kern_synch.c revision 117372
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 117372 2003-07-10 01:02:59Z peter $"); 43 44#include "opt_ddb.h" 45#include "opt_ktrace.h" 46 47#include <sys/param.h> 48#include <sys/systm.h> 49#include <sys/condvar.h> 50#include <sys/kernel.h> 51#include <sys/ktr.h> 52#include <sys/lock.h> 53#include <sys/mutex.h> 54#include <sys/proc.h> 55#include <sys/resourcevar.h> 56#include <sys/sched.h> 57#include <sys/signalvar.h> 58#include <sys/smp.h> 59#include <sys/sx.h> 60#include <sys/sysctl.h> 61#include <sys/sysproto.h> 62#include <sys/vmmeter.h> 63#ifdef DDB 64#include <ddb/ddb.h> 65#endif 66#ifdef KTRACE 67#include <sys/uio.h> 68#include <sys/ktrace.h> 69#endif 70 71#include <machine/cpu.h> 72 73static void sched_setup(void *dummy); 74SYSINIT(sched_setup, SI_SUB_KICK_SCHEDULER, SI_ORDER_FIRST, sched_setup, NULL) 75 76int hogticks; 77int lbolt; 78 79static struct callout loadav_callout; 80static struct callout lbolt_callout; 81 82struct loadavg averunnable = 83 { {0, 0, 0}, FSCALE }; /* load average, of runnable procs */ 84/* 85 * Constants for averages over 1, 5, and 15 minutes 86 * when sampling at 5 second intervals. 87 */ 88static fixpt_t cexp[3] = { 89 0.9200444146293232 * FSCALE, /* exp(-1/12) */ 90 0.9834714538216174 * FSCALE, /* exp(-1/60) */ 91 0.9944598480048967 * FSCALE, /* exp(-1/180) */ 92}; 93 94/* kernel uses `FSCALE', userland (SHOULD) use kern.fscale */ 95static int fscale __unused = FSCALE; 96SYSCTL_INT(_kern, OID_AUTO, fscale, CTLFLAG_RD, 0, FSCALE, ""); 97 98static void endtsleep(void *); 99static void loadav(void *arg); 100static void lboltcb(void *arg); 101 102/* 103 * We're only looking at 7 bits of the address; everything is 104 * aligned to 4, lots of things are aligned to greater powers 105 * of 2. Shift right by 8, i.e. drop the bottom 256 worth. 106 */ 107#define TABLESIZE 128 108static TAILQ_HEAD(slpquehead, thread) slpque[TABLESIZE]; 109#define LOOKUP(x) (((intptr_t)(x) >> 8) & (TABLESIZE - 1)) 110 111void 112sleepinit(void) 113{ 114 int i; 115 116 hogticks = (hz / 10) * 2; /* Default only. */ 117 for (i = 0; i < TABLESIZE; i++) 118 TAILQ_INIT(&slpque[i]); 119} 120 121/* 122 * General sleep call. Suspends the current process until a wakeup is 123 * performed on the specified identifier. The process will then be made 124 * runnable with the specified priority. Sleeps at most timo/hz seconds 125 * (0 means no timeout). If pri includes PCATCH flag, signals are checked 126 * before and after sleeping, else signals are not checked. Returns 0 if 127 * awakened, EWOULDBLOCK if the timeout expires. If PCATCH is set and a 128 * signal needs to be delivered, ERESTART is returned if the current system 129 * call should be restarted if possible, and EINTR is returned if the system 130 * call should be interrupted by the signal (return EINTR). 131 * 132 * The mutex argument is exited before the caller is suspended, and 133 * entered before msleep returns. If priority includes the PDROP 134 * flag the mutex is not entered before returning. 135 */ 136 137int 138msleep(ident, mtx, priority, wmesg, timo) 139 void *ident; 140 struct mtx *mtx; 141 int priority, timo; 142 const char *wmesg; 143{ 144 struct thread *td = curthread; 145 struct proc *p = td->td_proc; 146 int sig, catch = priority & PCATCH; 147 int rval = 0; 148 WITNESS_SAVE_DECL(mtx); 149 150#ifdef KTRACE 151 if (KTRPOINT(td, KTR_CSW)) 152 ktrcsw(1, 0); 153#endif 154 /* XXX: mtx == NULL ?? */ 155 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, &mtx->mtx_object, 156 "Sleeping on \"%s\"", wmesg); 157 KASSERT(timo != 0 || mtx_owned(&Giant) || mtx != NULL, 158 ("sleeping without a mutex")); 159 /* 160 * If we are capable of async syscalls and there isn't already 161 * another one ready to return, start a new thread 162 * and queue it as ready to run. Note that there is danger here 163 * because we need to make sure that we don't sleep allocating 164 * the thread (recursion here might be bad). 165 */ 166 mtx_lock_spin(&sched_lock); 167 if (p->p_flag & P_SA || p->p_numthreads > 1) { 168 /* 169 * Just don't bother if we are exiting 170 * and not the exiting thread or thread was marked as 171 * interrupted. 172 */ 173 if (catch) { 174 if ((p->p_flag & P_WEXIT) && p->p_singlethread != td) { 175 mtx_unlock_spin(&sched_lock); 176 return (EINTR); 177 } 178 if (td->td_flags & TDF_INTERRUPT) { 179 mtx_unlock_spin(&sched_lock); 180 return (td->td_intrval); 181 } 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 rval = td->td_intrval; 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 mtx_lock(&p->p_sigacts->ps_mtx); 296 if (sig != 0 || (sig = cursig(td))) { 297 if (SIGISMEMBER(p->p_sigacts->ps_sigintr, sig)) 298 rval = EINTR; 299 else 300 rval = ERESTART; 301 } 302 mtx_unlock(&p->p_sigacts->ps_mtx); 303 PROC_UNLOCK(p); 304 } 305#ifdef KTRACE 306 if (KTRPOINT(td, KTR_CSW)) 307 ktrcsw(0, 0); 308#endif 309 PICKUP_GIANT(); 310 if (mtx != NULL) { 311 mtx_lock(mtx); 312 WITNESS_RESTORE(&mtx->mtx_object, mtx); 313 } 314 return (rval); 315} 316 317/* 318 * Implement timeout for msleep() 319 * 320 * If process hasn't been awakened (wchan non-zero), 321 * set timeout flag and undo the sleep. If proc 322 * is stopped, just unsleep so it will remain stopped. 323 * MP-safe, called without the Giant mutex. 324 */ 325static void 326endtsleep(arg) 327 void *arg; 328{ 329 register struct thread *td = arg; 330 331 CTR3(KTR_PROC, "endtsleep: thread %p (pid %d, %s)", 332 td, td->td_proc->p_pid, td->td_proc->p_comm); 333 mtx_lock_spin(&sched_lock); 334 /* 335 * This is the other half of the synchronization with msleep() 336 * described above. If the TDS_TIMEOUT flag is set, we lost the 337 * race and just need to put the process back on the runqueue. 338 */ 339 if (TD_ON_SLEEPQ(td)) { 340 TAILQ_REMOVE(&slpque[LOOKUP(td->td_wchan)], td, td_slpq); 341 TD_CLR_ON_SLEEPQ(td); 342 td->td_flags |= TDF_TIMEOUT; 343 td->td_wmesg = NULL; 344 } else { 345 td->td_flags |= TDF_TIMOFAIL; 346 } 347 TD_CLR_SLEEPING(td); 348 setrunnable(td); 349 mtx_unlock_spin(&sched_lock); 350} 351 352/* 353 * Abort a thread, as if an interrupt had occured. Only abort 354 * interruptable waits (unfortunatly it isn't only safe to abort others). 355 * This is about identical to cv_abort(). 356 * Think about merging them? 357 * Also, whatever the signal code does... 358 */ 359void 360abortsleep(struct thread *td) 361{ 362 363 mtx_assert(&sched_lock, MA_OWNED); 364 /* 365 * If the TDF_TIMEOUT flag is set, just leave. A 366 * timeout is scheduled anyhow. 367 */ 368 if ((td->td_flags & (TDF_TIMEOUT | TDF_SINTR)) == TDF_SINTR) { 369 if (TD_ON_SLEEPQ(td)) { 370 unsleep(td); 371 TD_CLR_SLEEPING(td); 372 setrunnable(td); 373 } 374 } 375} 376 377/* 378 * Remove a process from its wait queue 379 */ 380void 381unsleep(struct thread *td) 382{ 383 384 mtx_lock_spin(&sched_lock); 385 if (TD_ON_SLEEPQ(td)) { 386 TAILQ_REMOVE(&slpque[LOOKUP(td->td_wchan)], td, td_slpq); 387 TD_CLR_ON_SLEEPQ(td); 388 td->td_wmesg = NULL; 389 } 390 mtx_unlock_spin(&sched_lock); 391} 392 393/* 394 * Make all processes sleeping on the specified identifier runnable. 395 */ 396void 397wakeup(ident) 398 register void *ident; 399{ 400 register struct slpquehead *qp; 401 register struct thread *td; 402 struct thread *ntd; 403 struct proc *p; 404 405 mtx_lock_spin(&sched_lock); 406 qp = &slpque[LOOKUP(ident)]; 407restart: 408 for (td = TAILQ_FIRST(qp); td != NULL; td = ntd) { 409 ntd = TAILQ_NEXT(td, td_slpq); 410 if (td->td_wchan == ident) { 411 unsleep(td); 412 TD_CLR_SLEEPING(td); 413 setrunnable(td); 414 p = td->td_proc; 415 CTR3(KTR_PROC,"wakeup: thread %p (pid %d, %s)", 416 td, p->p_pid, p->p_comm); 417 goto restart; 418 } 419 } 420 mtx_unlock_spin(&sched_lock); 421} 422 423/* 424 * Make a process sleeping on the specified identifier runnable. 425 * May wake more than one process if a target process is currently 426 * swapped out. 427 */ 428void 429wakeup_one(ident) 430 register void *ident; 431{ 432 register struct slpquehead *qp; 433 register struct thread *td; 434 register struct proc *p; 435 struct thread *ntd; 436 437 mtx_lock_spin(&sched_lock); 438 qp = &slpque[LOOKUP(ident)]; 439 for (td = TAILQ_FIRST(qp); td != NULL; td = ntd) { 440 ntd = TAILQ_NEXT(td, td_slpq); 441 if (td->td_wchan == ident) { 442 unsleep(td); 443 TD_CLR_SLEEPING(td); 444 setrunnable(td); 445 p = td->td_proc; 446 CTR3(KTR_PROC,"wakeup1: thread %p (pid %d, %s)", 447 td, p->p_pid, p->p_comm); 448 break; 449 } 450 } 451 mtx_unlock_spin(&sched_lock); 452} 453 454/* 455 * The machine independent parts of mi_switch(). 456 */ 457void 458mi_switch(void) 459{ 460 struct bintime new_switchtime; 461 struct thread *td; 462#if !defined(__alpha__) && !defined(__powerpc__) 463 struct thread *newtd; 464#endif 465 struct proc *p; 466 u_int sched_nest; 467 468 mtx_assert(&sched_lock, MA_OWNED | MA_NOTRECURSED); 469 td = curthread; /* XXX */ 470 p = td->td_proc; /* XXX */ 471 KASSERT(!TD_ON_RUNQ(td), ("mi_switch: called by old code")); 472#ifdef INVARIANTS 473 if (!TD_ON_LOCK(td) && !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_SA) 517 thread_switchout(td); 518 sched_switchout(td); 519 520#if !defined(__alpha__) && !defined(__powerpc__) 521 newtd = choosethread(); 522 if (td != newtd) 523 cpu_switch(td, newtd); /* SHAZAM!! */ 524#else 525 cpu_switch(); /* SHAZAM!!*/ 526#endif 527 528 sched_lock.mtx_recurse = sched_nest; 529 sched_lock.mtx_lock = (uintptr_t)td; 530 sched_switchin(td); 531 532 /* 533 * Start setting up stats etc. for the incoming thread. 534 * Similar code in fork_exit() is returned to by cpu_switch() 535 * in the case of a new thread/process. 536 */ 537 CTR3(KTR_PROC, "mi_switch: new thread %p (pid %d, %s)", td, p->p_pid, 538 p->p_comm); 539 if (PCPU_GET(switchtime.sec) == 0) 540 binuptime(PCPU_PTR(switchtime)); 541 PCPU_SET(switchticks, ticks); 542 543 /* 544 * Call the switchin function while still holding the scheduler lock 545 * (used by the idlezero code and the general page-zeroing code) 546 */ 547 if (td->td_switchin) 548 td->td_switchin(); 549 550 /* 551 * If the last thread was exiting, finish cleaning it up. 552 */ 553 if ((td = PCPU_GET(deadthread))) { 554 PCPU_SET(deadthread, NULL); 555 thread_stash(td); 556 } 557} 558 559/* 560 * Change process state to be runnable, 561 * placing it on the run queue if it is in memory, 562 * and awakening the swapper if it isn't in memory. 563 */ 564void 565setrunnable(struct thread *td) 566{ 567 struct proc *p = td->td_proc; 568 569 mtx_assert(&sched_lock, MA_OWNED); 570 switch (p->p_state) { 571 case PRS_ZOMBIE: 572 panic("setrunnable(1)"); 573 default: 574 break; 575 } 576 switch (td->td_state) { 577 case TDS_RUNNING: 578 case TDS_RUNQ: 579 return; 580 case TDS_INHIBITED: 581 /* 582 * If we are only inhibited because we are swapped out 583 * then arange to swap in this process. Otherwise just return. 584 */ 585 if (td->td_inhibitors != TDI_SWAPPED) 586 return; 587 /* XXX: intentional fall-through ? */ 588 case TDS_CAN_RUN: 589 break; 590 default: 591 printf("state is 0x%x", td->td_state); 592 panic("setrunnable(2)"); 593 } 594 if ((p->p_sflag & PS_INMEM) == 0) { 595 if ((p->p_sflag & PS_SWAPPINGIN) == 0) { 596 p->p_sflag |= PS_SWAPINREQ; 597 wakeup(&proc0); 598 } 599 } else 600 sched_wakeup(td); 601} 602 603/* 604 * Compute a tenex style load average of a quantity on 605 * 1, 5 and 15 minute intervals. 606 * XXXKSE Needs complete rewrite when correct info is available. 607 * Completely Bogus.. only works with 1:1 (but compiles ok now :-) 608 */ 609static void 610loadav(void *arg) 611{ 612 int i, nrun; 613 struct loadavg *avg; 614 struct proc *p; 615 struct thread *td; 616 617 avg = &averunnable; 618 sx_slock(&allproc_lock); 619 nrun = 0; 620 FOREACH_PROC_IN_SYSTEM(p) { 621 FOREACH_THREAD_IN_PROC(p, td) { 622 switch (td->td_state) { 623 case TDS_RUNQ: 624 case TDS_RUNNING: 625 if ((p->p_flag & P_NOLOAD) != 0) 626 goto nextproc; 627 nrun++; /* XXXKSE */ 628 default: 629 break; 630 } 631nextproc: 632 continue; 633 } 634 } 635 sx_sunlock(&allproc_lock); 636 for (i = 0; i < 3; i++) 637 avg->ldavg[i] = (cexp[i] * avg->ldavg[i] + 638 nrun * FSCALE * (FSCALE - cexp[i])) >> FSHIFT; 639 640 /* 641 * Schedule the next update to occur after 5 seconds, but add a 642 * random variation to avoid synchronisation with processes that 643 * run at regular intervals. 644 */ 645 callout_reset(&loadav_callout, hz * 4 + (int)(random() % (hz * 2 + 1)), 646 loadav, NULL); 647} 648 649static void 650lboltcb(void *arg) 651{ 652 wakeup(&lbolt); 653 callout_reset(&lbolt_callout, hz, lboltcb, NULL); 654} 655 656/* ARGSUSED */ 657static void 658sched_setup(dummy) 659 void *dummy; 660{ 661 callout_init(&loadav_callout, 0); 662 callout_init(&lbolt_callout, 1); 663 664 /* Kick off timeout driven events by calling first time. */ 665 loadav(NULL); 666 lboltcb(NULL); 667} 668 669/* 670 * General purpose yield system call 671 */ 672int 673yield(struct thread *td, struct yield_args *uap) 674{ 675 struct ksegrp *kg = td->td_ksegrp; 676 677 mtx_assert(&Giant, MA_NOTOWNED); 678 mtx_lock_spin(&sched_lock); 679 kg->kg_proc->p_stats->p_ru.ru_nvcsw++; 680 sched_prio(td, PRI_MAX_TIMESHARE); 681 mi_switch(); 682 mtx_unlock_spin(&sched_lock); 683 td->td_retval[0] = 0; 684 685 return (0); 686} 687 688