lock_object, &contested, &waittime);
#ifdef KDTRACE_HOOKS
	spin_time -= lockstat_nsecs(&m->lock_object);
#endif
	for (;;) {
		if (m->mtx_lock == MTX_UNOWNED && _mtx_obtain_lock(m, tid))
			break;
		/* Give interrupts a chance while we spin. */
		spinlock_exit();
		while (m->mtx_lock != MTX_UNOWNED) {
			if (lda.spin_cnt < 10000000) {
				lock_delay(&lda);
				continue;
			}
			lda.spin_cnt++;
			if (lda.spin_cnt < 60000000 || kdb_active ||
			    panicstr != NULL)
				DELAY(1);
			else
				_mtx_lock_spin_failed(m);
			cpu_spinwait();
		}
		spinlock_enter();
	}
#ifdef KDTRACE_HOOKS
	spin_time += lockstat_nsecs(&m->lock_object);
#endif

	if (LOCK_LOG_TEST(&m->lock_object, opts))
		CTR1(KTR_LOCK, "_mtx_lock_spin: %p spin done", m);
	KTR_STATE0(KTR_SCHED, "thread", sched_tdname((struct thread *)tid),
	    "running");

#ifdef KDTRACE_HOOKS
	LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(spin__acquire, m,
	    contested, waittime, file, line);
	if (spin_time != 0)
		LOCKSTAT_RECORD1(spin__spin, m, spin_time);
#endif
}
Exemple #9
0
/*
 * __mtx_lock_sleep: the tougher part of acquiring an MTX_DEF lock.
 *
 * We call this if the lock is either contested (i.e. we need to go to
 * sleep waiting for it), or if we need to recurse on it.
 */
void
__mtx_lock_sleep(volatile uintptr_t *c, uintptr_t tid, int opts,
    const char *file, int line)
{
	struct mtx *m;
	struct turnstile *ts;
	uintptr_t v;
#ifdef ADAPTIVE_MUTEXES
	volatile struct thread *owner;
#endif
#ifdef KTR
	int cont_logged = 0;
#endif
#ifdef LOCK_PROFILING
	int contested = 0;
	uint64_t waittime = 0;
#endif
#if defined(ADAPTIVE_MUTEXES) || defined(KDTRACE_HOOKS)
	struct lock_delay_arg lda;
#endif
#ifdef KDTRACE_HOOKS
	u_int sleep_cnt = 0;
	int64_t sleep_time = 0;
	int64_t all_time = 0;
#endif

	if (SCHEDULER_STOPPED())
		return;

#if defined(ADAPTIVE_MUTEXES)
	lock_delay_arg_init(&lda, &mtx_delay);
#elif defined(KDTRACE_HOOKS)
	lock_delay_arg_init(&lda, NULL);
#endif
	m = mtxlock2mtx(c);

	if (mtx_owned(m)) {
		KASSERT((m->lock_object.lo_flags & LO_RECURSABLE) != 0 ||
		    (opts & MTX_RECURSE) != 0,
	    ("_mtx_lock_sleep: recursed on non-recursive mutex %s @ %s:%d\n",
		    m->lock_object.lo_name, file, line));
		opts &= ~MTX_RECURSE;
		m->mtx_recurse++;
		atomic_set_ptr(&m->mtx_lock, MTX_RECURSED);
		if (LOCK_LOG_TEST(&m->lock_object, opts))
			CTR1(KTR_LOCK, "_mtx_lock_sleep: %p recursing", m);
		return;
	}
	opts &= ~MTX_RECURSE;

#ifdef HWPMC_HOOKS
	PMC_SOFT_CALL( , , lock, failed);
#endif
	lock_profile_obtain_lock_failed(&m->lock_object,
		    &contested, &waittime);
	if (LOCK_LOG_TEST(&m->lock_object, opts))
		CTR4(KTR_LOCK,
		    "_mtx_lock_sleep: %s contested (lock=%p) at %s:%d",
		    m->lock_object.lo_name, (void *)m->mtx_lock, file, line);
#ifdef KDTRACE_HOOKS
	all_time -= lockstat_nsecs(&m->lock_object);
#endif

	for (;;) {
		if (m->mtx_lock == MTX_UNOWNED && _mtx_obtain_lock(m, tid))
			break;
#ifdef KDTRACE_HOOKS
		lda.spin_cnt++;
#endif
#ifdef ADAPTIVE_MUTEXES
		/*
		 * If the owner is running on another CPU, spin until the
		 * owner stops running or the state of the lock changes.
		 */
		v = m->mtx_lock;
		if (v != MTX_UNOWNED) {
			owner = (struct thread *)(v & ~MTX_FLAGMASK);
			if (TD_IS_RUNNING(owner)) {
				if (LOCK_LOG_TEST(&m->lock_object, 0))
					CTR3(KTR_LOCK,
					    "%s: spinning on %p held by %p",
					    __func__, m, owner);
				KTR_STATE1(KTR_SCHED, "thread",
				    sched_tdname((struct thread *)tid),
				    "spinning", "lockname:\"%s\"",
				    m->lock_object.lo_name);
				while (mtx_owner(m) == owner &&
				    TD_IS_RUNNING(owner))
					lock_delay(&lda);
				KTR_STATE0(KTR_SCHED, "thread",
				    sched_tdname((struct thread *)tid),
				    "running");
				continue;
			}
		}
#endif

		ts = turnstile_trywait(&m->lock_object);
		v = m->mtx_lock;

		/*
		 * Check if the lock has been released while spinning for
		 * the turnstile chain lock.
		 */
		if (v == MTX_UNOWNED) {
			turnstile_cancel(ts);
			continue;
		}

#ifdef ADAPTIVE_MUTEXES
		/*
		 * The current lock owner might have started executing
		 * on another CPU (or the lock could have changed
		 * owners) while we were waiting on the turnstile
		 * chain lock.  If so, drop the turnstile lock and try
		 * again.
		 */
		owner = (struct thread *)(v & ~MTX_FLAGMASK);
		if (TD_IS_RUNNING(owner)) {
			turnstile_cancel(ts);
			continue;
		}
#endif

		/*
		 * If the mutex isn't already contested and a failure occurs
		 * setting the contested bit, the mutex was either released
		 * or the state of the MTX_RECURSED bit changed.
		 */
		if ((v & MTX_CONTESTED) == 0 &&
		    !atomic_cmpset_ptr(&m->mtx_lock, v, v | MTX_CONTESTED)) {
			turnstile_cancel(ts);
			continue;
		}

		/*
		 * We definitely must sleep for this lock.
		 */
		mtx_assert(m, MA_NOTOWNED);

#ifdef KTR
		if (!cont_logged) {
			CTR6(KTR_CONTENTION,
			    "contention: %p at %s:%d wants %s, taken by %s:%d",
			    (void *)tid, file, line, m->lock_object.lo_name,
			    WITNESS_FILE(&m->lock_object),
			    WITNESS_LINE(&m->lock_object));
			cont_logged = 1;
		}
#endif

		/*
		 * Block on the turnstile.
		 */
#ifdef KDTRACE_HOOKS
		sleep_time -= lockstat_nsecs(&m->lock_object);
#endif
		turnstile_wait(ts, mtx_owner(m), TS_EXCLUSIVE_QUEUE);
#ifdef KDTRACE_HOOKS
		sleep_time += lockstat_nsecs(&m->lock_object);
		sleep_cnt++;
#endif
	}
#ifdef KDTRACE_HOOKS
	all_time += lockstat_nsecs(&m->lock_object);
#endif
#ifdef KTR
	if (cont_logged) {
		CTR4(KTR_CONTENTION,
		    "contention end: %s acquired by %p at %s:%d",
		    m->lock_object.lo_name, (void *)tid, file, line);
	}
#endif
	LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(adaptive__acquire, m, contested,
	    waittime, file, line);
#ifdef KDTRACE_HOOKS
	if (sleep_time)
		LOCKSTAT_RECORD1(adaptive__block, m, sleep_time);

	/*
	 * Only record the loops spinning and not sleeping. 
	 */
	if (lda.spin_cnt > sleep_cnt)
		LOCKSTAT_RECORD1(adaptive__spin, m, all_time - sleep_time);
#endif
}