/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 2002 Poul-Henning Kamp
 * Copyright (c) 2002 Networks Associates Technology, Inc.
 * All rights reserved.
 *
 * This software was developed for the FreeBSD Project by Poul-Henning Kamp
 * and NAI Labs, the Security Research Division of Network Associates, Inc.
 * under DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"), as part of the
 * DARPA CHATS research program.
 *
 * 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.
 * 3. The names of the authors may not be used to endorse or promote
 *    products derived from this software without specific prior written
 *    permission.
 *
 * 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.
 */

/*
 * XXX: How do we in general know that objects referenced in events
 * have not been destroyed before we get around to handle the event ?
 */

#include <sys/param.h>
#include <sys/malloc.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/errno.h>
#include <sys/stdarg.h>
#include <sys/time.h>
#include <geom/geom.h>
#include <geom/geom_int.h>

TAILQ_HEAD(event_tailq_head, g_event);

static struct event_tailq_head g_events = TAILQ_HEAD_INITIALIZER(g_events);
static u_int g_pending_events;
static TAILQ_HEAD(,g_provider) g_doorstep = TAILQ_HEAD_INITIALIZER(g_doorstep);
static struct mtx g_eventlock;
static int g_wither_work;

#define G_N_EVENTREFS           20

struct g_event {
        TAILQ_ENTRY(g_event)    events;
        g_event_t               *func;
        void                    *arg;
        int                     flag;
        void                    *ref[G_N_EVENTREFS];
};

#define EV_DONE         0x80000
#define EV_WAKEUP       0x40000
#define EV_CANCELED     0x20000
#define EV_INPROGRESS   0x10000

void
g_waitidle(struct thread *td)
{

        g_topology_assert_not();

        mtx_lock(&g_eventlock);
        TSWAIT("GEOM events");
        while (!TAILQ_EMPTY(&g_events) || !TAILQ_EMPTY(&g_doorstep))
                msleep(&g_pending_events, &g_eventlock, PPAUSE,
                    "g_waitidle", 0);
        TSUNWAIT("GEOM events");
        mtx_unlock(&g_eventlock);
        td->td_pflags &= ~TDP_GEOM;
}

static void
ast_geom(struct thread *td, int tda __unused)
{
        /*
         * If this thread tickled GEOM, we need to wait for the giggling to
         * stop before we return to userland.
         */
        g_waitidle(td);
}

static void
geom_event_init(void *arg __unused)
{
        ast_register(TDA_GEOM, ASTR_ASTF_REQUIRED | ASTR_TDP | ASTR_KCLEAR,
            TDP_GEOM, ast_geom);
}
SYSINIT(geom_event, SI_SUB_INTRINSIC, SI_ORDER_ANY, geom_event_init, NULL);

struct g_attrchanged_args {
        struct g_provider *pp;
        const char *attr;
};

static void
g_attr_changed_event(void *arg, int flag)
{
        struct g_attrchanged_args *args;
        struct g_provider *pp;
        struct g_consumer *cp;
        struct g_consumer *next_cp;

        args = arg;
        pp = args->pp;

        g_topology_assert();
        if (flag != EV_CANCEL && g_shutdown == 0) {
                /*
                 * Tell all consumers of the change.
                 */
                LIST_FOREACH_SAFE(cp, &pp->consumers, consumers, next_cp) {
                        if (cp->geom->attrchanged != NULL)
                                cp->geom->attrchanged(cp, args->attr);
                }
        }
        g_free(args);
}

int
g_attr_changed(struct g_provider *pp, const char *attr, int flag)
{
        struct g_attrchanged_args *args;
        int error;

        args = g_malloc(sizeof(*args), flag);
        if (args == NULL)
                return (ENOMEM);
        args->pp = pp;
        args->attr = attr;
        error = g_post_event(g_attr_changed_event, args, flag, pp, NULL);
        if (error != 0)
                g_free(args);
        return (error);
}

void
g_orphan_provider(struct g_provider *pp, int error)
{

        /* G_VALID_PROVIDER(pp)  We likely lack topology lock */
        g_trace(G_T_TOPOLOGY, "g_orphan_provider(%p(%s), %d)",
            pp, pp->name, error);
        KASSERT(error != 0,
            ("g_orphan_provider(%p(%s), 0) error must be non-zero\n",
             pp, pp->name));

        pp->error = error;
        mtx_lock(&g_eventlock);
        KASSERT(!(pp->flags & G_PF_ORPHAN),
            ("g_orphan_provider(%p(%s)), already an orphan", pp, pp->name));
        pp->flags |= G_PF_ORPHAN;
        TAILQ_INSERT_TAIL(&g_doorstep, pp, orphan);
        mtx_unlock(&g_eventlock);
        wakeup(&g_wait_event);
}

/*
 * This function is called once on each provider which the event handler
 * finds on its g_doorstep.
 */

static void
g_orphan_register(struct g_provider *pp)
{
        struct g_consumer *cp, *cp2;
        int wf;

        g_topology_assert();
        G_VALID_PROVIDER(pp);
        g_trace(G_T_TOPOLOGY, "g_orphan_register(%s)", pp->name);

        g_cancel_event(pp);

        wf = pp->flags & G_PF_WITHER;
        pp->flags &= ~G_PF_WITHER;

        /*
         * Tell all consumers the bad news.
         * Don't be surprised if they self-destruct.
         */
        LIST_FOREACH_SAFE(cp, &pp->consumers, consumers, cp2) {
                KASSERT(cp->geom->orphan != NULL,
                    ("geom %s has no orphan, class %s",
                    cp->geom->name, cp->geom->class->name));
                /*
                 * XXX: g_dev_orphan method does deferred destroying
                 * and it is possible, that other event could already
                 * call the orphan method. Check consumer's flags to
                 * do not schedule it twice.
                 */
                if (cp->flags & G_CF_ORPHAN)
                        continue;
                cp->flags |= G_CF_ORPHAN;
                cp->geom->orphan(cp);
        }
        if (LIST_EMPTY(&pp->consumers) && wf)
                g_destroy_provider(pp);
        else
                pp->flags |= wf;
#ifdef notyet
        cp = LIST_FIRST(&pp->consumers);
        if (cp != NULL)
                return;
        if (pp->geom->flags & G_GEOM_WITHER)
                g_destroy_provider(pp);
#endif
}

static int
one_event(void)
{
        struct g_event *ep;
        struct g_provider *pp;

        g_topology_assert();
        mtx_lock(&g_eventlock);
        pp = TAILQ_FIRST(&g_doorstep);
        if (pp != NULL) {
                G_VALID_PROVIDER(pp);
                TAILQ_REMOVE(&g_doorstep, pp, orphan);
                mtx_unlock(&g_eventlock);
                g_orphan_register(pp);
                return (1);
        }

        ep = TAILQ_FIRST(&g_events);
        if (ep == NULL) {
                wakeup(&g_pending_events);
                return (0);
        }
        ep->flag |= EV_INPROGRESS;
        mtx_unlock(&g_eventlock);
        g_topology_assert();
        ep->func(ep->arg, 0);
        g_topology_assert();
        mtx_lock(&g_eventlock);
        TSRELEASE("GEOM events");
        TAILQ_REMOVE(&g_events, ep, events);
        ep->flag &= ~EV_INPROGRESS;
        if (ep->flag & EV_WAKEUP) {
                ep->flag |= EV_DONE;
                wakeup(ep);
                mtx_unlock(&g_eventlock);
        } else {
                mtx_unlock(&g_eventlock);
                g_free(ep);
        }
        return (1);
}

void
g_run_events(void)
{

        for (;;) {
                g_topology_lock();
                while (one_event())
                        ;
                mtx_assert(&g_eventlock, MA_OWNED);
                if (g_wither_work) {
                        g_wither_work = 0;
                        mtx_unlock(&g_eventlock);
                        g_wither_washer();
                        g_topology_unlock();
                } else {
                        g_topology_unlock();
                        msleep(&g_wait_event, &g_eventlock, PRIBIO | PDROP,
                            "-", 0);
                }
        }
        /* NOTREACHED */
}

void
g_cancel_event(void *ref)
{
        struct g_event *ep, *epn;
        struct g_provider *pp;
        u_int n;

        mtx_lock(&g_eventlock);
        TAILQ_FOREACH(pp, &g_doorstep, orphan) {
                if (pp != ref)
                        continue;
                TAILQ_REMOVE(&g_doorstep, pp, orphan);
                break;
        }
        TAILQ_FOREACH_SAFE(ep, &g_events, events, epn) {
                if (ep->flag & EV_INPROGRESS)
                        continue;
                for (n = 0; n < G_N_EVENTREFS; n++) {
                        if (ep->ref[n] == NULL)
                                break;
                        if (ep->ref[n] != ref)
                                continue;
                        TSRELEASE("GEOM events");
                        TAILQ_REMOVE(&g_events, ep, events);
                        ep->func(ep->arg, EV_CANCEL);
                        mtx_assert(&g_eventlock, MA_OWNED);
                        if (ep->flag & EV_WAKEUP) {
                                ep->flag |= (EV_DONE|EV_CANCELED);
                                wakeup(ep);
                        } else {
                                g_free(ep);
                        }
                        break;
                }
        }
        if (TAILQ_EMPTY(&g_events))
                wakeup(&g_pending_events);
        mtx_unlock(&g_eventlock);
}

struct g_event *
g_alloc_event(int flag)
{
        KASSERT(flag == M_WAITOK || flag == M_NOWAIT,
            ("Wrong flag to g_alloc_event"));

        return (g_malloc(sizeof(struct g_event), flag | M_ZERO));
}

static void
g_post_event_ep_va(g_event_t *func, void *arg, int wuflag,
    struct g_event *ep, va_list ap)
{
        struct thread *td;
        void *p;
        u_int n;

        ep->flag = wuflag;
        for (n = 0; n < G_N_EVENTREFS; n++) {
                p = va_arg(ap, void *);
                if (p == NULL)
                        break;
                g_trace(G_T_TOPOLOGY, "  ref %p", p);
                ep->ref[n] = p;
        }
        KASSERT(p == NULL, ("Too many references to event"));
        ep->func = func;
        ep->arg = arg;
        mtx_lock(&g_eventlock);
        TSHOLD("GEOM events");
        TAILQ_INSERT_TAIL(&g_events, ep, events);
        mtx_unlock(&g_eventlock);
        wakeup(&g_wait_event);

        td = curthread;
        if ((td->td_pflags & TDP_KTHREAD) == 0) {
                td->td_pflags |= TDP_GEOM;
                ast_sched(td, TDA_GEOM);
        }
}

void
g_post_event_ep(g_event_t *func, void *arg, struct g_event *ep, ...)
{
        va_list ap;

        va_start(ap, ep);
        g_post_event_ep_va(func, arg, 0, ep, ap);
        va_end(ap);
}


static int
g_post_event_x(g_event_t *func, void *arg, int flag, int wuflag, struct g_event **epp, va_list ap)
{
        struct g_event *ep;

        g_trace(G_T_TOPOLOGY, "g_post_event_x(%p, %p, %d, %d)",
            func, arg, flag, wuflag);
        KASSERT(wuflag == 0 || wuflag == EV_WAKEUP,
            ("Wrong wuflag in g_post_event_x(0x%x)", wuflag));
        ep = g_alloc_event(flag);
        if (ep == NULL)
                return (ENOMEM);
        if (epp != NULL)
                *epp = ep;
        g_post_event_ep_va(func, arg, wuflag, ep, ap);
        return (0);
}

int
g_post_event(g_event_t *func, void *arg, int flag, ...)
{
        va_list ap;
        int i;

        KASSERT(flag == M_WAITOK || flag == M_NOWAIT,
            ("Wrong flag to g_post_event"));
        va_start(ap, flag);
        i = g_post_event_x(func, arg, flag, 0, NULL, ap);
        va_end(ap);
        return (i);
}

void
g_do_wither(void)
{

        mtx_lock(&g_eventlock);
        g_wither_work = 1;
        mtx_unlock(&g_eventlock);
        wakeup(&g_wait_event);
}

/*
 * XXX: It might actually be useful to call this function with topology held.
 * XXX: This would ensure that the event gets created before anything else
 * XXX: changes.  At present all users have a handle on things in some other
 * XXX: way, so this remains an XXX for now.
 */

int
g_waitfor_event(g_event_t *func, void *arg, int flag, ...)
{
        va_list ap;
        struct g_event *ep;
        int error;

        g_topology_assert_not();
        KASSERT(flag == M_WAITOK || flag == M_NOWAIT,
            ("Wrong flag to g_post_event"));
        va_start(ap, flag);
        error = g_post_event_x(func, arg, flag, EV_WAKEUP, &ep, ap);
        va_end(ap);
        if (error)
                return (error);

        mtx_lock(&g_eventlock);
        while (!(ep->flag & EV_DONE))
                msleep(ep, &g_eventlock, PRIBIO, "g_waitfor_event", 0);
        if (ep->flag & EV_CANCELED)
                error = EAGAIN;
        mtx_unlock(&g_eventlock);

        g_free(ep);
        return (error);
}

void
g_event_init(void)
{

        mtx_init(&g_eventlock, "GEOM orphanage", NULL, MTX_DEF);
}