Ejemplo n.º 1
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 (!_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
}
Ejemplo n.º 2
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
}