Ejemplo n.º 1
0
void
__rw_rlock(volatile uintptr_t *c, const char *file, int line)
{
	struct rwlock *rw;
	struct turnstile *ts;
#ifdef ADAPTIVE_RWLOCKS
	volatile struct thread *owner;
	int spintries = 0;
	int i;
#endif
#ifdef LOCK_PROFILING
	uint64_t waittime = 0;
	int contested = 0;
#endif
	uintptr_t v;
#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;

	rw = rwlock2rw(c);

	KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(curthread),
	    ("rw_rlock() by idle thread %p on rwlock %s @ %s:%d",
	    curthread, rw->lock_object.lo_name, file, line));
	KASSERT(rw->rw_lock != RW_DESTROYED,
	    ("rw_rlock() of destroyed rwlock @ %s:%d", file, line));
	KASSERT(rw_wowner(rw) != curthread,
	    ("rw_rlock: wlock already held for %s @ %s:%d",
	    rw->lock_object.lo_name, file, line));
	WITNESS_CHECKORDER(&rw->lock_object, LOP_NEWORDER, file, line, NULL);

#ifdef KDTRACE_HOOKS
	all_time -= lockstat_nsecs(&rw->lock_object);
	state = rw->rw_lock;
#endif
	for (;;) {
		/*
		 * Handle the easy case.  If no other thread has a write
		 * lock, then try to bump up the count of read locks.  Note
		 * that we have to preserve the current state of the
		 * RW_LOCK_WRITE_WAITERS flag.  If we fail to acquire a
		 * read lock, then rw_lock must have changed, so restart
		 * the loop.  Note that this handles the case of a
		 * completely unlocked rwlock since such a lock is encoded
		 * as a read lock with no waiters.
		 */
		v = rw->rw_lock;
		if (RW_CAN_READ(v)) {
			/*
			 * The RW_LOCK_READ_WAITERS flag should only be set
			 * if the lock has been unlocked and write waiters
			 * were present.
			 */
			if (atomic_cmpset_acq_ptr(&rw->rw_lock, v,
			    v + RW_ONE_READER)) {
				if (LOCK_LOG_TEST(&rw->lock_object, 0))
					CTR4(KTR_LOCK,
					    "%s: %p succeed %p -> %p", __func__,
					    rw, (void *)v,
					    (void *)(v + RW_ONE_READER));
				break;
			}
			continue;
		}
#ifdef KDTRACE_HOOKS
		spin_cnt++;
#endif
#ifdef HWPMC_HOOKS
		PMC_SOFT_CALL( , , lock, failed);
#endif
		lock_profile_obtain_lock_failed(&rw->lock_object,
		    &contested, &waittime);

#ifdef ADAPTIVE_RWLOCKS
		/*
		 * If the owner is running on another CPU, spin until
		 * the owner stops running or the state of the lock
		 * changes.
		 */
		if ((v & RW_LOCK_READ) == 0) {
			owner = (struct thread *)RW_OWNER(v);
			if (TD_IS_RUNNING(owner)) {
				if (LOCK_LOG_TEST(&rw->lock_object, 0))
					CTR3(KTR_LOCK,
					    "%s: spinning on %p held by %p",
					    __func__, rw, owner);
				KTR_STATE1(KTR_SCHED, "thread",
				    sched_tdname(curthread), "spinning",
				    "lockname:\"%s\"", rw->lock_object.lo_name);
				while ((struct thread*)RW_OWNER(rw->rw_lock) ==
				    owner && TD_IS_RUNNING(owner)) {
					cpu_spinwait();
#ifdef KDTRACE_HOOKS
					spin_cnt++;
#endif
				}
				KTR_STATE0(KTR_SCHED, "thread",
				    sched_tdname(curthread), "running");
				continue;
			}
		} else if (spintries < rowner_retries) {
			spintries++;
			KTR_STATE1(KTR_SCHED, "thread", sched_tdname(curthread),
			    "spinning", "lockname:\"%s\"",
			    rw->lock_object.lo_name);
			for (i = 0; i < rowner_loops; i++) {
				v = rw->rw_lock;
				if ((v & RW_LOCK_READ) == 0 || RW_CAN_READ(v))
					break;
				cpu_spinwait();
			}
#ifdef KDTRACE_HOOKS
			spin_cnt += rowner_loops - i;
#endif
			KTR_STATE0(KTR_SCHED, "thread", sched_tdname(curthread),
			    "running");
			if (i != rowner_loops)
				continue;
		}
#endif

		/*
		 * Okay, now it's the hard case.  Some other thread already
		 * has a write lock or there are write waiters present,
		 * acquire the turnstile lock so we can begin the process
		 * of blocking.
		 */
		ts = turnstile_trywait(&rw->lock_object);

		/*
		 * The lock might have been released while we spun, so
		 * recheck its state and restart the loop if needed.
		 */
		v = rw->rw_lock;
		if (RW_CAN_READ(v)) {
			turnstile_cancel(ts);
			continue;
		}

#ifdef ADAPTIVE_RWLOCKS
		/*
		 * 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.
		 */
		if ((v & RW_LOCK_READ) == 0) {
			owner = (struct thread *)RW_OWNER(v);
			if (TD_IS_RUNNING(owner)) {
				turnstile_cancel(ts);
				continue;
			}
		}
#endif

		/*
		 * The lock is held in write mode or it already has waiters.
		 */
		MPASS(!RW_CAN_READ(v));

		/*
		 * If the RW_LOCK_READ_WAITERS flag is already set, then
		 * we can go ahead and block.  If it is not set then try
		 * to set it.  If we fail to set it drop the turnstile
		 * lock and restart the loop.
		 */
		if (!(v & RW_LOCK_READ_WAITERS)) {
			if (!atomic_cmpset_ptr(&rw->rw_lock, v,
			    v | RW_LOCK_READ_WAITERS)) {
				turnstile_cancel(ts);
				continue;
			}
			if (LOCK_LOG_TEST(&rw->lock_object, 0))
				CTR2(KTR_LOCK, "%s: %p set read waiters flag",
				    __func__, rw);
		}

		/*
		 * We were unable to acquire the lock and the read waiters
		 * flag is set, so we must block on the turnstile.
		 */
		if (LOCK_LOG_TEST(&rw->lock_object, 0))
			CTR2(KTR_LOCK, "%s: %p blocking on turnstile", __func__,
			    rw);
#ifdef KDTRACE_HOOKS
		sleep_time -= lockstat_nsecs(&rw->lock_object);
#endif
		turnstile_wait(ts, rw_owner(rw), TS_SHARED_QUEUE);
#ifdef KDTRACE_HOOKS
		sleep_time += lockstat_nsecs(&rw->lock_object);
		sleep_cnt++;
#endif
		if (LOCK_LOG_TEST(&rw->lock_object, 0))
			CTR2(KTR_LOCK, "%s: %p resuming from turnstile",
			    __func__, rw);
	}
#ifdef KDTRACE_HOOKS
	all_time += lockstat_nsecs(&rw->lock_object);
	if (sleep_time)
		LOCKSTAT_RECORD4(rw__block, rw, sleep_time,
		    LOCKSTAT_READER, (state & RW_LOCK_READ) == 0,
		    (state & RW_LOCK_READ) == 0 ? 0 : RW_READERS(state));

	/* Record only the loops spinning and not sleeping. */
	if (spin_cnt > sleep_cnt)
		LOCKSTAT_RECORD4(rw__spin, rw, all_time - sleep_time,
		    LOCKSTAT_READER, (state & RW_LOCK_READ) == 0,
		    (state & RW_LOCK_READ) == 0 ? 0 : RW_READERS(state));
#endif
	/*
	 * TODO: acquire "owner of record" here.  Here be turnstile dragons
	 * however.  turnstiles don't like owners changing between calls to
	 * turnstile_wait() currently.
	 */
	LOCKSTAT_PROFILE_OBTAIN_RWLOCK_SUCCESS(rw__acquire, rw, contested,
	    waittime, file, line, LOCKSTAT_READER);
	LOCK_LOG_LOCK("RLOCK", &rw->lock_object, 0, 0, file, line);
	WITNESS_LOCK(&rw->lock_object, 0, file, line);
	curthread->td_locks++;
	curthread->td_rw_rlocks++;
}
Ejemplo n.º 2
0
/*
 * This function is called when we are unable to obtain a write lock on the
 * first try.  This means that at least one other thread holds either a
 * read or write lock.
 */
void
__rw_wlock_hard(volatile uintptr_t *c, uintptr_t tid, const char *file,
    int line)
{
	struct rwlock *rw;
	struct turnstile *ts;
#ifdef ADAPTIVE_RWLOCKS
	volatile struct thread *owner;
	int spintries = 0;
	int i;
#endif
	uintptr_t v, x;
#ifdef LOCK_PROFILING
	uint64_t waittime = 0;
	int contested = 0;
#endif
#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;

	rw = rwlock2rw(c);

	if (rw_wlocked(rw)) {
		KASSERT(rw->lock_object.lo_flags & LO_RECURSABLE,
		    ("%s: recursing but non-recursive rw %s @ %s:%d\n",
		    __func__, rw->lock_object.lo_name, file, line));
		rw->rw_recurse++;
		if (LOCK_LOG_TEST(&rw->lock_object, 0))
			CTR2(KTR_LOCK, "%s: %p recursing", __func__, rw);
		return;
	}

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

#ifdef KDTRACE_HOOKS
	all_time -= lockstat_nsecs(&rw->lock_object);
	state = rw->rw_lock;
#endif
	while (!_rw_write_lock(rw, tid)) {
#ifdef KDTRACE_HOOKS
		spin_cnt++;
#endif
#ifdef HWPMC_HOOKS
		PMC_SOFT_CALL( , , lock, failed);
#endif
		lock_profile_obtain_lock_failed(&rw->lock_object,
		    &contested, &waittime);
#ifdef ADAPTIVE_RWLOCKS
		/*
		 * 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.
		 */
		v = rw->rw_lock;
		owner = (struct thread *)RW_OWNER(v);
		if (!(v & RW_LOCK_READ) && TD_IS_RUNNING(owner)) {
			if (LOCK_LOG_TEST(&rw->lock_object, 0))
				CTR3(KTR_LOCK, "%s: spinning on %p held by %p",
				    __func__, rw, owner);
			KTR_STATE1(KTR_SCHED, "thread", sched_tdname(curthread),
			    "spinning", "lockname:\"%s\"",
			    rw->lock_object.lo_name);
			while ((struct thread*)RW_OWNER(rw->rw_lock) == owner &&
			    TD_IS_RUNNING(owner)) {
				cpu_spinwait();
#ifdef KDTRACE_HOOKS
				spin_cnt++;
#endif
			}
			KTR_STATE0(KTR_SCHED, "thread", sched_tdname(curthread),
			    "running");
			continue;
		}
		if ((v & RW_LOCK_READ) && RW_READERS(v) &&
		    spintries < rowner_retries) {
			if (!(v & RW_LOCK_WRITE_SPINNER)) {
				if (!atomic_cmpset_ptr(&rw->rw_lock, v,
				    v | RW_LOCK_WRITE_SPINNER)) {
					continue;
				}
			}
			spintries++;
			KTR_STATE1(KTR_SCHED, "thread", sched_tdname(curthread),
			    "spinning", "lockname:\"%s\"",
			    rw->lock_object.lo_name);
			for (i = 0; i < rowner_loops; i++) {
				if ((rw->rw_lock & RW_LOCK_WRITE_SPINNER) == 0)
					break;
				cpu_spinwait();
			}
			KTR_STATE0(KTR_SCHED, "thread", sched_tdname(curthread),
			    "running");
#ifdef KDTRACE_HOOKS
			spin_cnt += rowner_loops - i;
#endif
			if (i != rowner_loops)
				continue;
		}
#endif
		ts = turnstile_trywait(&rw->lock_object);
		v = rw->rw_lock;

#ifdef ADAPTIVE_RWLOCKS
		/*
		 * 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.
		 */
		if (!(v & RW_LOCK_READ)) {
			owner = (struct thread *)RW_OWNER(v);
			if (TD_IS_RUNNING(owner)) {
				turnstile_cancel(ts);
				continue;
			}
		}
#endif
		/*
		 * Check for the waiters flags about this rwlock.
		 * If the lock was released, without maintain any pending
		 * waiters queue, simply try to acquire it.
		 * If a pending waiters queue is present, claim the lock
		 * ownership and maintain the pending queue.
		 */
		x = v & (RW_LOCK_WAITERS | RW_LOCK_WRITE_SPINNER);
		if ((v & ~x) == RW_UNLOCKED) {
			x &= ~RW_LOCK_WRITE_SPINNER;
			if (atomic_cmpset_acq_ptr(&rw->rw_lock, v, tid | x)) {
				if (x)
					turnstile_claim(ts);
				else
					turnstile_cancel(ts);
				break;
			}
			turnstile_cancel(ts);
			continue;
		}
		/*
		 * If the RW_LOCK_WRITE_WAITERS flag isn't set, then try to
		 * set it.  If we fail to set it, then loop back and try
		 * again.
		 */
		if (!(v & RW_LOCK_WRITE_WAITERS)) {
			if (!atomic_cmpset_ptr(&rw->rw_lock, v,
			    v | RW_LOCK_WRITE_WAITERS)) {
				turnstile_cancel(ts);
				continue;
			}
			if (LOCK_LOG_TEST(&rw->lock_object, 0))
				CTR2(KTR_LOCK, "%s: %p set write waiters flag",
				    __func__, rw);
		}
		/*
		 * We were unable to acquire the lock and the write waiters
		 * flag is set, so we must block on the turnstile.
		 */
		if (LOCK_LOG_TEST(&rw->lock_object, 0))
			CTR2(KTR_LOCK, "%s: %p blocking on turnstile", __func__,
			    rw);
#ifdef KDTRACE_HOOKS
		sleep_time -= lockstat_nsecs(&rw->lock_object);
#endif
		turnstile_wait(ts, rw_owner(rw), TS_EXCLUSIVE_QUEUE);
#ifdef KDTRACE_HOOKS
		sleep_time += lockstat_nsecs(&rw->lock_object);
		sleep_cnt++;
#endif
		if (LOCK_LOG_TEST(&rw->lock_object, 0))
			CTR2(KTR_LOCK, "%s: %p resuming from turnstile",
			    __func__, rw);
#ifdef ADAPTIVE_RWLOCKS
		spintries = 0;
#endif
	}
#ifdef KDTRACE_HOOKS
	all_time += lockstat_nsecs(&rw->lock_object);
	if (sleep_time)
		LOCKSTAT_RECORD4(rw__block, rw, sleep_time,
		    LOCKSTAT_WRITER, (state & RW_LOCK_READ) == 0,
		    (state & RW_LOCK_READ) == 0 ? 0 : RW_READERS(state));

	/* Record only the loops spinning and not sleeping. */
	if (spin_cnt > sleep_cnt)
		LOCKSTAT_RECORD4(rw__spin, rw, all_time - sleep_time,
		    LOCKSTAT_READER, (state & RW_LOCK_READ) == 0,
		    (state & RW_LOCK_READ) == 0 ? 0 : RW_READERS(state));
#endif
	LOCKSTAT_PROFILE_OBTAIN_RWLOCK_SUCCESS(rw__acquire, rw, contested,
	    waittime, file, line, LOCKSTAT_WRITER);
}
Ejemplo n.º 3
0
/*
 * This function represents the so-called 'hard case' for sx_slock
 * 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_slock_hard(struct sx *sx, int opts, const char *file, int line)
{
	GIANT_DECLARE;
#ifdef ADAPTIVE_SX
	volatile struct thread *owner;
#endif
#ifdef LOCK_PROFILING
	uint64_t waittime = 0;
	int contested = 0;
#endif
	uintptr_t x;
	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);

#ifdef KDTRACE_HOOKS
	state = sx->sx_lock;
	all_time -= lockstat_nsecs(&sx->lock_object);
#endif

	/*
	 * As with rwlocks, we don't make any attempt to try to block
	 * shared locks once there is an exclusive waiter.
	 */
	for (;;) {
#ifdef KDTRACE_HOOKS
		spin_cnt++;
#endif
		x = sx->sx_lock;

		/*
		 * If no other thread has an exclusive lock then try to bump up
		 * the count of sharers.  Since we have to preserve the state
		 * of SX_LOCK_EXCLUSIVE_WAITERS, if we fail to acquire the
		 * shared lock loop back and retry.
		 */
		if (x & SX_LOCK_SHARED) {
			MPASS(!(x & SX_LOCK_SHARED_WAITERS));
			if (atomic_cmpset_acq_ptr(&sx->sx_lock, x,
			    x + SX_ONE_SHARER)) {
				if (LOCK_LOG_TEST(&sx->lock_object, 0))
					CTR4(KTR_LOCK,
					    "%s: %p succeed %p -> %p", __func__,
					    sx, (void *)x,
					    (void *)(x + SX_ONE_SHARER));
				break;
			}
			continue;
		}
#ifdef HWPMC_HOOKS
		PMC_SOFT_CALL( , , lock, failed);
#endif
		lock_profile_obtain_lock_failed(&sx->lock_object, &contested,
		    &waittime);

#ifdef ADAPTIVE_SX
		/*
		 * If the owner is running on another CPU, spin until
		 * the owner stops running or the state of the lock
		 * changes.
		 */
		if ((sx->lock_object.lo_flags & SX_NOADAPTIVE) == 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)) {
#ifdef KDTRACE_HOOKS
					spin_cnt++;
#endif
					cpu_spinwait();
				}
				KTR_STATE0(KTR_SCHED, "thread",
				    sched_tdname(curthread), "running");
				continue;
			}
		}
#endif

		/*
		 * Some other thread already has an exclusive lock, so
		 * start the process of blocking.
		 */
		sleepq_lock(&sx->lock_object);
		x = sx->sx_lock;

		/*
		 * The lock could have been released while we spun.
		 * In this case loop back and retry.
		 */
		if (x & SX_LOCK_SHARED) {
			sleepq_release(&sx->lock_object);
			continue;
		}

#ifdef ADAPTIVE_SX
		/*
		 * If the owner is running on another CPU, spin until
		 * the owner stops running or the state of the lock
		 * changes.
		 */
		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

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

		/*
		 * Since we have been unable to acquire the shared lock,
		 * 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_SHARED_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_READER, (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_READER, (state & SX_LOCK_SHARED) == 0,
		    (state & SX_LOCK_SHARED) == 0 ? 0 : SX_SHARERS(state));
#endif
	if (error == 0)
		LOCKSTAT_PROFILE_OBTAIN_RWLOCK_SUCCESS(sx__acquire, sx,
		    contested, waittime, file, line, LOCKSTAT_READER);
	GIANT_RESTORE();
	return (error);
}
Ejemplo n.º 4
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);
}
Ejemplo n.º 5
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
}
Ejemplo n.º 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(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
}
Ejemplo n.º 7
0
void
_mtx_lock_spin_cookie(volatile uintptr_t *c, uintptr_t v)
#endif
{
	struct mtx *m;
	struct lock_delay_arg lda;
	uintptr_t tid;
#ifdef LOCK_PROFILING
	int contested = 0;
	uint64_t waittime = 0;
#endif
#ifdef KDTRACE_HOOKS
	int64_t spin_time = 0;
#endif
#if defined(KDTRACE_HOOKS) || defined(LOCK_PROFILING)
	int doing_lockprof;
#endif

	tid = (uintptr_t)curthread;
	m = mtxlock2mtx(c);

	if (__predict_false(v == MTX_UNOWNED))
		v = MTX_READ_VALUE(m);

	if (__predict_false(v == tid)) {
		m->mtx_recurse++;
		return;
	}

	if (SCHEDULER_STOPPED())
		return;

	lock_delay_arg_init(&lda, &mtx_spin_delay);

	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 LOCK_PROFILING
	doing_lockprof = 1;
#elif defined(KDTRACE_HOOKS)
	doing_lockprof = lockstat_enabled;
	if (__predict_false(doing_lockprof))
		spin_time -= lockstat_nsecs(&m->lock_object);
#endif
	for (;;) {
		if (v == MTX_UNOWNED) {
			if (_mtx_obtain_lock_fetch(m, &v, tid))
				break;
			continue;
		}
		/* Give interrupts a chance while we spin. */
		spinlock_exit();
		do {
			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();
			}
			v = MTX_READ_VALUE(m);
		} while (v != MTX_UNOWNED);
		spinlock_enter();
	}

	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");

#if defined(KDTRACE_HOOKS) || defined(LOCK_PROFILING)
	if (__predict_true(!doing_lockprof))
		return;
#endif
#ifdef KDTRACE_HOOKS
	spin_time += lockstat_nsecs(&m->lock_object);
#endif
	LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(spin__acquire, m,
	    contested, waittime, file, line);
#ifdef KDTRACE_HOOKS
	if (lda.spin_cnt != 0)
		LOCKSTAT_RECORD1(spin__spin, m, spin_time);
#endif
}