diff options
Diffstat (limited to 'sys/kern/kern_synch.c')
| -rw-r--r-- | sys/kern/kern_synch.c | 690 |
1 files changed, 690 insertions, 0 deletions
diff --git a/sys/kern/kern_synch.c b/sys/kern/kern_synch.c new file mode 100644 index 0000000..7b4784f --- /dev/null +++ b/sys/kern/kern_synch.c @@ -0,0 +1,690 @@ +/*- + * 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. + * 3. All advertising materials mentioning features or use of this software + * must display the following acknowledgement: + * This product includes software developed by the University of + * California, Berkeley and its contributors. + * 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("$FreeBSD$"); + +#include "opt_ddb.h" +#include "opt_ktrace.h" +#ifdef __i386__ +#include "opt_swtch.h" +#endif + +#include <sys/param.h> +#include <sys/systm.h> +#include <sys/condvar.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/smp.h> +#include <sys/sx.h> +#include <sys/sysctl.h> +#include <sys/sysproto.h> +#include <sys/vmmeter.h> +#ifdef DDB +#include <ddb/ddb.h> +#endif +#ifdef KTRACE +#include <sys/uio.h> +#include <sys/ktrace.h> +#endif + +#include <machine/cpu.h> + +static void sched_setup(void *dummy); +SYSINIT(sched_setup, SI_SUB_KICK_SCHEDULER, SI_ORDER_FIRST, sched_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 endtsleep(void *); +static void loadav(void *arg); +static void lboltcb(void *arg); + +/* + * We're only looking at 7 bits of the address; everything is + * aligned to 4, lots of things are aligned to greater powers + * of 2. Shift right by 8, i.e. drop the bottom 256 worth. + */ +#define TABLESIZE 128 +static TAILQ_HEAD(slpquehead, thread) slpque[TABLESIZE]; +#define LOOKUP(x) (((intptr_t)(x) >> 8) & (TABLESIZE - 1)) + +void +sleepinit(void) +{ + int i; + + hogticks = (hz / 10) * 2; /* Default only. */ + for (i = 0; i < TABLESIZE; i++) + TAILQ_INIT(&slpque[i]); +} + +/* + * 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 = curthread; + struct proc *p = td->td_proc; + int sig, catch = priority & PCATCH; + int rval = 0; + WITNESS_SAVE_DECL(mtx); + +#ifdef KTRACE + if (KTRPOINT(td, KTR_CSW)) + ktrcsw(1, 0); +#endif + /* XXX: mtx == NULL ?? */ + WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, &mtx->mtx_object, + "Sleeping on \"%s\"", wmesg); + KASSERT(timo != 0 || mtx_owned(&Giant) || mtx != NULL, + ("sleeping without a mutex")); + /* + * If we are capable of async syscalls and there isn't already + * another one ready to return, start a new thread + * and queue it as ready to run. Note that there is danger here + * because we need to make sure that we don't sleep allocating + * the thread (recursion here might be bad). + */ + mtx_lock_spin(&sched_lock); + if (p->p_flag & P_SA || p->p_numthreads > 1) { + /* + * Just don't bother if we are exiting + * and not the exiting thread or thread was marked as + * interrupted. + */ + if (catch) { + if ((p->p_flag & P_WEXIT) && p->p_singlethread != td) { + mtx_unlock_spin(&sched_lock); + return (EINTR); + } + if (td->td_flags & TDF_INTERRUPT) { + mtx_unlock_spin(&sched_lock); + return (td->td_intrval); + } + } + } + if (cold ) { + /* + * During autoconfiguration, just give interrupts + * a chance, then just return. + * Don't run any other procs or panic below, + * in case this is the idle process and already asleep. + */ + if (mtx != NULL && priority & PDROP) + mtx_unlock(mtx); + mtx_unlock_spin(&sched_lock); + return (0); + } + + DROP_GIANT(); + + if (mtx != NULL) { + mtx_assert(mtx, MA_OWNED | MA_NOTRECURSED); + WITNESS_SAVE(&mtx->mtx_object, mtx); + mtx_unlock(mtx); + if (priority & PDROP) + mtx = NULL; + } + + KASSERT(p != NULL, ("msleep1")); + KASSERT(ident != NULL && TD_IS_RUNNING(td), ("msleep")); + + CTR5(KTR_PROC, "msleep: thread %p (pid %d, %s) on %s (%p)", + td, p->p_pid, p->p_comm, wmesg, ident); + + td->td_wchan = ident; + td->td_wmesg = wmesg; + TAILQ_INSERT_TAIL(&slpque[LOOKUP(ident)], td, td_slpq); + TD_SET_ON_SLEEPQ(td); + if (timo) + callout_reset(&td->td_slpcallout, timo, endtsleep, td); + /* + * 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, td->td_wchan will be 0 upon return from cursig. + */ + if (catch) { + CTR3(KTR_PROC, "msleep caught: thread %p (pid %d, %s)", td, + p->p_pid, p->p_comm); + td->td_flags |= TDF_SINTR; + mtx_unlock_spin(&sched_lock); + PROC_LOCK(p); + mtx_lock(&p->p_sigacts->ps_mtx); + sig = cursig(td); + mtx_unlock(&p->p_sigacts->ps_mtx); + if (sig == 0 && thread_suspend_check(1)) + sig = SIGSTOP; + mtx_lock_spin(&sched_lock); + PROC_UNLOCK(p); + if (sig != 0) { + if (TD_ON_SLEEPQ(td)) + unsleep(td); + } else if (!TD_ON_SLEEPQ(td)) + catch = 0; + } else + sig = 0; + + /* + * Let the scheduler know we're about to voluntarily go to sleep. + */ + sched_sleep(td, priority & PRIMASK); + + if (TD_ON_SLEEPQ(td)) { + p->p_stats->p_ru.ru_nvcsw++; + TD_SET_SLEEPING(td); + mi_switch(); + } + /* + * We're awake from voluntary sleep. + */ + CTR3(KTR_PROC, "msleep resume: thread %p (pid %d, %s)", td, p->p_pid, + p->p_comm); + KASSERT(TD_IS_RUNNING(td), ("running but not TDS_RUNNING")); + td->td_flags &= ~TDF_SINTR; + if (td->td_flags & TDF_TIMEOUT) { + td->td_flags &= ~TDF_TIMEOUT; + if (sig == 0) + rval = EWOULDBLOCK; + } else if (td->td_flags & TDF_TIMOFAIL) { + td->td_flags &= ~TDF_TIMOFAIL; + } else if (timo && callout_stop(&td->td_slpcallout) == 0) { + /* + * This isn't supposed to be pretty. If we are here, then + * the endtsleep() callout is currently executing on another + * CPU and is either spinning on the sched_lock or will be + * soon. If we don't synchronize here, there is a chance + * that this process may msleep() again before the callout + * has a chance to run and the callout may end up waking up + * the wrong msleep(). Yuck. + */ + TD_SET_SLEEPING(td); + p->p_stats->p_ru.ru_nivcsw++; + mi_switch(); + td->td_flags &= ~TDF_TIMOFAIL; + } + if ((td->td_flags & TDF_INTERRUPT) && (priority & PCATCH) && + (rval == 0)) { + rval = td->td_intrval; + } + mtx_unlock_spin(&sched_lock); + + if (rval == 0 && catch) { + PROC_LOCK(p); + /* XXX: shouldn't we always be calling cursig() */ + mtx_lock(&p->p_sigacts->ps_mtx); + if (sig != 0 || (sig = cursig(td))) { + if (SIGISMEMBER(p->p_sigacts->ps_sigintr, sig)) + rval = EINTR; + else + rval = ERESTART; + } + mtx_unlock(&p->p_sigacts->ps_mtx); + PROC_UNLOCK(p); + } +#ifdef KTRACE + if (KTRPOINT(td, KTR_CSW)) + ktrcsw(0, 0); +#endif + PICKUP_GIANT(); + if (mtx != NULL) { + mtx_lock(mtx); + WITNESS_RESTORE(&mtx->mtx_object, mtx); + } + return (rval); +} + +/* + * Implement timeout for msleep() + * + * If process hasn't been awakened (wchan non-zero), + * set timeout flag and undo the sleep. If proc + * is stopped, just unsleep so it will remain stopped. + * MP-safe, called without the Giant mutex. + */ +static void +endtsleep(arg) + void *arg; +{ + register struct thread *td = arg; + + CTR3(KTR_PROC, "endtsleep: thread %p (pid %d, %s)", + td, td->td_proc->p_pid, td->td_proc->p_comm); + mtx_lock_spin(&sched_lock); + /* + * This is the other half of the synchronization with msleep() + * described above. If the TDS_TIMEOUT flag is set, we lost the + * race and just need to put the process back on the runqueue. + */ + if (TD_ON_SLEEPQ(td)) { + TAILQ_REMOVE(&slpque[LOOKUP(td->td_wchan)], td, td_slpq); + TD_CLR_ON_SLEEPQ(td); + td->td_flags |= TDF_TIMEOUT; + td->td_wmesg = NULL; + } else { + td->td_flags |= TDF_TIMOFAIL; + } + TD_CLR_SLEEPING(td); + setrunnable(td); + mtx_unlock_spin(&sched_lock); +} + +/* + * Abort a thread, as if an interrupt had occured. Only abort + * interruptable waits (unfortunatly it isn't only safe to abort others). + * This is about identical to cv_abort(). + * Think about merging them? + * Also, whatever the signal code does... + */ +void +abortsleep(struct thread *td) +{ + + mtx_assert(&sched_lock, MA_OWNED); + /* + * If the TDF_TIMEOUT flag is set, just leave. A + * timeout is scheduled anyhow. + */ + if ((td->td_flags & (TDF_TIMEOUT | TDF_SINTR)) == TDF_SINTR) { + if (TD_ON_SLEEPQ(td)) { + unsleep(td); + TD_CLR_SLEEPING(td); + setrunnable(td); + } + } +} + +/* + * Remove a process from its wait queue + */ +void +unsleep(struct thread *td) +{ + + mtx_lock_spin(&sched_lock); + if (TD_ON_SLEEPQ(td)) { + TAILQ_REMOVE(&slpque[LOOKUP(td->td_wchan)], td, td_slpq); + TD_CLR_ON_SLEEPQ(td); + td->td_wmesg = NULL; + } + mtx_unlock_spin(&sched_lock); +} + +/* + * Make all processes sleeping on the specified identifier runnable. + */ +void +wakeup(ident) + register void *ident; +{ + register struct slpquehead *qp; + register struct thread *td; + struct thread *ntd; + struct proc *p; + + mtx_lock_spin(&sched_lock); + qp = &slpque[LOOKUP(ident)]; +restart: + for (td = TAILQ_FIRST(qp); td != NULL; td = ntd) { + ntd = TAILQ_NEXT(td, td_slpq); + if (td->td_wchan == ident) { + unsleep(td); + TD_CLR_SLEEPING(td); + setrunnable(td); + p = td->td_proc; + CTR3(KTR_PROC,"wakeup: thread %p (pid %d, %s)", + td, p->p_pid, p->p_comm); + goto restart; + } + } + mtx_unlock_spin(&sched_lock); +} + +/* + * Make a process sleeping on the specified identifier runnable. + * May wake more than one process if a target process is currently + * swapped out. + */ +void +wakeup_one(ident) + register void *ident; +{ + register struct slpquehead *qp; + register struct thread *td; + register struct proc *p; + struct thread *ntd; + + mtx_lock_spin(&sched_lock); + qp = &slpque[LOOKUP(ident)]; + for (td = TAILQ_FIRST(qp); td != NULL; td = ntd) { + ntd = TAILQ_NEXT(td, td_slpq); + if (td->td_wchan == ident) { + unsleep(td); + TD_CLR_SLEEPING(td); + setrunnable(td); + p = td->td_proc; + CTR3(KTR_PROC,"wakeup1: thread %p (pid %d, %s)", + td, p->p_pid, p->p_comm); + break; + } + } + mtx_unlock_spin(&sched_lock); +} + +/* + * The machine independent parts of mi_switch(). + */ +void +mi_switch(void) +{ + struct bintime new_switchtime; + struct thread *td; +#if !defined(__alpha__) && !defined(__powerpc__) + struct thread *newtd; +#endif + struct proc *p; + u_int sched_nest; + + 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, + ("mi_switch: switch in a critical section")); + + /* + * 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_runtime, &new_switchtime); + bintime_sub(&p->p_runtime, PCPU_PTR(switchtime)); + +#ifdef DDB + /* + * Don't perform context switches from the debugger. + */ + if (db_active) { + mtx_unlock_spin(&sched_lock); + db_print_backtrace(); + db_error("Context switches not allowed in the debugger."); + } +#endif + + /* + * 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_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); + CTR3(KTR_PROC, "mi_switch: old thread %p (pid %d, %s)", td, p->p_pid, + p->p_comm); + sched_nest = sched_lock.mtx_recurse; + if (td->td_proc->p_flag & P_SA) + thread_switchout(td); + sched_switchout(td); + +#if !defined(__alpha__) && !defined(__powerpc__) + newtd = choosethread(); + if (td != newtd) + cpu_switch(td, newtd); /* SHAZAM!! */ +#else + cpu_switch(); /* SHAZAM!!*/ +#endif + + sched_lock.mtx_recurse = sched_nest; + sched_lock.mtx_lock = (uintptr_t)td; + sched_switchin(td); + + /* + * Start setting up stats etc. for the incoming thread. + * Similar code in fork_exit() is returned to by cpu_switch() + * in the case of a new thread/process. + */ + CTR3(KTR_PROC, "mi_switch: new thread %p (pid %d, %s)", td, p->p_pid, + p->p_comm); + if (PCPU_GET(switchtime.sec) == 0) + binuptime(PCPU_PTR(switchtime)); + PCPU_SET(switchticks, ticks); + + /* + * Call the switchin function while still holding the scheduler lock + * (used by the idlezero code and the general page-zeroing code) + */ + if (td->td_switchin) + td->td_switchin(); + + /* + * 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 = 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; + wakeup(&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; + struct proc *p; + struct thread *td; + + avg = &averunnable; + sx_slock(&allproc_lock); + nrun = 0; + FOREACH_PROC_IN_SYSTEM(p) { + FOREACH_THREAD_IN_PROC(p, td) { + switch (td->td_state) { + case TDS_RUNQ: + case TDS_RUNNING: + if ((p->p_flag & P_NOLOAD) != 0) + goto nextproc; + nrun++; /* XXXKSE */ + default: + break; + } +nextproc: + continue; + } + } + sx_sunlock(&allproc_lock); + 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 +sched_setup(dummy) + void *dummy; +{ + callout_init(&loadav_callout, 0); + callout_init(&lbolt_callout, 1); + + /* 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 = td->td_ksegrp; + + mtx_assert(&Giant, MA_NOTOWNED); + mtx_lock_spin(&sched_lock); + kg->kg_proc->p_stats->p_ru.ru_nvcsw++; + sched_prio(td, PRI_MAX_TIMESHARE); + mi_switch(); + mtx_unlock_spin(&sched_lock); + td->td_retval[0] = 0; + + return (0); +} + |
