The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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

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    1 /*-
    2  * Copyright (c) 1999 Peter Wemm <peter@FreeBSD.org>
    3  * All rights reserved.
    4  *
    5  * Redistribution and use in source and binary forms, with or without
    6  * modification, are permitted provided that the following conditions
    7  * are met:
    8  * 1. Redistributions of source code must retain the above copyright
    9  *    notice, this list of conditions and the following disclaimer.
   10  * 2. Redistributions in binary form must reproduce the above copyright
   11  *    notice, this list of conditions and the following disclaimer in the
   12  *    documentation and/or other materials provided with the distribution.
   13  *
   14  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
   15  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   16  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   17  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
   18  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   19  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   20  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   21  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   22  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   23  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   24  * SUCH DAMAGE.
   25  */
   26 
   27 #include <sys/cdefs.h>
   28 __FBSDID("$FreeBSD$");
   29 
   30 #include <sys/param.h>
   31 #include <sys/systm.h>
   32 #include <sys/kthread.h>
   33 #include <sys/lock.h>
   34 #include <sys/mutex.h>
   35 #include <sys/proc.h>
   36 #include <sys/resourcevar.h>
   37 #include <sys/signalvar.h>
   38 #include <sys/sx.h>
   39 #include <sys/unistd.h>
   40 #include <sys/wait.h>
   41 
   42 #include <machine/stdarg.h>
   43 
   44 /*
   45  * Start a kernel process.  This is called after a fork() call in
   46  * mi_startup() in the file kern/init_main.c.
   47  *
   48  * This function is used to start "internal" daemons and intended
   49  * to be called from SYSINIT().
   50  */
   51 void
   52 kproc_start(udata)
   53         const void *udata;
   54 {
   55         const struct kproc_desc *kp = udata;
   56         int error;
   57 
   58         error = kthread_create((void (*)(void *))kp->func, NULL,
   59                     kp->global_procpp, 0, 0, "%s", kp->arg0);
   60         if (error)
   61                 panic("kproc_start: %s: error %d", kp->arg0, error);
   62 }
   63 
   64 /*
   65  * Create a kernel process/thread/whatever.  It shares its address space
   66  * with proc0 - ie: kernel only.
   67  *
   68  * func is the function to start.
   69  * arg is the parameter to pass to function on first startup.
   70  * newpp is the return value pointing to the thread's struct proc.
   71  * flags are flags to fork1 (in unistd.h)
   72  * fmt and following will be *printf'd into (*newpp)->p_comm (for ps, etc.).
   73  */
   74 int
   75 kthread_create(void (*func)(void *), void *arg,
   76     struct proc **newpp, int flags, int pages, const char *fmt, ...)
   77 {
   78         int error;
   79         va_list ap;
   80         struct thread *td;
   81         struct proc *p2;
   82 
   83         if (!proc0.p_stats)
   84                 panic("kthread_create called too soon");
   85 
   86         error = fork1(&thread0, RFMEM | RFFDG | RFPROC | RFSTOPPED | flags,
   87             pages, &p2);
   88         if (error)
   89                 return error;
   90 
   91         /* save a global descriptor, if desired */
   92         if (newpp != NULL)
   93                 *newpp = p2;
   94 
   95         /* this is a non-swapped system process */
   96         PROC_LOCK(p2);
   97         p2->p_flag |= P_SYSTEM | P_KTHREAD;
   98         mtx_lock(&p2->p_sigacts->ps_mtx);
   99         p2->p_sigacts->ps_flag |= PS_NOCLDWAIT;
  100         mtx_unlock(&p2->p_sigacts->ps_mtx);
  101         PROC_UNLOCK(p2);
  102 
  103         /* set up arg0 for 'ps', et al */
  104         va_start(ap, fmt);
  105         vsnprintf(p2->p_comm, sizeof(p2->p_comm), fmt, ap);
  106         va_end(ap);
  107 
  108         /* call the processes' main()... */
  109         td = FIRST_THREAD_IN_PROC(p2);
  110         cpu_set_fork_handler(td, func, arg);
  111         TD_SET_CAN_RUN(td);
  112 
  113         /* Delay putting it on the run queue until now. */
  114         if (!(flags & RFSTOPPED)) {
  115                 mtx_lock_spin(&sched_lock);
  116                 setrunqueue(td, SRQ_BORING); 
  117                 mtx_unlock_spin(&sched_lock);
  118         }
  119 
  120         return 0;
  121 }
  122 
  123 void
  124 kthread_exit(int ecode)
  125 {
  126         struct thread *td;
  127         struct proc *p;
  128 
  129         td = curthread;
  130         p = td->td_proc;
  131         sx_xlock(&proctree_lock);
  132         PROC_LOCK(p);
  133         proc_reparent(p, initproc);
  134         PROC_UNLOCK(p);
  135         sx_xunlock(&proctree_lock);
  136         exit1(td, W_EXITCODE(ecode, 0));
  137 }
  138 
  139 /*
  140  * Advise a kernel process to suspend (or resume) in its main loop.
  141  * Participation is voluntary.
  142  */
  143 int
  144 kthread_suspend(struct proc *p, int timo)
  145 {
  146         /*
  147          * Make sure this is indeed a system process and we can safely
  148          * use the p_siglist field.
  149          */
  150         PROC_LOCK(p);
  151         if ((p->p_flag & P_KTHREAD) == 0) {
  152                 PROC_UNLOCK(p);
  153                 return (EINVAL);
  154         }
  155         SIGADDSET(p->p_siglist, SIGSTOP);
  156         wakeup(p);
  157         return msleep(&p->p_siglist, &p->p_mtx, PPAUSE | PDROP, "suspkt", timo);
  158 }
  159 
  160 int
  161 kthread_resume(struct proc *p)
  162 {
  163         /*
  164          * Make sure this is indeed a system process and we can safely
  165          * use the p_siglist field.
  166          */
  167         PROC_LOCK(p);
  168         if ((p->p_flag & P_KTHREAD) == 0) {
  169                 PROC_UNLOCK(p);
  170                 return (EINVAL);
  171         }
  172         SIGDELSET(p->p_siglist, SIGSTOP);
  173         PROC_UNLOCK(p);
  174         wakeup(&p->p_siglist);
  175         return (0);
  176 }
  177 
  178 void
  179 kthread_suspend_check(struct proc *p)
  180 {
  181         PROC_LOCK(p);
  182         while (SIGISMEMBER(p->p_siglist, SIGSTOP)) {
  183                 wakeup(&p->p_siglist);
  184                 msleep(&p->p_siglist, &p->p_mtx, PPAUSE, "ktsusp", 0);
  185         }
  186         PROC_UNLOCK(p);
  187 }

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