a8c1c80ef5
- Add a new _lock() call to each API that locks the associated chain lock for a lock_object pointer or wait channel. The _lookup() functions now require that the chain lock be locked via _lock() when they are called. - Change sleepq_add(), turnstile_wait() and turnstile_claim() to lookup the associated queue structure internally via _lookup() rather than accepting a pointer from the caller. For turnstiles, this means that the actual lookup of the turnstile in the hash table is only done when the thread actually blocks rather than being done on each loop iteration in _mtx_lock_sleep(). For sleep queues, this means that sleepq_lookup() is no longer used outside of the sleep queue code except to implement an assertion in cv_destroy(). - Change sleepq_broadcast() and sleepq_signal() to require that the chain lock is already required. For condition variables, this lets the cv_broadcast() and cv_signal() functions lock the sleep queue chain lock while testing the waiters count. This means that the waiters count internal to condition variables is no longer protected by the interlock mutex and cv_broadcast() and cv_signal() now no longer require that the interlock be held when they are called. This lets consumers of condition variables drop the lock before waking other threads which can result in fewer context switches. MFC after: 1 month
471 lines
13 KiB
C
471 lines
13 KiB
C
/*-
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* Copyright (c) 1982, 1986, 1990, 1991, 1993
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* The Regents of the University of California. All rights reserved.
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* (c) UNIX System Laboratories, Inc.
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* All or some portions of this file are derived from material licensed
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* to the University of California by American Telephone and Telegraph
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* Co. or Unix System Laboratories, Inc. and are reproduced herein with
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* the permission of UNIX System Laboratories, Inc.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* @(#)kern_synch.c 8.9 (Berkeley) 5/19/95
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*/
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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#include "opt_ktrace.h"
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#include <sys/param.h>
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#include <sys/systm.h>
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#include <sys/condvar.h>
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#include <sys/kdb.h>
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#include <sys/kernel.h>
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#include <sys/ktr.h>
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#include <sys/lock.h>
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#include <sys/mutex.h>
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#include <sys/proc.h>
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#include <sys/resourcevar.h>
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#include <sys/sched.h>
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#include <sys/signalvar.h>
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#include <sys/sleepqueue.h>
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#include <sys/smp.h>
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#include <sys/sx.h>
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#include <sys/sysctl.h>
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#include <sys/sysproto.h>
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#include <sys/vmmeter.h>
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#ifdef KTRACE
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#include <sys/uio.h>
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#include <sys/ktrace.h>
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#endif
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#include <machine/cpu.h>
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static void synch_setup(void *dummy);
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SYSINIT(synch_setup, SI_SUB_KICK_SCHEDULER, SI_ORDER_FIRST, synch_setup, NULL)
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int hogticks;
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int lbolt;
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static struct callout loadav_callout;
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static struct callout lbolt_callout;
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struct loadavg averunnable =
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{ {0, 0, 0}, FSCALE }; /* load average, of runnable procs */
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/*
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* Constants for averages over 1, 5, and 15 minutes
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* when sampling at 5 second intervals.
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*/
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static fixpt_t cexp[3] = {
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0.9200444146293232 * FSCALE, /* exp(-1/12) */
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0.9834714538216174 * FSCALE, /* exp(-1/60) */
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0.9944598480048967 * FSCALE, /* exp(-1/180) */
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};
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/* kernel uses `FSCALE', userland (SHOULD) use kern.fscale */
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static int fscale __unused = FSCALE;
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SYSCTL_INT(_kern, OID_AUTO, fscale, CTLFLAG_RD, 0, FSCALE, "");
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static void loadav(void *arg);
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static void lboltcb(void *arg);
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void
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sleepinit(void)
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{
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hogticks = (hz / 10) * 2; /* Default only. */
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init_sleepqueues();
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}
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/*
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* General sleep call. Suspends the current process until a wakeup is
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* performed on the specified identifier. The process will then be made
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* runnable with the specified priority. Sleeps at most timo/hz seconds
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* (0 means no timeout). If pri includes PCATCH flag, signals are checked
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* before and after sleeping, else signals are not checked. Returns 0 if
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* awakened, EWOULDBLOCK if the timeout expires. If PCATCH is set and a
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* signal needs to be delivered, ERESTART is returned if the current system
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* call should be restarted if possible, and EINTR is returned if the system
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* call should be interrupted by the signal (return EINTR).
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*
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* The mutex argument is exited before the caller is suspended, and
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* entered before msleep returns. If priority includes the PDROP
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* flag the mutex is not entered before returning.
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*/
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int
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msleep(ident, mtx, priority, wmesg, timo)
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void *ident;
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struct mtx *mtx;
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int priority, timo;
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const char *wmesg;
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{
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struct thread *td;
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struct proc *p;
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int catch, rval, sig, flags;
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WITNESS_SAVE_DECL(mtx);
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td = curthread;
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p = td->td_proc;
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#ifdef KTRACE
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if (KTRPOINT(td, KTR_CSW))
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ktrcsw(1, 0);
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#endif
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WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, mtx == NULL ? NULL :
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&mtx->mtx_object, "Sleeping on \"%s\"", wmesg);
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KASSERT(timo != 0 || mtx_owned(&Giant) || mtx != NULL,
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("sleeping without a mutex"));
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KASSERT(p != NULL, ("msleep1"));
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KASSERT(ident != NULL && TD_IS_RUNNING(td), ("msleep"));
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if (cold) {
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/*
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* During autoconfiguration, just return;
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* don't run any other threads or panic below,
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* in case this is the idle thread and already asleep.
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* XXX: this used to do "s = splhigh(); splx(safepri);
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* splx(s);" to give interrupts a chance, but there is
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* no way to give interrupts a chance now.
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*/
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if (mtx != NULL && priority & PDROP)
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mtx_unlock(mtx);
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return (0);
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}
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catch = priority & PCATCH;
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rval = 0;
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/*
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* If we are already on a sleep queue, then remove us from that
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* sleep queue first. We have to do this to handle recursive
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* sleeps.
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*/
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if (TD_ON_SLEEPQ(td))
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sleepq_remove(td, td->td_wchan);
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sleepq_lock(ident);
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if (catch) {
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/*
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* Don't bother sleeping if we are exiting and not the exiting
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* thread or if our thread is marked as interrupted.
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*/
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mtx_lock_spin(&sched_lock);
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rval = thread_sleep_check(td);
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mtx_unlock_spin(&sched_lock);
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if (rval != 0) {
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sleepq_release(ident);
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return (rval);
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}
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}
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CTR5(KTR_PROC, "msleep: thread %p (pid %ld, %s) on %s (%p)",
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(void *)td, (long)p->p_pid, p->p_comm, wmesg, ident);
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DROP_GIANT();
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if (mtx != NULL) {
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mtx_assert(mtx, MA_OWNED | MA_NOTRECURSED);
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WITNESS_SAVE(&mtx->mtx_object, mtx);
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mtx_unlock(mtx);
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}
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/*
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* We put ourselves on the sleep queue and start our timeout
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* before calling thread_suspend_check, as we could stop there,
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* and a wakeup or a SIGCONT (or both) could occur while we were
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* stopped without resuming us. Thus, we must be ready for sleep
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* when cursig() is called. If the wakeup happens while we're
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* stopped, then td will no longer be on a sleep queue upon
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* return from cursig().
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*/
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flags = SLEEPQ_MSLEEP;
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if (catch)
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flags |= SLEEPQ_INTERRUPTIBLE;
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sleepq_add(ident, mtx, wmesg, flags);
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if (timo)
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sleepq_set_timeout(ident, timo);
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if (catch) {
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sig = sleepq_catch_signals(ident);
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} else
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sig = 0;
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/*
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* Adjust this thread's priority.
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*
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* XXX: do we need to save priority in td_base_pri?
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*/
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mtx_lock_spin(&sched_lock);
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sched_prio(td, priority & PRIMASK);
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mtx_unlock_spin(&sched_lock);
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if (timo && catch)
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rval = sleepq_timedwait_sig(ident, sig != 0);
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else if (timo)
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rval = sleepq_timedwait(ident);
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else if (catch)
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rval = sleepq_wait_sig(ident);
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else {
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sleepq_wait(ident);
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rval = 0;
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}
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if (rval == 0 && catch)
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rval = sleepq_calc_signal_retval(sig);
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#ifdef KTRACE
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if (KTRPOINT(td, KTR_CSW))
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ktrcsw(0, 0);
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#endif
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PICKUP_GIANT();
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if (mtx != NULL && !(priority & PDROP)) {
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mtx_lock(mtx);
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WITNESS_RESTORE(&mtx->mtx_object, mtx);
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}
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return (rval);
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}
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/*
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* Make all threads sleeping on the specified identifier runnable.
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*/
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void
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wakeup(ident)
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register void *ident;
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{
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sleepq_lock(ident);
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sleepq_broadcast(ident, SLEEPQ_MSLEEP, -1);
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}
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/*
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* Make a thread sleeping on the specified identifier runnable.
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* May wake more than one thread if a target thread is currently
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* swapped out.
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*/
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void
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wakeup_one(ident)
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register void *ident;
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{
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sleepq_lock(ident);
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sleepq_signal(ident, SLEEPQ_MSLEEP, -1);
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}
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/*
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* The machine independent parts of context switching.
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*/
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void
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mi_switch(int flags, struct thread *newtd)
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{
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struct bintime new_switchtime;
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struct thread *td;
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struct proc *p;
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mtx_assert(&sched_lock, MA_OWNED | MA_NOTRECURSED);
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td = curthread; /* XXX */
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p = td->td_proc; /* XXX */
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KASSERT(!TD_ON_RUNQ(td), ("mi_switch: called by old code"));
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#ifdef INVARIANTS
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if (!TD_ON_LOCK(td) && !TD_IS_RUNNING(td))
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mtx_assert(&Giant, MA_NOTOWNED);
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#endif
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KASSERT(td->td_critnest == 1 || (td->td_critnest == 2 &&
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(td->td_pflags & TDP_OWEPREEMPT) != 0 && (flags & SW_INVOL) != 0 &&
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newtd == NULL),
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("mi_switch: switch in a critical section"));
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KASSERT((flags & (SW_INVOL | SW_VOL)) != 0,
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("mi_switch: switch must be voluntary or involuntary"));
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KASSERT(newtd != curthread, ("mi_switch: preempting back to ourself"));
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if (flags & SW_VOL)
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p->p_stats->p_ru.ru_nvcsw++;
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else
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p->p_stats->p_ru.ru_nivcsw++;
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/*
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* Compute the amount of time during which the current
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* process was running, and add that to its total so far.
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*/
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binuptime(&new_switchtime);
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bintime_add(&p->p_rux.rux_runtime, &new_switchtime);
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bintime_sub(&p->p_rux.rux_runtime, PCPU_PTR(switchtime));
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td->td_generation++; /* bump preempt-detect counter */
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/*
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* Don't perform context switches from the debugger.
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*/
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if (kdb_active) {
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mtx_unlock_spin(&sched_lock);
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kdb_backtrace();
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kdb_reenter();
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panic("%s: did not reenter debugger", __func__);
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}
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/*
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* Check if the process exceeds its cpu resource allocation. If
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* over max, arrange to kill the process in ast().
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*/
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if (p->p_cpulimit != RLIM_INFINITY &&
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p->p_rux.rux_runtime.sec > p->p_cpulimit) {
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p->p_sflag |= PS_XCPU;
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td->td_flags |= TDF_ASTPENDING;
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}
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/*
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* Finish up stats for outgoing thread.
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*/
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cnt.v_swtch++;
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PCPU_SET(switchtime, new_switchtime);
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PCPU_SET(switchticks, ticks);
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CTR4(KTR_PROC, "mi_switch: old thread %p (kse %p, pid %ld, %s)",
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(void *)td, td->td_sched, (long)p->p_pid, p->p_comm);
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if ((flags & SW_VOL) && (td->td_proc->p_flag & P_SA))
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newtd = thread_switchout(td, flags, newtd);
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sched_switch(td, newtd, flags);
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CTR4(KTR_PROC, "mi_switch: new thread %p (kse %p, pid %ld, %s)",
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(void *)td, td->td_sched, (long)p->p_pid, p->p_comm);
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/*
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* If the last thread was exiting, finish cleaning it up.
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*/
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if ((td = PCPU_GET(deadthread))) {
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PCPU_SET(deadthread, NULL);
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thread_stash(td);
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}
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}
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/*
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* Change process state to be runnable,
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* placing it on the run queue if it is in memory,
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* and awakening the swapper if it isn't in memory.
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*/
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void
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setrunnable(struct thread *td)
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{
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struct proc *p;
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p = td->td_proc;
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mtx_assert(&sched_lock, MA_OWNED);
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switch (p->p_state) {
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case PRS_ZOMBIE:
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panic("setrunnable(1)");
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default:
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break;
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}
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switch (td->td_state) {
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case TDS_RUNNING:
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case TDS_RUNQ:
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return;
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case TDS_INHIBITED:
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/*
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* If we are only inhibited because we are swapped out
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* then arange to swap in this process. Otherwise just return.
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*/
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if (td->td_inhibitors != TDI_SWAPPED)
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return;
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/* XXX: intentional fall-through ? */
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case TDS_CAN_RUN:
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break;
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default:
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printf("state is 0x%x", td->td_state);
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panic("setrunnable(2)");
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}
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if ((p->p_sflag & PS_INMEM) == 0) {
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if ((p->p_sflag & PS_SWAPPINGIN) == 0) {
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p->p_sflag |= PS_SWAPINREQ;
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#ifndef SMP
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/*
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* XXX: Disabled on SMP due to a LOR between
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* sched_lock and the sleepqueue chain locks.
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*/
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wakeup(&proc0);
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#endif
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}
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} else
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sched_wakeup(td);
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}
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/*
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* Compute a tenex style load average of a quantity on
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* 1, 5 and 15 minute intervals.
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* XXXKSE Needs complete rewrite when correct info is available.
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* Completely Bogus.. only works with 1:1 (but compiles ok now :-)
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*/
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static void
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loadav(void *arg)
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{
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int i, nrun;
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struct loadavg *avg;
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nrun = sched_load();
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avg = &averunnable;
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for (i = 0; i < 3; i++)
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avg->ldavg[i] = (cexp[i] * avg->ldavg[i] +
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nrun * FSCALE * (FSCALE - cexp[i])) >> FSHIFT;
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/*
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* Schedule the next update to occur after 5 seconds, but add a
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* random variation to avoid synchronisation with processes that
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* run at regular intervals.
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*/
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callout_reset(&loadav_callout, hz * 4 + (int)(random() % (hz * 2 + 1)),
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loadav, NULL);
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}
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static void
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lboltcb(void *arg)
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{
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wakeup(&lbolt);
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callout_reset(&lbolt_callout, hz, lboltcb, NULL);
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}
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/* ARGSUSED */
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static void
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synch_setup(dummy)
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void *dummy;
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{
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callout_init(&loadav_callout, CALLOUT_MPSAFE);
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callout_init(&lbolt_callout, CALLOUT_MPSAFE);
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/* Kick off timeout driven events by calling first time. */
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loadav(NULL);
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lboltcb(NULL);
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}
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/*
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* General purpose yield system call
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*/
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int
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yield(struct thread *td, struct yield_args *uap)
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{
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struct ksegrp *kg;
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kg = td->td_ksegrp;
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mtx_assert(&Giant, MA_NOTOWNED);
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mtx_lock_spin(&sched_lock);
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sched_prio(td, PRI_MAX_TIMESHARE);
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mi_switch(SW_VOL, NULL);
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mtx_unlock_spin(&sched_lock);
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td->td_retval[0] = 0;
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return (0);
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}
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