示例#1
0
boolean_t
lck_rw_lock_shared_to_exclusive(
	lck_rw_t	*lck)
{
	int	    i;
	boolean_t	    do_wakeup = FALSE;
	wait_result_t      res;
#if	MACH_LDEBUG
	int		   decrementer;
#endif	/* MACH_LDEBUG */
	boolean_t	istate;
#if	CONFIG_DTRACE
	uint64_t wait_interval = 0;
	int slept = 0;
	int readers_at_sleep = 0;
#endif

	istate = lck_interlock_lock(lck);

	lck->lck_rw_shared_count--;	

	if (lck->lck_rw_want_upgrade) {
		KERNEL_DEBUG(MACHDBG_CODE(DBG_MACH_LOCKS, LCK_RW_LCK_SH_TO_EX_CODE) | DBG_FUNC_START,
			     (int)lck, lck->lck_rw_shared_count, lck->lck_rw_want_upgrade, 0, 0);

		/*
		 *	Someone else has requested upgrade.
		 *	Since we've released a read lock, wake
		 *	him up.
		 */
		if (lck->lck_w_waiting && (lck->lck_rw_shared_count == 0)) {
			lck->lck_w_waiting = FALSE;
			do_wakeup = TRUE;
		}

		lck_interlock_unlock(lck, istate);

		if (do_wakeup) 
			thread_wakeup(RW_LOCK_WRITER_EVENT(lck));

		KERNEL_DEBUG(MACHDBG_CODE(DBG_MACH_LOCKS, LCK_RW_LCK_SH_TO_EX_CODE) | DBG_FUNC_END,
			     (int)lck, lck->lck_rw_shared_count, lck->lck_rw_want_upgrade, 0, 0);

		return (FALSE);
	}

	lck->lck_rw_want_upgrade = TRUE;

#if	MACH_LDEBUG
	decrementer = DECREMENTER_TIMEOUT;
#endif	/* MACH_LDEBUG */
	while (lck->lck_rw_shared_count != 0) {
#if	CONFIG_DTRACE
		if (lockstat_probemap[LS_LCK_RW_LOCK_SHARED_TO_EXCL_SPIN] && wait_interval == 0) {
			wait_interval = mach_absolute_time();
			readers_at_sleep = lck->lck_rw_shared_count;
		} else {
			wait_interval = -1;
		}
#endif
		i = lock_wait_time[lck->lck_rw_can_sleep ? 1 : 0];

		KERNEL_DEBUG(MACHDBG_CODE(DBG_MACH_LOCKS, LCK_RW_LCK_SH_TO_EX1_CODE) | DBG_FUNC_START,
			     (int)lck, lck->lck_rw_shared_count, i, 0, 0);

		if (i != 0) {
			lck_interlock_unlock(lck, istate);
#if	MACH_LDEBUG
			if (!--decrementer)
				Debugger("timeout - lck_rw_shared_count");
#endif	/* MACH_LDEBUG */
			while (--i != 0 && lck->lck_rw_shared_count != 0)
				lck_rw_lock_pause(istate);
			istate = lck_interlock_lock(lck);
		}

		if (lck->lck_rw_can_sleep && lck->lck_rw_shared_count != 0) {
			lck->lck_w_waiting = TRUE;
			res = assert_wait(RW_LOCK_WRITER_EVENT(lck), THREAD_UNINT);
			if (res == THREAD_WAITING) {
				lck_interlock_unlock(lck, istate);
				res = thread_block(THREAD_CONTINUE_NULL);
#if	CONFIG_DTRACE
				slept = 1;
#endif
				istate = lck_interlock_lock(lck);
			}
		}
		KERNEL_DEBUG(MACHDBG_CODE(DBG_MACH_LOCKS, LCK_RW_LCK_SH_TO_EX1_CODE) | DBG_FUNC_END,
			     (int)lck, lck->lck_rw_shared_count, 0, 0, 0);
	}

	lck_interlock_unlock(lck, istate);
#if	CONFIG_DTRACE
	/*
	 * We infer whether we took the sleep/spin path above by checking readers_at_sleep.
	 */
	if (wait_interval != 0 && wait_interval != (unsigned) -1 && readers_at_sleep) {
		if (slept == 0) {
			LOCKSTAT_RECORD2(LS_LCK_RW_LOCK_SHARED_TO_EXCL_SPIN, lck, mach_absolute_time() - wait_interval, 0);
		} else {
			LOCKSTAT_RECORD4(LS_LCK_RW_LOCK_SHARED_TO_EXCL_BLOCK, lck,
			    mach_absolute_time() - wait_interval, 1,
			    (readers_at_sleep == 0 ? 1 : 0), readers_at_sleep);
		}
	}

	LOCKSTAT_RECORD(LS_LCK_RW_LOCK_SHARED_TO_EXCL_UPGRADE, lck, 1);
#endif
	return (TRUE);
}
示例#2
0
/*
 *      Routine:        lck_rw_lock_exclusive
 */
void
lck_rw_lock_exclusive(
	lck_rw_t	*lck)
{
	int	   i;
	wait_result_t	res;
#if	MACH_LDEBUG
	int				decrementer;
#endif	/* MACH_LDEBUG */
	boolean_t	istate;
#if	CONFIG_DTRACE
	uint64_t wait_interval = 0;
	int slept = 0;
	int readers_at_sleep;
#endif

	istate = lck_interlock_lock(lck);
#if	CONFIG_DTRACE
	readers_at_sleep = lck->lck_rw_shared_count;
#endif

#if	MACH_LDEBUG
	decrementer = DECREMENTER_TIMEOUT;
#endif	/* MACH_LDEBUG */

	/*
	 *	Try to acquire the lck_rw_want_write bit.
	 */
	while (lck->lck_rw_want_write) {

		KERNEL_DEBUG(MACHDBG_CODE(DBG_MACH_LOCKS, LCK_RW_LCK_EXCLUSIVE_CODE) | DBG_FUNC_START, (int)lck, 0, 0, 0, 0);
		/*
		 * Either sleeping or spinning is happening, start
		 * a timing of our delay interval now.
		 */
#if	CONFIG_DTRACE
		if ((lockstat_probemap[LS_LCK_RW_LOCK_EXCL_SPIN] || lockstat_probemap[LS_LCK_RW_LOCK_EXCL_BLOCK]) && wait_interval == 0) {
			wait_interval = mach_absolute_time();
		} else {
			wait_interval = -1;
		}
#endif


		i = lock_wait_time[lck->lck_rw_can_sleep ? 1 : 0];
		if (i != 0) {
			lck_interlock_unlock(lck, istate);
#if	MACH_LDEBUG
			if (!--decrementer)
				Debugger("timeout - lck_rw_want_write");
#endif	/* MACH_LDEBUG */
			while (--i != 0 && lck->lck_rw_want_write)
				lck_rw_lock_pause(istate);
			istate = lck_interlock_lock(lck);
		}

		if (lck->lck_rw_can_sleep && lck->lck_rw_want_write) {
			lck->lck_w_waiting = TRUE;
			res = assert_wait(RW_LOCK_WRITER_EVENT(lck), THREAD_UNINT);
			if (res == THREAD_WAITING) {
				lck_interlock_unlock(lck, istate);
				res = thread_block(THREAD_CONTINUE_NULL);
#if	CONFIG_DTRACE
				slept = 1;
#endif
				istate = lck_interlock_lock(lck);
			}
		}
		KERNEL_DEBUG(MACHDBG_CODE(DBG_MACH_LOCKS, LCK_RW_LCK_EXCLUSIVE_CODE) | DBG_FUNC_END, (int)lck, res, 0, 0, 0);
	}
	lck->lck_rw_want_write = TRUE;

	/* Wait for readers (and upgrades) to finish */

#if	MACH_LDEBUG
	decrementer = DECREMENTER_TIMEOUT;
#endif	/* MACH_LDEBUG */
	while ((lck->lck_rw_shared_count != 0) || lck->lck_rw_want_upgrade) {

		i = lock_wait_time[lck->lck_rw_can_sleep ? 1 : 0];

		KERNEL_DEBUG(MACHDBG_CODE(DBG_MACH_LOCKS, LCK_RW_LCK_EXCLUSIVE1_CODE) | DBG_FUNC_START,
			     (int)lck, lck->lck_rw_shared_count, lck->lck_rw_want_upgrade, i, 0);

#if	CONFIG_DTRACE
		/*
		 * Either sleeping or spinning is happening, start
		 * a timing of our delay interval now.  If we set it
		 * to -1 we don't have accurate data so we cannot later
		 * decide to record a dtrace spin or sleep event.
		 */
		if ((lockstat_probemap[LS_LCK_RW_LOCK_EXCL_SPIN] || lockstat_probemap[LS_LCK_RW_LOCK_EXCL_BLOCK]) && wait_interval == 0) {
			wait_interval = mach_absolute_time();
		} else {
			wait_interval = (unsigned) -1;
		}
#endif

		if (i != 0) {
			lck_interlock_unlock(lck, istate);
#if	MACH_LDEBUG
			if (!--decrementer)
				Debugger("timeout - wait for readers");
#endif	/* MACH_LDEBUG */
			while (--i != 0 && (lck->lck_rw_shared_count != 0 ||
					    lck->lck_rw_want_upgrade))
				lck_rw_lock_pause(istate);
			istate = lck_interlock_lock(lck);
		}

		if (lck->lck_rw_can_sleep && (lck->lck_rw_shared_count != 0 || lck->lck_rw_want_upgrade)) {
			lck->lck_w_waiting = TRUE;
			res = assert_wait(RW_LOCK_WRITER_EVENT(lck), THREAD_UNINT);
			if (res == THREAD_WAITING) {
				lck_interlock_unlock(lck, istate);
				res = thread_block(THREAD_CONTINUE_NULL);
#if	CONFIG_DTRACE
				slept = 1;
#endif
				istate = lck_interlock_lock(lck);
			}
		}
		KERNEL_DEBUG(MACHDBG_CODE(DBG_MACH_LOCKS, LCK_RW_LCK_EXCLUSIVE1_CODE) | DBG_FUNC_END,
			     (int)lck, lck->lck_rw_shared_count, lck->lck_rw_want_upgrade, res, 0);
	}

	lck_interlock_unlock(lck, istate);
#if	CONFIG_DTRACE
	/*
	 * Decide what latencies we suffered that are Dtrace events.
	 * If we have set wait_interval, then we either spun or slept.
	 * At least we get out from under the interlock before we record
	 * which is the best we can do here to minimize the impact
	 * of the tracing.
	 * If we have set wait_interval to -1, then dtrace was not enabled when we
	 * started sleeping/spinning so we don't record this event.
	 */
	if (wait_interval != 0 && wait_interval != (unsigned) -1) {
		if (slept == 0) {
			LOCKSTAT_RECORD2(LS_LCK_RW_LOCK_EXCL_SPIN, lck,
			    mach_absolute_time() - wait_interval, 1);
		} else {
			/*
			 * For the blocking case, we also record if when we blocked
			 * it was held for read or write, and how many readers.
			 * Notice that above we recorded this before we dropped
			 * the interlock so the count is accurate.
			 */
			LOCKSTAT_RECORD4(LS_LCK_RW_LOCK_EXCL_BLOCK, lck,
			    mach_absolute_time() - wait_interval, 1,
			    (readers_at_sleep == 0 ? 1 : 0), readers_at_sleep);
		}
	}
	LOCKSTAT_RECORD(LS_LCK_RW_LOCK_EXCL_ACQUIRE, lck, 1);
#endif
}
示例#3
0
/*
 *	Routine:	lck_rw_lock_shared_gen
 */
void
lck_rw_lock_shared_gen(
	lck_rw_t	*lck)
{
	int		i;
	wait_result_t      res;
#if	MACH_LDEBUG
	int		decrementer;
#endif	/* MACH_LDEBUG */
	boolean_t	istate;
#if	CONFIG_DTRACE
	uint64_t wait_interval = 0;
	int slept = 0;
	int readers_at_sleep;
#endif

	istate = lck_interlock_lock(lck);
#if	CONFIG_DTRACE
	readers_at_sleep = lck->lck_rw_shared_count;
#endif

#if	MACH_LDEBUG
	decrementer = DECREMENTER_TIMEOUT;
#endif	/* MACH_LDEBUG */
	while ((lck->lck_rw_want_write || lck->lck_rw_want_upgrade) &&
	    ((lck->lck_rw_shared_count == 0) || lck->lck_rw_priv_excl)) {

		i = lock_wait_time[lck->lck_rw_can_sleep ? 1 : 0];

		KERNEL_DEBUG(MACHDBG_CODE(DBG_MACH_LOCKS, LCK_RW_LCK_SHARED_CODE) | DBG_FUNC_START,
			     (int)lck, lck->lck_rw_want_write, lck->lck_rw_want_upgrade, i, 0);
#if	CONFIG_DTRACE
		if ((lockstat_probemap[LS_LCK_RW_LOCK_SHARED_SPIN] || lockstat_probemap[LS_LCK_RW_LOCK_SHARED_BLOCK]) && wait_interval == 0) {
			wait_interval = mach_absolute_time();
		} else {
			wait_interval = -1;
		}
#endif

		if (i != 0) {
			lck_interlock_unlock(lck, istate);
#if	MACH_LDEBUG
			if (!--decrementer)
				Debugger("timeout - wait no writers");
#endif	/* MACH_LDEBUG */
			while (--i != 0 &&
			    (lck->lck_rw_want_write || lck->lck_rw_want_upgrade) &&
			       ((lck->lck_rw_shared_count == 0) || lck->lck_rw_priv_excl))
				lck_rw_lock_pause(istate);
			istate = lck_interlock_lock(lck);
		}

		if (lck->lck_rw_can_sleep &&
		    (lck->lck_rw_want_write || lck->lck_rw_want_upgrade) &&
		    ((lck->lck_rw_shared_count == 0) || lck->lck_rw_priv_excl)) {
			lck->lck_r_waiting = TRUE;
			res = assert_wait(RW_LOCK_READER_EVENT(lck), THREAD_UNINT);
			if (res == THREAD_WAITING) {
				lck_interlock_unlock(lck, istate);
				res = thread_block(THREAD_CONTINUE_NULL);
#if	CONFIG_DTRACE
				slept = 1;
#endif
				istate = lck_interlock_lock(lck);
			}
		}
		KERNEL_DEBUG(MACHDBG_CODE(DBG_MACH_LOCKS, LCK_RW_LCK_SHARED_CODE) | DBG_FUNC_END,
			     (int)lck, lck->lck_rw_want_write, lck->lck_rw_want_upgrade, res, 0);
	}

	lck->lck_rw_shared_count++;

	lck_interlock_unlock(lck, istate);
#if	CONFIG_DTRACE
	if (wait_interval != 0 && wait_interval != (unsigned) -1) {
		if (slept == 0) {
			LOCKSTAT_RECORD2(LS_LCK_RW_LOCK_SHARED_SPIN, lck, mach_absolute_time() - wait_interval, 0);
		} else {
			LOCKSTAT_RECORD4(LS_LCK_RW_LOCK_SHARED_BLOCK, lck,
			    mach_absolute_time() - wait_interval, 0,
			    (readers_at_sleep == 0 ? 1 : 0), readers_at_sleep);
		}
	}
	LOCKSTAT_RECORD(LS_LCK_RW_LOCK_SHARED_ACQUIRE, lck, 0);
#endif
}
示例#4
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);
}
示例#5
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++;
}
示例#6
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);
}
示例#7
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);
}