source: rtems-libbsd/freebsd/sys/kern/kern_intr.c

#include <machine/rtems-bsd-kernel-space.h>

/*-
 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
 *
 * Copyright (c) 1997, Stefan Esser <se@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 unmodified, 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 ``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 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.
 */

#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");

#include <rtems/bsd/local/opt_ddb.h>
#include <rtems/bsd/local/opt_kstack_usage_prof.h>

#include <sys/param.h>
#include <sys/bus.h>
#include <sys/conf.h>
#include <sys/cpuset.h>
#include <sys/rtprio.h>
#include <sys/systm.h>
#include <sys/interrupt.h>
#include <sys/kernel.h>
#include <sys/kthread.h>
#include <sys/ktr.h>
#include <sys/limits.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mutex.h>
#include <sys/priv.h>
#include <sys/proc.h>
#include <sys/random.h>
#include <sys/resourcevar.h>
#include <sys/sched.h>
#include <sys/smp.h>
#include <sys/sysctl.h>
#include <sys/syslog.h>
#include <rtems/bsd/sys/unistd.h>
#include <sys/vmmeter.h>
#include <machine/atomic.h>
#include <machine/cpu.h>
#ifndef __rtems__
#include <machine/md_var.h>
#else /* __rtems__ */
  #include <machine/rtems-bsd-thread.h>
  #define RTEMSBSD_SWI_WAKEUP_EVENT RTEMS_EVENT_31
  #include <rtems/score/threadimpl.h>
#endif /* __rtems__ */
#include <machine/stdarg.h>
#ifdef DDB
#include <ddb/ddb.h>
#include <ddb/db_sym.h>
#endif

/*
 * Describe an interrupt thread.  There is one of these per interrupt event.
 */
struct intr_thread {
        struct intr_event *it_event;
        struct thread *it_thread;       /* Kernel thread. */
        int     it_flags;               /* (j) IT_* flags. */
        int     it_need;                /* Needs service. */
};

/* Interrupt thread flags kept in it_flags */
#define IT_DEAD         0x000001        /* Thread is waiting to exit. */
#define IT_WAIT         0x000002        /* Thread is waiting for completion. */

struct  intr_entropy {
        struct  thread *td;
        uintptr_t event;
};

struct  intr_event *clk_intr_event;
#ifndef __rtems__
struct  intr_event *tty_intr_event;
void    *vm_ih;
struct proc *intrproc;
#endif /* __rtems__ */

static MALLOC_DEFINE(M_ITHREAD, "ithread", "Interrupt Threads");

static int intr_storm_threshold = 1000;
SYSCTL_INT(_hw, OID_AUTO, intr_storm_threshold, CTLFLAG_RWTUN,
    &intr_storm_threshold, 0,
    "Number of consecutive interrupts before storm protection is enabled");
static TAILQ_HEAD(, intr_event) event_list =
    TAILQ_HEAD_INITIALIZER(event_list);
static struct mtx event_lock;
MTX_SYSINIT(intr_event_list, &event_lock, "intr event list", MTX_DEF);

static void     intr_event_update(struct intr_event *ie);
static int      intr_event_schedule_thread(struct intr_event *ie);
static struct intr_thread *ithread_create(const char *name);
#ifndef __rtems__
static void     ithread_destroy(struct intr_thread *ithread);
#endif /* __rtems__ */
static void     ithread_execute_handlers(struct proc *p, 
                    struct intr_event *ie);
static void     ithread_loop(void *);
static void     ithread_update(struct intr_thread *ithd);
#ifndef __rtems__
static void     start_softintr(void *);

/* Map an interrupt type to an ithread priority. */
u_char
intr_priority(enum intr_type flags)
{
        u_char pri;

        flags &= (INTR_TYPE_TTY | INTR_TYPE_BIO | INTR_TYPE_NET |
            INTR_TYPE_CAM | INTR_TYPE_MISC | INTR_TYPE_CLK | INTR_TYPE_AV);
        switch (flags) {
        case INTR_TYPE_TTY:
                pri = PI_TTY;
                break;
        case INTR_TYPE_BIO:
                pri = PI_DISK;
                break;
        case INTR_TYPE_NET:
                pri = PI_NET;
                break;
        case INTR_TYPE_CAM:
                pri = PI_DISK;
                break;
        case INTR_TYPE_AV:
                pri = PI_AV;
                break;
        case INTR_TYPE_CLK:
                pri = PI_REALTIME;
                break;
        case INTR_TYPE_MISC:
                pri = PI_DULL;          /* don't care */
                break;
        default:
                /* We didn't specify an interrupt level. */
                panic("intr_priority: no interrupt type in flags");
        }

        return pri;
}

#endif /* __rtems__ */
/*
 * Update an ithread based on the associated intr_event.
 */
static void
ithread_update(struct intr_thread *ithd)
{
        struct intr_event *ie;
        struct thread *td;
        u_char pri;

        ie = ithd->it_event;
        td = ithd->it_thread;
        mtx_assert(&ie->ie_lock, MA_OWNED);

        /* Determine the overall priority of this event. */
        if (CK_SLIST_EMPTY(&ie->ie_handlers))
                pri = PRI_MAX_ITHD;
        else
                pri = CK_SLIST_FIRST(&ie->ie_handlers)->ih_pri;

        /* Update name and priority. */
#ifndef __rtems__
        strlcpy(td->td_name, ie->ie_fullname, sizeof(td->td_name));
#else /* __rtems__ */
        _Thread_Set_name(td->td_thread, ie->ie_fullname);
#endif /* __rtems__ */
#ifdef KTR
#ifndef __rtems__
        sched_clear_tdname(td);
#endif /* __rtems__ */
#endif
        thread_lock(td);
#ifndef __rtems__
        sched_prio(td, pri);
#else /* __rtems__ */
#warning TODO: set thread priority
#endif /* __rtems__ */
        thread_unlock(td);
}

/*
 * Regenerate the full name of an interrupt event and update its priority.
 */
static void
intr_event_update(struct intr_event *ie)
{
        struct intr_handler *ih;
        char *last;
        int missed, space;

        /* Start off with no entropy and just the name of the event. */
        mtx_assert(&ie->ie_lock, MA_OWNED);
        strlcpy(ie->ie_fullname, ie->ie_name, sizeof(ie->ie_fullname));
        ie->ie_flags &= ~IE_ENTROPY;
        missed = 0;
        space = 1;

        /* Run through all the handlers updating values. */
        CK_SLIST_FOREACH(ih, &ie->ie_handlers, ih_next) {
                if (strlen(ie->ie_fullname) + strlen(ih->ih_name) + 1 <
                    sizeof(ie->ie_fullname)) {
                        strcat(ie->ie_fullname, " ");
                        strcat(ie->ie_fullname, ih->ih_name);
                        space = 0;
                } else
                        missed++;
                if (ih->ih_flags & IH_ENTROPY)
                        ie->ie_flags |= IE_ENTROPY;
        }

        /*
         * If there is only one handler and its name is too long, just copy in
         * as much of the end of the name (includes the unit number) as will
         * fit.  Otherwise, we have multiple handlers and not all of the names
         * will fit.  Add +'s to indicate missing names.  If we run out of room
         * and still have +'s to add, change the last character from a + to a *.
         */
        if (missed == 1 && space == 1) {
                ih = CK_SLIST_FIRST(&ie->ie_handlers);
                missed = strlen(ie->ie_fullname) + strlen(ih->ih_name) + 2 -
                    sizeof(ie->ie_fullname);
                strcat(ie->ie_fullname, (missed == 0) ? " " : "-");
                strcat(ie->ie_fullname, &ih->ih_name[missed]);
                missed = 0;
        }
        last = &ie->ie_fullname[sizeof(ie->ie_fullname) - 2];
        while (missed-- > 0) {
                if (strlen(ie->ie_fullname) + 1 == sizeof(ie->ie_fullname)) {
                        if (*last == '+') {
                                *last = '*';
                                break;
                        } else
                                *last = '+';
                } else if (space) {
                        strcat(ie->ie_fullname, " +");
                        space = 0;
                } else
                        strcat(ie->ie_fullname, "+");
        }

        /*
         * If this event has an ithread, update it's priority and
         * name.
         */
        if (ie->ie_thread != NULL)
                ithread_update(ie->ie_thread);
        CTR2(KTR_INTR, "%s: updated %s", __func__, ie->ie_fullname);
}

int
intr_event_create(struct intr_event **event, void *source, int flags, int irq,
    void (*pre_ithread)(void *), void (*post_ithread)(void *),
    void (*post_filter)(void *), int (*assign_cpu)(void *, int),
    const char *fmt, ...)
{
        struct intr_event *ie;
        va_list ap;

        /* The only valid flag during creation is IE_SOFT. */
        if ((flags & ~IE_SOFT) != 0)
                return (EINVAL);
        ie = malloc(sizeof(struct intr_event), M_ITHREAD, M_WAITOK | M_ZERO);
        ie->ie_source = source;
        ie->ie_pre_ithread = pre_ithread;
        ie->ie_post_ithread = post_ithread;
        ie->ie_post_filter = post_filter;
        ie->ie_assign_cpu = assign_cpu;
        ie->ie_flags = flags;
        ie->ie_irq = irq;
        ie->ie_cpu = NOCPU;
        CK_SLIST_INIT(&ie->ie_handlers);
        mtx_init(&ie->ie_lock, "intr event", NULL, MTX_DEF);

        va_start(ap, fmt);
        vsnprintf(ie->ie_name, sizeof(ie->ie_name), fmt, ap);
        va_end(ap);
        strlcpy(ie->ie_fullname, ie->ie_name, sizeof(ie->ie_fullname));
        mtx_lock(&event_lock);
        TAILQ_INSERT_TAIL(&event_list, ie, ie_list);
        mtx_unlock(&event_lock);
        if (event != NULL)
                *event = ie;
        CTR2(KTR_INTR, "%s: created %s", __func__, ie->ie_name);
        return (0);
}

#ifndef __rtems__
/*
 * Bind an interrupt event to the specified CPU.  Note that not all
 * platforms support binding an interrupt to a CPU.  For those
 * platforms this request will fail.  Using a cpu id of NOCPU unbinds
 * the interrupt event.
 */
static int
_intr_event_bind(struct intr_event *ie, int cpu, bool bindirq, bool bindithread)
{
        lwpid_t id;
        int error;

        /* Need a CPU to bind to. */
        if (cpu != NOCPU && CPU_ABSENT(cpu))
                return (EINVAL);

        if (ie->ie_assign_cpu == NULL)
                return (EOPNOTSUPP);

        error = priv_check(curthread, PRIV_SCHED_CPUSET_INTR);
        if (error)
                return (error);

        /*
         * If we have any ithreads try to set their mask first to verify
         * permissions, etc.
         */
        if (bindithread) {
                mtx_lock(&ie->ie_lock);
                if (ie->ie_thread != NULL) {
                        id = ie->ie_thread->it_thread->td_tid;
                        mtx_unlock(&ie->ie_lock);
                        error = cpuset_setithread(id, cpu);
                        if (error)
                                return (error);
                } else
                        mtx_unlock(&ie->ie_lock);
        }
        if (bindirq)
                error = ie->ie_assign_cpu(ie->ie_source, cpu);
        if (error) {
                if (bindithread) {
                        mtx_lock(&ie->ie_lock);
                        if (ie->ie_thread != NULL) {
                                cpu = ie->ie_cpu;
                                id = ie->ie_thread->it_thread->td_tid;
                                mtx_unlock(&ie->ie_lock);
                                (void)cpuset_setithread(id, cpu);
                        } else
                                mtx_unlock(&ie->ie_lock);
                }
                return (error);
        }

        if (bindirq) {
                mtx_lock(&ie->ie_lock);
                ie->ie_cpu = cpu;
                mtx_unlock(&ie->ie_lock);
        }

        return (error);
}

/*
 * Bind an interrupt event to the specified CPU.  For supported platforms, any
 * associated ithreads as well as the primary interrupt context will be bound
 * to the specificed CPU.
 */
int
intr_event_bind(struct intr_event *ie, int cpu)
{

        return (_intr_event_bind(ie, cpu, true, true));
}

/*
 * Bind an interrupt event to the specified CPU, but do not bind associated
 * ithreads.
 */
int
intr_event_bind_irqonly(struct intr_event *ie, int cpu)
{

        return (_intr_event_bind(ie, cpu, true, false));
}

/*
 * Bind an interrupt event's ithread to the specified CPU.
 */
int
intr_event_bind_ithread(struct intr_event *ie, int cpu)
{

        return (_intr_event_bind(ie, cpu, false, true));
}

static struct intr_event *
intr_lookup(int irq)
{
        struct intr_event *ie;

        mtx_lock(&event_lock);
        TAILQ_FOREACH(ie, &event_list, ie_list)
                if (ie->ie_irq == irq &&
                    (ie->ie_flags & IE_SOFT) == 0 &&
                    CK_SLIST_FIRST(&ie->ie_handlers) != NULL)
                        break;
        mtx_unlock(&event_lock);
        return (ie);
}

int
intr_setaffinity(int irq, int mode, void *m)
{
        struct intr_event *ie;
        cpuset_t *mask;
        int cpu, n;

        mask = m;
        cpu = NOCPU;
        /*
         * If we're setting all cpus we can unbind.  Otherwise make sure
         * only one cpu is in the set.
         */
        if (CPU_CMP(cpuset_root, mask)) {
                for (n = 0; n < CPU_SETSIZE; n++) {
                        if (!CPU_ISSET(n, mask))
                                continue;
                        if (cpu != NOCPU)
                                return (EINVAL);
                        cpu = n;
                }
        }
        ie = intr_lookup(irq);
        if (ie == NULL)
                return (ESRCH);
        switch (mode) {
        case CPU_WHICH_IRQ:
                return (intr_event_bind(ie, cpu));
        case CPU_WHICH_INTRHANDLER:
                return (intr_event_bind_irqonly(ie, cpu));
        case CPU_WHICH_ITHREAD:
                return (intr_event_bind_ithread(ie, cpu));
        default:
                return (EINVAL);
        }
}

int
intr_getaffinity(int irq, int mode, void *m)
{
        struct intr_event *ie;
        struct thread *td;
        struct proc *p;
        cpuset_t *mask;
        lwpid_t id;
        int error;

        mask = m;
        ie = intr_lookup(irq);
        if (ie == NULL)
                return (ESRCH);

        error = 0;
        CPU_ZERO(mask);
        switch (mode) {
        case CPU_WHICH_IRQ:
        case CPU_WHICH_INTRHANDLER:
                mtx_lock(&ie->ie_lock);
                if (ie->ie_cpu == NOCPU)
                        CPU_COPY(cpuset_root, mask);
                else
                        CPU_SET(ie->ie_cpu, mask);
                mtx_unlock(&ie->ie_lock);
                break;
        case CPU_WHICH_ITHREAD:
                mtx_lock(&ie->ie_lock);
                if (ie->ie_thread == NULL) {
                        mtx_unlock(&ie->ie_lock);
                        CPU_COPY(cpuset_root, mask);
                } else {
                        id = ie->ie_thread->it_thread->td_tid;
                        mtx_unlock(&ie->ie_lock);
                        error = cpuset_which(CPU_WHICH_TID, id, &p, &td, NULL);
                        if (error != 0)
                                return (error);
                        CPU_COPY(&td->td_cpuset->cs_mask, mask);
                        PROC_UNLOCK(p);
                }
        default:
                return (EINVAL);
        }
        return (0);
}

int
intr_event_destroy(struct intr_event *ie)
{

        mtx_lock(&event_lock);
        mtx_lock(&ie->ie_lock);
        if (!CK_SLIST_EMPTY(&ie->ie_handlers)) {
                mtx_unlock(&ie->ie_lock);
                mtx_unlock(&event_lock);
                return (EBUSY);
        }
        TAILQ_REMOVE(&event_list, ie, ie_list);
#ifndef notyet
        if (ie->ie_thread != NULL) {
                ithread_destroy(ie->ie_thread);
                ie->ie_thread = NULL;
        }
#endif
        mtx_unlock(&ie->ie_lock);
        mtx_unlock(&event_lock);
        mtx_destroy(&ie->ie_lock);
        free(ie, M_ITHREAD);
        return (0);
}

#endif /* __rtems__ */
static struct intr_thread *
ithread_create(const char *name)
{
#ifdef __rtems__
        struct proc *intrproc;
#endif /* __rtems__ */
        struct intr_thread *ithd;
        struct thread *td;
        int error;

        ithd = malloc(sizeof(struct intr_thread), M_ITHREAD, M_WAITOK | M_ZERO);

        error = kproc_kthread_add(ithread_loop, ithd, &intrproc,
                    &td, RFSTOPPED | RFHIGHPID,
                    0, "intr", "%s", name);
        if (error)
                panic("kproc_create() failed with %d", error);
        thread_lock(td);
#ifndef __rtems__
        sched_class(td, PRI_ITHD);
        TD_SET_IWAIT(td);
#endif /* __rtems__ */
        thread_unlock(td);
#ifndef __rtems__
        td->td_pflags |= TDP_ITHREAD;
#endif /* __rtems__ */
        ithd->it_thread = td;
        CTR2(KTR_INTR, "%s: created %s", __func__, name);
        return (ithd);
}
#ifndef __rtems__

static void
ithread_destroy(struct intr_thread *ithread)
{
        struct thread *td;

        CTR2(KTR_INTR, "%s: killing %s", __func__, ithread->it_event->ie_name);
        td = ithread->it_thread;
        thread_lock(td);
        ithread->it_flags |= IT_DEAD;
        if (TD_AWAITING_INTR(td)) {
                TD_CLR_IWAIT(td);
                sched_add(td, SRQ_INTR);
        }
        thread_unlock(td);
}

#endif /* __rtems__ */
int
intr_event_add_handler(struct intr_event *ie, const char *name,
    driver_filter_t filter, driver_intr_t handler, void *arg, u_char pri,
    enum intr_type flags, void **cookiep)
{
        struct intr_handler *ih, *temp_ih;
        struct intr_handler **prevptr;
        struct intr_thread *it;

        if (ie == NULL || name == NULL || (handler == NULL && filter == NULL))
                return (EINVAL);

        /* Allocate and populate an interrupt handler structure. */
        ih = malloc(sizeof(struct intr_handler), M_ITHREAD, M_WAITOK | M_ZERO);
        ih->ih_filter = filter;
        ih->ih_handler = handler;
        ih->ih_argument = arg;
        strlcpy(ih->ih_name, name, sizeof(ih->ih_name));
        ih->ih_event = ie;
        ih->ih_pri = pri;
        if (flags & INTR_EXCL)
                ih->ih_flags = IH_EXCLUSIVE;
        if (flags & INTR_MPSAFE)
                ih->ih_flags |= IH_MPSAFE;
        if (flags & INTR_ENTROPY)
                ih->ih_flags |= IH_ENTROPY;

        /* We can only have one exclusive handler in a event. */
        mtx_lock(&ie->ie_lock);
        if (!CK_SLIST_EMPTY(&ie->ie_handlers)) {
                if ((flags & INTR_EXCL) ||
                    (CK_SLIST_FIRST(&ie->ie_handlers)->ih_flags & IH_EXCLUSIVE)) {
                        mtx_unlock(&ie->ie_lock);
                        free(ih, M_ITHREAD);
                        return (EINVAL);
                }
        }

        /* Create a thread if we need one. */
        while (ie->ie_thread == NULL && handler != NULL) {
                if (ie->ie_flags & IE_ADDING_THREAD)
                        msleep(ie, &ie->ie_lock, 0, "ithread", 0);
                else {
                        ie->ie_flags |= IE_ADDING_THREAD;
                        mtx_unlock(&ie->ie_lock);
                        it = ithread_create("intr: newborn");
                        mtx_lock(&ie->ie_lock);
                        ie->ie_flags &= ~IE_ADDING_THREAD;
                        ie->ie_thread = it;
                        it->it_event = ie;
                        ithread_update(it);
                        wakeup(ie);
                }
        }

        /* Add the new handler to the event in priority order. */
        CK_SLIST_FOREACH_PREVPTR(temp_ih, prevptr, &ie->ie_handlers, ih_next) {
                if (temp_ih->ih_pri > ih->ih_pri)
                        break;
        }
        CK_SLIST_INSERT_PREVPTR(prevptr, temp_ih, ih, ih_next);

        intr_event_update(ie);

        CTR3(KTR_INTR, "%s: added %s to %s", __func__, ih->ih_name,
            ie->ie_name);
        mtx_unlock(&ie->ie_lock);

        if (cookiep != NULL)
                *cookiep = ih;
        return (0);
}

#ifndef __rtems__
/*
 * Append a description preceded by a ':' to the name of the specified
 * interrupt handler.
 */
int
intr_event_describe_handler(struct intr_event *ie, void *cookie,
    const char *descr)
{
        struct intr_handler *ih;
        size_t space;
        char *start;

        mtx_lock(&ie->ie_lock);
#ifdef INVARIANTS
        CK_SLIST_FOREACH(ih, &ie->ie_handlers, ih_next) {
                if (ih == cookie)
                        break;
        }
        if (ih == NULL) {
                mtx_unlock(&ie->ie_lock);
                panic("handler %p not found in interrupt event %p", cookie, ie);
        }
#endif
        ih = cookie;

        /*
         * Look for an existing description by checking for an
         * existing ":".  This assumes device names do not include
         * colons.  If one is found, prepare to insert the new
         * description at that point.  If one is not found, find the
         * end of the name to use as the insertion point.
         */
        start = strchr(ih->ih_name, ':');
        if (start == NULL)
                start = strchr(ih->ih_name, 0);

        /*
         * See if there is enough remaining room in the string for the
         * description + ":".  The "- 1" leaves room for the trailing
         * '\0'.  The "+ 1" accounts for the colon.
         */
        space = sizeof(ih->ih_name) - (start - ih->ih_name) - 1;
        if (strlen(descr) + 1 > space) {
                mtx_unlock(&ie->ie_lock);
                return (ENOSPC);
        }

        /* Append a colon followed by the description. */
        *start = ':';
        strcpy(start + 1, descr);
        intr_event_update(ie);
        mtx_unlock(&ie->ie_lock);
        return (0);
}

/*
 * Return the ie_source field from the intr_event an intr_handler is
 * associated with.
 */
void *
intr_handler_source(void *cookie)
{
        struct intr_handler *ih;
        struct intr_event *ie;

        ih = (struct intr_handler *)cookie;
        if (ih == NULL)
                return (NULL);
        ie = ih->ih_event;
        KASSERT(ie != NULL,
            ("interrupt handler \"%s\" has a NULL interrupt event",
            ih->ih_name));
        return (ie->ie_source);
}

/*
 * If intr_event_handle() is running in the ISR context at the time of the call,
 * then wait for it to complete.
 */
static void
intr_event_barrier(struct intr_event *ie)
{
        int phase;

        mtx_assert(&ie->ie_lock, MA_OWNED);
        phase = ie->ie_phase;

        /*
         * Switch phase to direct future interrupts to the other active counter.
         * Make sure that any preceding stores are visible before the switch.
         */
        KASSERT(ie->ie_active[!phase] == 0, ("idle phase has activity"));
        atomic_store_rel_int(&ie->ie_phase, !phase);

        /*
         * This code cooperates with wait-free iteration of ie_handlers
         * in intr_event_handle.
         * Make sure that the removal and the phase update are not reordered
         * with the active count check.
         * Note that no combination of acquire and release fences can provide
         * that guarantee as Store->Load sequences can always be reordered.
         */
        atomic_thread_fence_seq_cst();

        /*
         * Now wait on the inactive phase.
         * The acquire fence is needed so that that all post-barrier accesses
         * are after the check.
         */
        while (ie->ie_active[phase] > 0)
                cpu_spinwait();
        atomic_thread_fence_acq();
}

static void
intr_handler_barrier(struct intr_handler *handler)
{
        struct intr_event *ie;

        ie = handler->ih_event;
        mtx_assert(&ie->ie_lock, MA_OWNED);
        KASSERT((handler->ih_flags & IH_DEAD) == 0,
            ("update for a removed handler"));

        if (ie->ie_thread == NULL) {
                intr_event_barrier(ie);
                return;
        }
        if ((handler->ih_flags & IH_CHANGED) == 0) {
                handler->ih_flags |= IH_CHANGED;
                intr_event_schedule_thread(ie);
        }
        while ((handler->ih_flags & IH_CHANGED) != 0)
                msleep(handler, &ie->ie_lock, 0, "ih_barr", 0);
}

/*
 * Sleep until an ithread finishes executing an interrupt handler.
 *
 * XXX Doesn't currently handle interrupt filters or fast interrupt
 * handlers.  This is intended for compatibility with linux drivers
 * only.  Do not use in BSD code.
 */
void
_intr_drain(int irq)
{
        struct intr_event *ie;
        struct intr_thread *ithd;
        struct thread *td;

        ie = intr_lookup(irq);
        if (ie == NULL)
                return;
        if (ie->ie_thread == NULL)
                return;
        ithd = ie->ie_thread;
        td = ithd->it_thread;
        /*
         * We set the flag and wait for it to be cleared to avoid
         * long delays with potentially busy interrupt handlers
         * were we to only sample TD_AWAITING_INTR() every tick.
         */
        thread_lock(td);
        if (!TD_AWAITING_INTR(td)) {
                ithd->it_flags |= IT_WAIT;
                while (ithd->it_flags & IT_WAIT) {
                        thread_unlock(td);
                        pause("idrain", 1);
                        thread_lock(td);
                }
        }
        thread_unlock(td);
        return;
}

int
intr_event_remove_handler(void *cookie)
{
        struct intr_handler *handler = (struct intr_handler *)cookie;
        struct intr_event *ie;
        struct intr_handler *ih;
        struct intr_handler **prevptr;
#ifdef notyet
        int dead;
#endif

        if (handler == NULL)
                return (EINVAL);
        ie = handler->ih_event;
        KASSERT(ie != NULL,
            ("interrupt handler \"%s\" has a NULL interrupt event",
            handler->ih_name));

        mtx_lock(&ie->ie_lock);
        CTR3(KTR_INTR, "%s: removing %s from %s", __func__, handler->ih_name,
            ie->ie_name);
        CK_SLIST_FOREACH_PREVPTR(ih, prevptr, &ie->ie_handlers, ih_next) {
                if (ih == handler)
                        break;
        }
        if (ih == NULL) {
                panic("interrupt handler \"%s\" not found in "
                    "interrupt event \"%s\"", handler->ih_name, ie->ie_name);
        }

        /*
         * If there is no ithread, then directly remove the handler.  Note that
         * intr_event_handle() iterates ie_handlers in a lock-less fashion, so
         * care needs to be taken to keep ie_handlers consistent and to free
         * the removed handler only when ie_handlers is quiescent.
         */
        if (ie->ie_thread == NULL) {
                CK_SLIST_REMOVE_PREVPTR(prevptr, ih, ih_next);
                intr_event_barrier(ie);
                intr_event_update(ie);
                mtx_unlock(&ie->ie_lock);
                free(handler, M_ITHREAD);
                return (0);
        }

        /*
         * Let the interrupt thread do the job.
         * The interrupt source is disabled when the interrupt thread is
         * running, so it does not have to worry about interaction with
         * intr_event_handle().
         */
        KASSERT((handler->ih_flags & IH_DEAD) == 0,
            ("duplicate handle remove"));
        handler->ih_flags |= IH_DEAD;
        intr_event_schedule_thread(ie);
        while (handler->ih_flags & IH_DEAD)
                msleep(handler, &ie->ie_lock, 0, "iev_rmh", 0);
        intr_event_update(ie);

#ifdef notyet
        /*
         * XXX: This could be bad in the case of ppbus(8).  Also, I think
         * this could lead to races of stale data when servicing an
         * interrupt.
         */
        dead = 1;
        CK_SLIST_FOREACH(ih, &ie->ie_handlers, ih_next) {
                if (ih->ih_handler != NULL) {
                        dead = 0;
                        break;
                }
        }
        if (dead) {
                ithread_destroy(ie->ie_thread);
                ie->ie_thread = NULL;
        }
#endif
        mtx_unlock(&ie->ie_lock);
        free(handler, M_ITHREAD);
        return (0);
}

int
intr_event_suspend_handler(void *cookie)
{
        struct intr_handler *handler = (struct intr_handler *)cookie;
        struct intr_event *ie;

        if (handler == NULL)
                return (EINVAL);
        ie = handler->ih_event;
        KASSERT(ie != NULL,
            ("interrupt handler \"%s\" has a NULL interrupt event",
            handler->ih_name));
        mtx_lock(&ie->ie_lock);
        handler->ih_flags |= IH_SUSP;
        intr_handler_barrier(handler);
        mtx_unlock(&ie->ie_lock);
        return (0);
}

int
intr_event_resume_handler(void *cookie)
{
        struct intr_handler *handler = (struct intr_handler *)cookie;
        struct intr_event *ie;

        if (handler == NULL)
                return (EINVAL);
        ie = handler->ih_event;
        KASSERT(ie != NULL,
            ("interrupt handler \"%s\" has a NULL interrupt event",
            handler->ih_name));

        /*
         * intr_handler_barrier() acts not only as a barrier,
         * it also allows to check for any pending interrupts.
         */
        mtx_lock(&ie->ie_lock);
        handler->ih_flags &= ~IH_SUSP;
        intr_handler_barrier(handler);
        mtx_unlock(&ie->ie_lock);
        return (0);
}
#endif /* __rtems__ */

static int
intr_event_schedule_thread(struct intr_event *ie)
{
        struct intr_entropy entropy;
        struct intr_thread *it;
        struct thread *td;
        struct thread *ctd;

        /*
         * If no ithread or no handlers, then we have a stray interrupt.
         */
        if (ie == NULL || CK_SLIST_EMPTY(&ie->ie_handlers) ||
            ie->ie_thread == NULL)
                return (EINVAL);

        ctd = curthread;
        it = ie->ie_thread;
        td = it->it_thread;

        /*
         * If any of the handlers for this ithread claim to be good
         * sources of entropy, then gather some.
         */
        if (ie->ie_flags & IE_ENTROPY) {
                entropy.event = (uintptr_t)ie;
                entropy.td = ctd;
                random_harvest_queue(&entropy, sizeof(entropy), RANDOM_INTERRUPT);
        }

#ifndef __rtems__
        KASSERT(td->td_proc != NULL, ("ithread %s has no process", ie->ie_name));
#endif /* __rtems__ */

        /*
         * Set it_need to tell the thread to keep running if it is already
         * running.  Then, lock the thread and see if we actually need to
         * put it on the runqueue.
         *
         * Use store_rel to arrange that the store to ih_need in
         * swi_sched() is before the store to it_need and prepare for
         * transfer of this order to loads in the ithread.
         */
        atomic_store_rel_int(&it->it_need, 1);
        thread_lock(td);
#ifndef __rtems__
        if (TD_AWAITING_INTR(td)) {
                CTR3(KTR_INTR, "%s: schedule pid %d (%s)", __func__, td->td_proc->p_pid,
                    td->td_name);
                TD_CLR_IWAIT(td);
                sched_add(td, SRQ_INTR);
        } else {
                CTR5(KTR_INTR, "%s: pid %d (%s): it_need %d, state %d",
                    __func__, td->td_proc->p_pid, td->td_name, it->it_need, td->td_state);
        }
#else /* __rtems__ */
        /* Send event to wake the thread up.
         * TODO: eventually replace event by a better mechanism
         */
        rtems_status_code sc = rtems_event_send(rtems_bsd_get_task_id(td), RTEMSBSD_SWI_WAKEUP_EVENT);
        BSD_ASSERT(sc == RTEMS_SUCCESSFUL);
#endif /* __rtems__ */
        thread_unlock(td);

        return (0);
}

/*
 * Allow interrupt event binding for software interrupt handlers -- a no-op,
 * since interrupts are generated in software rather than being directed by
 * a PIC.
 */
static int
swi_assign_cpu(void *arg, int cpu)
{

        return (0);
}

/*
 * Add a software interrupt handler to a specified event.  If a given event
 * is not specified, then a new event is created.
 */
int
swi_add(struct intr_event **eventp, const char *name, driver_intr_t handler,
            void *arg, int pri, enum intr_type flags, void **cookiep)
{
        struct intr_event *ie;
        int error;

        if (flags & INTR_ENTROPY)
                return (EINVAL);

        ie = (eventp != NULL) ? *eventp : NULL;

        if (ie != NULL) {
                if (!(ie->ie_flags & IE_SOFT))
                        return (EINVAL);
        } else {
                error = intr_event_create(&ie, NULL, IE_SOFT, 0,
                    NULL, NULL, NULL, swi_assign_cpu, "swi%d:", pri);
                if (error)
                        return (error);
                if (eventp != NULL)
                        *eventp = ie;
        }
        error = intr_event_add_handler(ie, name, NULL, handler, arg,
            PI_SWI(pri), flags, cookiep);
        return (error);
}

/*
 * Schedule a software interrupt thread.
 */
void
swi_sched(void *cookie, int flags)
{
        struct intr_handler *ih = (struct intr_handler *)cookie;
        struct intr_event *ie = ih->ih_event;
        struct intr_entropy entropy;
        int error __unused;

        CTR3(KTR_INTR, "swi_sched: %s %s need=%d", ie->ie_name, ih->ih_name,
            ih->ih_need);

        entropy.event = (uintptr_t)ih;
        entropy.td = curthread;
        random_harvest_queue(&entropy, sizeof(entropy), RANDOM_SWI);

        /*
         * Set ih_need for this handler so that if the ithread is already
         * running it will execute this handler on the next pass.  Otherwise,
         * it will execute it the next time it runs.
         */
        ih->ih_need = 1;

        if (!(flags & SWI_DELAY)) {
#ifndef __rtems__
                VM_CNT_INC(v_soft);
#endif /* __rtems__ */
                error = intr_event_schedule_thread(ie);
                KASSERT(error == 0, ("stray software interrupt"));
        }
}

#ifndef __rtems__
/*
 * Remove a software interrupt handler.  Currently this code does not
 * remove the associated interrupt event if it becomes empty.  Calling code
 * may do so manually via intr_event_destroy(), but that's not really
 * an optimal interface.
 */
int
swi_remove(void *cookie)
{

        return (intr_event_remove_handler(cookie));
}
#endif /* __rtems__ */

static void
intr_event_execute_handlers(struct proc *p, struct intr_event *ie)
{
        struct intr_handler *ih, *ihn, *ihp;

        ihp = NULL;
        CK_SLIST_FOREACH_SAFE(ih, &ie->ie_handlers, ih_next, ihn) {
                /*
                 * If this handler is marked for death, remove it from
                 * the list of handlers and wake up the sleeper.
                 */
                if (ih->ih_flags & IH_DEAD) {
                        mtx_lock(&ie->ie_lock);
                        if (ihp == NULL)
                                CK_SLIST_REMOVE_HEAD(&ie->ie_handlers, ih_next);
                        else
                                CK_SLIST_REMOVE_AFTER(ihp, ih_next);
                        ih->ih_flags &= ~IH_DEAD;
                        wakeup(ih);
                        mtx_unlock(&ie->ie_lock);
                        continue;
                }

                /*
                 * Now that we know that the current element won't be removed
                 * update the previous element.
                 */
                ihp = ih;

                if ((ih->ih_flags & IH_CHANGED) != 0) {
                        mtx_lock(&ie->ie_lock);
                        ih->ih_flags &= ~IH_CHANGED;
                        wakeup(ih);
                        mtx_unlock(&ie->ie_lock);
                }

                /* Skip filter only handlers */
                if (ih->ih_handler == NULL)
                        continue;

                /* Skip suspended handlers */
                if ((ih->ih_flags & IH_SUSP) != 0)
                        continue;

                /*
                 * For software interrupt threads, we only execute
                 * handlers that have their need flag set.  Hardware
                 * interrupt threads always invoke all of their handlers.
                 *
                 * ih_need can only be 0 or 1.  Failed cmpset below
                 * means that there is no request to execute handlers,
                 * so a retry of the cmpset is not needed.
                 */
                if ((ie->ie_flags & IE_SOFT) != 0 &&
                    atomic_cmpset_int(&ih->ih_need, 1, 0) == 0)
                        continue;

                /* Execute this handler. */
                CTR6(KTR_INTR, "%s: pid %d exec %p(%p) for %s flg=%x",
                    __func__, p->p_pid, (void *)ih->ih_handler, 
                    ih->ih_argument, ih->ih_name, ih->ih_flags);

                if (!(ih->ih_flags & IH_MPSAFE))
                        mtx_lock(&Giant);
                ih->ih_handler(ih->ih_argument);
                if (!(ih->ih_flags & IH_MPSAFE))
                        mtx_unlock(&Giant);
        }
}

static void
ithread_execute_handlers(struct proc *p, struct intr_event *ie)
{

#ifndef __rtems__
        /* Interrupt handlers should not sleep. */
        if (!(ie->ie_flags & IE_SOFT))
                THREAD_NO_SLEEPING();
        intr_event_execute_handlers(p, ie);
        if (!(ie->ie_flags & IE_SOFT))
                THREAD_SLEEPING_OK();
#else /* __rtems__ */
        /* We only have soft-threads, so the two queries are not necessary. */
        intr_event_execute_handlers(p, ie);
#endif /* __rtems__ */

        /*
         * Interrupt storm handling:
         *
         * If this interrupt source is currently storming, then throttle
         * it to only fire the handler once  per clock tick.
         *
         * If this interrupt source is not currently storming, but the
         * number of back to back interrupts exceeds the storm threshold,
         * then enter storming mode.
         */
        if (intr_storm_threshold != 0 && ie->ie_count >= intr_storm_threshold &&
            !(ie->ie_flags & IE_SOFT)) {
#ifndef __rtems__
                /* Report the message only once every second. */
                if (ppsratecheck(&ie->ie_warntm, &ie->ie_warncnt, 1)) {
                        printf(
        "interrupt storm detected on \"%s\"; throttling interrupt source\n",
                            ie->ie_name);
                }
#endif /* __rtems__ */
                pause("istorm", 1);
        } else
                ie->ie_count++;

        /*
         * Now that all the handlers have had a chance to run, reenable
         * the interrupt source.
         */
        if (ie->ie_post_ithread != NULL)
                ie->ie_post_ithread(ie->ie_source);
}

/*
 * This is the main code for interrupt threads.
 */
static void
ithread_loop(void *arg)
{
        struct intr_thread *ithd;
        struct intr_event *ie;
        struct thread *td;
        struct proc *p;
        int wake;

        td = curthread;
        p = td->td_proc;
        ithd = (struct intr_thread *)arg;
        KASSERT(ithd->it_thread == td,
            ("%s: ithread and proc linkage out of sync", __func__));
        ie = ithd->it_event;
        ie->ie_count = 0;
        wake = 0;

        /*
         * As long as we have interrupts outstanding, go through the
         * list of handlers, giving each one a go at it.
         */
        for (;;) {
                /*
                 * If we are an orphaned thread, then just die.
                 */
                if (ithd->it_flags & IT_DEAD) {
                        CTR3(KTR_INTR, "%s: pid %d (%s) exiting", __func__,
                            p->p_pid, td->td_name);
                        free(ithd, M_ITHREAD);
                        kthread_exit();
                }

                /*
                 * Service interrupts.  If another interrupt arrives while
                 * we are running, it will set it_need to note that we
                 * should make another pass.
                 *
                 * The load_acq part of the following cmpset ensures
                 * that the load of ih_need in ithread_execute_handlers()
                 * is ordered after the load of it_need here.
                 */
                while (atomic_cmpset_acq_int(&ithd->it_need, 1, 0) != 0)
                        ithread_execute_handlers(p, ie);
                WITNESS_WARN(WARN_PANIC, NULL, "suspending ithread");
                mtx_assert(&Giant, MA_NOTOWNED);

                /*
                 * Processed all our interrupts.  Now get the sched
                 * lock.  This may take a while and it_need may get
                 * set again, so we have to check it again.
                 */
                thread_lock(td);
                if (atomic_load_acq_int(&ithd->it_need) == 0 &&
                    (ithd->it_flags & (IT_DEAD | IT_WAIT)) == 0) {
#ifndef __rtems__
                        TD_SET_IWAIT(td);
                        ie->ie_count = 0;
                        mi_switch(SW_VOL | SWT_IWAIT, NULL);
#else /* __rtems__ */
                        /* wait for wakeup event
                         * TODO: eventually replace event by a better mechanism
                         */
                        rtems_event_set event_out;
                        rtems_status_code sc = rtems_event_receive(
                                RTEMSBSD_SWI_WAKEUP_EVENT,
                                RTEMS_WAIT | RTEMS_EVENT_ALL,
                                RTEMS_NO_TIMEOUT,
                                &event_out);
                        BSD_ASSERT(sc == RTEMS_SUCCESSFUL);
#endif /* __rtems__ */
                }
                if (ithd->it_flags & IT_WAIT) {
                        wake = 1;
                        ithd->it_flags &= ~IT_WAIT;
                }
                thread_unlock(td);
                if (wake) {
                        wakeup(ithd);
                        wake = 0;
                }
        }
}
#ifndef __rtems__

/*
 * Main interrupt handling body.
 *
 * Input:
 * o ie:                        the event connected to this interrupt.
 * o frame:                     some archs (i.e. i386) pass a frame to some.
 *                              handlers as their main argument.
 * Return value:
 * o 0:                         everything ok.
 * o EINVAL:                    stray interrupt.
 */
int
intr_event_handle(struct intr_event *ie, struct trapframe *frame)
{
        struct intr_handler *ih;
        struct trapframe *oldframe;
        struct thread *td;
        int phase;
        int ret;
        bool filter, thread;

        td = curthread;

#ifdef KSTACK_USAGE_PROF
        intr_prof_stack_use(td, frame);
#endif

        /* An interrupt with no event or handlers is a stray interrupt. */
        if (ie == NULL || CK_SLIST_EMPTY(&ie->ie_handlers))
                return (EINVAL);

        /*
         * Execute fast interrupt handlers directly.
         * To support clock handlers, if a handler registers
         * with a NULL argument, then we pass it a pointer to
         * a trapframe as its argument.
         */
        td->td_intr_nesting_level++;
        filter = false;
        thread = false;
        ret = 0;
        critical_enter();
        oldframe = td->td_intr_frame;
        td->td_intr_frame = frame;

        phase = ie->ie_phase;
        atomic_add_int(&ie->ie_active[phase], 1);

        /*
         * This fence is required to ensure that no later loads are
         * re-ordered before the ie_active store.
         */
        atomic_thread_fence_seq_cst();

        CK_SLIST_FOREACH(ih, &ie->ie_handlers, ih_next) {
                if ((ih->ih_flags & IH_SUSP) != 0)
                        continue;
                if (ih->ih_filter == NULL) {
                        thread = true;
                        continue;
                }
                CTR4(KTR_INTR, "%s: exec %p(%p) for %s", __func__,
                    ih->ih_filter, ih->ih_argument == NULL ? frame :
                    ih->ih_argument, ih->ih_name);
                if (ih->ih_argument == NULL)
                        ret = ih->ih_filter(frame);
                else
                        ret = ih->ih_filter(ih->ih_argument);
                KASSERT(ret == FILTER_STRAY ||
                    ((ret & (FILTER_SCHEDULE_THREAD | FILTER_HANDLED)) != 0 &&
                    (ret & ~(FILTER_SCHEDULE_THREAD | FILTER_HANDLED)) == 0),
                    ("%s: incorrect return value %#x from %s", __func__, ret,
                    ih->ih_name));
                filter = filter || ret == FILTER_HANDLED;

                /*
                 * Wrapper handler special handling:
                 *
                 * in some particular cases (like pccard and pccbb),
                 * the _real_ device handler is wrapped in a couple of
                 * functions - a filter wrapper and an ithread wrapper.
                 * In this case (and just in this case), the filter wrapper
                 * could ask the system to schedule the ithread and mask
                 * the interrupt source if the wrapped handler is composed
                 * of just an ithread handler.
                 *
                 * TODO: write a generic wrapper to avoid people rolling
                 * their own.
                 */
                if (!thread) {
                        if (ret == FILTER_SCHEDULE_THREAD)
                                thread = true;
                }
        }
        atomic_add_rel_int(&ie->ie_active[phase], -1);

        td->td_intr_frame = oldframe;

        if (thread) {
                if (ie->ie_pre_ithread != NULL)
                        ie->ie_pre_ithread(ie->ie_source);
        } else {
                if (ie->ie_post_filter != NULL)
                        ie->ie_post_filter(ie->ie_source);
        }

        /* Schedule the ithread if needed. */
        if (thread) {
                int error __unused;

                error =  intr_event_schedule_thread(ie);
                KASSERT(error == 0, ("bad stray interrupt"));
        }
        critical_exit();
        td->td_intr_nesting_level--;
#ifdef notyet
        /* The interrupt is not aknowledged by any filter and has no ithread. */
        if (!thread && !filter)
                return (EINVAL);
#endif
        return (0);
}

#ifdef DDB
/*
 * Dump details about an interrupt handler
 */
static void
db_dump_intrhand(struct intr_handler *ih)
{
        int comma;

        db_printf("\t%-10s ", ih->ih_name);
        switch (ih->ih_pri) {
        case PI_REALTIME:
                db_printf("CLK ");
                break;
        case PI_AV:
                db_printf("AV  ");
                break;
        case PI_TTY:
                db_printf("TTY ");
                break;
        case PI_NET:
                db_printf("NET ");
                break;
        case PI_DISK:
                db_printf("DISK");
                break;
        case PI_DULL:
                db_printf("DULL");
                break;
        default:
                if (ih->ih_pri >= PI_SOFT)
                        db_printf("SWI ");
                else
                        db_printf("%4u", ih->ih_pri);
                break;
        }
        db_printf(" ");
        if (ih->ih_filter != NULL) {
                db_printf("[F]");
                db_printsym((uintptr_t)ih->ih_filter, DB_STGY_PROC);
        }
        if (ih->ih_handler != NULL) {
                if (ih->ih_filter != NULL)
                        db_printf(",");
                db_printf("[H]");
                db_printsym((uintptr_t)ih->ih_handler, DB_STGY_PROC);
        }
        db_printf("(%p)", ih->ih_argument);
        if (ih->ih_need ||
            (ih->ih_flags & (IH_EXCLUSIVE | IH_ENTROPY | IH_DEAD |
            IH_MPSAFE)) != 0) {
                db_printf(" {");
                comma = 0;
                if (ih->ih_flags & IH_EXCLUSIVE) {
                        if (comma)
                                db_printf(", ");
                        db_printf("EXCL");
                        comma = 1;
                }
                if (ih->ih_flags & IH_ENTROPY) {
                        if (comma)
                                db_printf(", ");
                        db_printf("ENTROPY");
                        comma = 1;
                }
                if (ih->ih_flags & IH_DEAD) {
                        if (comma)
                                db_printf(", ");
                        db_printf("DEAD");
                        comma = 1;
                }
                if (ih->ih_flags & IH_MPSAFE) {
                        if (comma)
                                db_printf(", ");
                        db_printf("MPSAFE");
                        comma = 1;
                }
                if (ih->ih_need) {
                        if (comma)
                                db_printf(", ");
                        db_printf("NEED");
                }
                db_printf("}");
        }
        db_printf("\n");
}

/*
 * Dump details about a event.
 */
void
db_dump_intr_event(struct intr_event *ie, int handlers)
{
        struct intr_handler *ih;
        struct intr_thread *it;
        int comma;

        db_printf("%s ", ie->ie_fullname);
        it = ie->ie_thread;
        if (it != NULL)
                db_printf("(pid %d)", it->it_thread->td_proc->p_pid);
        else
                db_printf("(no thread)");
        if ((ie->ie_flags & (IE_SOFT | IE_ENTROPY | IE_ADDING_THREAD)) != 0 ||
            (it != NULL && it->it_need)) {
                db_printf(" {");
                comma = 0;
                if (ie->ie_flags & IE_SOFT) {
                        db_printf("SOFT");
                        comma = 1;
                }
                if (ie->ie_flags & IE_ENTROPY) {
                        if (comma)
                                db_printf(", ");
                        db_printf("ENTROPY");
                        comma = 1;
                }
                if (ie->ie_flags & IE_ADDING_THREAD) {
                        if (comma)
                                db_printf(", ");
                        db_printf("ADDING_THREAD");
                        comma = 1;
                }
                if (it != NULL && it->it_need) {
                        if (comma)
                                db_printf(", ");
                        db_printf("NEED");
                }
                db_printf("}");
        }
        db_printf("\n");

        if (handlers)
                CK_SLIST_FOREACH(ih, &ie->ie_handlers, ih_next)
                    db_dump_intrhand(ih);
}

/*
 * Dump data about interrupt handlers
 */
DB_SHOW_COMMAND(intr, db_show_intr)
{
        struct intr_event *ie;
        int all, verbose;

        verbose = strchr(modif, 'v') != NULL;
        all = strchr(modif, 'a') != NULL;
        TAILQ_FOREACH(ie, &event_list, ie_list) {
                if (!all && CK_SLIST_EMPTY(&ie->ie_handlers))
                        continue;
                db_dump_intr_event(ie, verbose);
                if (db_pager_quit)
                        break;
        }
}
#endif /* DDB */

/*
 * Start standard software interrupt threads
 */
static void
start_softintr(void *dummy)
{

        if (swi_add(NULL, "vm", swi_vm, NULL, SWI_VM, INTR_MPSAFE, &vm_ih))
                panic("died while creating vm swi ithread");
}
SYSINIT(start_softintr, SI_SUB_SOFTINTR, SI_ORDER_FIRST, start_softintr,
    NULL);

/*
 * Sysctls used by systat and others: hw.intrnames and hw.intrcnt.
 * The data for this machine dependent, and the declarations are in machine
 * dependent code.  The layout of intrnames and intrcnt however is machine
 * independent.
 *
 * We do not know the length of intrcnt and intrnames at compile time, so
 * calculate things at run time.
 */
static int
sysctl_intrnames(SYSCTL_HANDLER_ARGS)
{
        return (sysctl_handle_opaque(oidp, intrnames, sintrnames, req));
}

SYSCTL_PROC(_hw, OID_AUTO, intrnames, CTLTYPE_OPAQUE | CTLFLAG_RD,
    NULL, 0, sysctl_intrnames, "", "Interrupt Names");

static int
sysctl_intrcnt(SYSCTL_HANDLER_ARGS)
{
#ifdef SCTL_MASK32
        uint32_t *intrcnt32;
        unsigned i;
        int error;

        if (req->flags & SCTL_MASK32) {
                if (!req->oldptr)
                        return (sysctl_handle_opaque(oidp, NULL, sintrcnt / 2, req));
                intrcnt32 = malloc(sintrcnt / 2, M_TEMP, M_NOWAIT);
                if (intrcnt32 == NULL)
                        return (ENOMEM);
                for (i = 0; i < sintrcnt / sizeof (u_long); i++)
                        intrcnt32[i] = intrcnt[i];
                error = sysctl_handle_opaque(oidp, intrcnt32, sintrcnt / 2, req);
                free(intrcnt32, M_TEMP);
                return (error);
        }
#endif
        return (sysctl_handle_opaque(oidp, intrcnt, sintrcnt, req));
}

SYSCTL_PROC(_hw, OID_AUTO, intrcnt, CTLTYPE_OPAQUE | CTLFLAG_RD,
    NULL, 0, sysctl_intrcnt, "", "Interrupt Counts");

#ifdef DDB
/*
 * DDB command to dump the interrupt statistics.
 */
DB_SHOW_COMMAND(intrcnt, db_show_intrcnt)
{
        u_long *i;
        char *cp;
        u_int j;

        cp = intrnames;
        j = 0;
        for (i = intrcnt; j < (sintrcnt / sizeof(u_long)) && !db_pager_quit;
            i++, j++) {
                if (*cp == '\0')
                        break;
                if (*i != 0)
                        db_printf("%s\t%lu\n", cp, *i);
                cp += strlen(cp) + 1;
        }
}
#endif
#endif /* __rtems__ */