Example #1
0
// we assume to have exclusive ownership of DATA: we're the only ones allowed
// to write to it as the owning thread is (normally) dying.
// This assumption should remain valid until the moment we put the node (data)
// in the place of the "free" field of the SMR global data, at which time
// we relinquish ownership.
// A thread dequeueing a node from free should not assume to have ownership until
// it succeeds a CAS setting the new value of the free field in the SMR global data.
// That's why we set that field to NULL to assume ownership of the node as well. 
// Normally, no-one should be traversing the queue of nodes at that time, but 
// we take some measures to accomodate for that (im)possibility anyway.
// Also note we've added a flag to the local data type (hptr_local_data_t)
// which is 1 if the hptr scanning logic should no longer count on our 
// "next" field to be valid.
static void smr_hptr_free_list_enq(hptr_local_data_t * data)
{
	unsigned int i;
	hptr_local_data_t * exp;
	hptr_local_data_t * ptr = NULL;
	
	// make our node ready for inclusion in the free list
	// clear out all existing hazardous references
	for (i = 0; i < smr_global_data->k; i++)
		atomic_set_ptr(&(data->hp[i]), NULL);
	// set out flag
	atomic_set_int(&(data->flag), 1);
	// NOTE: we expect atomic_set_* to do the right thing concerning 
	// memory barriers: we expect the setting of the flag to be visible 
	// before the clearing of the next pointer!
	
	// clear out our next pointer
	atomic_set_ptr(&(data->next), NULL);
	// try to set it to smr_global_data->free first.
	exp = NULL;
	while (compare_and_exchange_ptr(&exp, &(smr_global_data->free), data) != 0)
	{	// Otherwise, set smr_global_data->free to NULL (and get whatever is in there);
		// set its old value to our next and put us in its place.
		// "Whatever is in there" is what we have in exp now..
		if (compare_and_exchange_ptr(&exp, &(smr_global_data->free), NULL) != 0)
			continue;
		// we may have been here more than once, in which case ptr holds whatever we have in our next field..
		if (compare_and_exchange_ptr(&ptr, &(data->next), NULL) != 0)
			assert(0); // just in case..
		// we now put whatever is in ptr at the end of exp - which might be a whole queue for all we know..
		if (exp != NULL && ptr != NULL) 
		{
			hptr_local_data_t * head = exp;
			hptr_local_data_t * tail = exp;
			
			while (1)
			{
				// find the tail of the queue in exp (now head)
				while (tail->next != NULL)
					tail = tail->next;
				// we expect a NULL at the end of this queue
				exp = NULL;
				// try to put ptr at the end of the queue
				if (compare_and_exchange_ptr(&exp, &(tail->next), ptr) != 0)
				{	// otherwise, we start over from scratch
					tail = head;
					continue;
				}
			}
			// when we get here, ptr is at the end of the queue we want to add to our node
			// so we add the queue...
			exp = NULL;
			if (compare_and_exchange_ptr(&exp, &(data->next), head) != 0)
				// someone was still writing to our node - that should be impossible..
				assert(0);
		}
		exp = NULL;
	}
	// when we get here, we're done.
}
Example #2
0
/* NOTE: this function is *not* thread-safe: we assume that only one
 * thread will call this function at any time! */
static void lt_sem_deq(lt_sem_t * sem)
{
	lt_thread_t * first;
	lt_thread_t * next;
	
	first = sem->queue;
	next = first->next;
	atomic_set_ptr(&(sem->queue), next);
	if (sem->queue == NULL)
		atomic_set_ptr(&(sem->tail), NULL);
}
Example #3
0
static void smr_hptr_free_list_enq(hptr_local_data_t * data)
{
	hptr_local_data_t * exp;
	
	for (i = 0; i < smr_global_data->k; i++)
		atomic_set_ptr(&(data->hp[i]), NULL);	// we need this to be atomic because some-one might be reading our hazard pointers
	atomic_set_int(&(data->flag), 1);
	atomic_set_ptr(&(data->next), NULL);
	
	exp = NULL;
	while (compare_and_exchange_ptr(&exp, &(smr_global_data->free), data) != 0)
	{
		data->next = exp;
	}
}
Example #4
0
int
sx_try_xlock_(struct sx *sx, const char *file, int line)
{
	int rval;

	if (SCHEDULER_STOPPED())
		return (1);

	KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(curthread),
	    ("sx_try_xlock() by idle thread %p on sx %s @ %s:%d",
	    curthread, sx->lock_object.lo_name, file, line));
	KASSERT(sx->sx_lock != SX_LOCK_DESTROYED,
	    ("sx_try_xlock() of destroyed sx @ %s:%d", file, line));

	if (sx_xlocked(sx) &&
	    (sx->lock_object.lo_flags & LO_RECURSABLE) != 0) {
		sx->sx_recurse++;
		atomic_set_ptr(&sx->sx_lock, SX_LOCK_RECURSED);
		rval = 1;
	} else
		rval = atomic_cmpset_acq_ptr(&sx->sx_lock, SX_LOCK_UNLOCKED,
		    (uintptr_t)curthread);
	LOCK_LOG_TRY("XLOCK", &sx->lock_object, 0, rval, file, line);
	if (rval) {
		WITNESS_LOCK(&sx->lock_object, LOP_EXCLUSIVE | LOP_TRYLOCK,
		    file, line);
		if (!sx_recursed(sx))
			LOCKSTAT_PROFILE_OBTAIN_RWLOCK_SUCCESS(sx__acquire,
			    sx, 0, 0, file, line, LOCKSTAT_WRITER);
		curthread->td_locks++;
	}

	return (rval);
}
Example #5
0
int
sx_try_xlock_(struct sx *sx, const char *file, int line)
{
    int rval;

    if (SCHEDULER_STOPPED())
        return (1);

    MPASS(curthread != NULL);
    KASSERT(sx->sx_lock != SX_LOCK_DESTROYED,
            ("sx_try_xlock() of destroyed sx @ %s:%d", file, line));

    if (sx_xlocked(sx) &&
            (sx->lock_object.lo_flags & LO_RECURSABLE) != 0) {
        sx->sx_recurse++;
        atomic_set_ptr(&sx->sx_lock, SX_LOCK_RECURSED);
        rval = 1;
    } else
        rval = atomic_cmpset_acq_ptr(&sx->sx_lock, SX_LOCK_UNLOCKED,
                                     (uintptr_t)curthread);
    LOCK_LOG_TRY("XLOCK", &sx->lock_object, 0, rval, file, line);
    if (rval) {
        WITNESS_LOCK(&sx->lock_object, LOP_EXCLUSIVE | LOP_TRYLOCK,
                     file, line);
        curthread->td_locks++;
    }

    return (rval);
}
Example #6
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_int(struct mtx *m, int opts LOCK_FILE_LINE_ARG_DEF)
{
	struct thread *td;
	uintptr_t tid, v;
#ifdef LOCK_PROFILING
	uint64_t waittime = 0;
	int contested = 0;
#endif
	int rval;
	bool recursed;

	td = curthread;
	tid = (uintptr_t)td;
	if (SCHEDULER_STOPPED_TD(td))
		return (1);

	KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(td),
	    ("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));

	rval = 1;
	recursed = false;
	v = MTX_UNOWNED;
	for (;;) {
		if (_mtx_obtain_lock_fetch(m, &v, tid))
			break;
		if (v == MTX_UNOWNED)
			continue;
		if (v == tid &&
		    ((m->lock_object.lo_flags & LO_RECURSABLE) != 0 ||
		    (opts & MTX_RECURSE) != 0)) {
			m->mtx_recurse++;
			atomic_set_ptr(&m->mtx_lock, MTX_RECURSED);
			recursed = true;
			break;
		}
		rval = 0;
		break;
	}

	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 (!recursed)
			LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(adaptive__acquire,
			    m, contested, waittime, file, line);
	}

	return (rval);
}
Example #7
0
/**
 * Clear sigwait cond of the current thread.
 * @param fsq is a pointer to the fs queue object.
 */
static void fsq_sigwait_clear(struct fs_queue * fsq, enum wait4end ep,
                              sigset_t * oldset)
{
    struct signals * sigs = &current_thread->sigs;
    struct signals ** waitsigsp = fsq_get_sigs(fsq, ep);

    ksignal_sigsmask(sigs, SIG_SETMASK, oldset, NULL);
    atomic_set_ptr((void **)waitsigsp, NULL);
}
Example #8
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);
}
Example #9
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 = _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);
}
Example #10
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
}
Example #11
0
/*
 * This function represents the so-called 'hard case' for sx_xlock
 * operation.  All 'easy case' failures are redirected to this.  Note
 * that ideally this would be a static function, but it needs to be
 * accessible from at least sx.h.
 */
int
_sx_xlock_hard(struct sx *sx, uintptr_t tid, int opts, const char *file,
    int line)
{
	GIANT_DECLARE;
#ifdef ADAPTIVE_SX
	volatile struct thread *owner;
	u_int i, spintries = 0;
#endif
	uintptr_t x;
#ifdef LOCK_PROFILING
	uint64_t waittime = 0;
	int contested = 0;
#endif
	int error = 0;
#ifdef	KDTRACE_HOOKS
	uintptr_t state;
	uint64_t spin_cnt = 0;
	uint64_t sleep_cnt = 0;
	int64_t sleep_time = 0;
	int64_t all_time = 0;
#endif

	if (SCHEDULER_STOPPED())
		return (0);

	/* If we already hold an exclusive lock, then recurse. */
	if (sx_xlocked(sx)) {
		KASSERT((sx->lock_object.lo_flags & LO_RECURSABLE) != 0,
	    ("_sx_xlock_hard: recursed on non-recursive sx %s @ %s:%d\n",
		    sx->lock_object.lo_name, file, line));
		sx->sx_recurse++;
		atomic_set_ptr(&sx->sx_lock, SX_LOCK_RECURSED);
		if (LOCK_LOG_TEST(&sx->lock_object, 0))
			CTR2(KTR_LOCK, "%s: %p recursing", __func__, sx);
		return (0);
	}

	if (LOCK_LOG_TEST(&sx->lock_object, 0))
		CTR5(KTR_LOCK, "%s: %s contested (lock=%p) at %s:%d", __func__,
		    sx->lock_object.lo_name, (void *)sx->sx_lock, file, line);

#ifdef KDTRACE_HOOKS
	all_time -= lockstat_nsecs(&sx->lock_object);
	state = sx->sx_lock;
#endif
	while (!atomic_cmpset_acq_ptr(&sx->sx_lock, SX_LOCK_UNLOCKED, tid)) {
#ifdef KDTRACE_HOOKS
		spin_cnt++;
#endif
#ifdef HWPMC_HOOKS
		PMC_SOFT_CALL( , , lock, failed);
#endif
		lock_profile_obtain_lock_failed(&sx->lock_object, &contested,
		    &waittime);
#ifdef ADAPTIVE_SX
		/*
		 * If the lock is write locked and the owner is
		 * running on another CPU, spin until the owner stops
		 * running or the state of the lock changes.
		 */
		x = sx->sx_lock;
		if ((sx->lock_object.lo_flags & SX_NOADAPTIVE) == 0) {
			if ((x & SX_LOCK_SHARED) == 0) {
				x = SX_OWNER(x);
				owner = (struct thread *)x;
				if (TD_IS_RUNNING(owner)) {
					if (LOCK_LOG_TEST(&sx->lock_object, 0))
						CTR3(KTR_LOCK,
					    "%s: spinning on %p held by %p",
						    __func__, sx, owner);
					KTR_STATE1(KTR_SCHED, "thread",
					    sched_tdname(curthread), "spinning",
					    "lockname:\"%s\"",
					    sx->lock_object.lo_name);
					GIANT_SAVE();
					while (SX_OWNER(sx->sx_lock) == x &&
					    TD_IS_RUNNING(owner)) {
						cpu_spinwait();
#ifdef KDTRACE_HOOKS
						spin_cnt++;
#endif
					}
					KTR_STATE0(KTR_SCHED, "thread",
					    sched_tdname(curthread), "running");
					continue;
				}
			} else if (SX_SHARERS(x) && spintries < asx_retries) {
				KTR_STATE1(KTR_SCHED, "thread",
				    sched_tdname(curthread), "spinning",
				    "lockname:\"%s\"", sx->lock_object.lo_name);
				GIANT_SAVE();
				spintries++;
				for (i = 0; i < asx_loops; i++) {
					if (LOCK_LOG_TEST(&sx->lock_object, 0))
						CTR4(KTR_LOCK,
				    "%s: shared spinning on %p with %u and %u",
						    __func__, sx, spintries, i);
					x = sx->sx_lock;
					if ((x & SX_LOCK_SHARED) == 0 ||
					    SX_SHARERS(x) == 0)
						break;
					cpu_spinwait();
#ifdef KDTRACE_HOOKS
					spin_cnt++;
#endif
				}
				KTR_STATE0(KTR_SCHED, "thread",
				    sched_tdname(curthread), "running");
				if (i != asx_loops)
					continue;
			}
		}
#endif

		sleepq_lock(&sx->lock_object);
		x = sx->sx_lock;

		/*
		 * If the lock was released while spinning on the
		 * sleep queue chain lock, try again.
		 */
		if (x == SX_LOCK_UNLOCKED) {
			sleepq_release(&sx->lock_object);
			continue;
		}

#ifdef ADAPTIVE_SX
		/*
		 * The current lock owner might have started executing
		 * on another CPU (or the lock could have changed
		 * owners) while we were waiting on the sleep queue
		 * chain lock.  If so, drop the sleep queue lock and try
		 * again.
		 */
		if (!(x & SX_LOCK_SHARED) &&
		    (sx->lock_object.lo_flags & SX_NOADAPTIVE) == 0) {
			owner = (struct thread *)SX_OWNER(x);
			if (TD_IS_RUNNING(owner)) {
				sleepq_release(&sx->lock_object);
				continue;
			}
		}
#endif

		/*
		 * If an exclusive lock was released with both shared
		 * and exclusive waiters and a shared waiter hasn't
		 * woken up and acquired the lock yet, sx_lock will be
		 * set to SX_LOCK_UNLOCKED | SX_LOCK_EXCLUSIVE_WAITERS.
		 * If we see that value, try to acquire it once.  Note
		 * that we have to preserve SX_LOCK_EXCLUSIVE_WAITERS
		 * as there are other exclusive waiters still.  If we
		 * fail, restart the loop.
		 */
		if (x == (SX_LOCK_UNLOCKED | SX_LOCK_EXCLUSIVE_WAITERS)) {
			if (atomic_cmpset_acq_ptr(&sx->sx_lock,
			    SX_LOCK_UNLOCKED | SX_LOCK_EXCLUSIVE_WAITERS,
			    tid | SX_LOCK_EXCLUSIVE_WAITERS)) {
				sleepq_release(&sx->lock_object);
				CTR2(KTR_LOCK, "%s: %p claimed by new writer",
				    __func__, sx);
				break;
			}
			sleepq_release(&sx->lock_object);
			continue;
		}

		/*
		 * Try to set the SX_LOCK_EXCLUSIVE_WAITERS.  If we fail,
		 * than loop back and retry.
		 */
		if (!(x & SX_LOCK_EXCLUSIVE_WAITERS)) {
			if (!atomic_cmpset_ptr(&sx->sx_lock, x,
			    x | SX_LOCK_EXCLUSIVE_WAITERS)) {
				sleepq_release(&sx->lock_object);
				continue;
			}
			if (LOCK_LOG_TEST(&sx->lock_object, 0))
				CTR2(KTR_LOCK, "%s: %p set excl waiters flag",
				    __func__, sx);
		}

		/*
		 * Since we have been unable to acquire the exclusive
		 * lock and the exclusive waiters flag is set, we have
		 * to sleep.
		 */
		if (LOCK_LOG_TEST(&sx->lock_object, 0))
			CTR2(KTR_LOCK, "%s: %p blocking on sleep queue",
			    __func__, sx);

#ifdef KDTRACE_HOOKS
		sleep_time -= lockstat_nsecs(&sx->lock_object);
#endif
		GIANT_SAVE();
		sleepq_add(&sx->lock_object, NULL, sx->lock_object.lo_name,
		    SLEEPQ_SX | ((opts & SX_INTERRUPTIBLE) ?
		    SLEEPQ_INTERRUPTIBLE : 0), SQ_EXCLUSIVE_QUEUE);
		if (!(opts & SX_INTERRUPTIBLE))
			sleepq_wait(&sx->lock_object, 0);
		else
			error = sleepq_wait_sig(&sx->lock_object, 0);
#ifdef KDTRACE_HOOKS
		sleep_time += lockstat_nsecs(&sx->lock_object);
		sleep_cnt++;
#endif
		if (error) {
			if (LOCK_LOG_TEST(&sx->lock_object, 0))
				CTR2(KTR_LOCK,
			"%s: interruptible sleep by %p suspended by signal",
				    __func__, sx);
			break;
		}
		if (LOCK_LOG_TEST(&sx->lock_object, 0))
			CTR2(KTR_LOCK, "%s: %p resuming from sleep queue",
			    __func__, sx);
	}
#ifdef KDTRACE_HOOKS
	all_time += lockstat_nsecs(&sx->lock_object);
	if (sleep_time)
		LOCKSTAT_RECORD4(sx__block, sx, sleep_time,
		    LOCKSTAT_WRITER, (state & SX_LOCK_SHARED) == 0,
		    (state & SX_LOCK_SHARED) == 0 ? 0 : SX_SHARERS(state));
	if (spin_cnt > sleep_cnt)
		LOCKSTAT_RECORD4(sx__spin, sx, all_time - sleep_time,
		    LOCKSTAT_WRITER, (state & SX_LOCK_SHARED) == 0,
		    (state & SX_LOCK_SHARED) == 0 ? 0 : SX_SHARERS(state));
#endif
	if (!error)
		LOCKSTAT_PROFILE_OBTAIN_RWLOCK_SUCCESS(sx__acquire, sx,
		    contested, waittime, file, line, LOCKSTAT_WRITER);
	GIANT_RESTORE();
	return (error);
}
Example #12
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
}