/*      $NetBSD: kern_kthread.c,v 1.51 2026/01/04 01:35:16 riastradh Exp $      */

/*-
 * Copyright (c) 1998, 1999, 2007, 2009, 2019, 2023
 *     The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This code is derived from software contributed to The NetBSD Foundation
 * by Jason R. Thorpe of the Numerical Aerospace Simulation Facility,
 * NASA Ames Research Center, and by Andrew Doran.
 *
 * 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 NETBSD FOUNDATION, INC. 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 FOUNDATION 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>
__KERNEL_RCSID(0, "$NetBSD: kern_kthread.c,v 1.51 2026/01/04 01:35:16 riastradh Exp $");

#include <sys/param.h>
#include <sys/types.h>

#include <sys/cpu.h>
#include <sys/kernel.h>
#include <sys/kmem.h>
#include <sys/kthread.h>
#include <sys/msan.h>
#include <sys/mutex.h>
#include <sys/sched.h>
#include <sys/sdt.h>
#include <sys/systm.h>

#include <uvm/uvm_extern.h>

static kmutex_t         kthread_lock;
static kcondvar_t       kthread_cv;

void
kthread_sysinit(void)
{

        mutex_init(&kthread_lock, MUTEX_DEFAULT, IPL_NONE);
        cv_init(&kthread_cv, "kthrwait");
}

/*
 * kthread_create: create a kernel thread, that is, system-only LWP.
 */
int
kthread_create(pri_t pri, int flag, struct cpu_info *ci,
    void (*func)(void *), void *arg, lwp_t **lp, const char *fmt, ...)
{
        lwp_t *l;
        vaddr_t uaddr;
        int error, lc;
        va_list ap;

        KASSERT((flag & KTHREAD_INTR) == 0 || (flag & KTHREAD_MPSAFE) != 0);

        uaddr = uvm_uarea_system_alloc(
           (flag & (KTHREAD_INTR|KTHREAD_IDLE)) == KTHREAD_IDLE ? ci : NULL);
        if (uaddr == 0) {
                return SET_ERROR(ENOMEM);
        }
        kmsan_orig((void *)uaddr, USPACE, KMSAN_TYPE_POOL, __RET_ADDR);
        if ((flag & KTHREAD_TS) != 0) {
                lc = SCHED_OTHER;
        } else {
                lc = SCHED_RR;
        }

        error = lwp_create(&lwp0, &proc0, uaddr, LWP_DETACHED, NULL,
            0, func, arg, &l, lc, &lwp0.l_sigmask, &lwp0.l_sigstk);
        if (error) {
                uvm_uarea_system_free(uaddr);
                return error;
        }
        if (fmt != NULL) {
                l->l_name = kmem_alloc(MAXCOMLEN, KM_SLEEP);
                va_start(ap, fmt);
                vsnprintf(l->l_name, MAXCOMLEN, fmt, ap);
                va_end(ap);
        }

        /*
         * Set parameters.
         */
        if (pri == PRI_NONE) {
                if ((flag & KTHREAD_TS) != 0) {
                        /* Maximum user priority level. */
                        pri = MAXPRI_USER;
                } else {
                        /* Minimum kernel priority level. */
                        pri = PRI_KTHREAD;
                }
        }
        mutex_enter(proc0.p_lock);
        lwp_lock(l);
        lwp_changepri(l, pri);
        if (ci != NULL) {
                if (ci != l->l_cpu) {
                        lwp_unlock_to(l, ci->ci_schedstate.spc_lwplock);
                        lwp_lock(l);
                        l->l_cpu = ci;
                }
                l->l_pflag |= LP_BOUND;
        }

        if ((flag & KTHREAD_MUSTJOIN) != 0) {
                KASSERT(lp != NULL);
                l->l_pflag |= LP_MUSTJOIN;
        }
        if ((flag & KTHREAD_INTR) != 0) {
                l->l_pflag |= LP_INTR;
        }
        if ((flag & KTHREAD_MPSAFE) == 0) {
                l->l_pflag &= ~LP_MPSAFE;
        }

        /*
         * Set the new LWP running, unless the caller has requested
         * otherwise.
         */
        KASSERT(l->l_stat == LSIDL);
        if ((flag & KTHREAD_IDLE) == 0) {
                setrunnable(l);
                /* LWP now unlocked */
        } else {
                lwp_unlock(l);
        }
        mutex_exit(proc0.p_lock);

        /* All done! */
        if (lp != NULL) {
                *lp = l;
        }
        return 0;
}

/*
 * Cause a kernel thread to exit.  Assumes the exiting thread is the
 * current context.
 */
void
kthread_exit(int ecode)
{
        const char *name;
        lwp_t *l = curlwp;

        /* If the kernel lock is held, we need to drop it now. */
        if ((l->l_pflag & LP_MPSAFE) == 0) {
                KERNEL_UNLOCK_LAST(l);
        }

        /* We can't do much with the exit code, so just report it. */
        if (ecode != 0) {
                if ((name = l->l_name) == NULL)
                        name = "unnamed";
                printf("WARNING: kthread `%s' (%d) exits with status %d\n",
                    name, l->l_lid, ecode);
        }

        /* Barrier for joining. */
        if (l->l_pflag & LP_MUSTJOIN) {
                bool *exitedp;

                mutex_enter(&kthread_lock);
                while ((exitedp = l->l_private) == NULL) {
                        cv_wait(&kthread_cv, &kthread_lock);
                }
                KASSERT(!*exitedp);
                *exitedp = true;
                cv_broadcast(&kthread_cv);
                mutex_exit(&kthread_lock);
        }

        /* And exit.. */
        lwp_exit(l);
        panic("kthread_exit");
}

/*
 * Wait for a kthread to exit, as pthread_join().
 */
int
kthread_join(lwp_t *l)
{
        bool exited = false;

        KASSERT((l->l_flag & LW_SYSTEM) != 0);
        KASSERT((l->l_pflag & LP_MUSTJOIN) != 0);

        /*
         * - Ask the kthread to write to `exited'.
         * - After this, touching l is forbidden -- it may be freed.
         * - Wait until the kthread has written to `exited'.
         */
        mutex_enter(&kthread_lock);
        KASSERT(l->l_private == NULL);
        l->l_private = &exited;
        cv_broadcast(&kthread_cv);
        while (!exited) {
                cv_wait(&kthread_cv, &kthread_lock);
        }
        mutex_exit(&kthread_lock);

        return 0;
}

/*
 * kthread_fpu_enter()
 *
 *      Allow the current lwp, which must be a kthread, to use the FPU.
 *      Return a cookie that must be passed to kthread_fpu_exit when
 *      done.  Must be used only in thread context.  Recursive -- you
 *      can call kthread_fpu_enter several times in a row as long as
 *      you pass the cookies in reverse order to kthread_fpu_exit.
 */
int
kthread_fpu_enter(void)
{
        struct lwp *l = curlwp;
        int s;

        KASSERTMSG(!cpu_intr_p(),
            "%s is not allowed in interrupt context", __func__);
        KASSERTMSG(!cpu_softintr_p(),
            "%s is not allowed in interrupt context", __func__);

        /*
         * Remember whether this thread already had FPU access, and
         * mark this thread as having FPU access.
         */
        lwp_lock(l);
        KASSERTMSG(l->l_flag & LW_SYSTEM,
            "%s is allowed only in kthreads", __func__);
        s = l->l_flag & LW_SYSTEM_FPU;
        l->l_flag |= LW_SYSTEM_FPU;
        lwp_unlock(l);

        /* Take MD steps to enable the FPU if necessary.  */
        if (s == 0)
                kthread_fpu_enter_md();

        return s;
}

/*
 * kthread_fpu_exit(s)
 *
 *      Restore the current lwp's FPU access to what it was before the
 *      matching call to kthread_fpu_enter() that returned s.  Must be
 *      used only in thread context.
 */
void
kthread_fpu_exit(int s)
{
        struct lwp *l = curlwp;

        KASSERT(s == (s & LW_SYSTEM_FPU));
        KASSERTMSG(!cpu_intr_p(),
            "%s is not allowed in interrupt context", __func__);
        KASSERTMSG(!cpu_softintr_p(),
            "%s is not allowed in interrupt context", __func__);

        lwp_lock(l);
        KASSERTMSG(l->l_flag & LW_SYSTEM,
            "%s is allowed only in kthreads", __func__);
        KASSERT(l->l_flag & LW_SYSTEM_FPU);
        l->l_flag ^= s ^ LW_SYSTEM_FPU;
        lwp_unlock(l);

        /* Take MD steps to zero and disable the FPU if necessary.  */
        if (s == 0)
                kthread_fpu_exit_md();
}