FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_kthread.c

     /*
      * Copyright (c) 1999 Peter Wemm <peter@FreeBSD.org>
      * All rights reserved.
      *
      * 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 AUTHOR 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 AUTHOR 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.
     *
     * $FreeBSD: src/sys/kern/kern_kthread.c,v 1.5.2.3 2001/12/25 01:51:14 dillon Exp $
     */
    
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/proc.h>
    #include <sys/kthread.h>
    #include <sys/ptrace.h>
    #include <sys/resourcevar.h>
    #include <sys/signalvar.h>
    #include <sys/unistd.h>
    #include <sys/wait.h>
    
    #include <machine/stdarg.h>
    
    static struct lwkt_token kpsus_token = LWKT_TOKEN_INITIALIZER(kpsus_token);
    
    
    /*
     * Create a new lightweight kernel thread.
     */
    static int
    _kthread_create(void (*func)(void *), void *arg,
        struct thread **tdp, int cpu, const char *fmt, __va_list ap)
    {
        thread_t td;
        int flags = 0;
    
        if (bootverbose)
            atomic_set_int(&flags, TDF_VERBOSE);
    
        td = lwkt_alloc_thread(NULL, LWKT_THREAD_STACK, cpu, flags);
        if (tdp)
            *tdp = td;
        cpu_set_thread_handler(td, kthread_exit, func, arg);
    
        /*
         * Set up arg0 for 'ps' etc
         */
        kvsnprintf(td->td_comm, sizeof(td->td_comm), fmt, ap);
    
        td->td_ucred = crhold(proc0.p_ucred);
    
        /*
         * Schedule the thread to run
         */
        lwkt_schedule(td);
    
        return 0;
    }
    
    /*
     * Creates a lwkt. No CPU preference.
     */
    int
    kthread_create(void (*func)(void *), void *arg,
                   struct thread **tdp, const char *fmt, ...)
    {
            __va_list ap;
            int ret;
    
            __va_start(ap, fmt);
            ret = _kthread_create(func, arg, tdp, -1, fmt, ap);
            __va_end(ap);
    
            return ret;
    }
    
    /*
     * Creates a lwkt and schedule it to run in a specific CPU.
     *
     */
    int
    kthread_create_cpu(void (*func)(void *), void *arg,
                      struct thread **tdp, int cpu, const char *fmt, ...)
   {
           __va_list ap;
           int ret;
   
           __va_start(ap, fmt);
           ret = _kthread_create(func, arg, tdp, cpu, fmt, ap);
           __va_end(ap);
   
           return ret;
   }
   
   #if 0
   /*
    * Same as kthread_create() but you can specify a custom stack size.
    */
   int
   kthread_create_stk(void (*func)(void *), void *arg,
                      struct thread **tdp, int stksize, const char *fmt, ...)
   {
       thread_t td;
       __va_list ap;
   
       td = lwkt_alloc_thread(NULL, stksize, -1, TDF_VERBOSE);
       if (tdp)
           *tdp = td;
       cpu_set_thread_handler(td, kthread_exit, func, arg);
   
       __va_start(ap, fmt);
       kvsnprintf(td->td_comm, sizeof(td->td_comm), fmt, ap);
       __va_end(ap);
   
       lwkt_schedule(td);
       return 0;
   }
   #endif
   
   /*
    * Destroy an LWKT thread.   Warning!  This function is not called when
    * a process exits, cpu_proc_exit() directly calls cpu_thread_exit() and
    * uses a different reaping mechanism.
    *
    * XXX duplicates lwkt_exit()
    */
   void
   kthread_exit(void)
   {
       lwkt_exit();
   }
   
   /*
    * Start a kernel process.  This is called after a fork() call in
    * mi_startup() in the file kern/init_main.c.
    *
    * This function is used to start "internal" daemons and intended
    * to be called from SYSINIT().
    *
    * These threads are created MPSAFE.
    */
   void
   kproc_start(const void *udata)
   {
           const struct kproc_desc *kp = udata;
           int error;
   
           error = kthread_create((void (*)(void *))kp->func, NULL,
                                   kp->global_threadpp, "%s", kp->arg0);
           lwkt_setpri(*kp->global_threadpp, TDPRI_KERN_DAEMON);
           if (error)
                   panic("kproc_start: %s: error %d", kp->arg0, error);
   }
   
   /*
    * Advise a kernel process to suspend (or resume) in its main loop.
    * Participation is voluntary.
    */
   int
   suspend_kproc(struct thread *td, int timo)
   {
           if (td->td_proc == NULL) {
                   lwkt_gettoken(&kpsus_token);
                   /* request thread pause */
                   atomic_set_int(&td->td_mpflags, TDF_MP_STOPREQ);
                   wakeup(td);
                   while (td->td_mpflags & TDF_MP_STOPREQ) {
                           int error = tsleep(td, 0, "suspkp", timo);
                           if (error == EWOULDBLOCK)
                                   break;
                   }
                   atomic_clear_int(&td->td_mpflags, TDF_MP_STOPREQ);
                   lwkt_reltoken(&kpsus_token);
                   return(0);
           } else {
                   return(EINVAL); /* not a kernel thread */
           }
   }
   
   void
   kproc_suspend_loop(void)
   {
           struct thread *td = curthread;
   
           if (td->td_mpflags & TDF_MP_STOPREQ) {
                   lwkt_gettoken(&kpsus_token);
                   atomic_clear_int(&td->td_mpflags, TDF_MP_STOPREQ);
                   while ((td->td_mpflags & TDF_MP_WAKEREQ) == 0) {
                           wakeup(td);
                           tsleep(td, 0, "kpsusp", 0);
                   }
                   atomic_clear_int(&td->td_mpflags, TDF_MP_WAKEREQ);
                   wakeup(td);
                   lwkt_reltoken(&kpsus_token);
           }
   }
   

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