/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */

/*
 * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

/*
 * Copyright 2018 Nexenta Systems, Inc. All rights reserved.
 */

/*
 * This file contains the semaphore operations.
 */

#include <sys/param.h>
#include <sys/types.h>
#include <sys/systm.h>
#include <sys/schedctl.h>
#include <sys/semaphore.h>
#include <sys/sema_impl.h>
#include <sys/t_lock.h>
#include <sys/thread.h>
#include <sys/proc.h>
#include <sys/cmn_err.h>
#include <sys/debug.h>
#include <sys/disp.h>
#include <sys/sobject.h>
#include <sys/cpuvar.h>
#include <sys/sleepq.h>
#include <sys/sdt.h>

static void sema_unsleep(kthread_t *t);
static void sema_change_pri(kthread_t *t, pri_t pri, pri_t *t_prip);
static kthread_t *sema_owner(ksema_t *);

/*
 * The sobj_ops vector exports a set of functions needed when a thread
 * is asleep on a synchronization object of this type.
 */
static sobj_ops_t sema_sobj_ops = {
        SOBJ_SEMA, sema_owner, sema_unsleep, sema_change_pri
};

/*
 * SEMA_BLOCK(sema_impl_t *s, disp_lock_t *lockp)
 */
#define SEMA_BLOCK(s, lockp)                                            \
        {                                                               \
                kthread_t       *tp;                                    \
                kthread_t       **tpp;                                  \
                pri_t           cpri;                                   \
                klwp_t  *lwp = ttolwp(curthread);                       \
                ASSERT(THREAD_LOCK_HELD(curthread));                    \
                ASSERT(curthread != CPU->cpu_idle_thread);              \
                ASSERT(CPU_ON_INTR(CPU) == 0);                          \
                ASSERT(curthread->t_wchan0 == NULL);                    \
                ASSERT(curthread->t_wchan == NULL);                     \
                ASSERT(curthread->t_state == TS_ONPROC);                \
                CL_SLEEP(curthread);                                    \
                THREAD_SLEEP(curthread, lockp);                         \
                curthread->t_wchan = (caddr_t)s;                        \
                curthread->t_sobj_ops = &sema_sobj_ops;                 \
                DTRACE_SCHED(sleep);                                    \
                if (lwp != NULL) {                                      \
                        lwp->lwp_ru.nvcsw++;                            \
                        (void) new_mstate(curthread, LMS_SLEEP);        \
                }                                                       \
                cpri = DISP_PRIO(curthread);                            \
                tpp = &s->s_slpq;                                       \
                while ((tp = *tpp) != NULL) {                           \
                        if (cpri > DISP_PRIO(tp))                       \
                                break;                                  \
                        tpp = &tp->t_link;                              \
                }                                                       \
                *tpp = curthread;                                       \
                curthread->t_link = tp;                                 \
                ASSERT(s->s_slpq != NULL);                              \
        }

/* ARGSUSED */
void
sema_init(ksema_t *sp, unsigned count, char *name, ksema_type_t type, void *arg)
{
        ((sema_impl_t *)sp)->s_count = count;
        ((sema_impl_t *)sp)->s_slpq = NULL;
}

void
sema_destroy(ksema_t *sp)
{
        ASSERT(((sema_impl_t *)sp)->s_slpq == NULL);
}

/*
 * Put a thread on the sleep queue for this semaphore.
 */
static void
sema_queue(ksema_t *sp, kthread_t *t)
{
        kthread_t       **tpp;
        kthread_t       *tp;
        pri_t           cpri;
        sema_impl_t     *s;

        ASSERT(THREAD_LOCK_HELD(t));
        s = (sema_impl_t *)sp;
        tpp = &s->s_slpq;
        cpri = DISP_PRIO(t);
        while ((tp = *tpp) != NULL) {
                if (cpri > DISP_PRIO(tp))
                        break;
                tpp = &tp->t_link;
        }
        *tpp = t;
        t->t_link = tp;
}

/*
 * Remove a thread from the sleep queue for this
 * semaphore.
 */
static void
sema_dequeue(ksema_t *sp, kthread_t *t)
{
        kthread_t       **tpp;
        kthread_t       *tp;
        sema_impl_t     *s;

        ASSERT(THREAD_LOCK_HELD(t));
        s = (sema_impl_t *)sp;
        tpp = &s->s_slpq;
        while ((tp = *tpp) != NULL) {
                if (tp == t) {
                        *tpp = t->t_link;
                        t->t_link = NULL;
                        return;
                }
                tpp = &tp->t_link;
        }
}

/* ARGSUSED */
static kthread_t *
sema_owner(ksema_t *sp)
{
        return ((kthread_t *)NULL);
}

/*
 * Wakeup a thread sleeping on a semaphore, and put it
 * on the dispatch queue.
 * Called via SOBJ_UNSLEEP().
 */
static void
sema_unsleep(kthread_t *t)
{
        kthread_t       **tpp;
        kthread_t       *tp;
        sema_impl_t     *s;

        ASSERT(THREAD_LOCK_HELD(t));
        s = (sema_impl_t *)t->t_wchan;
        tpp = &s->s_slpq;
        while ((tp = *tpp) != NULL) {
                if (tp == t) {
                        *tpp = t->t_link;
                        t->t_link = NULL;
                        t->t_sobj_ops = NULL;
                        t->t_wchan = NULL;
                        t->t_wchan0 = NULL;
                        /*
                         * Change thread to transition state and
                         * drop the semaphore sleep queue lock.
                         */
                        THREAD_TRANSITION(t);
                        CL_SETRUN(t);
                        return;
                }
                tpp = &tp->t_link;
        }
}

/*
 * operations to perform when changing the priority
 * of a thread asleep on a semaphore.
 * Called via SOBJ_CHANGE_PRI() and SOBJ_CHANGE_EPRI().
 */
static void
sema_change_pri(kthread_t *t, pri_t pri, pri_t *t_prip)
{
        ksema_t *sp;

        if ((sp = (ksema_t *)t->t_wchan) != NULL) {
                sema_dequeue(sp, t);
                *t_prip = pri;
                sema_queue(sp, t);
        } else
                panic("sema_change_pri: %p not on sleep queue", (void *)t);
}

/*
 * the semaphore is granted when the semaphore's
 * count is greater than zero and blocks when equal
 * to zero.
 */
void
sema_p(ksema_t *sp)
{
        sema_impl_t     *s;
        disp_lock_t     *sqlp;

        /* no-op during panic */
        if (panicstr)
                return;

        s = (sema_impl_t *)sp;
        sqlp = &SQHASH(s)->sq_lock;
        disp_lock_enter(sqlp);
        ASSERT(s->s_count >= 0);
        while (s->s_count == 0) {
                thread_lock_high(curthread);
                SEMA_BLOCK(s, sqlp);
                thread_unlock_nopreempt(curthread);
                swtch();
                disp_lock_enter(sqlp);
        }
        s->s_count--;
        disp_lock_exit(sqlp);
}

/*
 * similiar to sema_p except that it blocks at an interruptible
 * priority. if a signal is present then return 1 otherwise 0.
 */
int
sema_p_sig(ksema_t *sp)
{
        kthread_t       *t = curthread;
        klwp_t          *lwp = ttolwp(t);
        int             cancel_pending;
        int             cancelled = 0;
        sema_impl_t     *s;
        disp_lock_t     *sqlp;

        if (lwp == NULL) {
                sema_p(sp);
                return (0);
        }

        cancel_pending = schedctl_cancel_pending();
        s = (sema_impl_t *)sp;
        sqlp = &SQHASH(s)->sq_lock;
        disp_lock_enter(sqlp);
        ASSERT(s->s_count >= 0);
        while (s->s_count == 0) {
                proc_t *p = ttoproc(t);
                thread_lock_high(t);
                t->t_flag |= T_WAKEABLE;
                SEMA_BLOCK(s, sqlp);
                lwp->lwp_asleep = 1;
                lwp->lwp_sysabort = 0;
                thread_unlock_nopreempt(t);
                if (ISSIG(t, JUSTLOOKING) || MUSTRETURN(p, t) || cancel_pending)
                        setrun(t);
                swtch();
                t->t_flag &= ~T_WAKEABLE;
                if (ISSIG(t, FORREAL) || lwp->lwp_sysabort ||
                    MUSTRETURN(p, t) || (cancelled = cancel_pending) != 0) {
                        kthread_t *sq, *tp;
                        lwp->lwp_asleep = 0;
                        lwp->lwp_sysabort = 0;
                        disp_lock_enter(sqlp);
                        sq = s->s_slpq;
                        /*
                         * in case sema_v and interrupt happen
                         * at the same time, we need to pass the
                         * sema_v to the next thread.
                         */
                        if ((sq != NULL) && (s->s_count > 0)) {
                                tp = sq;
                                ASSERT(THREAD_LOCK_HELD(tp));
                                sq = sq->t_link;
                                tp->t_link = NULL;
                                DTRACE_SCHED1(wakeup, kthread_t *, tp);
                                tp->t_sobj_ops = NULL;
                                tp->t_wchan = NULL;
                                ASSERT(tp->t_state == TS_SLEEP);
                                CL_WAKEUP(tp);
                                s->s_slpq = sq;
                                disp_lock_exit_high(sqlp);
                                thread_unlock(tp);
                        } else {
                                disp_lock_exit(sqlp);
                        }
                        if (cancelled)
                                schedctl_cancel_eintr();
                        return (1);
                }
                lwp->lwp_asleep = 0;
                disp_lock_enter(sqlp);
        }
        s->s_count--;
        disp_lock_exit(sqlp);
        return (0);
}

/*
 * the semaphore's count is incremented by one. a blocked thread
 * is awakened and re-tries to acquire the semaphore.
 */
void
sema_v(ksema_t *sp)
{
        sema_impl_t     *s;
        kthread_t       *sq, *tp;
        disp_lock_t     *sqlp;

        /* no-op during panic */
        if (panicstr)
                return;

        s = (sema_impl_t *)sp;
        sqlp = &SQHASH(s)->sq_lock;
        disp_lock_enter(sqlp);
        s->s_count++;
        sq = s->s_slpq;
        if (sq != NULL) {
                tp = sq;
                ASSERT(THREAD_LOCK_HELD(tp));
                sq = sq->t_link;
                tp->t_link = NULL;
                DTRACE_SCHED1(wakeup, kthread_t *, tp);
                tp->t_sobj_ops = NULL;
                tp->t_wchan = NULL;
                ASSERT(tp->t_state == TS_SLEEP);
                CL_WAKEUP(tp);
                s->s_slpq = sq;
                disp_lock_exit_high(sqlp);
                thread_unlock(tp);
        } else {
                disp_lock_exit(sqlp);
        }
}

/*
 * try to acquire the semaphore. if the semaphore is greater than
 * zero, then the semaphore is granted and returns 1. otherwise
 * return 0.
 */
int
sema_tryp(ksema_t *sp)
{
        sema_impl_t     *s;
        sleepq_head_t   *sqh;

        int     gotit = 0;

        /* no-op during panic */
        if (panicstr)
                return (1);

        s = (sema_impl_t *)sp;
        sqh = SQHASH(s);
        disp_lock_enter(&sqh->sq_lock);
        if (s->s_count > 0) {
                s->s_count--;
                gotit = 1;
        }
        disp_lock_exit(&sqh->sq_lock);
        return (gotit);
}

int
sema_held(ksema_t *sp)
{
        sema_impl_t     *s;

        /* no-op during panic */
        if (panicstr)
                return (1);

        s = (sema_impl_t *)sp;
        return (s->s_count <= 0);
}