kern_synch.c revision 116930
1/*- 2 * Copyright (c) 1982, 1986, 1990, 1991, 1993 3 * The Regents of the University of California. All rights reserved. 4 * (c) UNIX System Laboratories, Inc. 5 * All or some portions of this file are derived from material licensed 6 * to the University of California by American Telephone and Telegraph 7 * Co. or Unix System Laboratories, Inc. and are reproduced herein with 8 * the permission of UNIX System Laboratories, Inc. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 3. All advertising materials mentioning features or use of this software 19 * must display the following acknowledgement: 20 * This product includes software developed by the University of 21 * California, Berkeley and its contributors. 22 * 4. Neither the name of the University nor the names of its contributors 23 * may be used to endorse or promote products derived from this software 24 * without specific prior written permission. 25 * 26 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 27 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 28 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 29 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 30 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 31 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 32 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 33 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 34 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 35 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 36 * SUCH DAMAGE. 37 * 38 * @(#)kern_synch.c 8.9 (Berkeley) 5/19/95 39 */ 40 41#include <sys/cdefs.h> 42__FBSDID("$FreeBSD: head/sys/kern/kern_synch.c 116930 2003-06-27 22:39:14Z peter $"); 43 44#include "opt_ddb.h" 45#include "opt_ktrace.h" 46#ifdef __i386__ 47#include "opt_swtch.h" 48#endif 49 50#include <sys/param.h> 51#include <sys/systm.h> 52#include <sys/condvar.h> 53#include <sys/kernel.h> 54#include <sys/ktr.h> 55#include <sys/lock.h> 56#include <sys/mutex.h> 57#include <sys/proc.h> 58#include <sys/resourcevar.h> 59#include <sys/sched.h> 60#include <sys/signalvar.h> 61#include <sys/smp.h> 62#include <sys/sx.h> 63#include <sys/sysctl.h> 64#include <sys/sysproto.h> 65#include <sys/vmmeter.h> 66#ifdef DDB 67#include <ddb/ddb.h> 68#endif 69#ifdef KTRACE 70#include <sys/uio.h> 71#include <sys/ktrace.h> 72#endif 73 74#include <machine/cpu.h> 75 76static void sched_setup(void *dummy); 77SYSINIT(sched_setup, SI_SUB_KICK_SCHEDULER, SI_ORDER_FIRST, sched_setup, NULL) 78 79int hogticks; 80int lbolt; 81 82static struct callout loadav_callout; 83static struct callout lbolt_callout; 84 85struct loadavg averunnable = 86 { {0, 0, 0}, FSCALE }; /* load average, of runnable procs */ 87/* 88 * Constants for averages over 1, 5, and 15 minutes 89 * when sampling at 5 second intervals. 90 */ 91static fixpt_t cexp[3] = { 92 0.9200444146293232 * FSCALE, /* exp(-1/12) */ 93 0.9834714538216174 * FSCALE, /* exp(-1/60) */ 94 0.9944598480048967 * FSCALE, /* exp(-1/180) */ 95}; 96 97/* kernel uses `FSCALE', userland (SHOULD) use kern.fscale */ 98static int fscale __unused = FSCALE; 99SYSCTL_INT(_kern, OID_AUTO, fscale, CTLFLAG_RD, 0, FSCALE, ""); 100 101static void endtsleep(void *); 102static void loadav(void *arg); 103static void lboltcb(void *arg); 104 105/* 106 * We're only looking at 7 bits of the address; everything is 107 * aligned to 4, lots of things are aligned to greater powers 108 * of 2. Shift right by 8, i.e. drop the bottom 256 worth. 109 */ 110#define TABLESIZE 128 111static TAILQ_HEAD(slpquehead, thread) slpque[TABLESIZE]; 112#define LOOKUP(x) (((intptr_t)(x) >> 8) & (TABLESIZE - 1)) 113 114void 115sleepinit(void) 116{ 117 int i; 118 119 hogticks = (hz / 10) * 2; /* Default only. */ 120 for (i = 0; i < TABLESIZE; i++) 121 TAILQ_INIT(&slpque[i]); 122} 123 124/* 125 * General sleep call. Suspends the current process until a wakeup is 126 * performed on the specified identifier. The process will then be made 127 * runnable with the specified priority. Sleeps at most timo/hz seconds 128 * (0 means no timeout). If pri includes PCATCH flag, signals are checked 129 * before and after sleeping, else signals are not checked. Returns 0 if 130 * awakened, EWOULDBLOCK if the timeout expires. If PCATCH is set and a 131 * signal needs to be delivered, ERESTART is returned if the current system 132 * call should be restarted if possible, and EINTR is returned if the system 133 * call should be interrupted by the signal (return EINTR). 134 * 135 * The mutex argument is exited before the caller is suspended, and 136 * entered before msleep returns. If priority includes the PDROP 137 * flag the mutex is not entered before returning. 138 */ 139 140int 141msleep(ident, mtx, priority, wmesg, timo) 142 void *ident; 143 struct mtx *mtx; 144 int priority, timo; 145 const char *wmesg; 146{ 147 struct thread *td = curthread; 148 struct proc *p = td->td_proc; 149 int sig, catch = priority & PCATCH; 150 int rval = 0; 151 WITNESS_SAVE_DECL(mtx); 152 153#ifdef KTRACE 154 if (KTRPOINT(td, KTR_CSW)) 155 ktrcsw(1, 0); 156#endif 157 /* XXX: mtx == NULL ?? */ 158 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, &mtx->mtx_object, 159 "Sleeping on \"%s\"", wmesg); 160 KASSERT(timo != 0 || mtx_owned(&Giant) || mtx != NULL, 161 ("sleeping without a mutex")); 162 /* 163 * If we are capable of async syscalls and there isn't already 164 * another one ready to return, start a new thread 165 * and queue it as ready to run. Note that there is danger here 166 * because we need to make sure that we don't sleep allocating 167 * the thread (recursion here might be bad). 168 */ 169 mtx_lock_spin(&sched_lock); 170 if (p->p_flag & P_SA || p->p_numthreads > 1) { 171 /* 172 * Just don't bother if we are exiting 173 * and not the exiting thread or thread was marked as 174 * interrupted. 175 */ 176 if (catch && 177 (((p->p_flag & P_WEXIT) && (p->p_singlethread != td)) || 178 (td->td_flags & TDF_INTERRUPT))) { 179 td->td_flags &= ~TDF_INTERRUPT; 180 mtx_unlock_spin(&sched_lock); 181 return (EINTR); 182 } 183 } 184 if (cold ) { 185 /* 186 * During autoconfiguration, just give interrupts 187 * a chance, then just return. 188 * Don't run any other procs or panic below, 189 * in case this is the idle process and already asleep. 190 */ 191 if (mtx != NULL && priority & PDROP) 192 mtx_unlock(mtx); 193 mtx_unlock_spin(&sched_lock); 194 return (0); 195 } 196 197 DROP_GIANT(); 198 199 if (mtx != NULL) { 200 mtx_assert(mtx, MA_OWNED | MA_NOTRECURSED); 201 WITNESS_SAVE(&mtx->mtx_object, mtx); 202 mtx_unlock(mtx); 203 if (priority & PDROP) 204 mtx = NULL; 205 } 206 207 KASSERT(p != NULL, ("msleep1")); 208 KASSERT(ident != NULL && TD_IS_RUNNING(td), ("msleep")); 209 210 CTR5(KTR_PROC, "msleep: thread %p (pid %d, %s) on %s (%p)", 211 td, p->p_pid, p->p_comm, wmesg, ident); 212 213 td->td_wchan = ident; 214 td->td_wmesg = wmesg; 215 TAILQ_INSERT_TAIL(&slpque[LOOKUP(ident)], td, td_slpq); 216 TD_SET_ON_SLEEPQ(td); 217 if (timo) 218 callout_reset(&td->td_slpcallout, timo, endtsleep, td); 219 /* 220 * We put ourselves on the sleep queue and start our timeout 221 * before calling thread_suspend_check, as we could stop there, and 222 * a wakeup or a SIGCONT (or both) could occur while we were stopped. 223 * without resuming us, thus we must be ready for sleep 224 * when cursig is called. If the wakeup happens while we're 225 * stopped, td->td_wchan will be 0 upon return from cursig. 226 */ 227 if (catch) { 228 CTR3(KTR_PROC, "msleep caught: thread %p (pid %d, %s)", td, 229 p->p_pid, p->p_comm); 230 td->td_flags |= TDF_SINTR; 231 mtx_unlock_spin(&sched_lock); 232 PROC_LOCK(p); 233 mtx_lock(&p->p_sigacts->ps_mtx); 234 sig = cursig(td); 235 mtx_unlock(&p->p_sigacts->ps_mtx); 236 if (sig == 0 && thread_suspend_check(1)) 237 sig = SIGSTOP; 238 mtx_lock_spin(&sched_lock); 239 PROC_UNLOCK(p); 240 if (sig != 0) { 241 if (TD_ON_SLEEPQ(td)) 242 unsleep(td); 243 } else if (!TD_ON_SLEEPQ(td)) 244 catch = 0; 245 } else 246 sig = 0; 247 248 /* 249 * Let the scheduler know we're about to voluntarily go to sleep. 250 */ 251 sched_sleep(td, priority & PRIMASK); 252 253 if (TD_ON_SLEEPQ(td)) { 254 p->p_stats->p_ru.ru_nvcsw++; 255 TD_SET_SLEEPING(td); 256 mi_switch(); 257 } 258 /* 259 * We're awake from voluntary sleep. 260 */ 261 CTR3(KTR_PROC, "msleep resume: thread %p (pid %d, %s)", td, p->p_pid, 262 p->p_comm); 263 KASSERT(TD_IS_RUNNING(td), ("running but not TDS_RUNNING")); 264 td->td_flags &= ~TDF_SINTR; 265 if (td->td_flags & TDF_TIMEOUT) { 266 td->td_flags &= ~TDF_TIMEOUT; 267 if (sig == 0) 268 rval = EWOULDBLOCK; 269 } else if (td->td_flags & TDF_TIMOFAIL) { 270 td->td_flags &= ~TDF_TIMOFAIL; 271 } else if (timo && callout_stop(&td->td_slpcallout) == 0) { 272 /* 273 * This isn't supposed to be pretty. If we are here, then 274 * the endtsleep() callout is currently executing on another 275 * CPU and is either spinning on the sched_lock or will be 276 * soon. If we don't synchronize here, there is a chance 277 * that this process may msleep() again before the callout 278 * has a chance to run and the callout may end up waking up 279 * the wrong msleep(). Yuck. 280 */ 281 TD_SET_SLEEPING(td); 282 p->p_stats->p_ru.ru_nivcsw++; 283 mi_switch(); 284 td->td_flags &= ~TDF_TIMOFAIL; 285 } 286 if ((td->td_flags & TDF_INTERRUPT) && (priority & PCATCH) && 287 (rval == 0)) { 288 td->td_flags &= ~TDF_INTERRUPT; 289 rval = EINTR; 290 } 291 mtx_unlock_spin(&sched_lock); 292 293 if (rval == 0 && catch) { 294 PROC_LOCK(p); 295 /* XXX: shouldn't we always be calling cursig() */ 296 mtx_lock(&p->p_sigacts->ps_mtx); 297 if (sig != 0 || (sig = cursig(td))) { 298 if (SIGISMEMBER(p->p_sigacts->ps_sigintr, sig)) 299 rval = EINTR; 300 else 301 rval = ERESTART; 302 } 303 mtx_unlock(&p->p_sigacts->ps_mtx); 304 PROC_UNLOCK(p); 305 } 306#ifdef KTRACE 307 if (KTRPOINT(td, KTR_CSW)) 308 ktrcsw(0, 0); 309#endif 310 PICKUP_GIANT(); 311 if (mtx != NULL) { 312 mtx_lock(mtx); 313 WITNESS_RESTORE(&mtx->mtx_object, mtx); 314 } 315 return (rval); 316} 317 318/* 319 * Implement timeout for msleep() 320 * 321 * If process hasn't been awakened (wchan non-zero), 322 * set timeout flag and undo the sleep. If proc 323 * is stopped, just unsleep so it will remain stopped. 324 * MP-safe, called without the Giant mutex. 325 */ 326static void 327endtsleep(arg) 328 void *arg; 329{ 330 register struct thread *td = arg; 331 332 CTR3(KTR_PROC, "endtsleep: thread %p (pid %d, %s)", 333 td, td->td_proc->p_pid, td->td_proc->p_comm); 334 mtx_lock_spin(&sched_lock); 335 /* 336 * This is the other half of the synchronization with msleep() 337 * described above. If the TDS_TIMEOUT flag is set, we lost the 338 * race and just need to put the process back on the runqueue. 339 */ 340 if (TD_ON_SLEEPQ(td)) { 341 TAILQ_REMOVE(&slpque[LOOKUP(td->td_wchan)], td, td_slpq); 342 TD_CLR_ON_SLEEPQ(td); 343 td->td_flags |= TDF_TIMEOUT; 344 td->td_wmesg = NULL; 345 } else { 346 td->td_flags |= TDF_TIMOFAIL; 347 } 348 TD_CLR_SLEEPING(td); 349 setrunnable(td); 350 mtx_unlock_spin(&sched_lock); 351} 352 353/* 354 * Abort a thread, as if an interrupt had occured. Only abort 355 * interruptable waits (unfortunatly it isn't only safe to abort others). 356 * This is about identical to cv_abort(). 357 * Think about merging them? 358 * Also, whatever the signal code does... 359 */ 360void 361abortsleep(struct thread *td) 362{ 363 364 mtx_assert(&sched_lock, MA_OWNED); 365 /* 366 * If the TDF_TIMEOUT flag is set, just leave. A 367 * timeout is scheduled anyhow. 368 */ 369 if ((td->td_flags & (TDF_TIMEOUT | TDF_SINTR)) == TDF_SINTR) { 370 if (TD_ON_SLEEPQ(td)) { 371 unsleep(td); 372 TD_CLR_SLEEPING(td); 373 setrunnable(td); 374 } 375 } 376} 377 378/* 379 * Remove a process from its wait queue 380 */ 381void 382unsleep(struct thread *td) 383{ 384 385 mtx_lock_spin(&sched_lock); 386 if (TD_ON_SLEEPQ(td)) { 387 TAILQ_REMOVE(&slpque[LOOKUP(td->td_wchan)], td, td_slpq); 388 TD_CLR_ON_SLEEPQ(td); 389 td->td_wmesg = NULL; 390 } 391 mtx_unlock_spin(&sched_lock); 392} 393 394/* 395 * Make all processes sleeping on the specified identifier runnable. 396 */ 397void 398wakeup(ident) 399 register void *ident; 400{ 401 register struct slpquehead *qp; 402 register struct thread *td; 403 struct thread *ntd; 404 struct proc *p; 405 406 mtx_lock_spin(&sched_lock); 407 qp = &slpque[LOOKUP(ident)]; 408restart: 409 for (td = TAILQ_FIRST(qp); td != NULL; td = ntd) { 410 ntd = TAILQ_NEXT(td, td_slpq); 411 if (td->td_wchan == ident) { 412 unsleep(td); 413 TD_CLR_SLEEPING(td); 414 setrunnable(td); 415 p = td->td_proc; 416 CTR3(KTR_PROC,"wakeup: thread %p (pid %d, %s)", 417 td, p->p_pid, p->p_comm); 418 goto restart; 419 } 420 } 421 mtx_unlock_spin(&sched_lock); 422} 423 424/* 425 * Make a process sleeping on the specified identifier runnable. 426 * May wake more than one process if a target process is currently 427 * swapped out. 428 */ 429void 430wakeup_one(ident) 431 register void *ident; 432{ 433 register struct slpquehead *qp; 434 register struct thread *td; 435 register struct proc *p; 436 struct thread *ntd; 437 438 mtx_lock_spin(&sched_lock); 439 qp = &slpque[LOOKUP(ident)]; 440 for (td = TAILQ_FIRST(qp); td != NULL; td = ntd) { 441 ntd = TAILQ_NEXT(td, td_slpq); 442 if (td->td_wchan == ident) { 443 unsleep(td); 444 TD_CLR_SLEEPING(td); 445 setrunnable(td); 446 p = td->td_proc; 447 CTR3(KTR_PROC,"wakeup1: thread %p (pid %d, %s)", 448 td, p->p_pid, p->p_comm); 449 break; 450 } 451 } 452 mtx_unlock_spin(&sched_lock); 453} 454 455/* 456 * The machine independent parts of mi_switch(). 457 */ 458void 459mi_switch(void) 460{ 461 struct bintime new_switchtime; 462 struct thread *td; 463#if !defined(__alpha__) && !defined(__powerpc__) 464 struct thread *newtd; 465#endif 466 struct proc *p; 467 u_int sched_nest; 468 469 mtx_assert(&sched_lock, MA_OWNED | MA_NOTRECURSED); 470 td = curthread; /* XXX */ 471 p = td->td_proc; /* XXX */ 472 KASSERT(!TD_ON_RUNQ(td), ("mi_switch: called by old code")); 473#ifdef INVARIANTS 474 if (!TD_ON_LOCK(td) && !TD_IS_RUNNING(td)) 475 mtx_assert(&Giant, MA_NOTOWNED); 476#endif 477 KASSERT(td->td_critnest == 1, 478 ("mi_switch: switch in a critical section")); 479 480 /* 481 * Compute the amount of time during which the current 482 * process was running, and add that to its total so far. 483 */ 484 binuptime(&new_switchtime); 485 bintime_add(&p->p_runtime, &new_switchtime); 486 bintime_sub(&p->p_runtime, PCPU_PTR(switchtime)); 487 488#ifdef DDB 489 /* 490 * Don't perform context switches from the debugger. 491 */ 492 if (db_active) { 493 mtx_unlock_spin(&sched_lock); 494 db_print_backtrace(); 495 db_error("Context switches not allowed in the debugger."); 496 } 497#endif 498 499 /* 500 * Check if the process exceeds its cpu resource allocation. If 501 * over max, arrange to kill the process in ast(). 502 */ 503 if (p->p_cpulimit != RLIM_INFINITY && 504 p->p_runtime.sec > p->p_cpulimit) { 505 p->p_sflag |= PS_XCPU; 506 td->td_flags |= TDF_ASTPENDING; 507 } 508 509 /* 510 * Finish up stats for outgoing thread. 511 */ 512 cnt.v_swtch++; 513 PCPU_SET(switchtime, new_switchtime); 514 CTR3(KTR_PROC, "mi_switch: old thread %p (pid %d, %s)", td, p->p_pid, 515 p->p_comm); 516 sched_nest = sched_lock.mtx_recurse; 517 if (td->td_proc->p_flag & P_SA) 518 thread_switchout(td); 519 sched_switchout(td); 520 521#if !defined(__alpha__) && !defined(__powerpc__) 522 newtd = choosethread(); 523 if (td != newtd) 524 cpu_switch(td, newtd); /* SHAZAM!! */ 525#else 526 cpu_switch(); /* SHAZAM!!*/ 527#endif 528 529 sched_lock.mtx_recurse = sched_nest; 530 sched_lock.mtx_lock = (uintptr_t)td; 531 sched_switchin(td); 532 533 /* 534 * Start setting up stats etc. for the incoming thread. 535 * Similar code in fork_exit() is returned to by cpu_switch() 536 * in the case of a new thread/process. 537 */ 538 CTR3(KTR_PROC, "mi_switch: new thread %p (pid %d, %s)", td, p->p_pid, 539 p->p_comm); 540 if (PCPU_GET(switchtime.sec) == 0) 541 binuptime(PCPU_PTR(switchtime)); 542 PCPU_SET(switchticks, ticks); 543 544 /* 545 * Call the switchin function while still holding the scheduler lock 546 * (used by the idlezero code and the general page-zeroing code) 547 */ 548 if (td->td_switchin) 549 td->td_switchin(); 550 551 /* 552 * If the last thread was exiting, finish cleaning it up. 553 */ 554 if ((td = PCPU_GET(deadthread))) { 555 PCPU_SET(deadthread, NULL); 556 thread_stash(td); 557 } 558} 559 560/* 561 * Change process state to be runnable, 562 * placing it on the run queue if it is in memory, 563 * and awakening the swapper if it isn't in memory. 564 */ 565void 566setrunnable(struct thread *td) 567{ 568 struct proc *p = td->td_proc; 569 570 mtx_assert(&sched_lock, MA_OWNED); 571 switch (p->p_state) { 572 case PRS_ZOMBIE: 573 panic("setrunnable(1)"); 574 default: 575 break; 576 } 577 switch (td->td_state) { 578 case TDS_RUNNING: 579 case TDS_RUNQ: 580 return; 581 case TDS_INHIBITED: 582 /* 583 * If we are only inhibited because we are swapped out 584 * then arange to swap in this process. Otherwise just return. 585 */ 586 if (td->td_inhibitors != TDI_SWAPPED) 587 return; 588 /* XXX: intentional fall-through ? */ 589 case TDS_CAN_RUN: 590 break; 591 default: 592 printf("state is 0x%x", td->td_state); 593 panic("setrunnable(2)"); 594 } 595 if ((p->p_sflag & PS_INMEM) == 0) { 596 if ((p->p_sflag & PS_SWAPPINGIN) == 0) { 597 p->p_sflag |= PS_SWAPINREQ; 598 wakeup(&proc0); 599 } 600 } else 601 sched_wakeup(td); 602} 603 604/* 605 * Compute a tenex style load average of a quantity on 606 * 1, 5 and 15 minute intervals. 607 * XXXKSE Needs complete rewrite when correct info is available. 608 * Completely Bogus.. only works with 1:1 (but compiles ok now :-) 609 */ 610static void 611loadav(void *arg) 612{ 613 int i, nrun; 614 struct loadavg *avg; 615 struct proc *p; 616 struct thread *td; 617 618 avg = &averunnable; 619 sx_slock(&allproc_lock); 620 nrun = 0; 621 FOREACH_PROC_IN_SYSTEM(p) { 622 FOREACH_THREAD_IN_PROC(p, td) { 623 switch (td->td_state) { 624 case TDS_RUNQ: 625 case TDS_RUNNING: 626 if ((p->p_flag & P_NOLOAD) != 0) 627 goto nextproc; 628 nrun++; /* XXXKSE */ 629 default: 630 break; 631 } 632nextproc: 633 continue; 634 } 635 } 636 sx_sunlock(&allproc_lock); 637 for (i = 0; i < 3; i++) 638 avg->ldavg[i] = (cexp[i] * avg->ldavg[i] + 639 nrun * FSCALE * (FSCALE - cexp[i])) >> FSHIFT; 640 641 /* 642 * Schedule the next update to occur after 5 seconds, but add a 643 * random variation to avoid synchronisation with processes that 644 * run at regular intervals. 645 */ 646 callout_reset(&loadav_callout, hz * 4 + (int)(random() % (hz * 2 + 1)), 647 loadav, NULL); 648} 649 650static void 651lboltcb(void *arg) 652{ 653 wakeup(&lbolt); 654 callout_reset(&lbolt_callout, hz, lboltcb, NULL); 655} 656 657/* ARGSUSED */ 658static void 659sched_setup(dummy) 660 void *dummy; 661{ 662 callout_init(&loadav_callout, 0); 663 callout_init(&lbolt_callout, 1); 664 665 /* Kick off timeout driven events by calling first time. */ 666 loadav(NULL); 667 lboltcb(NULL); 668} 669 670/* 671 * General purpose yield system call 672 */ 673int 674yield(struct thread *td, struct yield_args *uap) 675{ 676 struct ksegrp *kg = td->td_ksegrp; 677 678 mtx_assert(&Giant, MA_NOTOWNED); 679 mtx_lock_spin(&sched_lock); 680 kg->kg_proc->p_stats->p_ru.ru_nvcsw++; 681 sched_prio(td, PRI_MAX_TIMESHARE); 682 mi_switch(); 683 mtx_unlock_spin(&sched_lock); 684 td->td_retval[0] = 0; 685 686 return (0); 687} 688 689