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: releng/7.3/sys/kern/kern_kthread.c 170307 2007-06-05 00:00:57Z jeff $");
   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 #include <sys/sched.h>
   42 
   43 #include <machine/stdarg.h>
   44 
   45 /*
   46  * Start a kernel process.  This is called after a fork() call in
   47  * mi_startup() in the file kern/init_main.c.
   48  *
   49  * This function is used to start "internal" daemons and intended
   50  * to be called from SYSINIT().
   51  */
   52 void
   53 kproc_start(udata)
   54         const void *udata;
   55 {
   56         const struct kproc_desc *kp = udata;
   57         int error;
   58 
   59         error = kthread_create((void (*)(void *))kp->func, NULL,
   60                     kp->global_procpp, 0, 0, "%s", kp->arg0);
   61         if (error)
   62                 panic("kproc_start: %s: error %d", kp->arg0, error);
   63 }
   64 
   65 /*
   66  * Create a kernel process/thread/whatever.  It shares its address space
   67  * with proc0 - ie: kernel only.
   68  *
   69  * func is the function to start.
   70  * arg is the parameter to pass to function on first startup.
   71  * newpp is the return value pointing to the thread's struct proc.
   72  * flags are flags to fork1 (in unistd.h)
   73  * fmt and following will be *printf'd into (*newpp)->p_comm (for ps, etc.).
   74  */
   75 int
   76 kthread_create(void (*func)(void *), void *arg,
   77     struct proc **newpp, int flags, int pages, const char *fmt, ...)
   78 {
   79         int error;
   80         va_list ap;
   81         struct thread *td;
   82         struct proc *p2;
   83 
   84         if (!proc0.p_stats)
   85                 panic("kthread_create called too soon");
   86 
   87         error = fork1(&thread0, RFMEM | RFFDG | RFPROC | RFSTOPPED | flags,
   88             pages, &p2);
   89         if (error)
   90                 return error;
   91 
   92         /* save a global descriptor, if desired */
   93         if (newpp != NULL)
   94                 *newpp = p2;
   95 
   96         /* this is a non-swapped system process */
   97         PROC_LOCK(p2);
   98         p2->p_flag |= P_SYSTEM | P_KTHREAD;
   99         mtx_lock(&p2->p_sigacts->ps_mtx);
  100         p2->p_sigacts->ps_flag |= PS_NOCLDWAIT;
  101         mtx_unlock(&p2->p_sigacts->ps_mtx);
  102         PROC_UNLOCK(p2);
  103 
  104         /* set up arg0 for 'ps', et al */
  105         va_start(ap, fmt);
  106         vsnprintf(p2->p_comm, sizeof(p2->p_comm), fmt, ap);
  107         va_end(ap);
  108 
  109         /* call the processes' main()... */
  110         td = FIRST_THREAD_IN_PROC(p2);
  111         cpu_set_fork_handler(td, func, arg);
  112         TD_SET_CAN_RUN(td);
  113 
  114         /* Delay putting it on the run queue until now. */
  115         if (!(flags & RFSTOPPED)) {
  116                 thread_lock(td);
  117                 sched_add(td, SRQ_BORING); 
  118                 thread_unlock(td);
  119         }
  120 
  121         return 0;
  122 }
  123 
  124 void
  125 kthread_exit(int ecode)
  126 {
  127         struct thread *td;
  128         struct proc *p;
  129 
  130         td = curthread;
  131         p = td->td_proc;
  132 
  133         /*
  134          * Reparent curthread from proc0 to init so that the zombie
  135          * is harvested.
  136          */
  137         sx_xlock(&proctree_lock);
  138         PROC_LOCK(p);
  139         proc_reparent(p, initproc);
  140         PROC_UNLOCK(p);
  141         sx_xunlock(&proctree_lock);
  142 
  143         /*
  144          * Wakeup anyone waiting for us to exit.
  145          */
  146         wakeup(p);
  147 
  148         /* Buh-bye! */
  149         exit1(td, W_EXITCODE(ecode, 0));
  150 }
  151 
  152 /*
  153  * Advise a kernel process to suspend (or resume) in its main loop.
  154  * Participation is voluntary.
  155  */
  156 int
  157 kthread_suspend(struct proc *p, int timo)
  158 {
  159         /*
  160          * Make sure this is indeed a system process and we can safely
  161          * use the p_siglist field.
  162          */
  163         PROC_LOCK(p);
  164         if ((p->p_flag & P_KTHREAD) == 0) {
  165                 PROC_UNLOCK(p);
  166                 return (EINVAL);
  167         }
  168         SIGADDSET(p->p_siglist, SIGSTOP);
  169         wakeup(p);
  170         return msleep(&p->p_siglist, &p->p_mtx, PPAUSE | PDROP, "suspkt", timo);
  171 }
  172 
  173 int
  174 kthread_resume(struct proc *p)
  175 {
  176         /*
  177          * Make sure this is indeed a system process and we can safely
  178          * use the p_siglist field.
  179          */
  180         PROC_LOCK(p);
  181         if ((p->p_flag & P_KTHREAD) == 0) {
  182                 PROC_UNLOCK(p);
  183                 return (EINVAL);
  184         }
  185         SIGDELSET(p->p_siglist, SIGSTOP);
  186         PROC_UNLOCK(p);
  187         wakeup(&p->p_siglist);
  188         return (0);
  189 }
  190 
  191 void
  192 kthread_suspend_check(struct proc *p)
  193 {
  194         PROC_LOCK(p);
  195         while (SIGISMEMBER(p->p_siglist, SIGSTOP)) {
  196                 wakeup(&p->p_siglist);
  197                 msleep(&p->p_siglist, &p->p_mtx, PPAUSE, "ktsusp", 0);
  198         }
  199         PROC_UNLOCK(p);
  200 }

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