SLEEPQUEUE(9): Import from FreeBSD

2 files changed, 1353 insertions, 0 deletions

diff --git a/freebsd/sys/kern/subr_sleepqueue.c b/freebsd/sys/kern/subr_sleepqueue.c
new file mode 100644
index 00000000..3774e66d
--- /dev/null
+++ b/freebsd/sys/kern/subr_sleepqueue.c
@@ -0,0 +1,1236 @@
+#include <machine/rtems-bsd-kernel-space.h>
+
+/*-
+ * Copyright (c) 2004 John Baldwin <jhb@FreeBSD.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+/*
+ * Implementation of sleep queues used to hold queue of threads blocked on
+ * a wait channel.  Sleep queues different from turnstiles in that wait
+ * channels are not owned by anyone, so there is no priority propagation.
+ * Sleep queues can also provide a timeout and can also be interrupted by
+ * signals.  That said, there are several similarities between the turnstile
+ * and sleep queue implementations.  (Note: turnstiles were implemented
+ * first.)  For example, both use a hash table of the same size where each
+ * bucket is referred to as a "chain" that contains both a spin lock and
+ * a linked list of queues.  An individual queue is located by using a hash
+ * to pick a chain, locking the chain, and then walking the chain searching
+ * for the queue.  This means that a wait channel object does not need to
+ * embed it's queue head just as locks do not embed their turnstile queue
+ * head.  Threads also carry around a sleep queue that they lend to the
+ * wait channel when blocking.  Just as in turnstiles, the queue includes
+ * a free list of the sleep queues of other threads blocked on the same
+ * wait channel in the case of multiple waiters.
+ *
+ * Some additional functionality provided by sleep queues include the
+ * ability to set a timeout.  The timeout is managed using a per-thread
+ * callout that resumes a thread if it is asleep.  A thread may also
+ * catch signals while it is asleep (aka an interruptible sleep).  The
+ * signal code uses sleepq_abort() to interrupt a sleeping thread.  Finally,
+ * sleep queues also provide some extra assertions.  One is not allowed to
+ * mix the sleep/wakeup and cv APIs for a given wait channel.  Also, one
+ * must consistently use the same lock to synchronize with a wait channel,
+ * though this check is currently only a warning for sleep/wakeup due to
+ * pre-existing abuse of that API.  The same lock must also be held when
+ * awakening threads, though that is currently only enforced for condition
+ * variables.
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <rtems/bsd/local/opt_sleepqueue_profiling.h>
+#include <rtems/bsd/local/opt_ddb.h>
+#include <rtems/bsd/local/opt_kdtrace.h>
+#include <rtems/bsd/local/opt_sched.h>
+
+#include <rtems/bsd/sys/param.h>
+#include <sys/systm.h>
+#include <rtems/bsd/sys/lock.h>
+#include <sys/kernel.h>
+#include <sys/ktr.h>
+#include <sys/mutex.h>
+#include <sys/proc.h>
+#include <sys/sbuf.h>
+#include <sys/sched.h>
+#include <sys/sdt.h>
+#include <sys/signalvar.h>
+#include <sys/sleepqueue.h>
+#include <sys/sysctl.h>
+
+#include <vm/uma.h>
+
+#ifdef DDB
+#include <ddb/ddb.h>
+#endif
+
+/*
+ * Constants for the hash table of sleep queue chains.  These constants are
+ * the same ones that 4BSD (and possibly earlier versions of BSD) used.
+ * Basically, we ignore the lower 8 bits of the address since most wait
+ * channel pointers are aligned and only look at the next 7 bits for the
+ * hash.  SC_TABLESIZE must be a power of two for SC_MASK to work properly.
+ */
+#define	SC_TABLESIZE	128			/* Must be power of 2. */
+#define	SC_MASK		(SC_TABLESIZE - 1)
+#define	SC_SHIFT	8
+#define	SC_HASH(wc)	(((uintptr_t)(wc) >> SC_SHIFT) & SC_MASK)
+#define	SC_LOOKUP(wc)	&sleepq_chains[SC_HASH(wc)]
+#define NR_SLEEPQS      2
+/*
+ * There two different lists of sleep queues.  Both lists are connected
+ * via the sq_hash entries.  The first list is the sleep queue chain list
+ * that a sleep queue is on when it is attached to a wait channel.  The
+ * second list is the free list hung off of a sleep queue that is attached
+ * to a wait channel.
+ *
+ * Each sleep queue also contains the wait channel it is attached to, the
+ * list of threads blocked on that wait channel, flags specific to the
+ * wait channel, and the lock used to synchronize with a wait channel.
+ * The flags are used to catch mismatches between the various consumers
+ * of the sleep queue API (e.g. sleep/wakeup and condition variables).
+ * The lock pointer is only used when invariants are enabled for various
+ * debugging checks.
+ *
+ * Locking key:
+ *  c - sleep queue chain lock
+ */
+struct sleepqueue {
+	TAILQ_HEAD(, thread) sq_blocked[NR_SLEEPQS];	/* (c) Blocked threads. */
+	u_int sq_blockedcnt[NR_SLEEPQS];	/* (c) N. of blocked threads. */
+	LIST_ENTRY(sleepqueue) sq_hash;		/* (c) Chain and free list. */
+	LIST_HEAD(, sleepqueue) sq_free;	/* (c) Free queues. */
+	void	*sq_wchan;			/* (c) Wait channel. */
+	int	sq_type;			/* (c) Queue type. */
+#ifdef INVARIANTS
+	struct lock_object *sq_lock;		/* (c) Associated lock. */
+#endif
+};
+
+struct sleepqueue_chain {
+	LIST_HEAD(, sleepqueue) sc_queues;	/* List of sleep queues. */
+	struct mtx sc_lock;			/* Spin lock for this chain. */
+#ifdef SLEEPQUEUE_PROFILING
+	u_int	sc_depth;			/* Length of sc_queues. */
+	u_int	sc_max_depth;			/* Max length of sc_queues. */
+#endif
+};
+
+#ifdef SLEEPQUEUE_PROFILING
+u_int sleepq_max_depth;
+static SYSCTL_NODE(_debug, OID_AUTO, sleepq, CTLFLAG_RD, 0, "sleepq profiling");
+static SYSCTL_NODE(_debug_sleepq, OID_AUTO, chains, CTLFLAG_RD, 0,
+    "sleepq chain stats");
+SYSCTL_UINT(_debug_sleepq, OID_AUTO, max_depth, CTLFLAG_RD, &sleepq_max_depth,
+    0, "maxmimum depth achieved of a single chain");
+
+static void	sleepq_profile(const char *wmesg);
+static int	prof_enabled;
+#endif
+static struct sleepqueue_chain sleepq_chains[SC_TABLESIZE];
+static uma_zone_t sleepq_zone;
+
+/*
+ * Prototypes for non-exported routines.
+ */
+static int	sleepq_catch_signals(void *wchan, int pri);
+static int	sleepq_check_signals(void);
+static int	sleepq_check_timeout(void);
+#ifdef INVARIANTS
+static void	sleepq_dtor(void *mem, int size, void *arg);
+#endif
+static int	sleepq_init(void *mem, int size, int flags);
+static int	sleepq_resume_thread(struct sleepqueue *sq, struct thread *td,
+		    int pri);
+static void	sleepq_switch(void *wchan, int pri);
+static void	sleepq_timeout(void *arg);
+
+SDT_PROBE_DECLARE(sched, , , sleep);
+SDT_PROBE_DECLARE(sched, , , wakeup);
+
+/*
+ * Early initialization of sleep queues that is called from the sleepinit()
+ * SYSINIT.
+ */
+void
+init_sleepqueues(void)
+{
+#ifdef SLEEPQUEUE_PROFILING
+	struct sysctl_oid *chain_oid;
+	char chain_name[10];
+#endif
+	int i;
+
+	for (i = 0; i < SC_TABLESIZE; i++) {
+		LIST_INIT(&sleepq_chains[i].sc_queues);
+		mtx_init(&sleepq_chains[i].sc_lock, "sleepq chain", NULL,
+		    MTX_SPIN | MTX_RECURSE);
+#ifdef SLEEPQUEUE_PROFILING
+		snprintf(chain_name, sizeof(chain_name), "%d", i);
+		chain_oid = SYSCTL_ADD_NODE(NULL, 
+		    SYSCTL_STATIC_CHILDREN(_debug_sleepq_chains), OID_AUTO,
+		    chain_name, CTLFLAG_RD, NULL, "sleepq chain stats");
+		SYSCTL_ADD_UINT(NULL, SYSCTL_CHILDREN(chain_oid), OID_AUTO,
+		    "depth", CTLFLAG_RD, &sleepq_chains[i].sc_depth, 0, NULL);
+		SYSCTL_ADD_UINT(NULL, SYSCTL_CHILDREN(chain_oid), OID_AUTO,
+		    "max_depth", CTLFLAG_RD, &sleepq_chains[i].sc_max_depth, 0,
+		    NULL);
+#endif
+	}
+	sleepq_zone = uma_zcreate("SLEEPQUEUE", sizeof(struct sleepqueue),
+#ifdef INVARIANTS
+	    NULL, sleepq_dtor, sleepq_init, NULL, UMA_ALIGN_CACHE, 0);
+#else
+	    NULL, NULL, sleepq_init, NULL, UMA_ALIGN_CACHE, 0);
+#endif
+	
+	thread0.td_sleepqueue = sleepq_alloc();
+}
+
+/*
+ * Get a sleep queue for a new thread.
+ */
+struct sleepqueue *
+sleepq_alloc(void)
+{
+
+	return (uma_zalloc(sleepq_zone, M_WAITOK));
+}
+
+/*
+ * Free a sleep queue when a thread is destroyed.
+ */
+void
+sleepq_free(struct sleepqueue *sq)
+{
+
+	uma_zfree(sleepq_zone, sq);
+}
+
+/*
+ * Lock the sleep queue chain associated with the specified wait channel.
+ */
+void
+sleepq_lock(void *wchan)
+{
+	struct sleepqueue_chain *sc;
+
+	sc = SC_LOOKUP(wchan);
+	mtx_lock_spin(&sc->sc_lock);
+}
+
+/*
+ * Look up the sleep queue associated with a given wait channel in the hash
+ * table locking the associated sleep queue chain.  If no queue is found in
+ * the table, NULL is returned.
+ */
+struct sleepqueue *
+sleepq_lookup(void *wchan)
+{
+	struct sleepqueue_chain *sc;
+	struct sleepqueue *sq;
+
+	KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__));
+	sc = SC_LOOKUP(wchan);
+	mtx_assert(&sc->sc_lock, MA_OWNED);
+	LIST_FOREACH(sq, &sc->sc_queues, sq_hash)
+		if (sq->sq_wchan == wchan)
+			return (sq);
+	return (NULL);
+}
+
+/*
+ * Unlock the sleep queue chain associated with a given wait channel.
+ */
+void
+sleepq_release(void *wchan)
+{
+	struct sleepqueue_chain *sc;
+
+	sc = SC_LOOKUP(wchan);
+	mtx_unlock_spin(&sc->sc_lock);
+}
+
+/*
+ * Places the current thread on the sleep queue for the specified wait
+ * channel.  If INVARIANTS is enabled, then it associates the passed in
+ * lock with the sleepq to make sure it is held when that sleep queue is
+ * woken up.
+ */
+void
+sleepq_add(void *wchan, struct lock_object *lock, const char *wmesg, int flags,
+    int queue)
+{
+	struct sleepqueue_chain *sc;
+	struct sleepqueue *sq;
+	struct thread *td;
+
+	td = curthread;
+	sc = SC_LOOKUP(wchan);
+	mtx_assert(&sc->sc_lock, MA_OWNED);
+	MPASS(td->td_sleepqueue != NULL);
+	MPASS(wchan != NULL);
+	MPASS((queue >= 0) && (queue < NR_SLEEPQS));
+
+	/* If this thread is not allowed to sleep, die a horrible death. */
+	KASSERT(!(td->td_pflags & TDP_NOSLEEPING),
+	    ("Trying sleep, but thread marked as sleeping prohibited"));
+
+	/* Look up the sleep queue associated with the wait channel 'wchan'. */
+	sq = sleepq_lookup(wchan);
+
+	/*
+	 * If the wait channel does not already have a sleep queue, use
+	 * this thread's sleep queue.  Otherwise, insert the current thread
+	 * into the sleep queue already in use by this wait channel.
+	 */
+	if (sq == NULL) {
+#ifdef INVARIANTS
+		int i;
+
+		sq = td->td_sleepqueue;
+		for (i = 0; i < NR_SLEEPQS; i++) {
+			KASSERT(TAILQ_EMPTY(&sq->sq_blocked[i]),
+			    ("thread's sleep queue %d is not empty", i));
+			KASSERT(sq->sq_blockedcnt[i] == 0,
+			    ("thread's sleep queue %d count mismatches", i));
+		}
+		KASSERT(LIST_EMPTY(&sq->sq_free),
+		    ("thread's sleep queue has a non-empty free list"));
+		KASSERT(sq->sq_wchan == NULL, ("stale sq_wchan pointer"));
+		sq->sq_lock = lock;
+#endif
+#ifdef SLEEPQUEUE_PROFILING
+		sc->sc_depth++;
+		if (sc->sc_depth > sc->sc_max_depth) {
+			sc->sc_max_depth = sc->sc_depth;
+			if (sc->sc_max_depth > sleepq_max_depth)
+				sleepq_max_depth = sc->sc_max_depth;
+		}
+#endif
+		sq = td->td_sleepqueue;
+		LIST_INSERT_HEAD(&sc->sc_queues, sq, sq_hash);
+		sq->sq_wchan = wchan;
+		sq->sq_type = flags & SLEEPQ_TYPE;
+	} else {
+		MPASS(wchan == sq->sq_wchan);
+		MPASS(lock == sq->sq_lock);
+		MPASS((flags & SLEEPQ_TYPE) == sq->sq_type);
+		LIST_INSERT_HEAD(&sq->sq_free, td->td_sleepqueue, sq_hash);
+	}
+	thread_lock(td);
+	TAILQ_INSERT_TAIL(&sq->sq_blocked[queue], td, td_slpq);
+	sq->sq_blockedcnt[queue]++;
+	td->td_sleepqueue = NULL;
+	td->td_sqqueue = queue;
+	td->td_wchan = wchan;
+	td->td_wmesg = wmesg;
+	if (flags & SLEEPQ_INTERRUPTIBLE) {
+		td->td_flags |= TDF_SINTR;
+		td->td_flags &= ~TDF_SLEEPABORT;
+	}
+	thread_unlock(td);
+}
+
+/*
+ * Sets a timeout that will remove the current thread from the specified
+ * sleep queue after timo ticks if the thread has not already been awakened.
+ */
+void
+sleepq_set_timeout(void *wchan, int timo)
+{
+	struct sleepqueue_chain *sc;
+	struct thread *td;
+
+	td = curthread;
+	sc = SC_LOOKUP(wchan);
+	mtx_assert(&sc->sc_lock, MA_OWNED);
+	MPASS(TD_ON_SLEEPQ(td));
+	MPASS(td->td_sleepqueue == NULL);
+	MPASS(wchan != NULL);
+	callout_reset_curcpu(&td->td_slpcallout, timo, sleepq_timeout, td);
+}
+
+/*
+ * Return the number of actual sleepers for the specified queue.
+ */
+u_int
+sleepq_sleepcnt(void *wchan, int queue)
+{
+	struct sleepqueue *sq;
+
+	KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__));
+	MPASS((queue >= 0) && (queue < NR_SLEEPQS));
+	sq = sleepq_lookup(wchan);
+	if (sq == NULL)
+		return (0);
+	return (sq->sq_blockedcnt[queue]);
+}
+
+/*
+ * Marks the pending sleep of the current thread as interruptible and
+ * makes an initial check for pending signals before putting a thread
+ * to sleep. Enters and exits with the thread lock held.  Thread lock
+ * may have transitioned from the sleepq lock to a run lock.
+ */
+static int
+sleepq_catch_signals(void *wchan, int pri)
+{
+	struct sleepqueue_chain *sc;
+	struct sleepqueue *sq;
+	struct thread *td;
+	struct proc *p;
+	struct sigacts *ps;
+	int sig, ret, stop_allowed;
+
+	td = curthread;
+	p = curproc;
+	sc = SC_LOOKUP(wchan);
+	mtx_assert(&sc->sc_lock, MA_OWNED);
+	MPASS(wchan != NULL);
+	if ((td->td_pflags & TDP_WAKEUP) != 0) {
+		td->td_pflags &= ~TDP_WAKEUP;
+		ret = EINTR;
+		thread_lock(td);
+		goto out;
+	}
+
+	/*
+	 * See if there are any pending signals for this thread.  If not
+	 * we can switch immediately.  Otherwise do the signal processing
+	 * directly.
+	 */
+	thread_lock(td);
+	if ((td->td_flags & (TDF_NEEDSIGCHK | TDF_NEEDSUSPCHK)) == 0) {
+		sleepq_switch(wchan, pri);
+		return (0);
+	}
+	stop_allowed = (td->td_flags & TDF_SBDRY) ? SIG_STOP_NOT_ALLOWED :
+	    SIG_STOP_ALLOWED;
+	thread_unlock(td);
+	mtx_unlock_spin(&sc->sc_lock);
+	CTR3(KTR_PROC, "sleepq catching signals: thread %p (pid %ld, %s)",
+		(void *)td, (long)p->p_pid, td->td_name);
+	PROC_LOCK(p);
+	ps = p->p_sigacts;
+	mtx_lock(&ps->ps_mtx);
+	sig = cursig(td, stop_allowed);
+	if (sig == 0) {
+		mtx_unlock(&ps->ps_mtx);
+		ret = thread_suspend_check(1);
+		MPASS(ret == 0 || ret == EINTR || ret == ERESTART);
+	} else {
+		if (SIGISMEMBER(ps->ps_sigintr, sig))
+			ret = EINTR;
+		else
+			ret = ERESTART;
+		mtx_unlock(&ps->ps_mtx);
+	}
+	/*
+	 * Lock the per-process spinlock prior to dropping the PROC_LOCK
+	 * to avoid a signal delivery race.  PROC_LOCK, PROC_SLOCK, and
+	 * thread_lock() are currently held in tdsendsignal().
+	 */
+	PROC_SLOCK(p);
+	mtx_lock_spin(&sc->sc_lock);
+	PROC_UNLOCK(p);
+	thread_lock(td);
+	PROC_SUNLOCK(p);
+	if (ret == 0) {
+		sleepq_switch(wchan, pri);
+		return (0);
+	}
+out:
+	/*
+	 * There were pending signals and this thread is still
+	 * on the sleep queue, remove it from the sleep queue.
+	 */
+	if (TD_ON_SLEEPQ(td)) {
+		sq = sleepq_lookup(wchan);
+		if (sleepq_resume_thread(sq, td, 0)) {
+#ifdef INVARIANTS
+			/*
+			 * This thread hasn't gone to sleep yet, so it
+			 * should not be swapped out.
+			 */
+			panic("not waking up swapper");
+#endif
+		}
+	}
+	mtx_unlock_spin(&sc->sc_lock);
+	MPASS(td->td_lock != &sc->sc_lock);
+	return (ret);
+}
+
+/*
+ * Switches to another thread if we are still asleep on a sleep queue.
+ * Returns with thread lock.
+ */
+static void
+sleepq_switch(void *wchan, int pri)
+{
+	struct sleepqueue_chain *sc;
+	struct sleepqueue *sq;
+	struct thread *td;
+
+	td = curthread;
+	sc = SC_LOOKUP(wchan);
+	mtx_assert(&sc->sc_lock, MA_OWNED);
+	THREAD_LOCK_ASSERT(td, MA_OWNED);
+
+	/* 
+	 * If we have a sleep queue, then we've already been woken up, so
+	 * just return.
+	 */
+	if (td->td_sleepqueue != NULL) {
+		mtx_unlock_spin(&sc->sc_lock);
+		return;
+	}
+
+	/*
+	 * If TDF_TIMEOUT is set, then our sleep has been timed out
+	 * already but we are still on the sleep queue, so dequeue the
+	 * thread and return.
+	 */
+	if (td->td_flags & TDF_TIMEOUT) {
+		MPASS(TD_ON_SLEEPQ(td));
+		sq = sleepq_lookup(wchan);
+		if (sleepq_resume_thread(sq, td, 0)) {
+#ifdef INVARIANTS
+			/*
+			 * This thread hasn't gone to sleep yet, so it
+			 * should not be swapped out.
+			 */
+			panic("not waking up swapper");
+#endif
+		}
+		mtx_unlock_spin(&sc->sc_lock);
+		return;		
+	}
+#ifdef SLEEPQUEUE_PROFILING
+	if (prof_enabled)
+		sleepq_profile(td->td_wmesg);
+#endif
+	MPASS(td->td_sleepqueue == NULL);
+	sched_sleep(td, pri);
+	thread_lock_set(td, &sc->sc_lock);
+	SDT_PROBE0(sched, , , sleep);
+	TD_SET_SLEEPING(td);
+	mi_switch(SW_VOL | SWT_SLEEPQ, NULL);
+	KASSERT(TD_IS_RUNNING(td), ("running but not TDS_RUNNING"));
+	CTR3(KTR_PROC, "sleepq resume: thread %p (pid %ld, %s)",
+	    (void *)td, (long)td->td_proc->p_pid, (void *)td->td_name);
+}
+
+/*
+ * Check to see if we timed out.
+ */
+static int
+sleepq_check_timeout(void)
+{
+	struct thread *td;
+
+	td = curthread;
+	THREAD_LOCK_ASSERT(td, MA_OWNED);
+
+	/*
+	 * If TDF_TIMEOUT is set, we timed out.
+	 */
+	if (td->td_flags & TDF_TIMEOUT) {
+		td->td_flags &= ~TDF_TIMEOUT;
+		return (EWOULDBLOCK);
+	}
+
+	/*
+	 * If TDF_TIMOFAIL is set, the timeout ran after we had
+	 * already been woken up.
+	 */
+	if (td->td_flags & TDF_TIMOFAIL)
+		td->td_flags &= ~TDF_TIMOFAIL;
+
+	/*
+	 * If callout_stop() fails, then the timeout is running on
+	 * another CPU, so synchronize with it to avoid having it
+	 * accidentally wake up a subsequent sleep.
+	 */
+	else if (callout_stop(&td->td_slpcallout) == 0) {
+		td->td_flags |= TDF_TIMEOUT;
+		TD_SET_SLEEPING(td);
+		mi_switch(SW_INVOL | SWT_SLEEPQTIMO, NULL);
+	}
+	return (0);
+}
+
+/*
+ * Check to see if we were awoken by a signal.
+ */
+static int
+sleepq_check_signals(void)
+{
+	struct thread *td;
+
+	td = curthread;
+	THREAD_LOCK_ASSERT(td, MA_OWNED);
+
+	/* We are no longer in an interruptible sleep. */
+	if (td->td_flags & TDF_SINTR)
+		td->td_flags &= ~TDF_SINTR;
+
+	if (td->td_flags & TDF_SLEEPABORT) {
+		td->td_flags &= ~TDF_SLEEPABORT;
+		return (td->td_intrval);
+	}
+
+	return (0);
+}
+
+/*
+ * Block the current thread until it is awakened from its sleep queue.
+ */
+void
+sleepq_wait(void *wchan, int pri)
+{
+	struct thread *td;
+
+	td = curthread;
+	MPASS(!(td->td_flags & TDF_SINTR));
+	thread_lock(td);
+	sleepq_switch(wchan, pri);
+	thread_unlock(td);
+}
+
+/*
+ * Block the current thread until it is awakened from its sleep queue
+ * or it is interrupted by a signal.
+ */
+int
+sleepq_wait_sig(void *wchan, int pri)
+{
+	int rcatch;
+	int rval;
+
+	rcatch = sleepq_catch_signals(wchan, pri);
+	rval = sleepq_check_signals();
+	thread_unlock(curthread);
+	if (rcatch)
+		return (rcatch);
+	return (rval);
+}
+
+/*
+ * Block the current thread until it is awakened from its sleep queue
+ * or it times out while waiting.
+ */
+int
+sleepq_timedwait(void *wchan, int pri)
+{
+	struct thread *td;
+	int rval;
+
+	td = curthread;
+	MPASS(!(td->td_flags & TDF_SINTR));
+	thread_lock(td);
+	sleepq_switch(wchan, pri);
+	rval = sleepq_check_timeout();
+	thread_unlock(td);
+
+	return (rval);
+}
+
+/*
+ * Block the current thread until it is awakened from its sleep queue,
+ * it is interrupted by a signal, or it times out waiting to be awakened.
+ */
+int
+sleepq_timedwait_sig(void *wchan, int pri)
+{
+	int rcatch, rvalt, rvals;
+
+	rcatch = sleepq_catch_signals(wchan, pri);
+	rvalt = sleepq_check_timeout();
+	rvals = sleepq_check_signals();
+	thread_unlock(curthread);
+	if (rcatch)
+		return (rcatch);
+	if (rvals)
+		return (rvals);
+	return (rvalt);
+}
+
+/*
+ * Returns the type of sleepqueue given a waitchannel.
+ */
+int
+sleepq_type(void *wchan)
+{
+	struct sleepqueue *sq;
+	int type;
+
+	MPASS(wchan != NULL);
+
+	sleepq_lock(wchan);
+	sq = sleepq_lookup(wchan);
+	if (sq == NULL) {
+		sleepq_release(wchan);
+		return (-1);
+	}
+	type = sq->sq_type;
+	sleepq_release(wchan);
+	return (type);
+}
+
+/*
+ * Removes a thread from a sleep queue and makes it
+ * runnable.
+ */
+static int
+sleepq_resume_thread(struct sleepqueue *sq, struct thread *td, int pri)
+{
+	struct sleepqueue_chain *sc;
+
+	MPASS(td != NULL);
+	MPASS(sq->sq_wchan != NULL);
+	MPASS(td->td_wchan == sq->sq_wchan);
+	MPASS(td->td_sqqueue < NR_SLEEPQS && td->td_sqqueue >= 0);
+	THREAD_LOCK_ASSERT(td, MA_OWNED);
+	sc = SC_LOOKUP(sq->sq_wchan);
+	mtx_assert(&sc->sc_lock, MA_OWNED);
+
+	SDT_PROBE2(sched, , , wakeup, td, td->td_proc);
+
+	/* Remove the thread from the queue. */
+	sq->sq_blockedcnt[td->td_sqqueue]--;
+	TAILQ_REMOVE(&sq->sq_blocked[td->td_sqqueue], td, td_slpq);
+
+	/*
+	 * Get a sleep queue for this thread.  If this is the last waiter,
+	 * use the queue itself and take it out of the chain, otherwise,
+	 * remove a queue from the free list.
+	 */
+	if (LIST_EMPTY(&sq->sq_free)) {
+		td->td_sleepqueue = sq;
+#ifdef INVARIANTS
+		sq->sq_wchan = NULL;
+#endif
+#ifdef SLEEPQUEUE_PROFILING
+		sc->sc_depth--;
+#endif
+	} else
+		td->td_sleepqueue = LIST_FIRST(&sq->sq_free);
+	LIST_REMOVE(td->td_sleepqueue, sq_hash);
+
+	td->td_wmesg = NULL;
+	td->td_wchan = NULL;
+	td->td_flags &= ~TDF_SINTR;
+
+	CTR3(KTR_PROC, "sleepq_wakeup: thread %p (pid %ld, %s)",
+	    (void *)td, (long)td->td_proc->p_pid, td->td_name);
+
+	/* Adjust priority if requested. */
+	MPASS(pri == 0 || (pri >= PRI_MIN && pri <= PRI_MAX));
+	if (pri != 0 && td->td_priority > pri &&
+	    PRI_BASE(td->td_pri_class) == PRI_TIMESHARE)
+		sched_prio(td, pri);
+
+	/*
+	 * Note that thread td might not be sleeping if it is running
+	 * sleepq_catch_signals() on another CPU or is blocked on its
+	 * proc lock to check signals.  There's no need to mark the
+	 * thread runnable in that case.
+	 */
+	if (TD_IS_SLEEPING(td)) {
+		TD_CLR_SLEEPING(td);
+		return (setrunnable(td));
+	}
+	return (0);
+}
+
+#ifdef INVARIANTS
+/*
+ * UMA zone item deallocator.
+ */
+static void
+sleepq_dtor(void *mem, int size, void *arg)
+{
+	struct sleepqueue *sq;
+	int i;
+
+	sq = mem;
+	for (i = 0; i < NR_SLEEPQS; i++) {
+		MPASS(TAILQ_EMPTY(&sq->sq_blocked[i]));
+		MPASS(sq->sq_blockedcnt[i] == 0);
+	}
+}
+#endif
+
+/*
+ * UMA zone item initializer.
+ */
+static int
+sleepq_init(void *mem, int size, int flags)
+{
+	struct sleepqueue *sq;
+	int i;
+
+	bzero(mem, size);
+	sq = mem;
+	for (i = 0; i < NR_SLEEPQS; i++) {
+		TAILQ_INIT(&sq->sq_blocked[i]);
+		sq->sq_blockedcnt[i] = 0;
+	}
+	LIST_INIT(&sq->sq_free);
+	return (0);
+}
+
+/*
+ * Find the highest priority thread sleeping on a wait channel and resume it.
+ */
+int
+sleepq_signal(void *wchan, int flags, int pri, int queue)
+{
+	struct sleepqueue *sq;
+	struct thread *td, *besttd;
+	int wakeup_swapper;
+
+	CTR2(KTR_PROC, "sleepq_signal(%p, %d)", wchan, flags);
+	KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__));
+	MPASS((queue >= 0) && (queue < NR_SLEEPQS));
+	sq = sleepq_lookup(wchan);
+	if (sq == NULL)
+		return (0);
+	KASSERT(sq->sq_type == (flags & SLEEPQ_TYPE),
+	    ("%s: mismatch between sleep/wakeup and cv_*", __func__));
+
+	/*
+	 * Find the highest priority thread on the queue.  If there is a
+	 * tie, use the thread that first appears in the queue as it has
+	 * been sleeping the longest since threads are always added to
+	 * the tail of sleep queues.
+	 */
+	besttd = NULL;
+	TAILQ_FOREACH(td, &sq->sq_blocked[queue], td_slpq) {
+		if (besttd == NULL || td->td_priority < besttd->td_priority)
+			besttd = td;
+	}
+	MPASS(besttd != NULL);
+	thread_lock(besttd);
+	wakeup_swapper = sleepq_resume_thread(sq, besttd, pri);
+	thread_unlock(besttd);
+	return (wakeup_swapper);
+}
+
+/*
+ * Resume all threads sleeping on a specified wait channel.
+ */
+int
+sleepq_broadcast(void *wchan, int flags, int pri, int queue)
+{
+	struct sleepqueue *sq;
+	struct thread *td, *tdn;
+	int wakeup_swapper;
+
+	CTR2(KTR_PROC, "sleepq_broadcast(%p, %d)", wchan, flags);
+	KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__));
+	MPASS((queue >= 0) && (queue < NR_SLEEPQS));
+	sq = sleepq_lookup(wchan);
+	if (sq == NULL)
+		return (0);
+	KASSERT(sq->sq_type == (flags & SLEEPQ_TYPE),
+	    ("%s: mismatch between sleep/wakeup and cv_*", __func__));
+
+	/* Resume all blocked threads on the sleep queue. */
+	wakeup_swapper = 0;
+	TAILQ_FOREACH_SAFE(td, &sq->sq_blocked[queue], td_slpq, tdn) {
+		thread_lock(td);
+		if (sleepq_resume_thread(sq, td, pri))
+			wakeup_swapper = 1;
+		thread_unlock(td);
+	}
+	return (wakeup_swapper);
+}
+
+/*
+ * Time sleeping threads out.  When the timeout expires, the thread is
+ * removed from the sleep queue and made runnable if it is still asleep.
+ */
+static void
+sleepq_timeout(void *arg)
+{
+	struct sleepqueue_chain *sc;
+	struct sleepqueue *sq;
+	struct thread *td;
+	void *wchan;
+	int wakeup_swapper;
+
+	td = arg;
+	wakeup_swapper = 0;
+	CTR3(KTR_PROC, "sleepq_timeout: thread %p (pid %ld, %s)",
+	    (void *)td, (long)td->td_proc->p_pid, (void *)td->td_name);
+
+	/*
+	 * First, see if the thread is asleep and get the wait channel if
+	 * it is.
+	 */
+	thread_lock(td);
+	if (TD_IS_SLEEPING(td) && TD_ON_SLEEPQ(td)) {
+		wchan = td->td_wchan;
+		sc = SC_LOOKUP(wchan);
+		THREAD_LOCKPTR_ASSERT(td, &sc->sc_lock);
+		sq = sleepq_lookup(wchan);
+		MPASS(sq != NULL);
+		td->td_flags |= TDF_TIMEOUT;
+		wakeup_swapper = sleepq_resume_thread(sq, td, 0);
+		thread_unlock(td);
+		if (wakeup_swapper)
+			kick_proc0();
+		return;
+	}
+
+	/*
+	 * If the thread is on the SLEEPQ but isn't sleeping yet, it
+	 * can either be on another CPU in between sleepq_add() and
+	 * one of the sleepq_*wait*() routines or it can be in
+	 * sleepq_catch_signals().
+	 */
+	if (TD_ON_SLEEPQ(td)) {
+		td->td_flags |= TDF_TIMEOUT;
+		thread_unlock(td);
+		return;
+	}
+
+	/*
+	 * Now check for the edge cases.  First, if TDF_TIMEOUT is set,
+	 * then the other thread has already yielded to us, so clear
+	 * the flag and resume it.  If TDF_TIMEOUT is not set, then the
+	 * we know that the other thread is not on a sleep queue, but it
+	 * hasn't resumed execution yet.  In that case, set TDF_TIMOFAIL
+	 * to let it know that the timeout has already run and doesn't
+	 * need to be canceled.
+	 */
+	if (td->td_flags & TDF_TIMEOUT) {
+		MPASS(TD_IS_SLEEPING(td));
+		td->td_flags &= ~TDF_TIMEOUT;
+		TD_CLR_SLEEPING(td);
+		wakeup_swapper = setrunnable(td);
+	} else
+		td->td_flags |= TDF_TIMOFAIL;
+	thread_unlock(td);
+	if (wakeup_swapper)
+		kick_proc0();
+}
+
+/*
+ * Resumes a specific thread from the sleep queue associated with a specific
+ * wait channel if it is on that queue.
+ */
+void
+sleepq_remove(struct thread *td, void *wchan)
+{
+	struct sleepqueue *sq;
+	int wakeup_swapper;
+
+	/*
+	 * Look up the sleep queue for this wait channel, then re-check
+	 * that the thread is asleep on that channel, if it is not, then
+	 * bail.
+	 */
+	MPASS(wchan != NULL);
+	sleepq_lock(wchan);
+	sq = sleepq_lookup(wchan);
+	/*
+	 * We can not lock the thread here as it may be sleeping on a
+	 * different sleepq.  However, holding the sleepq lock for this
+	 * wchan can guarantee that we do not miss a wakeup for this
+	 * channel.  The asserts below will catch any false positives.
+	 */
+	if (!TD_ON_SLEEPQ(td) || td->td_wchan != wchan) {
+		sleepq_release(wchan);
+		return;
+	}
+	/* Thread is asleep on sleep queue sq, so wake it up. */
+	thread_lock(td);
+	MPASS(sq != NULL);
+	MPASS(td->td_wchan == wchan);
+	wakeup_swapper = sleepq_resume_thread(sq, td, 0);
+	thread_unlock(td);
+	sleepq_release(wchan);
+	if (wakeup_swapper)
+		kick_proc0();
+}
+
+/*
+ * Abort a thread as if an interrupt had occurred.  Only abort
+ * interruptible waits (unfortunately it isn't safe to abort others).
+ */
+int
+sleepq_abort(struct thread *td, int intrval)
+{
+	struct sleepqueue *sq;
+	void *wchan;
+
+	THREAD_LOCK_ASSERT(td, MA_OWNED);
+	MPASS(TD_ON_SLEEPQ(td));
+	MPASS(td->td_flags & TDF_SINTR);
+	MPASS(intrval == EINTR || intrval == ERESTART);
+
+	/*
+	 * If the TDF_TIMEOUT flag is set, just leave. A
+	 * timeout is scheduled anyhow.
+	 */
+	if (td->td_flags & TDF_TIMEOUT)
+		return (0);
+
+	CTR3(KTR_PROC, "sleepq_abort: thread %p (pid %ld, %s)",
+	    (void *)td, (long)td->td_proc->p_pid, (void *)td->td_name);
+	td->td_intrval = intrval;
+	td->td_flags |= TDF_SLEEPABORT;
+	/*
+	 * If the thread has not slept yet it will find the signal in
+	 * sleepq_catch_signals() and call sleepq_resume_thread.  Otherwise
+	 * we have to do it here.
+	 */
+	if (!TD_IS_SLEEPING(td))
+		return (0);
+	wchan = td->td_wchan;
+	MPASS(wchan != NULL);
+	sq = sleepq_lookup(wchan);
+	MPASS(sq != NULL);
+
+	/* Thread is asleep on sleep queue sq, so wake it up. */
+	return (sleepq_resume_thread(sq, td, 0));
+}
+
+#ifdef SLEEPQUEUE_PROFILING
+#define	SLEEPQ_PROF_LOCATIONS	1024
+#define	SLEEPQ_SBUFSIZE		512
+struct sleepq_prof {
+	LIST_ENTRY(sleepq_prof) sp_link;
+	const char	*sp_wmesg;
+	long		sp_count;
+};
+
+LIST_HEAD(sqphead, sleepq_prof);
+
+struct sqphead sleepq_prof_free;
+struct sqphead sleepq_hash[SC_TABLESIZE];
+static struct sleepq_prof sleepq_profent[SLEEPQ_PROF_LOCATIONS];
+static struct mtx sleepq_prof_lock;
+MTX_SYSINIT(sleepq_prof_lock, &sleepq_prof_lock, "sleepq_prof", MTX_SPIN);
+
+static void
+sleepq_profile(const char *wmesg)
+{
+	struct sleepq_prof *sp;
+
+	mtx_lock_spin(&sleepq_prof_lock);
+	if (prof_enabled == 0)
+		goto unlock;
+	LIST_FOREACH(sp, &sleepq_hash[SC_HASH(wmesg)], sp_link)
+		if (sp->sp_wmesg == wmesg)
+			goto done;
+	sp = LIST_FIRST(&sleepq_prof_free);
+	if (sp == NULL)
+		goto unlock;
+	sp->sp_wmesg = wmesg;
+	LIST_REMOVE(sp, sp_link);
+	LIST_INSERT_HEAD(&sleepq_hash[SC_HASH(wmesg)], sp, sp_link);
+done:
+	sp->sp_count++;
+unlock:
+	mtx_unlock_spin(&sleepq_prof_lock);
+	return;
+}
+
+static void
+sleepq_prof_reset(void)
+{
+	struct sleepq_prof *sp;
+	int enabled;
+	int i;
+
+	mtx_lock_spin(&sleepq_prof_lock);
+	enabled = prof_enabled;
+	prof_enabled = 0;
+	for (i = 0; i < SC_TABLESIZE; i++)
+		LIST_INIT(&sleepq_hash[i]);
+	LIST_INIT(&sleepq_prof_free);
+	for (i = 0; i < SLEEPQ_PROF_LOCATIONS; i++) {
+		sp = &sleepq_profent[i];
+		sp->sp_wmesg = NULL;
+		sp->sp_count = 0;
+		LIST_INSERT_HEAD(&sleepq_prof_free, sp, sp_link);
+	}
+	prof_enabled = enabled;
+	mtx_unlock_spin(&sleepq_prof_lock);
+}
+
+static int
+enable_sleepq_prof(SYSCTL_HANDLER_ARGS)
+{
+	int error, v;
+
+	v = prof_enabled;
+	error = sysctl_handle_int(oidp, &v, v, req);
+	if (error)
+		return (error);
+	if (req->newptr == NULL)
+		return (error);
+	if (v == prof_enabled)
+		return (0);
+	if (v == 1)
+		sleepq_prof_reset();
+	mtx_lock_spin(&sleepq_prof_lock);
+	prof_enabled = !!v;
+	mtx_unlock_spin(&sleepq_prof_lock);
+
+	return (0);
+}
+
+static int
+reset_sleepq_prof_stats(SYSCTL_HANDLER_ARGS)
+{
+	int error, v;
+
+	v = 0;
+	error = sysctl_handle_int(oidp, &v, 0, req);
+	if (error)
+		return (error);
+	if (req->newptr == NULL)
+		return (error);
+	if (v == 0)
+		return (0);
+	sleepq_prof_reset();
+
+	return (0);
+}
+
+static int
+dump_sleepq_prof_stats(SYSCTL_HANDLER_ARGS)
+{
+	struct sleepq_prof *sp;
+	struct sbuf *sb;
+	int enabled;
+	int error;
+	int i;
+
+	error = sysctl_wire_old_buffer(req, 0);
+	if (error != 0)
+		return (error);
+	sb = sbuf_new_for_sysctl(NULL, NULL, SLEEPQ_SBUFSIZE, req);
+	sbuf_printf(sb, "\nwmesg\tcount\n");
+	enabled = prof_enabled;
+	mtx_lock_spin(&sleepq_prof_lock);
+	prof_enabled = 0;
+	mtx_unlock_spin(&sleepq_prof_lock);
+	for (i = 0; i < SC_TABLESIZE; i++) {
+		LIST_FOREACH(sp, &sleepq_hash[i], sp_link) {
+			sbuf_printf(sb, "%s\t%ld\n",
+			    sp->sp_wmesg, sp->sp_count);
+		}
+	}
+	mtx_lock_spin(&sleepq_prof_lock);
+	prof_enabled = enabled;
+	mtx_unlock_spin(&sleepq_prof_lock);
+
+	error = sbuf_finish(sb);
+	sbuf_delete(sb);
+	return (error);
+}
+
+SYSCTL_PROC(_debug_sleepq, OID_AUTO, stats, CTLTYPE_STRING | CTLFLAG_RD,
+    NULL, 0, dump_sleepq_prof_stats, "A", "Sleepqueue profiling statistics");
+SYSCTL_PROC(_debug_sleepq, OID_AUTO, reset, CTLTYPE_INT | CTLFLAG_RW,
+    NULL, 0, reset_sleepq_prof_stats, "I",
+    "Reset sleepqueue profiling statistics");
+SYSCTL_PROC(_debug_sleepq, OID_AUTO, enable, CTLTYPE_INT | CTLFLAG_RW,
+    NULL, 0, enable_sleepq_prof, "I", "Enable sleepqueue profiling");
+#endif
+
+#ifdef DDB
+DB_SHOW_COMMAND(sleepq, db_show_sleepqueue)
+{
+	struct sleepqueue_chain *sc;
+	struct sleepqueue *sq;
+#ifdef INVARIANTS
+	struct lock_object *lock;
+#endif
+	struct thread *td;
+	void *wchan;
+	int i;
+
+	if (!have_addr)
+		return;
+
+	/*
+	 * First, see if there is an active sleep queue for the wait channel
+	 * indicated by the address.
+	 */
+	wchan = (void *)addr;
+	sc = SC_LOOKUP(wchan);
+	LIST_FOREACH(sq, &sc->sc_queues, sq_hash)
+		if (sq->sq_wchan == wchan)
+			goto found;
+
+	/*
+	 * Second, see if there is an active sleep queue at the address
+	 * indicated.
+	 */
+	for (i = 0; i < SC_TABLESIZE; i++)
+		LIST_FOREACH(sq, &sleepq_chains[i].sc_queues, sq_hash) {
+			if (sq == (struct sleepqueue *)addr)
+				goto found;
+		}
+
+	db_printf("Unable to locate a sleep queue via %p\n", (void *)addr);
+	return;
+found:
+	db_printf("Wait channel: %p\n", sq->sq_wchan);
+	db_printf("Queue type: %d\n", sq->sq_type);
+#ifdef INVARIANTS
+	if (sq->sq_lock) {
+		lock = sq->sq_lock;
+		db_printf("Associated Interlock: %p - (%s) %s\n", lock,
+		    LOCK_CLASS(lock)->lc_name, lock->lo_name);
+	}
+#endif
+	db_printf("Blocked threads:\n");
+	for (i = 0; i < NR_SLEEPQS; i++) {
+		db_printf("\nQueue[%d]:\n", i);
+		if (TAILQ_EMPTY(&sq->sq_blocked[i]))
+			db_printf("\tempty\n");
+		else
+			TAILQ_FOREACH(td, &sq->sq_blocked[0],
+				      td_slpq) {
+				db_printf("\t%p (tid %d, pid %d, \"%s\")\n", td,
+					  td->td_tid, td->td_proc->p_pid,
+					  td->td_name);
+			}
+		db_printf("(expected: %u)\n", sq->sq_blockedcnt[i]);
+	}
+}
+
+/* Alias 'show sleepqueue' to 'show sleepq'. */
+DB_SHOW_ALIAS(sleepqueue, db_show_sleepqueue);
+#endif
diff --git a/freebsd/sys/sys/sleepqueue.h b/freebsd/sys/sys/sleepqueue.h
new file mode 100644
index 00000000..ddec1478
--- /dev/null
+++ b/freebsd/sys/sys/sleepqueue.h
@@ -0,0 +1,117 @@
+/*-
+ * Copyright (c) 2004 John Baldwin <jhb@FreeBSD.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ * $FreeBSD$
+ */
+
+#ifndef _SYS_SLEEPQUEUE_H_
+#define _SYS_SLEEPQUEUE_H_
+
+/*
+ * Sleep queue interface.  Sleep/wakeup, condition variables, and sx
+ * locks use a sleep queue for the queue of threads blocked on a sleep
+ * channel.
+ *
+ * A thread calls sleepq_lock() to lock the sleep queue chain associated
+ * with a given wait channel.  A thread can then call call sleepq_add() to
+ * add themself onto a sleep queue and call one of the sleepq_wait()
+ * functions to actually go to sleep.  If a thread needs to abort a sleep
+ * operation it should call sleepq_release() to unlock the associated sleep
+ * queue chain lock.  If the thread also needs to remove itself from a queue
+ * it just enqueued itself on, it can use sleepq_remove() instead.
+ *
+ * If the thread only wishes to sleep for a limited amount of time, it can
+ * call sleepq_set_timeout() after sleepq_add() to setup a timeout.  It
+ * should then use one of the sleepq_timedwait() functions to block.
+ *
+ * If the thread wants the sleep to be interruptible by signals, it can
+ * call sleepq_catch_signals() after sleepq_add().  It should then use
+ * one of the sleepq_wait_sig() functions to block.  After the thread has
+ * been resumed, it should call sleepq_calc_signal_retval() to determine
+ * if it should return EINTR or ERESTART passing in the value returned from
+ * the earlier call to sleepq_catch_signals().
+ *
+ * A thread is normally resumed from a sleep queue by either the
+ * sleepq_signal() or sleepq_broadcast() functions.  Sleepq_signal() wakes
+ * the thread with the highest priority that is sleeping on the specified
+ * wait channel.  Sleepq_broadcast() wakes all threads that are sleeping
+ * on the specified wait channel.  A thread sleeping in an interruptible
+ * sleep can be interrupted by calling sleepq_abort().  A thread can also
+ * be removed from a specified sleep queue using the sleepq_remove()
+ * function.  Note that the sleep queue chain must first be locked via
+ * sleepq_lock() before calling sleepq_abort(), sleepq_broadcast(), or
+ * sleepq_signal().  These routines each return a boolean that will be true
+ * if at least one swapped-out thread was resumed.  In that case, the caller
+ * is responsible for waking up the swapper by calling kick_proc0() after
+ * releasing the sleep queue chain lock.
+ *
+ * Each thread allocates a sleep queue at thread creation via sleepq_alloc()
+ * and releases it at thread destruction via sleepq_free().  Note that
+ * a sleep queue is not tied to a specific thread and that the sleep queue
+ * released at thread destruction may not be the same sleep queue that the
+ * thread allocated when it was created.
+ *
+ * XXX: Some other parts of the kernel such as ithread sleeping may end up
+ * using this interface as well (death to TDI_IWAIT!)
+ */
+
+struct lock_object;
+struct sleepqueue;
+struct thread;
+
+#ifdef _KERNEL
+
+#define	SLEEPQ_TYPE		0x0ff		/* Mask of sleep queue types. */
+#define	SLEEPQ_SLEEP		0x00		/* Used by sleep/wakeup. */
+#define	SLEEPQ_CONDVAR		0x01		/* Used for a cv. */
+#define	SLEEPQ_PAUSE		0x02		/* Used by pause. */
+#define	SLEEPQ_SX		0x03		/* Used by an sx lock. */
+#define	SLEEPQ_LK		0x04		/* Used by a lockmgr. */
+#define	SLEEPQ_INTERRUPTIBLE	0x100		/* Sleep is interruptible. */
+#define	SLEEPQ_STOP_ON_BDRY	0x200		/* Stop sleeping thread on
+						   user mode boundary */
+
+void	init_sleepqueues(void);
+int	sleepq_abort(struct thread *td, int intrval);
+void	sleepq_add(void *wchan, struct lock_object *lock, const char *wmesg,
+	    int flags, int queue);
+struct sleepqueue *sleepq_alloc(void);
+int	sleepq_broadcast(void *wchan, int flags, int pri, int queue);
+void	sleepq_free(struct sleepqueue *sq);
+void	sleepq_lock(void *wchan);
+struct sleepqueue *sleepq_lookup(void *wchan);
+void	sleepq_release(void *wchan);
+void	sleepq_remove(struct thread *td, void *wchan);
+int	sleepq_signal(void *wchan, int flags, int pri, int queue);
+void	sleepq_set_timeout(void *wchan, int timo);
+u_int	sleepq_sleepcnt(void *wchan, int queue);
+int	sleepq_timedwait(void *wchan, int pri);
+int	sleepq_timedwait_sig(void *wchan, int pri);
+int	sleepq_type(void *wchan);
+void	sleepq_wait(void *wchan, int pri);
+int	sleepq_wait_sig(void *wchan, int pri);
+
+#endif	/* _KERNEL */
+#endif	/* !_SYS_SLEEPQUEUE_H_ */