kern_synch.c revision 107719
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 107719 2002-12-10 02:33:45Z julian $ 40 */ 41 42#include "opt_ddb.h" 43#include "opt_ktrace.h" 44 45#include <sys/param.h> 46#include <sys/systm.h> 47#include <sys/condvar.h> 48#include <sys/kernel.h> 49#include <sys/ktr.h> 50#include <sys/lock.h> 51#include <sys/mutex.h> 52#include <sys/proc.h> 53#include <sys/resourcevar.h> 54#include <sys/sched.h> 55#include <sys/signalvar.h> 56#include <sys/smp.h> 57#include <sys/sx.h> 58#include <sys/sysctl.h> 59#include <sys/sysproto.h> 60#include <sys/vmmeter.h> 61#ifdef DDB 62#include <ddb/ddb.h> 63#endif 64#ifdef KTRACE 65#include <sys/uio.h> 66#include <sys/ktrace.h> 67#endif 68 69#include <machine/cpu.h> 70 71static void sched_setup(void *dummy); 72SYSINIT(sched_setup, SI_SUB_KICK_SCHEDULER, SI_ORDER_FIRST, sched_setup, NULL) 73 74int hogticks; 75int lbolt; 76 77static struct callout loadav_callout; 78static struct callout lbolt_callout; 79 80struct loadavg averunnable = 81 { {0, 0, 0}, FSCALE }; /* load average, of runnable procs */ 82/* 83 * Constants for averages over 1, 5, and 15 minutes 84 * when sampling at 5 second intervals. 85 */ 86static fixpt_t cexp[3] = { 87 0.9200444146293232 * FSCALE, /* exp(-1/12) */ 88 0.9834714538216174 * FSCALE, /* exp(-1/60) */ 89 0.9944598480048967 * FSCALE, /* exp(-1/180) */ 90}; 91 92/* kernel uses `FSCALE', userland (SHOULD) use kern.fscale */ 93static int fscale __unused = FSCALE; 94SYSCTL_INT(_kern, OID_AUTO, fscale, CTLFLAG_RD, 0, FSCALE, ""); 95 96static void endtsleep(void *); 97static void loadav(void *arg); 98static void lboltcb(void *arg); 99 100/* 101 * We're only looking at 7 bits of the address; everything is 102 * aligned to 4, lots of things are aligned to greater powers 103 * of 2. Shift right by 8, i.e. drop the bottom 256 worth. 104 */ 105#define TABLESIZE 128 106static TAILQ_HEAD(slpquehead, thread) slpque[TABLESIZE]; 107#define LOOKUP(x) (((intptr_t)(x) >> 8) & (TABLESIZE - 1)) 108 109void 110sleepinit(void) 111{ 112 int i; 113 114 hogticks = (hz / 10) * 2; /* Default only. */ 115 for (i = 0; i < TABLESIZE; i++) 116 TAILQ_INIT(&slpque[i]); 117} 118 119/* 120 * General sleep call. Suspends the current process until a wakeup is 121 * performed on the specified identifier. The process will then be made 122 * runnable with the specified priority. Sleeps at most timo/hz seconds 123 * (0 means no timeout). If pri includes PCATCH flag, signals are checked 124 * before and after sleeping, else signals are not checked. Returns 0 if 125 * awakened, EWOULDBLOCK if the timeout expires. If PCATCH is set and a 126 * signal needs to be delivered, ERESTART is returned if the current system 127 * call should be restarted if possible, and EINTR is returned if the system 128 * call should be interrupted by the signal (return EINTR). 129 * 130 * The mutex argument is exited before the caller is suspended, and 131 * entered before msleep returns. If priority includes the PDROP 132 * flag the mutex is not entered before returning. 133 */ 134 135int 136msleep(ident, mtx, priority, wmesg, timo) 137 void *ident; 138 struct mtx *mtx; 139 int priority, timo; 140 const char *wmesg; 141{ 142 struct thread *td = curthread; 143 struct proc *p = td->td_proc; 144 int sig, catch = priority & PCATCH; 145 int rval = 0; 146 WITNESS_SAVE_DECL(mtx); 147 148#ifdef KTRACE 149 if (KTRPOINT(td, KTR_CSW)) 150 ktrcsw(1, 0); 151#endif 152 WITNESS_SLEEP(0, &mtx->mtx_object); 153 KASSERT(timo != 0 || mtx_owned(&Giant) || mtx != NULL, 154 ("sleeping without a mutex")); 155 /* 156 * If we are capable of async syscalls and there isn't already 157 * another one ready to return, start a new thread 158 * and queue it as ready to run. Note that there is danger here 159 * because we need to make sure that we don't sleep allocating 160 * the thread (recursion here might be bad). 161 * Hence the TDF_INMSLEEP flag. 162 */ 163 if (p->p_flag & P_KSES) { 164 /* 165 * Just don't bother if we are exiting 166 * and not the exiting thread or thread was marked as 167 * interrupted. 168 */ 169 if (catch && 170 (((p->p_flag & P_WEXIT) && (p->p_singlethread != td)) || 171 (td->td_flags & TDF_INTERRUPT))) { 172 td->td_flags &= ~TDF_INTERRUPT; 173 return (EINTR); 174 } 175 mtx_lock_spin(&sched_lock); 176 if ((td->td_flags & (TDF_UNBOUND|TDF_INMSLEEP)) == 177 TDF_UNBOUND) { 178 /* 179 * Arrange for an upcall to be readied. 180 * it will not actually happen until all 181 * pending in-kernel work for this KSEGRP 182 * has been done. 183 */ 184 /* Don't recurse here! */ 185 td->td_flags |= TDF_INMSLEEP; 186 thread_schedule_upcall(td, td->td_kse); 187 td->td_flags &= ~TDF_INMSLEEP; 188 } 189 } else { 190 mtx_lock_spin(&sched_lock); 191 } 192 if (cold ) { 193 /* 194 * During autoconfiguration, just give interrupts 195 * a chance, then just return. 196 * Don't run any other procs or panic below, 197 * in case this is the idle process and already asleep. 198 */ 199 if (mtx != NULL && priority & PDROP) 200 mtx_unlock(mtx); 201 mtx_unlock_spin(&sched_lock); 202 return (0); 203 } 204 205 DROP_GIANT(); 206 207 if (mtx != NULL) { 208 mtx_assert(mtx, MA_OWNED | MA_NOTRECURSED); 209 WITNESS_SAVE(&mtx->mtx_object, mtx); 210 mtx_unlock(mtx); 211 if (priority & PDROP) 212 mtx = NULL; 213 } 214 215 KASSERT(p != NULL, ("msleep1")); 216 KASSERT(ident != NULL && TD_IS_RUNNING(td), ("msleep")); 217 218 CTR5(KTR_PROC, "msleep: thread %p (pid %d, %s) on %s (%p)", 219 td, p->p_pid, p->p_comm, wmesg, ident); 220 221 td->td_wchan = ident; 222 td->td_wmesg = wmesg; 223 TAILQ_INSERT_TAIL(&slpque[LOOKUP(ident)], td, td_slpq); 224 TD_SET_ON_SLEEPQ(td); 225 if (timo) 226 callout_reset(&td->td_slpcallout, timo, endtsleep, td); 227 /* 228 * We put ourselves on the sleep queue and start our timeout 229 * before calling thread_suspend_check, as we could stop there, and 230 * a wakeup or a SIGCONT (or both) could occur while we were stopped. 231 * without resuming us, thus we must be ready for sleep 232 * when cursig is called. If the wakeup happens while we're 233 * stopped, td->td_wchan will be 0 upon return from cursig. 234 */ 235 if (catch) { 236 CTR3(KTR_PROC, "msleep caught: thread %p (pid %d, %s)", td, 237 p->p_pid, p->p_comm); 238 td->td_flags |= TDF_SINTR; 239 mtx_unlock_spin(&sched_lock); 240 PROC_LOCK(p); 241 sig = cursig(td); 242 if (sig == 0 && thread_suspend_check(1)) 243 sig = SIGSTOP; 244 mtx_lock_spin(&sched_lock); 245 PROC_UNLOCK(p); 246 if (sig != 0) { 247 if (TD_ON_SLEEPQ(td)) 248 unsleep(td); 249 } else if (!TD_ON_SLEEPQ(td)) 250 catch = 0; 251 } else 252 sig = 0; 253 254 /* 255 * Let the scheduler know we're about to voluntarily go to sleep. 256 */ 257 sched_sleep(td, priority & PRIMASK); 258 259 if (TD_ON_SLEEPQ(td)) { 260 p->p_stats->p_ru.ru_nvcsw++; 261 TD_SET_SLEEPING(td); 262 mi_switch(); 263 } 264 /* 265 * We're awake from voluntary sleep. 266 */ 267 CTR3(KTR_PROC, "msleep resume: thread %p (pid %d, %s)", td, p->p_pid, 268 p->p_comm); 269 KASSERT(TD_IS_RUNNING(td), ("running but not TDS_RUNNING")); 270 td->td_flags &= ~TDF_SINTR; 271 if (td->td_flags & TDF_TIMEOUT) { 272 td->td_flags &= ~TDF_TIMEOUT; 273 if (sig == 0) 274 rval = EWOULDBLOCK; 275 } else if (td->td_flags & TDF_TIMOFAIL) { 276 td->td_flags &= ~TDF_TIMOFAIL; 277 } else if (timo && callout_stop(&td->td_slpcallout) == 0) { 278 /* 279 * This isn't supposed to be pretty. If we are here, then 280 * the endtsleep() callout is currently executing on another 281 * CPU and is either spinning on the sched_lock or will be 282 * soon. If we don't synchronize here, there is a chance 283 * that this process may msleep() again before the callout 284 * has a chance to run and the callout may end up waking up 285 * the wrong msleep(). Yuck. 286 */ 287 TD_SET_SLEEPING(td); 288 p->p_stats->p_ru.ru_nivcsw++; 289 mi_switch(); 290 td->td_flags &= ~TDF_TIMOFAIL; 291 } 292 if ((td->td_flags & TDF_INTERRUPT) && (priority & PCATCH) && 293 (rval == 0)) { 294 td->td_flags &= ~TDF_INTERRUPT; 295 rval = EINTR; 296 } 297 mtx_unlock_spin(&sched_lock); 298 299 if (rval == 0 && catch) { 300 PROC_LOCK(p); 301 /* XXX: shouldn't we always be calling cursig() */ 302 if (sig != 0 || (sig = cursig(td))) { 303 if (SIGISMEMBER(p->p_sigacts->ps_sigintr, sig)) 304 rval = EINTR; 305 else 306 rval = ERESTART; 307 } 308 PROC_UNLOCK(p); 309 } 310#ifdef KTRACE 311 if (KTRPOINT(td, KTR_CSW)) 312 ktrcsw(0, 0); 313#endif 314 PICKUP_GIANT(); 315 if (mtx != NULL) { 316 mtx_lock(mtx); 317 WITNESS_RESTORE(&mtx->mtx_object, mtx); 318 } 319 return (rval); 320} 321 322/* 323 * Implement timeout for msleep() 324 * 325 * If process hasn't been awakened (wchan non-zero), 326 * set timeout flag and undo the sleep. If proc 327 * is stopped, just unsleep so it will remain stopped. 328 * MP-safe, called without the Giant mutex. 329 */ 330static void 331endtsleep(arg) 332 void *arg; 333{ 334 register struct thread *td = arg; 335 336 CTR3(KTR_PROC, "endtsleep: thread %p (pid %d, %s)", 337 td, td->td_proc->p_pid, td->td_proc->p_comm); 338 mtx_lock_spin(&sched_lock); 339 /* 340 * This is the other half of the synchronization with msleep() 341 * described above. If the TDS_TIMEOUT flag is set, we lost the 342 * race and just need to put the process back on the runqueue. 343 */ 344 if (TD_ON_SLEEPQ(td)) { 345 TAILQ_REMOVE(&slpque[LOOKUP(td->td_wchan)], td, td_slpq); 346 TD_CLR_ON_SLEEPQ(td); 347 td->td_flags |= TDF_TIMEOUT; 348 } else { 349 td->td_flags |= TDF_TIMOFAIL; 350 } 351 TD_CLR_SLEEPING(td); 352 setrunnable(td); 353 mtx_unlock_spin(&sched_lock); 354} 355 356/* 357 * Abort a thread, as if an interrupt had occured. Only abort 358 * interruptable waits (unfortunatly it isn't only safe to abort others). 359 * This is about identical to cv_abort(). 360 * Think about merging them? 361 * Also, whatever the signal code does... 362 */ 363void 364abortsleep(struct thread *td) 365{ 366 367 mtx_assert(&sched_lock, MA_OWNED); 368 /* 369 * If the TDF_TIMEOUT flag is set, just leave. A 370 * timeout is scheduled anyhow. 371 */ 372 if ((td->td_flags & (TDF_TIMEOUT | TDF_SINTR)) == TDF_SINTR) { 373 if (TD_ON_SLEEPQ(td)) { 374 unsleep(td); 375 TD_CLR_SLEEPING(td); 376 setrunnable(td); 377 } 378 } 379} 380 381/* 382 * Remove a process from its wait queue 383 */ 384void 385unsleep(struct thread *td) 386{ 387 388 mtx_lock_spin(&sched_lock); 389 if (TD_ON_SLEEPQ(td)) { 390 TAILQ_REMOVE(&slpque[LOOKUP(td->td_wchan)], td, td_slpq); 391 TD_CLR_ON_SLEEPQ(td); 392 } 393 mtx_unlock_spin(&sched_lock); 394} 395 396/* 397 * Make all processes sleeping on the specified identifier runnable. 398 */ 399void 400wakeup(ident) 401 register void *ident; 402{ 403 register struct slpquehead *qp; 404 register struct thread *td; 405 struct thread *ntd; 406 struct proc *p; 407 408 mtx_lock_spin(&sched_lock); 409 qp = &slpque[LOOKUP(ident)]; 410restart: 411 for (td = TAILQ_FIRST(qp); td != NULL; td = ntd) { 412 ntd = TAILQ_NEXT(td, td_slpq); 413 if (td->td_wchan == ident) { 414 unsleep(td); 415 TD_CLR_SLEEPING(td); 416 setrunnable(td); 417 p = td->td_proc; 418 CTR3(KTR_PROC,"wakeup: thread %p (pid %d, %s)", 419 td, p->p_pid, p->p_comm); 420 goto restart; 421 } 422 } 423 mtx_unlock_spin(&sched_lock); 424} 425 426/* 427 * Make a process sleeping on the specified identifier runnable. 428 * May wake more than one process if a target process is currently 429 * swapped out. 430 */ 431void 432wakeup_one(ident) 433 register void *ident; 434{ 435 register struct slpquehead *qp; 436 register struct thread *td; 437 register struct proc *p; 438 struct thread *ntd; 439 440 mtx_lock_spin(&sched_lock); 441 qp = &slpque[LOOKUP(ident)]; 442 for (td = TAILQ_FIRST(qp); td != NULL; td = ntd) { 443 ntd = TAILQ_NEXT(td, td_slpq); 444 if (td->td_wchan == ident) { 445 unsleep(td); 446 TD_CLR_SLEEPING(td); 447 setrunnable(td); 448 p = td->td_proc; 449 CTR3(KTR_PROC,"wakeup1: thread %p (pid %d, %s)", 450 td, p->p_pid, p->p_comm); 451 break; 452 } 453 } 454 mtx_unlock_spin(&sched_lock); 455} 456 457/* 458 * The machine independent parts of mi_switch(). 459 */ 460void 461mi_switch(void) 462{ 463 struct bintime new_switchtime; 464 struct thread *td = curthread; /* XXX */ 465 struct proc *p = td->td_proc; /* XXX */ 466 struct kse *ke = td->td_kse; 467 u_int sched_nest; 468 469 mtx_assert(&sched_lock, MA_OWNED | MA_NOTRECURSED); 470 471 KASSERT(!TD_ON_RUNQ(td), ("mi_switch: called by old code")); 472#ifdef INVARIANTS 473 if (!TD_ON_LOCK(td) && 474 !TD_ON_RUNQ(td) && 475 !TD_IS_RUNNING(td)) 476 mtx_assert(&Giant, MA_NOTOWNED); 477#endif 478 KASSERT(td->td_critnest == 1, 479 ("mi_switch: switch in a critical section")); 480 481 /* 482 * Compute the amount of time during which the current 483 * process was running, and add that to its total so far. 484 */ 485 binuptime(&new_switchtime); 486 bintime_add(&p->p_runtime, &new_switchtime); 487 bintime_sub(&p->p_runtime, PCPU_PTR(switchtime)); 488 489#ifdef DDB 490 /* 491 * Don't perform context switches from the debugger. 492 */ 493 if (db_active) { 494 mtx_unlock_spin(&sched_lock); 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 ke->ke_flags |= KEF_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); 516 517 sched_nest = sched_lock.mtx_recurse; 518 sched_switchout(td); 519 520 cpu_switch(); /* SHAZAM!!*/ 521 522 sched_lock.mtx_recurse = sched_nest; 523 sched_lock.mtx_lock = (uintptr_t)td; 524 sched_switchin(td); 525 526 /* 527 * Start setting up stats etc. for the incoming thread. 528 * Similar code in fork_exit() is returned to by cpu_switch() 529 * in the case of a new thread/process. 530 */ 531 CTR3(KTR_PROC, "mi_switch: new thread %p (pid %d, %s)", td, p->p_pid, 532 p->p_comm); 533 if (PCPU_GET(switchtime.sec) == 0) 534 binuptime(PCPU_PTR(switchtime)); 535 PCPU_SET(switchticks, ticks); 536 537 /* 538 * Call the switchin function while still holding the scheduler lock 539 * (used by the idlezero code and the general page-zeroing code) 540 */ 541 if (td->td_switchin) 542 td->td_switchin(); 543 544 /* 545 * If the last thread was exiting, finish cleaning it up. 546 */ 547 if ((td = PCPU_GET(deadthread))) { 548 PCPU_SET(deadthread, NULL); 549 thread_stash(td); 550 } 551} 552 553/* 554 * Change process state to be runnable, 555 * placing it on the run queue if it is in memory, 556 * and awakening the swapper if it isn't in memory. 557 */ 558void 559setrunnable(struct thread *td) 560{ 561 struct proc *p = td->td_proc; 562 563 mtx_assert(&sched_lock, MA_OWNED); 564 switch (p->p_state) { 565 case PRS_ZOMBIE: 566 panic("setrunnable(1)"); 567 default: 568 break; 569 } 570 switch (td->td_state) { 571 case TDS_RUNNING: 572 case TDS_RUNQ: 573 return; 574 case TDS_INHIBITED: 575 /* 576 * If we are only inhibited because we are swapped out 577 * then arange to swap in this process. Otherwise just return. 578 */ 579 if (td->td_inhibitors != TDI_SWAPPED) 580 return; 581 case TDS_CAN_RUN: 582 break; 583 default: 584 printf("state is 0x%x", td->td_state); 585 panic("setrunnable(2)"); 586 } 587 if ((p->p_sflag & PS_INMEM) == 0) { 588 if ((p->p_sflag & PS_SWAPPINGIN) == 0) { 589 p->p_sflag |= PS_SWAPINREQ; 590 wakeup(&proc0); 591 } 592 } else 593 sched_wakeup(td); 594} 595 596/* 597 * Compute a tenex style load average of a quantity on 598 * 1, 5 and 15 minute intervals. 599 * XXXKSE Needs complete rewrite when correct info is available. 600 * Completely Bogus.. only works with 1:1 (but compiles ok now :-) 601 */ 602static void 603loadav(void *arg) 604{ 605 int i, nrun; 606 struct loadavg *avg; 607 struct proc *p; 608 struct thread *td; 609 610 avg = &averunnable; 611 sx_slock(&allproc_lock); 612 nrun = 0; 613 FOREACH_PROC_IN_SYSTEM(p) { 614 FOREACH_THREAD_IN_PROC(p, td) { 615 switch (td->td_state) { 616 case TDS_RUNQ: 617 case TDS_RUNNING: 618 if ((p->p_flag & P_NOLOAD) != 0) 619 goto nextproc; 620 nrun++; /* XXXKSE */ 621 default: 622 break; 623 } 624nextproc: 625 continue; 626 } 627 } 628 sx_sunlock(&allproc_lock); 629 for (i = 0; i < 3; i++) 630 avg->ldavg[i] = (cexp[i] * avg->ldavg[i] + 631 nrun * FSCALE * (FSCALE - cexp[i])) >> FSHIFT; 632 633 /* 634 * Schedule the next update to occur after 5 seconds, but add a 635 * random variation to avoid synchronisation with processes that 636 * run at regular intervals. 637 */ 638 callout_reset(&loadav_callout, hz * 4 + (int)(random() % (hz * 2 + 1)), 639 loadav, NULL); 640} 641 642static void 643lboltcb(void *arg) 644{ 645 wakeup(&lbolt); 646 callout_reset(&lbolt_callout, hz, lboltcb, NULL); 647} 648 649/* ARGSUSED */ 650static void 651sched_setup(dummy) 652 void *dummy; 653{ 654 callout_init(&loadav_callout, 0); 655 callout_init(&lbolt_callout, 1); 656 657 /* Kick off timeout driven events by calling first time. */ 658 loadav(NULL); 659 lboltcb(NULL); 660} 661 662/* 663 * General purpose yield system call 664 */ 665int 666yield(struct thread *td, struct yield_args *uap) 667{ 668 struct ksegrp *kg = td->td_ksegrp; 669 670 mtx_assert(&Giant, MA_NOTOWNED); 671 mtx_lock_spin(&sched_lock); 672 kg->kg_proc->p_stats->p_ru.ru_nvcsw++; 673 sched_prio(td, PRI_MAX_TIMESHARE); 674 mi_switch(); 675 mtx_unlock_spin(&sched_lock); 676 td->td_retval[0] = 0; 677 678 return (0); 679} 680 681