/*
 * 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 2009 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 * Copyright (c) 2016 by Delphix. All rights reserved.
 */

/*      Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T */

#include <sys/param.h>
#include <sys/types.h>
#include <sys/sysmacros.h>
#include <sys/systm.h>
#include <sys/prsystm.h>
#include <sys/cred.h>
#include <sys/errno.h>
#include <sys/proc.h>
#include <sys/signal.h>
#include <sys/kmem.h>
#include <sys/unistd.h>
#include <sys/cmn_err.h>
#include <sys/schedctl.h>
#include <sys/debug.h>
#include <sys/contract/process_impl.h>

kthread_t *
idtot(proc_t *p, id_t lwpid)
{
        lwpdir_t *ldp;

        if ((ldp = lwp_hash_lookup(p, lwpid)) != NULL)
                return (ldp->ld_entry->le_thread);
        return (NULL);
}

/*
 * Same as idtot(), but acquire and return
 * the tid hash table entry lock on success.
 * This allows lwp_unpark() to do its job without acquiring
 * p->p_lock (and thereby causing congestion problems when
 * the application calls lwp_unpark() too often).
 */
static kthread_t *
idtot_and_lock(proc_t *p, id_t lwpid, kmutex_t **mpp)
{
        lwpdir_t *ldp;
        kthread_t *t;

        if ((ldp = lwp_hash_lookup_and_lock(p, lwpid, mpp)) != NULL) {
                if ((t = ldp->ld_entry->le_thread) == NULL)
                        mutex_exit(*mpp);
                return (t);
        }
        return (NULL);
}

/*
 * Stop an lwp of the current process
 */
int
syslwp_suspend(id_t lwpid)
{
        kthread_t *t;
        int error;
        proc_t *p = ttoproc(curthread);

        mutex_enter(&p->p_lock);
        if ((t = idtot(p, lwpid)) == NULL)
                error = ESRCH;
        else
                error = lwp_suspend(t);
        mutex_exit(&p->p_lock);
        if (error)
                return (set_errno(error));
        return (0);
}

int
syslwp_continue(id_t lwpid)
{
        kthread_t *t;
        proc_t *p = ttoproc(curthread);

        mutex_enter(&p->p_lock);
        if ((t = idtot(p, lwpid)) == NULL) {
                mutex_exit(&p->p_lock);
                return (set_errno(ESRCH));
        }
        lwp_continue(t);
        mutex_exit(&p->p_lock);
        return (0);
}

int
lwp_kill(id_t lwpid, int sig)
{
        sigqueue_t *sqp;
        kthread_t *t;
        proc_t *p = ttoproc(curthread);

        if (sig < 0 || sig >= NSIG)
                return (set_errno(EINVAL));
        if (sig != 0)
                sqp = kmem_zalloc(sizeof (sigqueue_t), KM_SLEEP);
        mutex_enter(&p->p_lock);
        if ((t = idtot(p, lwpid)) == NULL) {
                mutex_exit(&p->p_lock);
                if (sig != 0)
                        kmem_free(sqp, sizeof (sigqueue_t));
                return (set_errno(ESRCH));
        }
        if (sig == 0) {
                mutex_exit(&p->p_lock);
                return (0);
        }
        sqp->sq_info.si_signo = sig;
        sqp->sq_info.si_code = SI_LWP;
        sqp->sq_info.si_pid = p->p_pid;
        sqp->sq_info.si_ctid = PRCTID(p);
        sqp->sq_info.si_zoneid = getzoneid();
        sqp->sq_info.si_uid = crgetruid(CRED());
        sigaddqa(p, t, sqp);
        mutex_exit(&p->p_lock);
        return (0);
}

/*
 * This is the specification of lwp_wait() from the _lwp_wait(2) manual page:
 *
 * The lwp_wait() function blocks the current lwp until the lwp specified
 * by 'lwpid' terminates.  If the specified lwp terminated prior to the call
 * to lwp_wait(), then lwp_wait() returns immediately.  If 'lwpid' is zero,
 * then lwp_wait() waits for any undetached lwp in the current process.
 * If 'lwpid' is not zero, then it must specify an undetached lwp in the
 * current process.  If 'departed' is not NULL, then it points to a location
 * where the id of the exited lwp is stored.
 *
 * When an lwp exits and there are one or more lwps in the process waiting
 * for this specific lwp to exit, then one of the waiting lwps is unblocked
 * and it returns from lwp_wait() successfully.  Any other lwps waiting for
 * this same lwp to exit are also unblocked, however, they return from
 * lwp_wait() with the error ESRCH.  If there are no lwps in the process
 * waiting for this specific lwp to exit but there are one or more lwps
 * waiting for any lwp to exit, then one of the waiting lwps is unblocked
 * and it returns from lwp_wait() successfully.
 *
 * If an lwp is waiting for any lwp to exit, it blocks until an undetached
 * lwp for which no other lwp is waiting terminates, at which time it returns
 * successfully, or until all other lwps in the process are either daemon
 * lwps or lwps waiting in lwp_wait(), in which case it returns EDEADLK.
 */
int
lwp_wait(id_t lwpid, id_t *departed)
{
        proc_t *p = ttoproc(curthread);
        int error = 0;
        int daemon = (curthread->t_proc_flag & TP_DAEMON)? 1 : 0;
        lwpent_t *target_lep;
        lwpdir_t *ldp;
        lwpent_t *lep;

        /*
         * lwp_wait() is not supported for the /proc agent lwp.
         */
        if (curthread == p->p_agenttp)
                return (set_errno(ENOTSUP));

        mutex_enter(&p->p_lock);
        prbarrier(p);

        curthread->t_waitfor = lwpid;
        p->p_lwpwait++;
        p->p_lwpdwait += daemon;
        target_lep = NULL;

        if (lwpid != 0) {
                if ((ldp = lwp_hash_lookup(p, lwpid)) == NULL)
                        target_lep = NULL;
                else {
                        target_lep = ldp->ld_entry;
                        target_lep->le_waiters++;
                        target_lep->le_dwaiters += daemon;
                }
        }

        while (error == 0) {
                kthread_t *t;
                id_t tid;
                int i;

                if (lwpid != 0) {
                        /*
                         * Look for a specific zombie lwp.
                         */
                        if (target_lep == NULL)
                                error = ESRCH;
                        else if ((t = target_lep->le_thread) != NULL) {
                                if (!(t->t_proc_flag & TP_TWAIT))
                                        error = EINVAL;
                        } else {
                                /*
                                 * We found the zombie we are waiting for.
                                 */
                                ASSERT(p->p_zombcnt > 0);
                                p->p_zombcnt--;
                                p->p_lwpwait--;
                                p->p_lwpdwait -= daemon;
                                curthread->t_waitfor = -1;
                                lwp_hash_out(p, lwpid);
                                mutex_exit(&p->p_lock);
                                if (departed != NULL &&
                                    copyout(&lwpid, departed, sizeof (id_t)))
                                        return (set_errno(EFAULT));
                                return (0);
                        }
                } else {
                        /*
                         * Look for any zombie lwp.
                         */
                        int some_non_daemon_will_return = 0;

                        /* for each entry in the lwp directory... */
                        ldp = p->p_lwpdir;
                        for (i = 0; i < p->p_lwpdir_sz; i++, ldp++) {

                                if ((lep = ldp->ld_entry) == NULL ||
                                    lep->le_thread != NULL)
                                        continue;

                                /*
                                 * We found a zombie lwp.  If there is some
                                 * other thread waiting specifically for the
                                 * zombie we just found, then defer to the other
                                 * waiting thread and continue searching for
                                 * another zombie.  Also check to see if there
                                 * is some non-daemon thread sleeping here in
                                 * lwp_wait() that will succeed and return when
                                 * we drop p->p_lock.  This is tested below.
                                 */
                                tid = lep->le_lwpid;
                                if (lep->le_waiters != 0) {
                                        if (lep->le_waiters - lep->le_dwaiters)
                                                some_non_daemon_will_return = 1;
                                        continue;
                                }

                                /*
                                 * We found a zombie that no one else
                                 * is specifically waiting for.
                                 */
                                ASSERT(p->p_zombcnt > 0);
                                p->p_zombcnt--;
                                p->p_lwpwait--;
                                p->p_lwpdwait -= daemon;
                                curthread->t_waitfor = -1;
                                lwp_hash_out(p, tid);
                                mutex_exit(&p->p_lock);
                                if (departed != NULL &&
                                    copyout(&tid, departed, sizeof (id_t)))
                                        return (set_errno(EFAULT));
                                return (0);
                        }

                        /*
                         * We are waiting for anyone.  If all non-daemon lwps
                         * are waiting here, and if we determined above that
                         * no non-daemon lwp will return, we have deadlock.
                         */
                        if (!some_non_daemon_will_return &&
                            p->p_lwpcnt == p->p_lwpdaemon +
                            (p->p_lwpwait - p->p_lwpdwait))
                                error = EDEADLK;
                }

                if (error == 0 && lwpid != 0) {
                        /*
                         * We are waiting for a specific non-zombie lwp.
                         * Fail if there is a deadlock loop.
                         */
                        for (;;) {
                                if (t == curthread) {
                                        error = EDEADLK;
                                        break;
                                }
                                /* who are they waiting for? */
                                if ((tid = t->t_waitfor) == -1)
                                        break;
                                if (tid == 0) {
                                        /*
                                         * The lwp we are waiting for is
                                         * waiting for anyone (transitively).
                                         * If there are no zombies right now
                                         * and if we would have deadlock due
                                         * to all non-daemon lwps waiting here,
                                         * wake up the lwp that is waiting for
                                         * anyone so it can return EDEADLK.
                                         */
                                        if (p->p_zombcnt == 0 &&
                                            p->p_lwpcnt == p->p_lwpdaemon +
                                            p->p_lwpwait - p->p_lwpdwait)
                                                cv_broadcast(&p->p_lwpexit);
                                        break;
                                }
                                if ((ldp = lwp_hash_lookup(p, tid)) == NULL ||
                                    (t = ldp->ld_entry->le_thread) == NULL)
                                        break;
                        }
                }

                if (error)
                        break;

                /*
                 * Wait for some lwp to terminate.
                 */
                if (!cv_wait_sig(&p->p_lwpexit, &p->p_lock))
                        error = EINTR;
                prbarrier(p);

                if (lwpid != 0) {
                        if ((ldp = lwp_hash_lookup(p, lwpid)) == NULL)
                                target_lep = NULL;
                        else
                                target_lep = ldp->ld_entry;
                }
        }

        if (lwpid != 0 && target_lep != NULL) {
                target_lep->le_waiters--;
                target_lep->le_dwaiters -= daemon;
        }
        p->p_lwpwait--;
        p->p_lwpdwait -= daemon;
        curthread->t_waitfor = -1;
        mutex_exit(&p->p_lock);
        return (set_errno(error));
}

int
lwp_detach(id_t lwpid)
{
        kthread_t *t;
        proc_t *p = ttoproc(curthread);
        lwpdir_t *ldp;
        int error = 0;

        mutex_enter(&p->p_lock);
        prbarrier(p);
        if ((ldp = lwp_hash_lookup(p, lwpid)) == NULL)
                error = ESRCH;
        else if ((t = ldp->ld_entry->le_thread) != NULL) {
                if (!(t->t_proc_flag & TP_TWAIT))
                        error = EINVAL;
                else {
                        t->t_proc_flag &= ~TP_TWAIT;
                        cv_broadcast(&p->p_lwpexit);
                }
        } else {
                ASSERT(p->p_zombcnt > 0);
                p->p_zombcnt--;
                lwp_hash_out(p, lwpid);
        }
        mutex_exit(&p->p_lock);

        if (error)
                return (set_errno(error));
        return (0);
}

/*
 * Unpark the specified lwp.
 */
static int
lwp_unpark(id_t lwpid)
{
        proc_t *p = ttoproc(curthread);
        kthread_t *t;
        kmutex_t *mp;
        int error = 0;

        if ((t = idtot_and_lock(p, lwpid, &mp)) == NULL) {
                error = ESRCH;
        } else {
                mutex_enter(&t->t_delay_lock);
                t->t_unpark = 1;
                cv_signal(&t->t_delay_cv);
                mutex_exit(&t->t_delay_lock);
                mutex_exit(mp);
        }
        return (error);
}

/*
 * Cancel a previous unpark for the specified lwp.
 *
 * This interface exists ONLY to support older versions of libthread, which
 * called lwp_unpark(self) to force calls to lwp_park(self) to return
 * immediately.  These older libthreads required a mechanism to cancel the
 * lwp_unpark(self).
 *
 * libc does not call this interface.  Instead, the sc_park flag in the
 * schedctl page is cleared to force calls to lwp_park() to return
 * immediately.
 */
static int
lwp_unpark_cancel(id_t lwpid)
{
        proc_t *p = ttoproc(curthread);
        kthread_t *t;
        kmutex_t *mp;
        int error = 0;

        if ((t = idtot_and_lock(p, lwpid, &mp)) == NULL) {
                error = ESRCH;
        } else {
                mutex_enter(&t->t_delay_lock);
                t->t_unpark = 0;
                mutex_exit(&t->t_delay_lock);
                mutex_exit(mp);
        }
        return (error);
}

/*
 * Sleep until we are set running by lwp_unpark() or until we are
 * interrupted by a signal or until we exhaust our timeout.
 * timeoutp is an in/out parameter.  On entry, it contains the relative
 * time until timeout.  On exit, we copyout the residual time left to it.
 */
static int
lwp_park(timespec_t *timeoutp, id_t lwpid)
{
        timespec_t rqtime;
        timespec_t rmtime;
        timespec_t now;
        timespec_t *rqtp = NULL;
        kthread_t *t = curthread;
        int timecheck = 0;
        int error = 0;
        model_t datamodel = ttoproc(t)->p_model;

        if (lwpid != 0)         /* unpark the other lwp, if any */
                (void) lwp_unpark(lwpid);

        if (timeoutp) {
                timecheck = timechanged;
                gethrestime(&now);
                if (datamodel == DATAMODEL_NATIVE) {
                        if (copyin(timeoutp, &rqtime, sizeof (timespec_t))) {
                                error = EFAULT;
                                goto out;
                        }
                } else {
                        timespec32_t timeout32;

                        if (copyin(timeoutp, &timeout32, sizeof (timeout32))) {
                                error = EFAULT;
                                goto out;
                        }
                        TIMESPEC32_TO_TIMESPEC(&rqtime, &timeout32)
                }

                if (itimerspecfix(&rqtime)) {
                        error = EINVAL;
                        goto out;
                }
                /*
                 * Convert the timespec value into absolute time.
                 */
                timespecadd(&rqtime, &now);
                rqtp = &rqtime;
        }

        (void) new_mstate(t, LMS_USER_LOCK);

        mutex_enter(&t->t_delay_lock);
        if (!schedctl_is_park())
                error = EINTR;
        while (error == 0 && t->t_unpark == 0) {
                switch (cv_waituntil_sig(&t->t_delay_cv,
                    &t->t_delay_lock, rqtp, timecheck)) {
                case 0:
                        error = EINTR;
                        break;
                case -1:
                        error = ETIME;
                        break;
                }
        }
        t->t_unpark = 0;
        mutex_exit(&t->t_delay_lock);

        if (timeoutp != NULL) {
                rmtime.tv_sec = rmtime.tv_nsec = 0;
                if (error != ETIME) {
                        gethrestime(&now);
                        if ((now.tv_sec < rqtime.tv_sec) ||
                            ((now.tv_sec == rqtime.tv_sec) &&
                            (now.tv_nsec < rqtime.tv_nsec))) {
                                rmtime = rqtime;
                                timespecsub(&rmtime, &now);
                        }
                }
                if (datamodel == DATAMODEL_NATIVE) {
                        if (copyout(&rmtime, timeoutp, sizeof (rmtime)))
                                error = EFAULT;
                } else {
                        timespec32_t rmtime32;

                        TIMESPEC_TO_TIMESPEC32(&rmtime32, &rmtime);
                        if (copyout(&rmtime32, timeoutp, sizeof (rmtime32)))
                                error = EFAULT;
                }
        }
out:
        schedctl_unpark();
        if (t->t_mstate == LMS_USER_LOCK)
                (void) new_mstate(t, LMS_SYSTEM);
        return (error);
}

#define MAXLWPIDS       1024

/*
 * Unpark all of the specified lwps.
 * Do it in chunks of MAXLWPIDS to avoid allocating too much memory.
 */
static int
lwp_unpark_all(id_t *lwpidp, int nids)
{
        proc_t *p = ttoproc(curthread);
        kthread_t *t;
        kmutex_t *mp;
        int error = 0;
        id_t *lwpid;
        size_t lwpidsz;
        int n;
        int i;

        if (nids <= 0)
                return (EINVAL);

        lwpidsz = MIN(nids, MAXLWPIDS) * sizeof (id_t);
        lwpid = kmem_alloc(lwpidsz, KM_SLEEP);
        while (nids > 0) {
                n = MIN(nids, MAXLWPIDS);
                if (copyin(lwpidp, lwpid, n * sizeof (id_t))) {
                        error = EFAULT;
                        break;
                }
                for (i = 0; i < n; i++) {
                        if ((t = idtot_and_lock(p, lwpid[i], &mp)) == NULL) {
                                error = ESRCH;
                        } else {
                                mutex_enter(&t->t_delay_lock);
                                t->t_unpark = 1;
                                cv_signal(&t->t_delay_cv);
                                mutex_exit(&t->t_delay_lock);
                                mutex_exit(mp);
                        }
                }
                lwpidp += n;
                nids -= n;
        }
        kmem_free(lwpid, lwpidsz);
        return (error);
}

/*
 * SYS_lwp_park() system call.
 */
int
syslwp_park(int which, uintptr_t arg1, uintptr_t arg2)
{
        int error;

        switch (which) {
        case 0:
                error = lwp_park((timespec_t *)arg1, (id_t)arg2);
                break;
        case 1:
                error = lwp_unpark((id_t)arg1);
                break;
        case 2:
                error = lwp_unpark_all((id_t *)arg1, (int)arg2);
                break;
        case 3:
                /*
                 * This subcode is not used by libc.  It exists ONLY to
                 * support older versions of libthread which do not use
                 * the sc_park flag in the schedctl page.
                 *
                 * These versions of libthread need to be modifed or emulated
                 * to change calls to syslwp_park(1, tid, 0) to
                 * syslwp_park(3, tid).
                 */
                error = lwp_unpark_cancel((id_t)arg1);
                break;
        case 4:
                /*
                 * This subcode is not used by libc.  It exists ONLY to
                 * support older versions of libthread which do not use
                 * the sc_park flag in the schedctl page.
                 *
                 * These versions of libthread need to be modified or emulated
                 * to change calls to syslwp_park(0, ts, tid) to
                 * syslwp_park(4, ts, tid).
                 */
                schedctl_set_park();
                error = lwp_park((timespec_t *)arg1, (id_t)arg2);
                break;
        default:
                error = EINVAL;
                break;
        }

        if (error)
                return (set_errno(error));
        return (0);
}