/*      $NetBSD: kern_kthread.c,v 1.49 2023/09/23 14:40:42 ad 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 1.49 2023/09/23 14:40:42 ad Exp $");

#include <sys/param.h>
#include <sys/cpu.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/kthread.h>
#include <sys/mutex.h>
#include <sys/sched.h>
#include <sys/kmem.h>
#include <sys/msan.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 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();
}

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