/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 1982, 1986, 1990, 1991, 1993
 *      The Regents of the University of California.  All rights reserved.
 * (c) UNIX System Laboratories, Inc.
 * All or some portions of this file are derived from material licensed
 * to the University of California by American Telephone and Telegraph
 * Co. or Unix System Laboratories, Inc. and are reproduced herein with
 * the permission of UNIX System Laboratories, Inc.
 *
 * 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. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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.
 */

#include <sys/cdefs.h>
#include "opt_ktrace.h"
#include "opt_sched.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/blockcount.h>
#include <sys/condvar.h>
#include <sys/kdb.h>
#include <sys/kernel.h>
#include <sys/ktr.h>
#include <sys/ktrace.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/resourcevar.h>
#include <sys/sched.h>
#include <sys/sdt.h>
#include <sys/signalvar.h>
#include <sys/sleepqueue.h>
#include <sys/smp.h>
#include <sys/sx.h>
#include <sys/sysctl.h>
#include <sys/sysproto.h>
#include <sys/vmmeter.h>
#ifdef KTRACE
#include <sys/uio.h>
#endif
#ifdef EPOCH_TRACE
#include <sys/epoch.h>
#endif

#include <machine/cpu.h>

static void synch_setup(void *dummy);
SYSINIT(synch_setup, SI_SUB_KICK_SCHEDULER, SI_ORDER_FIRST, synch_setup,
    NULL);

int     hogticks;
static const char pause_wchan[MAXCPU];

static struct callout loadav_callout;

struct loadavg averunnable =
        { {0, 0, 0}, FSCALE };  /* load average, of runnable procs */
/*
 * Constants for averages over 1, 5, and 15 minutes
 * when sampling at 5 second intervals.
 */
static uint64_t cexp[3] = {
        0.9200444146293232 * FSCALE,    /* exp(-1/12) */
        0.9834714538216174 * FSCALE,    /* exp(-1/60) */
        0.9944598480048967 * FSCALE,    /* exp(-1/180) */
};

/* kernel uses `FSCALE', userland (SHOULD) use kern.fscale */
SYSCTL_INT(_kern, OID_AUTO, fscale, CTLFLAG_RD, SYSCTL_NULL_INT_PTR, FSCALE,
    "Fixed-point scale factor used for calculating load average values");

static void     loadav(void *arg);

SDT_PROVIDER_DECLARE(sched);
SDT_PROBE_DEFINE(sched, , , preempt);

static void
sleepinit(void *unused)
{

        hogticks = (hz / 10) * 2;       /* Default only. */
        init_sleepqueues();
}

/*
 * vmem tries to lock the sleepq mutexes when free'ing kva, so make sure
 * it is available.
 */
SYSINIT(sleepinit, SI_SUB_KMEM, SI_ORDER_ANY, sleepinit, NULL);

/*
 * General sleep call.  Suspends the current thread until a wakeup is
 * performed on the specified identifier.  The thread will then be made
 * runnable with the specified priority.  Sleeps at most sbt units of time
 * (0 means no timeout).  If pri includes the PCATCH flag, let signals
 * interrupt the sleep, otherwise ignore them while sleeping.  Returns 0 if
 * awakened, EWOULDBLOCK if the timeout expires.  If PCATCH is set and a
 * signal becomes pending, ERESTART is returned if the current system
 * call should be restarted if possible, and EINTR is returned if the system
 * call should be interrupted by the signal (return EINTR).
 *
 * The lock argument is unlocked before the caller is suspended, and
 * re-locked before _sleep() returns.  If priority includes the PDROP
 * flag the lock is not re-locked before returning.
 */
int
_sleep(const void *ident, struct lock_object *lock, int priority,
    const char *wmesg, sbintime_t sbt, sbintime_t pr, int flags)
{
        struct thread *td __ktrace_used;
        struct lock_class *class;
        struct timespec sw_out_tv __ktrace_used;
        uintptr_t lock_state;
        int catch, pri, rval, sleepq_flags;
        WITNESS_SAVE_DECL(lock_witness);

        TSENTER();
        td = curthread;
#ifdef KTRACE
        if (KTRPOINT(td, KTR_CSW))
                nanotime(&sw_out_tv);
#endif
        WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, lock,
            "Sleeping on \"%s\"", wmesg);
        KASSERT(sbt != 0 || mtx_owned(&Giant) || lock != NULL ||
            (priority & PNOLOCK) != 0,
            ("sleeping without a lock"));
        KASSERT(ident != NULL, ("_sleep: NULL ident"));
        KASSERT(TD_IS_RUNNING(td), ("_sleep: curthread not running"));
        if (priority & PDROP)
                KASSERT(lock != NULL && lock != &Giant.lock_object,
                    ("PDROP requires a non-Giant lock"));
        if (lock != NULL)
                class = LOCK_CLASS(lock);
        else
                class = NULL;

        if (SCHEDULER_STOPPED()) {
                if (lock != NULL && priority & PDROP)
                        class->lc_unlock(lock);
                return (0);
        }
        catch = priority & PCATCH;
        pri = priority & PRIMASK;

        KASSERT(!TD_ON_SLEEPQ(td), ("recursive sleep"));

        if ((uintptr_t)ident >= (uintptr_t)&pause_wchan[0] &&
            (uintptr_t)ident <= (uintptr_t)&pause_wchan[MAXCPU - 1])
                sleepq_flags = SLEEPQ_PAUSE;
        else
                sleepq_flags = SLEEPQ_SLEEP;
        if (catch)
                sleepq_flags |= SLEEPQ_INTERRUPTIBLE;

        sleepq_lock(ident);
        CTR5(KTR_PROC, "sleep: thread %ld (pid %ld, %s) on %s (%p)",
            td->td_tid, td->td_proc->p_pid, td->td_name, wmesg, ident);

        if (lock == &Giant.lock_object)
                mtx_assert(&Giant, MA_OWNED);
        DROP_GIANT();
        if (lock != NULL && lock != &Giant.lock_object &&
            !(class->lc_flags & LC_SLEEPABLE)) {
                KASSERT(!(class->lc_flags & LC_SPINLOCK),
                    ("spin locks can only use msleep_spin"));
                WITNESS_SAVE(lock, lock_witness);
                lock_state = class->lc_unlock(lock);
        } else
                /* GCC needs to follow the Yellow Brick Road */
                lock_state = -1;

        /*
         * We put ourselves on the sleep queue and start our timeout
         * before calling thread_suspend_check, as we could stop there,
         * and a wakeup or a SIGCONT (or both) could occur while we were
         * stopped without resuming us.  Thus, we must be ready for sleep
         * when cursig() is called.  If the wakeup happens while we're
         * stopped, then td will no longer be on a sleep queue upon
         * return from cursig().
         */
        sleepq_add(ident, lock, wmesg, sleepq_flags, 0);
        if (sbt != 0)
                sleepq_set_timeout_sbt(ident, sbt, pr, flags);
        if (lock != NULL && class->lc_flags & LC_SLEEPABLE) {
                sleepq_release(ident);
                WITNESS_SAVE(lock, lock_witness);
                lock_state = class->lc_unlock(lock);
                sleepq_lock(ident);
        }
        if (sbt != 0 && catch)
                rval = sleepq_timedwait_sig(ident, pri);
        else if (sbt != 0)
                rval = sleepq_timedwait(ident, pri);
        else if (catch)
                rval = sleepq_wait_sig(ident, pri);
        else {
                sleepq_wait(ident, pri);
                rval = 0;
        }
#ifdef KTRACE
        if (KTRPOINT(td, KTR_CSW)) {
                ktrcsw_out(&sw_out_tv, wmesg);
                ktrcsw(0, 0, wmesg);
        }
#endif
        PICKUP_GIANT();
        if (lock != NULL && lock != &Giant.lock_object && !(priority & PDROP)) {
                class->lc_lock(lock, lock_state);
                WITNESS_RESTORE(lock, lock_witness);
        }
        TSEXIT();
        return (rval);
}

int
msleep_spin_sbt(const void *ident, struct mtx *mtx, const char *wmesg,
    sbintime_t sbt, sbintime_t pr, int flags)
{
        struct thread *td __ktrace_used;
        struct timespec sw_out_tv __ktrace_used;
        int rval;
        WITNESS_SAVE_DECL(mtx);

        td = curthread;
        KASSERT(mtx != NULL, ("sleeping without a mutex"));
        KASSERT(ident != NULL, ("msleep_spin_sbt: NULL ident"));
        KASSERT(TD_IS_RUNNING(td), ("msleep_spin_sbt: curthread not running"));

        if (SCHEDULER_STOPPED())
                return (0);

        sleepq_lock(ident);
        CTR5(KTR_PROC, "msleep_spin: thread %ld (pid %ld, %s) on %s (%p)",
            td->td_tid, td->td_proc->p_pid, td->td_name, wmesg, ident);

        DROP_GIANT();
        mtx_assert(mtx, MA_OWNED | MA_NOTRECURSED);
        WITNESS_SAVE(&mtx->lock_object, mtx);
        mtx_unlock_spin(mtx);

        /*
         * We put ourselves on the sleep queue and start our timeout.
         */
        sleepq_add(ident, &mtx->lock_object, wmesg, SLEEPQ_SLEEP, 0);
        if (sbt != 0)
                sleepq_set_timeout_sbt(ident, sbt, pr, flags);

#ifdef KTRACE
        if (KTRPOINT(td, KTR_CSW))
                nanotime(&sw_out_tv);
#endif
#ifdef WITNESS
        sleepq_release(ident);
        WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, "Sleeping on \"%s\"",
            wmesg);
        sleepq_lock(ident);
#endif
        if (sbt != 0)
                rval = sleepq_timedwait(ident, 0);
        else {
                sleepq_wait(ident, 0);
                rval = 0;
        }
#ifdef KTRACE
        if (KTRPOINT(td, KTR_CSW)) {
                ktrcsw_out(&sw_out_tv, wmesg);
                ktrcsw(0, 0, wmesg);
        }
#endif
        PICKUP_GIANT();
        mtx_lock_spin(mtx);
        WITNESS_RESTORE(&mtx->lock_object, mtx);
        return (rval);
}

/*
 * pause_sbt() delays the calling thread by the given signed binary
 * time. During cold bootup, pause_sbt() uses the DELAY() function
 * instead of the _sleep() function to do the waiting. The "sbt"
 * argument must be greater than or equal to zero. A "sbt" value of
 * zero is equivalent to a "sbt" value of one tick.
 */
int
pause_sbt(const char *wmesg, sbintime_t sbt, sbintime_t pr, int flags)
{
        KASSERT(sbt >= 0, ("pause_sbt: timeout must be >= 0"));

        /* silently convert invalid timeouts */
        if (sbt == 0)
                sbt = tick_sbt;

        if ((cold && curthread == &thread0) || kdb_active ||
            SCHEDULER_STOPPED()) {
                /*
                 * We delay one second at a time to avoid overflowing the
                 * system specific DELAY() function(s):
                 */
                while (sbt >= SBT_1S) {
                        DELAY(1000000);
                        sbt -= SBT_1S;
                }
                /* Do the delay remainder, if any */
                sbt = howmany(sbt, SBT_1US);
                if (sbt > 0)
                        DELAY(sbt);
                return (EWOULDBLOCK);
        }
        return (_sleep(&pause_wchan[curcpu], NULL,
            (flags & C_CATCH) ? PCATCH : 0, wmesg, sbt, pr, flags));
}

/*
 * Make all threads sleeping on the specified identifier runnable.
 */
void
wakeup(const void *ident)
{
        sleepq_lock(ident);
        sleepq_broadcast(ident, SLEEPQ_SLEEP, 0, 0);
        sleepq_release(ident);
}

/*
 * Make a thread sleeping on the specified identifier runnable.
 * May wake more than one thread if a target thread is currently
 * swapped out.
 */
void
wakeup_one(const void *ident)
{
        sleepq_lock(ident);
        sleepq_signal(ident, SLEEPQ_SLEEP | SLEEPQ_DROP, 0, 0);
}

void
wakeup_any(const void *ident)
{
        sleepq_lock(ident);
        sleepq_signal(ident, SLEEPQ_SLEEP | SLEEPQ_UNFAIR | SLEEPQ_DROP, 0, 0);
}

/*
 * Signal sleeping waiters after the counter has reached zero.
 */
void
_blockcount_wakeup(blockcount_t *bc, u_int old)
{

        KASSERT(_BLOCKCOUNT_WAITERS(old),
            ("%s: no waiters on %p", __func__, bc));

        if (atomic_cmpset_int(&bc->__count, _BLOCKCOUNT_WAITERS_FLAG, 0))
                wakeup(bc);
}

/*
 * Wait for a wakeup or a signal.  This does not guarantee that the count is
 * still zero on return.  Callers wanting a precise answer should use
 * blockcount_wait() with an interlock.
 *
 * If there is no work to wait for, return 0.  If the sleep was interrupted by a
 * signal, return EINTR or ERESTART, and return EAGAIN otherwise.
 */
int
_blockcount_sleep(blockcount_t *bc, struct lock_object *lock, const char *wmesg,
    int prio)
{
        void *wchan;
        uintptr_t lock_state;
        u_int old;
        int ret;
        bool catch, drop;

        KASSERT(lock != &Giant.lock_object,
            ("%s: cannot use Giant as the interlock", __func__));

        catch = (prio & PCATCH) != 0;
        drop = (prio & PDROP) != 0;
        prio &= PRIMASK;

        /*
         * Synchronize with the fence in blockcount_release().  If we end up
         * waiting, the sleepqueue lock acquisition will provide the required
         * side effects.
         *
         * If there is no work to wait for, but waiters are present, try to put
         * ourselves to sleep to avoid jumping ahead.
         */
        if (atomic_load_acq_int(&bc->__count) == 0) {
                if (lock != NULL && drop)
                        LOCK_CLASS(lock)->lc_unlock(lock);
                return (0);
        }
        lock_state = 0;
        wchan = bc;
        sleepq_lock(wchan);
        DROP_GIANT();
        if (lock != NULL)
                lock_state = LOCK_CLASS(lock)->lc_unlock(lock);
        old = blockcount_read(bc);
        ret = 0;
        do {
                if (_BLOCKCOUNT_COUNT(old) == 0) {
                        sleepq_release(wchan);
                        goto out;
                }
                if (_BLOCKCOUNT_WAITERS(old))
                        break;
        } while (!atomic_fcmpset_int(&bc->__count, &old,
            old | _BLOCKCOUNT_WAITERS_FLAG));
        sleepq_add(wchan, NULL, wmesg, catch ? SLEEPQ_INTERRUPTIBLE : 0, 0);
        if (catch)
                ret = sleepq_wait_sig(wchan, prio);
        else
                sleepq_wait(wchan, prio);
        if (ret == 0)
                ret = EAGAIN;

out:
        PICKUP_GIANT();
        if (lock != NULL && !drop)
                LOCK_CLASS(lock)->lc_lock(lock, lock_state);

        return (ret);
}

static void
kdb_switch(void)
{
        thread_unlock(curthread);
        kdb_backtrace();
        kdb_reenter();
        panic("%s: did not reenter debugger", __func__);
}

/*
 * mi_switch(9): The machine-independent parts of context switching.
 *
 * The thread lock is required on entry and is no longer held on return.
 */
void
mi_switch(int flags)
{
        uint64_t runtime, new_switchtime;
        struct thread *td;

        td = curthread;                 /* XXX */
        THREAD_LOCK_ASSERT(td, MA_OWNED | MA_NOTRECURSED);
        KASSERT(!TD_ON_RUNQ(td), ("mi_switch: called by old code"));
#ifdef INVARIANTS
        if (!TD_ON_LOCK(td) && !TD_IS_RUNNING(td))
                mtx_assert(&Giant, MA_NOTOWNED);
#endif
        /* thread_lock() performs spinlock_enter(). */
        KASSERT(td->td_critnest == 1 || KERNEL_PANICKED(),
            ("mi_switch: switch in a critical section"));
        KASSERT((flags & (SW_INVOL | SW_VOL)) != 0,
            ("mi_switch: switch must be voluntary or involuntary"));
        KASSERT((flags & SW_TYPE_MASK) != 0,
            ("mi_switch: a switch reason (type) must be specified"));
        KASSERT((flags & SW_TYPE_MASK) < SWT_COUNT,
            ("mi_switch: invalid switch reason %d", (flags & SW_TYPE_MASK)));

        /*
         * Don't perform context switches from the debugger.
         */
        if (kdb_active)
                kdb_switch();
        if (SCHEDULER_STOPPED())
                return;
        if (flags & SW_VOL) {
                td->td_ru.ru_nvcsw++;
                td->td_swvoltick = ticks;
        } else {
                td->td_ru.ru_nivcsw++;
                td->td_swinvoltick = ticks;
        }
#ifdef SCHED_STATS
        SCHED_STAT_INC(sched_switch_stats[flags & SW_TYPE_MASK]);
#endif
        /*
         * Compute the amount of time during which the current
         * thread was running, and add that to its total so far.
         */
        new_switchtime = cpu_ticks();
        runtime = new_switchtime - PCPU_GET(switchtime);
        td->td_runtime += runtime;
        td->td_incruntime += runtime;
        PCPU_SET(switchtime, new_switchtime);
        td->td_generation++;    /* bump preempt-detect counter */
        VM_CNT_INC(v_swtch);
        PCPU_SET(switchticks, ticks);
        CTR4(KTR_PROC, "mi_switch: old thread %ld (td_sched %p, pid %ld, %s)",
            td->td_tid, td_get_sched(td), td->td_proc->p_pid, td->td_name);
#ifdef KDTRACE_HOOKS
        if (SDT_PROBES_ENABLED() &&
            ((flags & SW_PREEMPT) != 0 || ((flags & SW_INVOL) != 0 &&
            (flags & SW_TYPE_MASK) == SWT_NEEDRESCHED)))
                SDT_PROBE0(sched, , , preempt);
#endif
        sched_switch(td, flags);
        CTR4(KTR_PROC, "mi_switch: new thread %ld (td_sched %p, pid %ld, %s)",
            td->td_tid, td_get_sched(td), td->td_proc->p_pid, td->td_name);

        /* 
         * If the last thread was exiting, finish cleaning it up.
         */
        if ((td = PCPU_GET(deadthread))) {
                PCPU_SET(deadthread, NULL);
                thread_stash(td);
        }
        spinlock_exit();
}

/*
 * Change thread state to be runnable, placing it on the run queue.
 *
 * Requires the thread lock on entry, drops on exit.
 */
void
setrunnable(struct thread *td, int srqflags)
{
        THREAD_LOCK_ASSERT(td, MA_OWNED);
        KASSERT(td->td_proc->p_state != PRS_ZOMBIE,
            ("setrunnable: pid %d is a zombie", td->td_proc->p_pid));

        switch (TD_GET_STATE(td)) {
        case TDS_RUNNING:
        case TDS_RUNQ:
        case TDS_INHIBITED:
                if ((srqflags & (SRQ_HOLD | SRQ_HOLDTD)) == 0)
                        thread_unlock(td);
                break;
        case TDS_CAN_RUN:
                KASSERT((td->td_flags & TDF_INMEM) != 0,
                    ("setrunnable: td %p not in mem, flags 0x%X inhibit 0x%X",
                    td, td->td_flags, td->td_inhibitors));
                /* unlocks thread lock according to flags */
                sched_wakeup(td, srqflags);
                break;
        default:
                panic("setrunnable: state 0x%x", TD_GET_STATE(td));
        }
}

/*
 * Compute a tenex style load average of a quantity on
 * 1, 5 and 15 minute intervals.
 */
static void
loadav(void *arg)
{
        int i;
        uint64_t nrun;
        struct loadavg *avg;

        nrun = (uint64_t)sched_load();
        avg = &averunnable;

        for (i = 0; i < 3; i++)
                avg->ldavg[i] = (cexp[i] * (uint64_t)avg->ldavg[i] +
                    nrun * FSCALE * (FSCALE - cexp[i])) >> FSHIFT;

        /*
         * Schedule the next update to occur after 5 seconds, but add a
         * random variation to avoid synchronisation with processes that
         * run at regular intervals.
         */
        callout_reset_sbt(&loadav_callout,
            SBT_1US * (4000000 + (int)(random() % 2000001)), SBT_1US,
            loadav, NULL, C_DIRECT_EXEC | C_PREL(32));
}

void
ast_scheduler(struct thread *td, int tda __unused)
{
#ifdef KTRACE
        if (KTRPOINT(td, KTR_CSW))
                ktrcsw(1, 1, __func__);
#endif
        thread_lock(td);
        sched_prio(td, td->td_user_pri);
        mi_switch(SW_INVOL | SWT_NEEDRESCHED);
#ifdef KTRACE
        if (KTRPOINT(td, KTR_CSW))
                ktrcsw(0, 1, __func__);
#endif
}

static void
synch_setup(void *dummy __unused)
{
        callout_init(&loadav_callout, 1);
        ast_register(TDA_SCHED, ASTR_ASTF_REQUIRED, 0, ast_scheduler);

        /* Kick off timeout driven events by calling first time. */
        loadav(NULL);
}

bool
should_yield(void)
{

        return ((u_int)ticks - (u_int)curthread->td_swvoltick >= hogticks);
}

void
maybe_yield(void)
{

        if (should_yield())
                kern_yield(PRI_USER);
}

void
kern_yield(int prio)
{
        struct thread *td;

        td = curthread;
        DROP_GIANT();
        thread_lock(td);
        if (prio == PRI_USER)
                prio = td->td_user_pri;
        if (prio >= 0)
                sched_prio(td, prio);
        mi_switch(SW_VOL | SWT_RELINQUISH);
        PICKUP_GIANT();
}

/*
 * General purpose yield system call.
 */
int
sys_yield(struct thread *td, struct yield_args *uap)
{

        thread_lock(td);
        if (PRI_BASE(td->td_pri_class) == PRI_TIMESHARE)
                sched_prio(td, PRI_MAX_TIMESHARE);
        mi_switch(SW_VOL | SWT_RELINQUISH);
        td->td_retval[0] = 0;
        return (0);
}

int
sys_sched_getcpu(struct thread *td, struct sched_getcpu_args *uap)
{
        td->td_retval[0] = td->td_oncpu;
        return (0);
}