/*      $NetBSD: ltsleep.c,v 1.36 2020/03/14 20:23:51 ad Exp $  */

/*
 * Copyright (c) 2009, 2010 Antti Kantee.  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 ``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 the tsleep/mtsleep kernel sleep interface.  There
 * are two sides to our implementation.  For historic spinlocks we
 * assume the kernel is giantlocked and use kernel giantlock as the
 * wait interlock.  For mtsleep, we use the interlock supplied by
 * the caller.  This duality leads to some if/else messiness in the code ...
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: ltsleep.c,v 1.36 2020/03/14 20:23:51 ad Exp $");

#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/proc.h>
#include <sys/queue.h>

#include <rump-sys/kern.h>

#include <rump/rumpuser.h>

struct ltsleeper {
        wchan_t id;
        union {
                struct rumpuser_cv *user;
                kcondvar_t kern;
        } u;
        bool iskwait;
        LIST_ENTRY(ltsleeper) entries;
};
#define ucv u.user
#define kcv u.kern

static LIST_HEAD(, ltsleeper) sleepers = LIST_HEAD_INITIALIZER(sleepers);
static kmutex_t qlock;

static int
sleeper(wchan_t ident, int timo, bool kinterlock)
{
        struct ltsleeper lts;
        struct timespec ts;
        int rv;

        lts.id = ident;
        if (kinterlock) {
                lts.iskwait = true;
                cv_init(&lts.kcv, "mtsleep");
        } else {
                lts.iskwait = false;
                rumpuser_cv_init(&lts.ucv);
        }

        LIST_INSERT_HEAD(&sleepers, &lts, entries);

        if (timo) {
                if (kinterlock) {
                        rv = cv_timedwait(&lts.kcv, &qlock, timo);
                } else {
                        /*
                         * Calculate wakeup-time.
                         */
                        ts.tv_sec = timo / hz;
                        ts.tv_nsec = (timo % hz) * (1000000000/hz);
                        mutex_spin_exit(&qlock);
                        rv = rumpuser_cv_timedwait(lts.ucv, rump_giantlock,
                            ts.tv_sec, ts.tv_nsec);
                        mutex_spin_enter(&qlock);
                }

                if (rv != 0)
                        rv = EWOULDBLOCK;
        } else {
                if (kinterlock) {
                        cv_wait(&lts.kcv, &qlock);
                } else {
                        mutex_spin_exit(&qlock);
                        rumpuser_cv_wait(lts.ucv, rump_giantlock);
                        mutex_spin_enter(&qlock);
                }
                rv = 0;
        }

        LIST_REMOVE(&lts, entries);
        mutex_spin_exit(&qlock);

        if (kinterlock)
                cv_destroy(&lts.kcv);
        else
                rumpuser_cv_destroy(lts.ucv);

        return rv;
}

int
tsleep(wchan_t ident, pri_t prio, const char *wmesg, int timo)
{
        int rv, nlocks;

        /*
         * Since we cannot use slock as the rumpuser interlock,
         * require that everyone using this prehistoric interface
         * is biglocked.  Wrap around the biglock and drop lockcnt,
         * but retain the rumpuser mutex so that we can use it as an
         * interlock to rumpuser_cv_wait().
         */
        rump_kernel_bigwrap(&nlocks);
        mutex_spin_enter(&qlock);
        rv = sleeper(ident, timo, false);
        rump_kernel_bigunwrap(nlocks);

        return rv;
}

int
mtsleep(wchan_t ident, pri_t prio, const char *wmesg, int timo, kmutex_t *lock)
{
        int rv;

        mutex_spin_enter(&qlock);
        mutex_exit(lock);
        rv = sleeper(ident, timo, true);
        if ((prio & PNORELOCK) == 0)
                mutex_enter(lock);

        return rv;
}

void
wakeup(wchan_t ident)
{
        struct ltsleeper *ltsp;

        mutex_spin_enter(&qlock);
        LIST_FOREACH(ltsp, &sleepers, entries) {
                if (ltsp->id == ident) {
                        if (ltsp->iskwait) {
                                cv_broadcast(&ltsp->kcv);
                        } else {
                                rumpuser_cv_broadcast(ltsp->ucv);
                        }
                }
        }
        mutex_exit(&qlock);
}

void
rump_tsleep_init()
{

        mutex_init(&qlock, MUTEX_SPIN, IPL_NONE);
}