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.
     */
    
    #include <sys/cdefs.h>
    __FBSDID("$FreeBSD$");
    
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/cpuset.h>
    #include <sys/kthread.h>
    #include <sys/lock.h>
    #include <sys/mutex.h>
    #include <sys/proc.h>
    #include <sys/resourcevar.h>
    #include <sys/rwlock.h>
    #include <sys/signalvar.h>
    #include <sys/sx.h>
    #include <sys/unistd.h>
    #include <sys/wait.h>
    #include <sys/sched.h>
    #include <vm/vm.h>
    #include <vm/vm_extern.h>
    
    #include <machine/stdarg.h>
    
    /*
     * 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().
     */
    void
    kproc_start(udata)
            const void *udata;
    {
            const struct kproc_desc *kp = udata;
            int error;
    
            error = kproc_create((void (*)(void *))kp->func, NULL,
                        kp->global_procpp, 0, 0, "%s", kp->arg0);
            if (error)
                    panic("kproc_start: %s: error %d", kp->arg0, error);
    }
    
    /*
     * Create a kernel process/thread/whatever.  It shares its address space
     * with proc0 - ie: kernel only.
     *
     * func is the function to start.
     * arg is the parameter to pass to function on first startup.
     * newpp is the return value pointing to the thread's struct proc.
     * flags are flags to fork1 (in unistd.h)
     * fmt and following will be *printf'd into (*newpp)->p_comm (for ps, etc.).
     */
    int
    kproc_create(void (*func)(void *), void *arg,
        struct proc **newpp, int flags, int pages, const char *fmt, ...)
    {
            int error;
            va_list ap;
            struct thread *td;
            struct proc *p2;
    
            if (!proc0.p_stats)
                    panic("kproc_create called too soon");
    
            error = fork1(&thread0, RFMEM | RFFDG | RFPROC | RFSTOPPED | flags,
                pages, &p2, NULL, 0);
            if (error)
                    return error;
    
            /* save a global descriptor, if desired */
            if (newpp != NULL)
                    *newpp = p2;
    
           /* this is a non-swapped system process */
           PROC_LOCK(p2);
           td = FIRST_THREAD_IN_PROC(p2);
           p2->p_flag |= P_SYSTEM | P_KTHREAD;
           td->td_pflags |= TDP_KTHREAD;
           mtx_lock(&p2->p_sigacts->ps_mtx);
           p2->p_sigacts->ps_flag |= PS_NOCLDWAIT;
           mtx_unlock(&p2->p_sigacts->ps_mtx);
           PROC_UNLOCK(p2);
   
           /* set up arg0 for 'ps', et al */
           va_start(ap, fmt);
           vsnprintf(p2->p_comm, sizeof(p2->p_comm), fmt, ap);
           va_end(ap);
           /* set up arg0 for 'ps', et al */
           va_start(ap, fmt);
           vsnprintf(td->td_name, sizeof(td->td_name), fmt, ap);
           va_end(ap);
   #ifdef KTR
           sched_clear_tdname(td);
   #endif
   
           /* call the processes' main()... */
           cpu_set_fork_handler(td, func, arg);
   
           /* Avoid inheriting affinity from a random parent. */
           cpuset_setthread(td->td_tid, cpuset_root);
           thread_lock(td);
           TD_SET_CAN_RUN(td);
           sched_prio(td, PVM);
           sched_user_prio(td, PUSER);
   
           /* Delay putting it on the run queue until now. */
           if (!(flags & RFSTOPPED))
                   sched_add(td, SRQ_BORING); 
           thread_unlock(td);
   
           return 0;
   }
   
   void
   kproc_exit(int ecode)
   {
           struct thread *td;
           struct proc *p;
   
           td = curthread;
           p = td->td_proc;
   
           /*
            * Reparent curthread from proc0 to init so that the zombie
            * is harvested.
            */
           sx_xlock(&proctree_lock);
           PROC_LOCK(p);
           proc_reparent(p, initproc);
           PROC_UNLOCK(p);
           sx_xunlock(&proctree_lock);
   
           /*
            * Wakeup anyone waiting for us to exit.
            */
           wakeup(p);
   
           /* Buh-bye! */
           exit1(td, W_EXITCODE(ecode, 0));
   }
   
   /*
    * Advise a kernel process to suspend (or resume) in its main loop.
    * Participation is voluntary.
    */
   int
   kproc_suspend(struct proc *p, int timo)
   {
           /*
            * Make sure this is indeed a system process and we can safely
            * use the p_siglist field.
            */
           PROC_LOCK(p);
           if ((p->p_flag & P_KTHREAD) == 0) {
                   PROC_UNLOCK(p);
                   return (EINVAL);
           }
           SIGADDSET(p->p_siglist, SIGSTOP);
           wakeup(p);
           return msleep(&p->p_siglist, &p->p_mtx, PPAUSE | PDROP, "suspkp", timo);
   }
   
   int
   kproc_resume(struct proc *p)
   {
           /*
            * Make sure this is indeed a system process and we can safely
            * use the p_siglist field.
            */
           PROC_LOCK(p);
           if ((p->p_flag & P_KTHREAD) == 0) {
                   PROC_UNLOCK(p);
                   return (EINVAL);
           }
           SIGDELSET(p->p_siglist, SIGSTOP);
           PROC_UNLOCK(p);
           wakeup(&p->p_siglist);
           return (0);
   }
   
   void
   kproc_suspend_check(struct proc *p)
   {
           PROC_LOCK(p);
           while (SIGISMEMBER(p->p_siglist, SIGSTOP)) {
                   wakeup(&p->p_siglist);
                   msleep(&p->p_siglist, &p->p_mtx, PPAUSE, "kpsusp", 0);
           }
           PROC_UNLOCK(p);
   }
   
   
   /*
    * Start a kernel thread.  
    *
    * This function is used to start "internal" daemons and intended
    * to be called from SYSINIT().
    */
   
   void
   kthread_start(udata)
           const void *udata;
   {
           const struct kthread_desc       *kp = udata;
           int error;
   
           error = kthread_add((void (*)(void *))kp->func, NULL,
                       NULL, kp->global_threadpp, 0, 0, "%s", kp->arg0);
           if (error)
                   panic("kthread_start: %s: error %d", kp->arg0, error);
   }
   
   /*
    * Create a kernel thread.  It shares its address space
    * with proc0 - ie: kernel only.
    *
    * func is the function to start.
    * arg is the parameter to pass to function on first startup.
    * newtdp is the return value pointing to the thread's struct thread.
    *  ** XXX fix this --> flags are flags to fork1 (in unistd.h) 
    * fmt and following will be *printf'd into (*newtd)->td_name (for ps, etc.).
    */
   int
   kthread_add(void (*func)(void *), void *arg, struct proc *p,
       struct thread **newtdp, int flags, int pages, const char *fmt, ...)
   {
           va_list ap;
           struct thread *newtd, *oldtd;
   
           if (!proc0.p_stats)
                   panic("kthread_add called too soon");
   
           /* If no process supplied, put it on proc0 */
           if (p == NULL)
                   p = &proc0;
   
           /* Initialize our new td  */
           newtd = thread_alloc(pages);
           if (newtd == NULL)
                   return (ENOMEM);
   
           PROC_LOCK(p);
           oldtd = FIRST_THREAD_IN_PROC(p);
   
           bzero(&newtd->td_startzero,
               __rangeof(struct thread, td_startzero, td_endzero));
   /* XXX check if we should zero. */
           bcopy(&oldtd->td_startcopy, &newtd->td_startcopy,
               __rangeof(struct thread, td_startcopy, td_endcopy));
   
           /* set up arg0 for 'ps', et al */
           va_start(ap, fmt);
           vsnprintf(newtd->td_name, sizeof(newtd->td_name), fmt, ap);
           va_end(ap);
   
           newtd->td_proc = p;  /* needed for cpu_set_upcall */
   
           /* XXX optimise this probably? */
           /* On x86 (and probably the others too) it is way too full of junk */
           /* Needs a better name */
           cpu_set_upcall(newtd, oldtd);
           /* put the designated function(arg) as the resume context */
           cpu_set_fork_handler(newtd, func, arg);
   
           newtd->td_pflags |= TDP_KTHREAD;
           newtd->td_ucred = crhold(p->p_ucred);
   
           /* this code almost the same as create_thread() in kern_thr.c */
           p->p_flag |= P_HADTHREADS;
           newtd->td_sigmask = oldtd->td_sigmask; /* XXX dubious */
           thread_link(newtd, p);
           thread_lock(oldtd);
           /* let the scheduler know about these things. */
           sched_fork_thread(oldtd, newtd);
           TD_SET_CAN_RUN(newtd);
           thread_unlock(oldtd);
           PROC_UNLOCK(p);
   
           tidhash_add(newtd);
   
           /* Avoid inheriting affinity from a random parent. */
           cpuset_setthread(newtd->td_tid, cpuset_root);
   
           /* Delay putting it on the run queue until now. */
           if (!(flags & RFSTOPPED)) {
                   thread_lock(newtd);
                   sched_add(newtd, SRQ_BORING); 
                   thread_unlock(newtd);
           }
           if (newtdp)
                   *newtdp = newtd;
           return 0;
   }
   
   void
   kthread_exit(void)
   {
           struct proc *p;
   
           p = curthread->td_proc;
   
           /* A module may be waiting for us to exit. */
           wakeup(curthread);
   
           /*
            * The last exiting thread in a kernel process must tear down
            * the whole process.
            */
           rw_wlock(&tidhash_lock);
           PROC_LOCK(p);
           if (p->p_numthreads == 1) {
                   PROC_UNLOCK(p);
                   rw_wunlock(&tidhash_lock);
                   kproc_exit(0);
           }
           LIST_REMOVE(curthread, td_hash);
           rw_wunlock(&tidhash_lock);
           PROC_SLOCK(p);
           thread_exit();
   }
   
   /*
    * Advise a kernel process to suspend (or resume) in its main loop.
    * Participation is voluntary.
    */
   int
   kthread_suspend(struct thread *td, int timo)
   {
           struct proc *p;
   
           p = td->td_proc;
   
           /*
            * td_pflags should not be read by any thread other than
            * curthread, but as long as this flag is invariant during the
            * thread's lifetime, it is OK to check its state.
            */
           if ((td->td_pflags & TDP_KTHREAD) == 0)
                   return (EINVAL);
   
           /*
            * The caller of the primitive should have already checked that the
            * thread is up and running, thus not being blocked by other
            * conditions.
            */
           PROC_LOCK(p);
           thread_lock(td);
           td->td_flags |= TDF_KTH_SUSP;
           thread_unlock(td);
           return (msleep(&td->td_flags, &p->p_mtx, PPAUSE | PDROP, "suspkt",
               timo));
   }
   
   /*
    * Resume a thread previously put asleep with kthread_suspend().
    */
   int
   kthread_resume(struct thread *td)
   {
           struct proc *p;
   
           p = td->td_proc;
   
           /*
            * td_pflags should not be read by any thread other than
            * curthread, but as long as this flag is invariant during the
            * thread's lifetime, it is OK to check its state.
            */
           if ((td->td_pflags & TDP_KTHREAD) == 0)
                   return (EINVAL);
   
           PROC_LOCK(p);
           thread_lock(td);
           td->td_flags &= ~TDF_KTH_SUSP;
           thread_unlock(td);
           wakeup(&td->td_flags);
           PROC_UNLOCK(p);
           return (0);
   }
   
   /*
    * Used by the thread to poll as to whether it should yield/sleep
    * and notify the caller that is has happened.
    */
   void
   kthread_suspend_check()
   {
           struct proc *p;
           struct thread *td;
   
           td = curthread;
           p = td->td_proc;
   
           if ((td->td_pflags & TDP_KTHREAD) == 0)
                   panic("%s: curthread is not a valid kthread", __func__);
   
           /*
            * As long as the double-lock protection is used when accessing the
            * TDF_KTH_SUSP flag, synchronizing the read operation via proc mutex
            * is fine.
            */
           PROC_LOCK(p);
           while (td->td_flags & TDF_KTH_SUSP) {
                   wakeup(&td->td_flags);
                   msleep(&td->td_flags, &p->p_mtx, PPAUSE, "ktsusp", 0);
           }
           PROC_UNLOCK(p);
   }
   
   int
   kproc_kthread_add(void (*func)(void *), void *arg,
               struct proc **procptr, struct thread **tdptr,
               int flags, int pages, const char *procname, const char *fmt, ...) 
   {
           int error;
           va_list ap;
           char buf[100];
           struct thread *td;
   
           if (*procptr == 0) {
                   error = kproc_create(func, arg,
                           procptr, flags, pages, "%s", procname);
                   if (error)
                           return (error);
                   td = FIRST_THREAD_IN_PROC(*procptr);
                   if (tdptr)
                           *tdptr = td;
                   va_start(ap, fmt);
                   vsnprintf(td->td_name, sizeof(td->td_name), fmt, ap);
                   va_end(ap);
   #ifdef KTR
                   sched_clear_tdname(td);
   #endif
                   return (0); 
           }
           va_start(ap, fmt);
           vsnprintf(buf, sizeof(buf), fmt, ap);
           va_end(ap);
           error = kthread_add(func, arg, *procptr,
                       tdptr, flags, pages, "%s", buf);
           return (error);
   }

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