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

     /*-
      * Copyright (c) 1982, 1986, 1990, 1991, 1993
      *      The Regents of the University of California.  All rights reserved.
      * (c) UNIX System Laboratories, Inc.
      * All or some portions of this file are derived from material licensed
      * to the University of California by American Telephone and Telegraph
      * Co. or Unix System Laboratories, Inc. and are reproduced herein with
      * the permission of UNIX System Laboratories, Inc.
      *
     * 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.
     * 4. Neither the name of the University nor the names of its contributors
     *    may be used to endorse or promote products derived from this software
     *    without specific prior written permission.
     *
     * THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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.
     *
     *      @(#)kern_synch.c        8.9 (Berkeley) 5/19/95
     */
    
    #include <sys/cdefs.h>
    __FBSDID("$FreeBSD: releng/6.0/sys/kern/kern_synch.c 146554 2005-05-23 23:01:53Z ups $");
    
    #include "opt_ktrace.h"
    
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/condvar.h>
    #include <sys/kdb.h>
    #include <sys/kernel.h>
    #include <sys/ktr.h>
    #include <sys/lock.h>
    #include <sys/mutex.h>
    #include <sys/proc.h>
    #include <sys/resourcevar.h>
    #include <sys/sched.h>
    #include <sys/signalvar.h>
    #include <sys/sleepqueue.h>
    #include <sys/smp.h>
    #include <sys/sx.h>
    #include <sys/sysctl.h>
    #include <sys/sysproto.h>
    #include <sys/vmmeter.h>
    #ifdef KTRACE
    #include <sys/uio.h>
    #include <sys/ktrace.h>
    #endif
    
    #include <machine/cpu.h>
    
    static void synch_setup(void *dummy);
    SYSINIT(synch_setup, SI_SUB_KICK_SCHEDULER, SI_ORDER_FIRST, synch_setup, NULL)
    
    int     hogticks;
    int     lbolt;
    
    static struct callout loadav_callout;
    static struct callout lbolt_callout;
    
    struct loadavg averunnable =
            { {0, 0, 0}, FSCALE };  /* load average, of runnable procs */
    /*
     * Constants for averages over 1, 5, and 15 minutes
     * when sampling at 5 second intervals.
     */
    static fixpt_t cexp[3] = {
            0.9200444146293232 * FSCALE,    /* exp(-1/12) */
            0.9834714538216174 * FSCALE,    /* exp(-1/60) */
            0.9944598480048967 * FSCALE,    /* exp(-1/180) */
    };
    
    /* kernel uses `FSCALE', userland (SHOULD) use kern.fscale */
    static int      fscale __unused = FSCALE;
    SYSCTL_INT(_kern, OID_AUTO, fscale, CTLFLAG_RD, 0, FSCALE, "");
    
    static void     loadav(void *arg);
    static void     lboltcb(void *arg);
    
    void
    sleepinit(void)
    {
    
            hogticks = (hz / 10) * 2;       /* Default only. */
           init_sleepqueues();
   }
   
   /*
    * General sleep call.  Suspends the current process until a wakeup is
    * performed on the specified identifier.  The process will then be made
    * runnable with the specified priority.  Sleeps at most timo/hz seconds
    * (0 means no timeout).  If pri includes PCATCH flag, signals are checked
    * before and after sleeping, else signals are not checked.  Returns 0 if
    * awakened, EWOULDBLOCK if the timeout expires.  If PCATCH is set and a
    * signal needs to be delivered, ERESTART is returned if the current system
    * call should be restarted if possible, and EINTR is returned if the system
    * call should be interrupted by the signal (return EINTR).
    *
    * The mutex argument is exited before the caller is suspended, and
    * entered before msleep returns.  If priority includes the PDROP
    * flag the mutex is not entered before returning.
    */
   int
   msleep(ident, mtx, priority, wmesg, timo)
           void *ident;
           struct mtx *mtx;
           int priority, timo;
           const char *wmesg;
   {
           struct thread *td;
           struct proc *p;
           int catch, rval, sig, flags;
           WITNESS_SAVE_DECL(mtx);
   
           td = curthread;
           p = td->td_proc;
   #ifdef KTRACE
           if (KTRPOINT(td, KTR_CSW))
                   ktrcsw(1, 0);
   #endif
           WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, mtx == NULL ? NULL :
               &mtx->mtx_object, "Sleeping on \"%s\"", wmesg);
           KASSERT(timo != 0 || mtx_owned(&Giant) || mtx != NULL,
               ("sleeping without a mutex"));
           KASSERT(p != NULL, ("msleep1"));
           KASSERT(ident != NULL && TD_IS_RUNNING(td), ("msleep"));
   
           if (cold) {
                   /*
                    * During autoconfiguration, just return;
                    * don't run any other threads or panic below,
                    * in case this is the idle thread and already asleep.
                    * XXX: this used to do "s = splhigh(); splx(safepri);
                    * splx(s);" to give interrupts a chance, but there is
                    * no way to give interrupts a chance now.
                    */
                   if (mtx != NULL && priority & PDROP)
                           mtx_unlock(mtx);
                   return (0);
           }
           catch = priority & PCATCH;
           rval = 0;
   
           /*
            * If we are already on a sleep queue, then remove us from that
            * sleep queue first.  We have to do this to handle recursive
            * sleeps.
            */
           if (TD_ON_SLEEPQ(td))
                   sleepq_remove(td, td->td_wchan);
   
           sleepq_lock(ident);
           if (catch) {
                   /*
                    * Don't bother sleeping if we are exiting and not the exiting
                    * thread or if our thread is marked as interrupted.
                    */
                   mtx_lock_spin(&sched_lock);
                   rval = thread_sleep_check(td);
                   mtx_unlock_spin(&sched_lock);
                   if (rval != 0) {
                           sleepq_release(ident);
                           if (mtx != NULL && priority & PDROP)
                                   mtx_unlock(mtx);
                           return (rval);
                   }
           }
           CTR5(KTR_PROC, "msleep: thread %p (pid %ld, %s) on %s (%p)",
               (void *)td, (long)p->p_pid, p->p_comm, wmesg, ident);
   
           DROP_GIANT();
           if (mtx != NULL) {
                   mtx_assert(mtx, MA_OWNED | MA_NOTRECURSED);
                   WITNESS_SAVE(&mtx->mtx_object, mtx);
                   mtx_unlock(mtx);
           }
   
           /*
            * We put ourselves on the sleep queue and start our timeout
            * before calling thread_suspend_check, as we could stop there,
            * and a wakeup or a SIGCONT (or both) could occur while we were
            * stopped without resuming us.  Thus, we must be ready for sleep
            * when cursig() is called.  If the wakeup happens while we're
            * stopped, then td will no longer be on a sleep queue upon
            * return from cursig().
            */
           flags = SLEEPQ_MSLEEP;
           if (catch)
                   flags |= SLEEPQ_INTERRUPTIBLE;
           sleepq_add(ident, mtx, wmesg, flags);
           if (timo)
                   sleepq_set_timeout(ident, timo);
           if (catch) {
                   sig = sleepq_catch_signals(ident);
           } else
                   sig = 0;
   
           /*
            * Adjust this thread's priority.
            */
           mtx_lock_spin(&sched_lock);
           sched_prio(td, priority & PRIMASK);
           mtx_unlock_spin(&sched_lock);
   
           if (timo && catch)
                   rval = sleepq_timedwait_sig(ident, sig != 0);
           else if (timo)
                   rval = sleepq_timedwait(ident);
           else if (catch)
                   rval = sleepq_wait_sig(ident);
           else {
                   sleepq_wait(ident);
                   rval = 0;
           }
           if (rval == 0 && catch)
                   rval = sleepq_calc_signal_retval(sig);
   #ifdef KTRACE
           if (KTRPOINT(td, KTR_CSW))
                   ktrcsw(0, 0);
   #endif
           PICKUP_GIANT();
           if (mtx != NULL && !(priority & PDROP)) {
                   mtx_lock(mtx);
                   WITNESS_RESTORE(&mtx->mtx_object, mtx);
           }
           return (rval);
   }
   
   /*
    * Make all threads sleeping on the specified identifier runnable.
    */
   void
   wakeup(ident)
           register void *ident;
   {
   
           sleepq_lock(ident);
           sleepq_broadcast(ident, SLEEPQ_MSLEEP, -1);
   }
   
   /*
    * Make a thread sleeping on the specified identifier runnable.
    * May wake more than one thread if a target thread is currently
    * swapped out.
    */
   void
   wakeup_one(ident)
           register void *ident;
   {
   
           sleepq_lock(ident);
           sleepq_signal(ident, SLEEPQ_MSLEEP, -1);
   }
   
   /*
    * The machine independent parts of context switching.
    */
   void
   mi_switch(int flags, struct thread *newtd)
   {
           struct bintime new_switchtime;
           struct thread *td;
           struct proc *p;
   
           mtx_assert(&sched_lock, MA_OWNED | MA_NOTRECURSED);
           td = curthread;                 /* XXX */
           p = td->td_proc;                /* XXX */
           KASSERT(!TD_ON_RUNQ(td), ("mi_switch: called by old code"));
   #ifdef INVARIANTS
           if (!TD_ON_LOCK(td) && !TD_IS_RUNNING(td))
                   mtx_assert(&Giant, MA_NOTOWNED);
   #endif
           KASSERT(td->td_critnest == 1 || (td->td_critnest == 2 &&
               (td->td_owepreempt) && (flags & SW_INVOL) != 0 &&
               newtd == NULL) || panicstr,
               ("mi_switch: switch in a critical section"));
           KASSERT((flags & (SW_INVOL | SW_VOL)) != 0,
               ("mi_switch: switch must be voluntary or involuntary"));
           KASSERT(newtd != curthread, ("mi_switch: preempting back to ourself"));
   
           if (flags & SW_VOL)
                   p->p_stats->p_ru.ru_nvcsw++;
           else
                   p->p_stats->p_ru.ru_nivcsw++;
   
           /*
            * Compute the amount of time during which the current
            * process was running, and add that to its total so far.
            */
           binuptime(&new_switchtime);
           bintime_add(&p->p_rux.rux_runtime, &new_switchtime);
           bintime_sub(&p->p_rux.rux_runtime, PCPU_PTR(switchtime));
   
           td->td_generation++;    /* bump preempt-detect counter */
   
           /*
            * Don't perform context switches from the debugger.
            */
           if (kdb_active) {
                   mtx_unlock_spin(&sched_lock);
                   kdb_backtrace();
                   kdb_reenter();
                   panic("%s: did not reenter debugger", __func__);
           }
   
           /*
            * Check if the process exceeds its cpu resource allocation.  If
            * over max, arrange to kill the process in ast().
            */
           if (p->p_cpulimit != RLIM_INFINITY &&
               p->p_rux.rux_runtime.sec > p->p_cpulimit) {
                   p->p_sflag |= PS_XCPU;
                   td->td_flags |= TDF_ASTPENDING;
           }
   
           /*
            * Finish up stats for outgoing thread.
            */
           cnt.v_swtch++;
           PCPU_SET(switchtime, new_switchtime);
           PCPU_SET(switchticks, ticks);
           CTR4(KTR_PROC, "mi_switch: old thread %p (kse %p, pid %ld, %s)",
               (void *)td, td->td_sched, (long)p->p_pid, p->p_comm);
           if ((flags & SW_VOL) && (td->td_proc->p_flag & P_SA))
                   newtd = thread_switchout(td, flags, newtd);
   #if (KTR_COMPILE & KTR_SCHED) != 0
           if (td == PCPU_GET(idlethread))
                   CTR3(KTR_SCHED, "mi_switch: %p(%s) prio %d idle",
                       td, td->td_proc->p_comm, td->td_priority);
           else if (newtd != NULL)
                   CTR5(KTR_SCHED,
                       "mi_switch: %p(%s) prio %d preempted by %p(%s)",
                       td, td->td_proc->p_comm, td->td_priority, newtd,
                       newtd->td_proc->p_comm);
           else
                   CTR6(KTR_SCHED,
                       "mi_switch: %p(%s) prio %d inhibit %d wmesg %s lock %s",
                       td, td->td_proc->p_comm, td->td_priority,
                       td->td_inhibitors, td->td_wmesg, td->td_lockname);
   #endif
           sched_switch(td, newtd, flags);
           CTR3(KTR_SCHED, "mi_switch: running %p(%s) prio %d",
               td, td->td_proc->p_comm, td->td_priority);
   
           CTR4(KTR_PROC, "mi_switch: new thread %p (kse %p, pid %ld, %s)",
               (void *)td, td->td_sched, (long)p->p_pid, p->p_comm);
   
           /* 
            * If the last thread was exiting, finish cleaning it up.
            */
           if ((td = PCPU_GET(deadthread))) {
                   PCPU_SET(deadthread, NULL);
                   thread_stash(td);
           }
   }
   
   /*
    * Change process state to be runnable,
    * placing it on the run queue if it is in memory,
    * and awakening the swapper if it isn't in memory.
    */
   void
   setrunnable(struct thread *td)
   {
           struct proc *p;
   
           p = td->td_proc;
           mtx_assert(&sched_lock, MA_OWNED);
           switch (p->p_state) {
           case PRS_ZOMBIE:
                   panic("setrunnable(1)");
           default:
                   break;
           }
           switch (td->td_state) {
           case TDS_RUNNING:
           case TDS_RUNQ:
                   return;
           case TDS_INHIBITED:
                   /*
                    * If we are only inhibited because we are swapped out
                    * then arange to swap in this process. Otherwise just return.
                    */
                   if (td->td_inhibitors != TDI_SWAPPED)
                           return;
                   /* XXX: intentional fall-through ? */
           case TDS_CAN_RUN:
                   break;
           default:
                   printf("state is 0x%x", td->td_state);
                   panic("setrunnable(2)");
           }
           if ((p->p_sflag & PS_INMEM) == 0) {
                   if ((p->p_sflag & PS_SWAPPINGIN) == 0) {
                           p->p_sflag |= PS_SWAPINREQ;
                           /*
                            * due to a LOR between sched_lock and
                            * the sleepqueue chain locks, use
                            * lower level scheduling functions.
                            */
                           kick_proc0();
                   }
           } else
                   sched_wakeup(td);
   }
   
   /*
    * Compute a tenex style load average of a quantity on
    * 1, 5 and 15 minute intervals.
    * XXXKSE   Needs complete rewrite when correct info is available.
    * Completely Bogus.. only works with 1:1 (but compiles ok now :-)
    */
   static void
   loadav(void *arg)
   {
           int i, nrun;
           struct loadavg *avg;
   
           nrun = sched_load();
           avg = &averunnable;
   
           for (i = 0; i < 3; i++)
                   avg->ldavg[i] = (cexp[i] * avg->ldavg[i] +
                       nrun * FSCALE * (FSCALE - cexp[i])) >> FSHIFT;
   
           /*
            * Schedule the next update to occur after 5 seconds, but add a
            * random variation to avoid synchronisation with processes that
            * run at regular intervals.
            */
           callout_reset(&loadav_callout, hz * 4 + (int)(random() % (hz * 2 + 1)),
               loadav, NULL);
   }
   
   static void
   lboltcb(void *arg)
   {
           wakeup(&lbolt);
           callout_reset(&lbolt_callout, hz, lboltcb, NULL);
   }
   
   /* ARGSUSED */
   static void
   synch_setup(dummy)
           void *dummy;
   {
           callout_init(&loadav_callout, CALLOUT_MPSAFE);
           callout_init(&lbolt_callout, CALLOUT_MPSAFE);
   
           /* Kick off timeout driven events by calling first time. */
           loadav(NULL);
           lboltcb(NULL);
   }
   
   /*
    * General purpose yield system call
    */
   int
   yield(struct thread *td, struct yield_args *uap)
   {
           struct ksegrp *kg;
   
           kg = td->td_ksegrp;
           mtx_assert(&Giant, MA_NOTOWNED);
           mtx_lock_spin(&sched_lock);
           sched_prio(td, PRI_MAX_TIMESHARE);
           mi_switch(SW_VOL, NULL);
           mtx_unlock_spin(&sched_lock);
           td->td_retval[0] = 0;
           return (0);
   }

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