d72e80f09a
- Adapt sleepqueues to the new thread_lock() mechanism. - Delay assigning the sleep queue spinlock as the thread lock until after we've checked for signals. It is illegal for a thread to return in mi_switch() with any lock assigned to td_lock other than the scheduler locks. - Change sleepq_catch_signals() to do the switch if necessary to simplify the callers. - Simplify timeout handling now that locking a sleeping thread has the side-effect of locking the sleepqueue. Some previous races are no longer possible. Tested by: kris, current@ Tested on: i386, amd64, ULE, 4BSD, libthr, libkse, PREEMPTION, etc. Discussed with: kris, attilio, kmacy, jhb, julian, bde (small parts each)
567 lines
15 KiB
C
567 lines
15 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 int pause_wchan;
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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 thread until a wakeup is
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* performed on the specified identifier. The thread 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 lock argument is unlocked before the caller is suspended, and
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* re-locked before _sleep() returns. If priority includes the PDROP
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* flag the lock is not re-locked before returning.
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*/
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int
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_sleep(ident, lock, priority, wmesg, timo)
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void *ident;
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struct lock_object *lock;
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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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struct lock_class *class;
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int catch, flags, lock_state, pri, rval;
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WITNESS_SAVE_DECL(lock_witness);
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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, lock,
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"Sleeping on \"%s\"", wmesg);
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KASSERT(timo != 0 || mtx_owned(&Giant) || lock != NULL ||
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ident == &lbolt, ("sleeping without a lock"));
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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 (lock != NULL)
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class = LOCK_CLASS(lock);
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else
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class = NULL;
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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 (lock != NULL && priority & PDROP)
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class->lc_unlock(lock);
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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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if (ident == &pause_wchan)
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flags = SLEEPQ_PAUSE;
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else
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flags = SLEEPQ_SLEEP;
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if (catch)
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flags |= SLEEPQ_INTERRUPTIBLE;
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sleepq_lock(ident);
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CTR5(KTR_PROC, "sleep: thread %ld (pid %ld, %s) on %s (%p)",
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td->td_tid, p->p_pid, p->p_comm, wmesg, ident);
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DROP_GIANT();
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if (lock != NULL && !(class->lc_flags & LC_SLEEPABLE)) {
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WITNESS_SAVE(lock, lock_witness);
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lock_state = class->lc_unlock(lock);
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} else
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/* GCC needs to follow the Yellow Brick Road */
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lock_state = -1;
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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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sleepq_add(ident, ident == &lbolt ? NULL : lock, wmesg, flags, 0);
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if (timo)
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sleepq_set_timeout(ident, timo);
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if (lock != NULL && class->lc_flags & LC_SLEEPABLE) {
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sleepq_release(ident);
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WITNESS_SAVE(lock, lock_witness);
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lock_state = class->lc_unlock(lock);
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sleepq_lock(ident);
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}
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/*
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* Adjust this thread's priority, if necessary.
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*/
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pri = priority & PRIMASK;
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if (pri != 0 && pri != td->td_priority) {
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thread_lock(td);
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sched_prio(td, pri);
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thread_unlock(td);
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}
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if (timo && catch)
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rval = sleepq_timedwait_sig(ident);
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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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#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 (lock != NULL && !(priority & PDROP)) {
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class->lc_lock(lock, lock_state);
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WITNESS_RESTORE(lock, lock_witness);
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}
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return (rval);
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}
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int
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msleep_spin(ident, mtx, wmesg, timo)
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void *ident;
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struct mtx *mtx;
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const char *wmesg;
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int timo;
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{
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struct thread *td;
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struct proc *p;
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int rval;
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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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KASSERT(mtx != NULL, ("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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return (0);
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}
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sleepq_lock(ident);
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CTR5(KTR_PROC, "msleep_spin: thread %ld (pid %ld, %s) on %s (%p)",
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td->td_tid, p->p_pid, p->p_comm, wmesg, ident);
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DROP_GIANT();
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mtx_assert(mtx, MA_OWNED | MA_NOTRECURSED);
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WITNESS_SAVE(&mtx->lock_object, mtx);
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mtx_unlock_spin(mtx);
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/*
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* We put ourselves on the sleep queue and start our timeout.
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*/
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sleepq_add(ident, &mtx->lock_object, wmesg, SLEEPQ_SLEEP, 0);
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if (timo)
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sleepq_set_timeout(ident, timo);
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/*
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* Can't call ktrace with any spin locks held so it can lock the
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* ktrace_mtx lock, and WITNESS_WARN considers it an error to hold
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* any spin lock. Thus, we have to drop the sleepq spin lock while
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* we handle those requests. This is safe since we have placed our
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* thread on the sleep queue already.
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*/
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#ifdef KTRACE
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if (KTRPOINT(td, KTR_CSW)) {
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sleepq_release(ident);
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ktrcsw(1, 0);
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sleepq_lock(ident);
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}
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#endif
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#ifdef WITNESS
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sleepq_release(ident);
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WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, "Sleeping on \"%s\"",
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wmesg);
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sleepq_lock(ident);
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#endif
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if (timo)
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rval = sleepq_timedwait(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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#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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mtx_lock_spin(mtx);
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WITNESS_RESTORE(&mtx->lock_object, mtx);
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return (rval);
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}
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/*
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* pause() is like tsleep() except that the intention is to not be
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* explicitly woken up by another thread. Instead, the current thread
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* simply wishes to sleep until the timeout expires. It is
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* implemented using a dummy wait channel.
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*/
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int
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pause(wmesg, timo)
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const char *wmesg;
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int timo;
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{
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KASSERT(timo != 0, ("pause: timeout required"));
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return (tsleep(&pause_wchan, 0, wmesg, timo));
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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_SLEEP, -1, 0);
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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_SLEEP, -1, 0);
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sleepq_release(ident);
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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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uint64_t new_switchtime;
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struct thread *td;
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struct proc *p;
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td = curthread; /* XXX */
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THREAD_LOCK_ASSERT(td, MA_OWNED | MA_NOTRECURSED);
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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_owepreempt) && (flags & SW_INVOL) != 0 &&
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newtd == NULL) || panicstr,
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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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/*
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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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thread_unlock(td);
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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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if (flags & SW_VOL)
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td->td_ru.ru_nvcsw++;
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else
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td->td_ru.ru_nivcsw++;
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/*
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* Compute the amount of time during which the current
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* thread was running, and add that to its total so far.
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*/
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new_switchtime = cpu_ticks();
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td->td_runtime += new_switchtime - PCPU_GET(switchtime);
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PCPU_SET(switchtime, new_switchtime);
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td->td_generation++; /* bump preempt-detect counter */
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PCPU_INC(cnt.v_swtch);
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PCPU_SET(switchticks, ticks);
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CTR4(KTR_PROC, "mi_switch: old thread %ld (kse %p, pid %ld, %s)",
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td->td_tid, td->td_sched, p->p_pid, p->p_comm);
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#if (KTR_COMPILE & KTR_SCHED) != 0
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if (TD_IS_IDLETHREAD(td))
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CTR3(KTR_SCHED, "mi_switch: %p(%s) prio %d idle",
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td, td->td_proc->p_comm, td->td_priority);
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else if (newtd != NULL)
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CTR5(KTR_SCHED,
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"mi_switch: %p(%s) prio %d preempted by %p(%s)",
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td, td->td_proc->p_comm, td->td_priority, newtd,
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newtd->td_proc->p_comm);
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else
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CTR6(KTR_SCHED,
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"mi_switch: %p(%s) prio %d inhibit %d wmesg %s lock %s",
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td, td->td_proc->p_comm, td->td_priority,
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td->td_inhibitors, td->td_wmesg, td->td_lockname);
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#endif
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/*
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* We call thread_switchout after the KTR_SCHED prints above so kse
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* selecting a new thread to run does not show up as a preemption.
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*/
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#ifdef KSE
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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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#endif
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sched_switch(td, newtd, flags);
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CTR3(KTR_SCHED, "mi_switch: running %p(%s) prio %d",
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td, td->td_proc->p_comm, td->td_priority);
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CTR4(KTR_PROC, "mi_switch: new thread %ld (kse %p, pid %ld, %s)",
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td->td_tid, td->td_sched, 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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THREAD_LOCK_ASSERT(td, 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:
|
|
/*
|
|
* 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 the thread 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)
|
|
{
|
|
mtx_assert(&Giant, MA_NOTOWNED);
|
|
(void)uap;
|
|
sched_relinquish(td);
|
|
return (0);
|
|
}
|