kern_synch.c revision 114336
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 * $FreeBSD: head/sys/kern/kern_synch.c 114336 2003-04-30 21:45:03Z peter $ 40 */ 41 42#include "opt_ddb.h" 43#include "opt_ktrace.h" 44#ifdef __i386__ 45#include "opt_swtch.h" 46#endif 47 48#include <sys/param.h> 49#include <sys/systm.h> 50#include <sys/condvar.h> 51#include <sys/kernel.h> 52#include <sys/ktr.h> 53#include <sys/lock.h> 54#include <sys/mutex.h> 55#include <sys/proc.h> 56#include <sys/resourcevar.h> 57#include <sys/sched.h> 58#include <sys/signalvar.h> 59#include <sys/smp.h> 60#include <sys/sx.h> 61#include <sys/sysctl.h> 62#include <sys/sysproto.h> 63#include <sys/vmmeter.h> 64#ifdef DDB 65#include <ddb/ddb.h> 66#endif 67#ifdef KTRACE 68#include <sys/uio.h> 69#include <sys/ktrace.h> 70#endif 71 72#include <machine/cpu.h> 73#ifdef SWTCH_OPTIM_STATS 74#include <machine/md_var.h> 75#endif 76 77static void sched_setup(void *dummy); 78SYSINIT(sched_setup, SI_SUB_KICK_SCHEDULER, SI_ORDER_FIRST, sched_setup, NULL) 79 80int hogticks; 81int lbolt; 82 83static struct callout loadav_callout; 84static struct callout lbolt_callout; 85 86struct loadavg averunnable = 87 { {0, 0, 0}, FSCALE }; /* load average, of runnable procs */ 88/* 89 * Constants for averages over 1, 5, and 15 minutes 90 * when sampling at 5 second intervals. 91 */ 92static fixpt_t cexp[3] = { 93 0.9200444146293232 * FSCALE, /* exp(-1/12) */ 94 0.9834714538216174 * FSCALE, /* exp(-1/60) */ 95 0.9944598480048967 * FSCALE, /* exp(-1/180) */ 96}; 97 98/* kernel uses `FSCALE', userland (SHOULD) use kern.fscale */ 99static int fscale __unused = FSCALE; 100SYSCTL_INT(_kern, OID_AUTO, fscale, CTLFLAG_RD, 0, FSCALE, ""); 101 102static void endtsleep(void *); 103static void loadav(void *arg); 104static void lboltcb(void *arg); 105 106/* 107 * We're only looking at 7 bits of the address; everything is 108 * aligned to 4, lots of things are aligned to greater powers 109 * of 2. Shift right by 8, i.e. drop the bottom 256 worth. 110 */ 111#define TABLESIZE 128 112static TAILQ_HEAD(slpquehead, thread) slpque[TABLESIZE]; 113#define LOOKUP(x) (((intptr_t)(x) >> 8) & (TABLESIZE - 1)) 114 115void 116sleepinit(void) 117{ 118 int i; 119 120 hogticks = (hz / 10) * 2; /* Default only. */ 121 for (i = 0; i < TABLESIZE; i++) 122 TAILQ_INIT(&slpque[i]); 123} 124 125/* 126 * General sleep call. Suspends the current process until a wakeup is 127 * performed on the specified identifier. The process will then be made 128 * runnable with the specified priority. Sleeps at most timo/hz seconds 129 * (0 means no timeout). If pri includes PCATCH flag, signals are checked 130 * before and after sleeping, else signals are not checked. Returns 0 if 131 * awakened, EWOULDBLOCK if the timeout expires. If PCATCH is set and a 132 * signal needs to be delivered, ERESTART is returned if the current system 133 * call should be restarted if possible, and EINTR is returned if the system 134 * call should be interrupted by the signal (return EINTR). 135 * 136 * The mutex argument is exited before the caller is suspended, and 137 * entered before msleep returns. If priority includes the PDROP 138 * flag the mutex is not entered before returning. 139 */ 140 141int 142msleep(ident, mtx, priority, wmesg, timo) 143 void *ident; 144 struct mtx *mtx; 145 int priority, timo; 146 const char *wmesg; 147{ 148 struct thread *td = curthread; 149 struct proc *p = td->td_proc; 150 int sig, catch = priority & PCATCH; 151 int rval = 0; 152 WITNESS_SAVE_DECL(mtx); 153 154#ifdef KTRACE 155 if (KTRPOINT(td, KTR_CSW)) 156 ktrcsw(1, 0); 157#endif 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 * Hence the TDF_INMSLEEP flag. 169 */ 170 mtx_lock_spin(&sched_lock); 171 if (p->p_flag & P_THREADED || p->p_numthreads > 1) { 172 /* 173 * Just don't bother if we are exiting 174 * and not the exiting thread or thread was marked as 175 * interrupted. 176 */ 177 if (catch && 178 (((p->p_flag & P_WEXIT) && (p->p_singlethread != td)) || 179 (td->td_flags & TDF_INTERRUPT))) { 180 td->td_flags &= ~TDF_INTERRUPT; 181 mtx_unlock_spin(&sched_lock); 182 return (EINTR); 183 } 184 } 185 if (cold ) { 186 /* 187 * During autoconfiguration, just give interrupts 188 * a chance, then just return. 189 * Don't run any other procs or panic below, 190 * in case this is the idle process and already asleep. 191 */ 192 if (mtx != NULL && priority & PDROP) 193 mtx_unlock(mtx); 194 mtx_unlock_spin(&sched_lock); 195 return (0); 196 } 197 198 DROP_GIANT(); 199 200 if (mtx != NULL) { 201 mtx_assert(mtx, MA_OWNED | MA_NOTRECURSED); 202 WITNESS_SAVE(&mtx->mtx_object, mtx); 203 mtx_unlock(mtx); 204 if (priority & PDROP) 205 mtx = NULL; 206 } 207 208 KASSERT(p != NULL, ("msleep1")); 209 KASSERT(ident != NULL && TD_IS_RUNNING(td), ("msleep")); 210 211 CTR5(KTR_PROC, "msleep: thread %p (pid %d, %s) on %s (%p)", 212 td, p->p_pid, p->p_comm, wmesg, ident); 213 214 td->td_wchan = ident; 215 td->td_wmesg = wmesg; 216 TAILQ_INSERT_TAIL(&slpque[LOOKUP(ident)], td, td_slpq); 217 TD_SET_ON_SLEEPQ(td); 218 if (timo) 219 callout_reset(&td->td_slpcallout, timo, endtsleep, td); 220 /* 221 * We put ourselves on the sleep queue and start our timeout 222 * before calling thread_suspend_check, as we could stop there, and 223 * a wakeup or a SIGCONT (or both) could occur while we were stopped. 224 * without resuming us, thus we must be ready for sleep 225 * when cursig is called. If the wakeup happens while we're 226 * stopped, td->td_wchan will be 0 upon return from cursig. 227 */ 228 if (catch) { 229 CTR3(KTR_PROC, "msleep caught: thread %p (pid %d, %s)", td, 230 p->p_pid, p->p_comm); 231 td->td_flags |= TDF_SINTR; 232 mtx_unlock_spin(&sched_lock); 233 PROC_LOCK(p); 234 sig = cursig(td); 235 if (sig == 0 && thread_suspend_check(1)) 236 sig = SIGSTOP; 237 mtx_lock_spin(&sched_lock); 238 PROC_UNLOCK(p); 239 if (sig != 0) { 240 if (TD_ON_SLEEPQ(td)) 241 unsleep(td); 242 } else if (!TD_ON_SLEEPQ(td)) 243 catch = 0; 244 } else 245 sig = 0; 246 247 /* 248 * Let the scheduler know we're about to voluntarily go to sleep. 249 */ 250 sched_sleep(td, priority & PRIMASK); 251 252 if (TD_ON_SLEEPQ(td)) { 253 p->p_stats->p_ru.ru_nvcsw++; 254 TD_SET_SLEEPING(td); 255 mi_switch(); 256 } 257 /* 258 * We're awake from voluntary sleep. 259 */ 260 CTR3(KTR_PROC, "msleep resume: thread %p (pid %d, %s)", td, p->p_pid, 261 p->p_comm); 262 KASSERT(TD_IS_RUNNING(td), ("running but not TDS_RUNNING")); 263 td->td_flags &= ~TDF_SINTR; 264 if (td->td_flags & TDF_TIMEOUT) { 265 td->td_flags &= ~TDF_TIMEOUT; 266 if (sig == 0) 267 rval = EWOULDBLOCK; 268 } else if (td->td_flags & TDF_TIMOFAIL) { 269 td->td_flags &= ~TDF_TIMOFAIL; 270 } else if (timo && callout_stop(&td->td_slpcallout) == 0) { 271 /* 272 * This isn't supposed to be pretty. If we are here, then 273 * the endtsleep() callout is currently executing on another 274 * CPU and is either spinning on the sched_lock or will be 275 * soon. If we don't synchronize here, there is a chance 276 * that this process may msleep() again before the callout 277 * has a chance to run and the callout may end up waking up 278 * the wrong msleep(). Yuck. 279 */ 280 TD_SET_SLEEPING(td); 281 p->p_stats->p_ru.ru_nivcsw++; 282 mi_switch(); 283 td->td_flags &= ~TDF_TIMOFAIL; 284 } 285 if ((td->td_flags & TDF_INTERRUPT) && (priority & PCATCH) && 286 (rval == 0)) { 287 td->td_flags &= ~TDF_INTERRUPT; 288 rval = EINTR; 289 } 290 mtx_unlock_spin(&sched_lock); 291 292 if (rval == 0 && catch) { 293 PROC_LOCK(p); 294 /* XXX: shouldn't we always be calling cursig() */ 295 if (sig != 0 || (sig = cursig(td))) { 296 if (SIGISMEMBER(p->p_sigacts->ps_sigintr, sig)) 297 rval = EINTR; 298 else 299 rval = ERESTART; 300 } 301 PROC_UNLOCK(p); 302 } 303#ifdef KTRACE 304 if (KTRPOINT(td, KTR_CSW)) 305 ktrcsw(0, 0); 306#endif 307 PICKUP_GIANT(); 308 if (mtx != NULL) { 309 mtx_lock(mtx); 310 WITNESS_RESTORE(&mtx->mtx_object, mtx); 311 } 312 return (rval); 313} 314 315/* 316 * Implement timeout for msleep() 317 * 318 * If process hasn't been awakened (wchan non-zero), 319 * set timeout flag and undo the sleep. If proc 320 * is stopped, just unsleep so it will remain stopped. 321 * MP-safe, called without the Giant mutex. 322 */ 323static void 324endtsleep(arg) 325 void *arg; 326{ 327 register struct thread *td = arg; 328 329 CTR3(KTR_PROC, "endtsleep: thread %p (pid %d, %s)", 330 td, td->td_proc->p_pid, td->td_proc->p_comm); 331 mtx_lock_spin(&sched_lock); 332 /* 333 * This is the other half of the synchronization with msleep() 334 * described above. If the TDS_TIMEOUT flag is set, we lost the 335 * race and just need to put the process back on the runqueue. 336 */ 337 if (TD_ON_SLEEPQ(td)) { 338 TAILQ_REMOVE(&slpque[LOOKUP(td->td_wchan)], td, td_slpq); 339 TD_CLR_ON_SLEEPQ(td); 340 td->td_flags |= TDF_TIMEOUT; 341 td->td_wmesg = NULL; 342 } else { 343 td->td_flags |= TDF_TIMOFAIL; 344 } 345 TD_CLR_SLEEPING(td); 346 setrunnable(td); 347 mtx_unlock_spin(&sched_lock); 348} 349 350/* 351 * Abort a thread, as if an interrupt had occured. Only abort 352 * interruptable waits (unfortunatly it isn't only safe to abort others). 353 * This is about identical to cv_abort(). 354 * Think about merging them? 355 * Also, whatever the signal code does... 356 */ 357void 358abortsleep(struct thread *td) 359{ 360 361 mtx_assert(&sched_lock, MA_OWNED); 362 /* 363 * If the TDF_TIMEOUT flag is set, just leave. A 364 * timeout is scheduled anyhow. 365 */ 366 if ((td->td_flags & (TDF_TIMEOUT | TDF_SINTR)) == TDF_SINTR) { 367 if (TD_ON_SLEEPQ(td)) { 368 unsleep(td); 369 TD_CLR_SLEEPING(td); 370 setrunnable(td); 371 } 372 } 373} 374 375/* 376 * Remove a process from its wait queue 377 */ 378void 379unsleep(struct thread *td) 380{ 381 382 mtx_lock_spin(&sched_lock); 383 if (TD_ON_SLEEPQ(td)) { 384 TAILQ_REMOVE(&slpque[LOOKUP(td->td_wchan)], td, td_slpq); 385 TD_CLR_ON_SLEEPQ(td); 386 td->td_wmesg = NULL; 387 } 388 mtx_unlock_spin(&sched_lock); 389} 390 391/* 392 * Make all processes sleeping on the specified identifier runnable. 393 */ 394void 395wakeup(ident) 396 register void *ident; 397{ 398 register struct slpquehead *qp; 399 register struct thread *td; 400 struct thread *ntd; 401 struct proc *p; 402 403 mtx_lock_spin(&sched_lock); 404 qp = &slpque[LOOKUP(ident)]; 405restart: 406 for (td = TAILQ_FIRST(qp); td != NULL; td = ntd) { 407 ntd = TAILQ_NEXT(td, td_slpq); 408 if (td->td_wchan == ident) { 409 unsleep(td); 410 TD_CLR_SLEEPING(td); 411 setrunnable(td); 412 p = td->td_proc; 413 CTR3(KTR_PROC,"wakeup: thread %p (pid %d, %s)", 414 td, p->p_pid, p->p_comm); 415 goto restart; 416 } 417 } 418 mtx_unlock_spin(&sched_lock); 419} 420 421/* 422 * Make a process sleeping on the specified identifier runnable. 423 * May wake more than one process if a target process is currently 424 * swapped out. 425 */ 426void 427wakeup_one(ident) 428 register void *ident; 429{ 430 register struct slpquehead *qp; 431 register struct thread *td; 432 register struct proc *p; 433 struct thread *ntd; 434 435 mtx_lock_spin(&sched_lock); 436 qp = &slpque[LOOKUP(ident)]; 437 for (td = TAILQ_FIRST(qp); td != NULL; td = ntd) { 438 ntd = TAILQ_NEXT(td, td_slpq); 439 if (td->td_wchan == ident) { 440 unsleep(td); 441 TD_CLR_SLEEPING(td); 442 setrunnable(td); 443 p = td->td_proc; 444 CTR3(KTR_PROC,"wakeup1: thread %p (pid %d, %s)", 445 td, p->p_pid, p->p_comm); 446 break; 447 } 448 } 449 mtx_unlock_spin(&sched_lock); 450} 451 452/* 453 * The machine independent parts of mi_switch(). 454 */ 455void 456mi_switch(void) 457{ 458 struct bintime new_switchtime; 459 struct thread *td; 460#if defined(__i386__) || defined(__sparc64__) || defined(__amd64__) 461 struct thread *newtd; 462#endif 463 struct proc *p; 464 u_int sched_nest; 465 466 mtx_assert(&sched_lock, MA_OWNED | MA_NOTRECURSED); 467 td = curthread; /* XXX */ 468 p = td->td_proc; /* XXX */ 469 KASSERT(!TD_ON_RUNQ(td), ("mi_switch: called by old code")); 470#ifdef INVARIANTS 471 if (!TD_ON_LOCK(td) && 472 !TD_ON_RUNQ(td) && 473 !TD_IS_RUNNING(td)) 474 mtx_assert(&Giant, MA_NOTOWNED); 475#endif 476 KASSERT(td->td_critnest == 1, 477 ("mi_switch: switch in a critical section")); 478 479 /* 480 * Compute the amount of time during which the current 481 * process was running, and add that to its total so far. 482 */ 483 binuptime(&new_switchtime); 484 bintime_add(&p->p_runtime, &new_switchtime); 485 bintime_sub(&p->p_runtime, PCPU_PTR(switchtime)); 486 487#ifdef DDB 488 /* 489 * Don't perform context switches from the debugger. 490 */ 491 if (db_active) { 492 mtx_unlock_spin(&sched_lock); 493 db_print_backtrace(); 494 db_error("Context switches not allowed in the debugger."); 495 } 496#endif 497 498 /* 499 * Check if the process exceeds its cpu resource allocation. If 500 * over max, arrange to kill the process in ast(). 501 */ 502 if (p->p_cpulimit != RLIM_INFINITY && 503 p->p_runtime.sec > p->p_cpulimit) { 504 p->p_sflag |= PS_XCPU; 505 td->td_flags |= TDF_ASTPENDING; 506 } 507 508 /* 509 * Finish up stats for outgoing thread. 510 */ 511 cnt.v_swtch++; 512 PCPU_SET(switchtime, new_switchtime); 513 CTR3(KTR_PROC, "mi_switch: old thread %p (pid %d, %s)", td, p->p_pid, 514 p->p_comm); 515 sched_nest = sched_lock.mtx_recurse; 516 if (td->td_proc->p_flag & P_THREADED) 517 thread_switchout(td); 518 sched_switchout(td); 519 520#if defined(__i386__) || defined(__sparc64__) || defined(__amd64__) 521 newtd = choosethread(); 522 if (td != newtd) 523 cpu_switch(td, newtd); /* SHAZAM!! */ 524#ifdef SWTCH_OPTIM_STATS 525 else 526 stupid_switch++; 527#endif 528#else 529 cpu_switch(); /* SHAZAM!!*/ 530#endif 531 532 sched_lock.mtx_recurse = sched_nest; 533 sched_lock.mtx_lock = (uintptr_t)td; 534 sched_switchin(td); 535 536 /* 537 * Start setting up stats etc. for the incoming thread. 538 * Similar code in fork_exit() is returned to by cpu_switch() 539 * in the case of a new thread/process. 540 */ 541 CTR3(KTR_PROC, "mi_switch: new thread %p (pid %d, %s)", td, p->p_pid, 542 p->p_comm); 543 if (PCPU_GET(switchtime.sec) == 0) 544 binuptime(PCPU_PTR(switchtime)); 545 PCPU_SET(switchticks, ticks); 546 547 /* 548 * Call the switchin function while still holding the scheduler lock 549 * (used by the idlezero code and the general page-zeroing code) 550 */ 551 if (td->td_switchin) 552 td->td_switchin(); 553 554 /* 555 * If the last thread was exiting, finish cleaning it up. 556 */ 557 if ((td = PCPU_GET(deadthread))) { 558 PCPU_SET(deadthread, NULL); 559 thread_stash(td); 560 } 561} 562 563/* 564 * Change process state to be runnable, 565 * placing it on the run queue if it is in memory, 566 * and awakening the swapper if it isn't in memory. 567 */ 568void 569setrunnable(struct thread *td) 570{ 571 struct proc *p = td->td_proc; 572 573 mtx_assert(&sched_lock, MA_OWNED); 574 switch (p->p_state) { 575 case PRS_ZOMBIE: 576 panic("setrunnable(1)"); 577 default: 578 break; 579 } 580 switch (td->td_state) { 581 case TDS_RUNNING: 582 case TDS_RUNQ: 583 return; 584 case TDS_INHIBITED: 585 /* 586 * If we are only inhibited because we are swapped out 587 * then arange to swap in this process. Otherwise just return. 588 */ 589 if (td->td_inhibitors != TDI_SWAPPED) 590 return; 591 case TDS_CAN_RUN: 592 break; 593 default: 594 printf("state is 0x%x", td->td_state); 595 panic("setrunnable(2)"); 596 } 597 if ((p->p_sflag & PS_INMEM) == 0) { 598 if ((p->p_sflag & PS_SWAPPINGIN) == 0) { 599 p->p_sflag |= PS_SWAPINREQ; 600 wakeup(&proc0); 601 } 602 } else 603 sched_wakeup(td); 604} 605 606/* 607 * Compute a tenex style load average of a quantity on 608 * 1, 5 and 15 minute intervals. 609 * XXXKSE Needs complete rewrite when correct info is available. 610 * Completely Bogus.. only works with 1:1 (but compiles ok now :-) 611 */ 612static void 613loadav(void *arg) 614{ 615 int i, nrun; 616 struct loadavg *avg; 617 struct proc *p; 618 struct thread *td; 619 620 avg = &averunnable; 621 sx_slock(&allproc_lock); 622 nrun = 0; 623 FOREACH_PROC_IN_SYSTEM(p) { 624 FOREACH_THREAD_IN_PROC(p, td) { 625 switch (td->td_state) { 626 case TDS_RUNQ: 627 case TDS_RUNNING: 628 if ((p->p_flag & P_NOLOAD) != 0) 629 goto nextproc; 630 nrun++; /* XXXKSE */ 631 default: 632 break; 633 } 634nextproc: 635 continue; 636 } 637 } 638 sx_sunlock(&allproc_lock); 639 for (i = 0; i < 3; i++) 640 avg->ldavg[i] = (cexp[i] * avg->ldavg[i] + 641 nrun * FSCALE * (FSCALE - cexp[i])) >> FSHIFT; 642 643 /* 644 * Schedule the next update to occur after 5 seconds, but add a 645 * random variation to avoid synchronisation with processes that 646 * run at regular intervals. 647 */ 648 callout_reset(&loadav_callout, hz * 4 + (int)(random() % (hz * 2 + 1)), 649 loadav, NULL); 650} 651 652static void 653lboltcb(void *arg) 654{ 655 wakeup(&lbolt); 656 callout_reset(&lbolt_callout, hz, lboltcb, NULL); 657} 658 659/* ARGSUSED */ 660static void 661sched_setup(dummy) 662 void *dummy; 663{ 664 callout_init(&loadav_callout, 0); 665 callout_init(&lbolt_callout, 1); 666 667 /* Kick off timeout driven events by calling first time. */ 668 loadav(NULL); 669 lboltcb(NULL); 670} 671 672/* 673 * General purpose yield system call 674 */ 675int 676yield(struct thread *td, struct yield_args *uap) 677{ 678 struct ksegrp *kg = td->td_ksegrp; 679 680 mtx_assert(&Giant, MA_NOTOWNED); 681 mtx_lock_spin(&sched_lock); 682 kg->kg_proc->p_stats->p_ru.ru_nvcsw++; 683 sched_prio(td, PRI_MAX_TIMESHARE); 684 mi_switch(); 685 mtx_unlock_spin(&sched_lock); 686 td->td_retval[0] = 0; 687 688 return (0); 689} 690 691