1 /*- 2 * SPDX-License-Identifier: BSD-3-Clause 3 * 4 * Copyright (c) 1982, 1986, 1990, 1991, 1993 5 * The Regents of the University of California. All rights reserved. 6 * (c) UNIX System Laboratories, Inc. 7 * All or some portions of this file are derived from material licensed 8 * to the University of California by American Telephone and Telegraph 9 * Co. or Unix System Laboratories, Inc. and are reproduced herein with 10 * the permission of UNIX System Laboratories, Inc. 11 * 12 * Redistribution and use in source and binary forms, with or without 13 * modification, are permitted provided that the following conditions 14 * are met: 15 * 1. Redistributions of source code must retain the above copyright 16 * notice, this list of conditions and the following disclaimer. 17 * 2. Redistributions in binary form must reproduce the above copyright 18 * notice, this list of conditions and the following disclaimer in the 19 * documentation and/or other materials provided with the distribution. 20 * 3. Neither the name of the University nor the names of its contributors 21 * may be used to endorse or promote products derived from this software 22 * without specific prior written permission. 23 * 24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 27 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 34 * SUCH DAMAGE. 35 * 36 * @(#)kern_synch.c 8.9 (Berkeley) 5/19/95 37 */ 38 39 #include <sys/cdefs.h> 40 __FBSDID("$FreeBSD$"); 41 42 #include "opt_ktrace.h" 43 #include "opt_sched.h" 44 45 #include <sys/param.h> 46 #include <sys/systm.h> 47 #include <sys/blockcount.h> 48 #include <sys/condvar.h> 49 #include <sys/kdb.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/sdt.h> 58 #include <sys/signalvar.h> 59 #include <sys/sleepqueue.h> 60 #include <sys/smp.h> 61 #include <sys/sx.h> 62 #include <sys/sysctl.h> 63 #include <sys/sysproto.h> 64 #include <sys/vmmeter.h> 65 #ifdef KTRACE 66 #include <sys/uio.h> 67 #include <sys/ktrace.h> 68 #endif 69 #ifdef EPOCH_TRACE 70 #include <sys/epoch.h> 71 #endif 72 73 #include <machine/cpu.h> 74 75 static void synch_setup(void *dummy); 76 SYSINIT(synch_setup, SI_SUB_KICK_SCHEDULER, SI_ORDER_FIRST, synch_setup, 77 NULL); 78 79 int hogticks; 80 static const char pause_wchan[MAXCPU]; 81 82 static struct callout loadav_callout; 83 84 struct loadavg averunnable = 85 { {0, 0, 0}, FSCALE }; /* load average, of runnable procs */ 86 /* 87 * Constants for averages over 1, 5, and 15 minutes 88 * when sampling at 5 second intervals. 89 */ 90 static fixpt_t cexp[3] = { 91 0.9200444146293232 * FSCALE, /* exp(-1/12) */ 92 0.9834714538216174 * FSCALE, /* exp(-1/60) */ 93 0.9944598480048967 * FSCALE, /* exp(-1/180) */ 94 }; 95 96 /* kernel uses `FSCALE', userland (SHOULD) use kern.fscale */ 97 SYSCTL_INT(_kern, OID_AUTO, fscale, CTLFLAG_RD, SYSCTL_NULL_INT_PTR, FSCALE, 98 "Fixed-point scale factor used for calculating load average values"); 99 100 static void loadav(void *arg); 101 102 SDT_PROVIDER_DECLARE(sched); 103 SDT_PROBE_DEFINE(sched, , , preempt); 104 105 static void 106 sleepinit(void *unused) 107 { 108 109 hogticks = (hz / 10) * 2; /* Default only. */ 110 init_sleepqueues(); 111 } 112 113 /* 114 * vmem tries to lock the sleepq mutexes when free'ing kva, so make sure 115 * it is available. 116 */ 117 SYSINIT(sleepinit, SI_SUB_KMEM, SI_ORDER_ANY, sleepinit, NULL); 118 119 /* 120 * General sleep call. Suspends the current thread until a wakeup is 121 * performed on the specified identifier. The thread will then be made 122 * runnable with the specified priority. Sleeps at most sbt units of time 123 * (0 means no timeout). If pri includes the PCATCH flag, let signals 124 * interrupt the sleep, otherwise ignore them while sleeping. Returns 0 if 125 * awakened, EWOULDBLOCK if the timeout expires. If PCATCH is set and a 126 * signal becomes pending, 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 lock argument is unlocked before the caller is suspended, and 131 * re-locked before _sleep() returns. If priority includes the PDROP 132 * flag the lock is not re-locked before returning. 133 */ 134 int 135 _sleep(const void *ident, struct lock_object *lock, int priority, 136 const char *wmesg, sbintime_t sbt, sbintime_t pr, int flags) 137 { 138 struct thread *td; 139 struct lock_class *class; 140 uintptr_t lock_state; 141 int catch, pri, rval, sleepq_flags; 142 WITNESS_SAVE_DECL(lock_witness); 143 144 td = curthread; 145 #ifdef KTRACE 146 if (KTRPOINT(td, KTR_CSW)) 147 ktrcsw(1, 0, wmesg); 148 #endif 149 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, lock, 150 "Sleeping on \"%s\"", wmesg); 151 KASSERT(sbt != 0 || mtx_owned(&Giant) || lock != NULL || 152 (priority & PNOLOCK) != 0, 153 ("sleeping without a lock")); 154 KASSERT(ident != NULL, ("_sleep: NULL ident")); 155 KASSERT(TD_IS_RUNNING(td), ("_sleep: curthread not running")); 156 if (priority & PDROP) 157 KASSERT(lock != NULL && lock != &Giant.lock_object, 158 ("PDROP requires a non-Giant lock")); 159 if (lock != NULL) 160 class = LOCK_CLASS(lock); 161 else 162 class = NULL; 163 164 if (SCHEDULER_STOPPED_TD(td)) { 165 if (lock != NULL && priority & PDROP) 166 class->lc_unlock(lock); 167 return (0); 168 } 169 catch = priority & PCATCH; 170 pri = priority & PRIMASK; 171 172 KASSERT(!TD_ON_SLEEPQ(td), ("recursive sleep")); 173 174 if ((uintptr_t)ident >= (uintptr_t)&pause_wchan[0] && 175 (uintptr_t)ident <= (uintptr_t)&pause_wchan[MAXCPU - 1]) 176 sleepq_flags = SLEEPQ_PAUSE; 177 else 178 sleepq_flags = SLEEPQ_SLEEP; 179 if (catch) 180 sleepq_flags |= SLEEPQ_INTERRUPTIBLE; 181 182 sleepq_lock(ident); 183 CTR5(KTR_PROC, "sleep: thread %ld (pid %ld, %s) on %s (%p)", 184 td->td_tid, td->td_proc->p_pid, td->td_name, wmesg, ident); 185 186 if (lock == &Giant.lock_object) 187 mtx_assert(&Giant, MA_OWNED); 188 DROP_GIANT(); 189 if (lock != NULL && lock != &Giant.lock_object && 190 !(class->lc_flags & LC_SLEEPABLE)) { 191 WITNESS_SAVE(lock, lock_witness); 192 lock_state = class->lc_unlock(lock); 193 } else 194 /* GCC needs to follow the Yellow Brick Road */ 195 lock_state = -1; 196 197 /* 198 * We put ourselves on the sleep queue and start our timeout 199 * before calling thread_suspend_check, as we could stop there, 200 * and a wakeup or a SIGCONT (or both) could occur while we were 201 * stopped without resuming us. Thus, we must be ready for sleep 202 * when cursig() is called. If the wakeup happens while we're 203 * stopped, then td will no longer be on a sleep queue upon 204 * return from cursig(). 205 */ 206 sleepq_add(ident, lock, wmesg, sleepq_flags, 0); 207 if (sbt != 0) 208 sleepq_set_timeout_sbt(ident, sbt, pr, flags); 209 if (lock != NULL && class->lc_flags & LC_SLEEPABLE) { 210 sleepq_release(ident); 211 WITNESS_SAVE(lock, lock_witness); 212 lock_state = class->lc_unlock(lock); 213 sleepq_lock(ident); 214 } 215 if (sbt != 0 && catch) 216 rval = sleepq_timedwait_sig(ident, pri); 217 else if (sbt != 0) 218 rval = sleepq_timedwait(ident, pri); 219 else if (catch) 220 rval = sleepq_wait_sig(ident, pri); 221 else { 222 sleepq_wait(ident, pri); 223 rval = 0; 224 } 225 #ifdef KTRACE 226 if (KTRPOINT(td, KTR_CSW)) 227 ktrcsw(0, 0, wmesg); 228 #endif 229 PICKUP_GIANT(); 230 if (lock != NULL && lock != &Giant.lock_object && !(priority & PDROP)) { 231 class->lc_lock(lock, lock_state); 232 WITNESS_RESTORE(lock, lock_witness); 233 } 234 return (rval); 235 } 236 237 int 238 msleep_spin_sbt(const void *ident, struct mtx *mtx, const char *wmesg, 239 sbintime_t sbt, sbintime_t pr, int flags) 240 { 241 struct thread *td; 242 int rval; 243 WITNESS_SAVE_DECL(mtx); 244 245 td = curthread; 246 KASSERT(mtx != NULL, ("sleeping without a mutex")); 247 KASSERT(ident != NULL, ("msleep_spin_sbt: NULL ident")); 248 KASSERT(TD_IS_RUNNING(td), ("msleep_spin_sbt: curthread not running")); 249 250 if (SCHEDULER_STOPPED_TD(td)) 251 return (0); 252 253 sleepq_lock(ident); 254 CTR5(KTR_PROC, "msleep_spin: thread %ld (pid %ld, %s) on %s (%p)", 255 td->td_tid, td->td_proc->p_pid, td->td_name, wmesg, ident); 256 257 DROP_GIANT(); 258 mtx_assert(mtx, MA_OWNED | MA_NOTRECURSED); 259 WITNESS_SAVE(&mtx->lock_object, mtx); 260 mtx_unlock_spin(mtx); 261 262 /* 263 * We put ourselves on the sleep queue and start our timeout. 264 */ 265 sleepq_add(ident, &mtx->lock_object, wmesg, SLEEPQ_SLEEP, 0); 266 if (sbt != 0) 267 sleepq_set_timeout_sbt(ident, sbt, pr, flags); 268 269 /* 270 * Can't call ktrace with any spin locks held so it can lock the 271 * ktrace_mtx lock, and WITNESS_WARN considers it an error to hold 272 * any spin lock. Thus, we have to drop the sleepq spin lock while 273 * we handle those requests. This is safe since we have placed our 274 * thread on the sleep queue already. 275 */ 276 #ifdef KTRACE 277 if (KTRPOINT(td, KTR_CSW)) { 278 sleepq_release(ident); 279 ktrcsw(1, 0, wmesg); 280 sleepq_lock(ident); 281 } 282 #endif 283 #ifdef WITNESS 284 sleepq_release(ident); 285 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, "Sleeping on \"%s\"", 286 wmesg); 287 sleepq_lock(ident); 288 #endif 289 if (sbt != 0) 290 rval = sleepq_timedwait(ident, 0); 291 else { 292 sleepq_wait(ident, 0); 293 rval = 0; 294 } 295 #ifdef KTRACE 296 if (KTRPOINT(td, KTR_CSW)) 297 ktrcsw(0, 0, wmesg); 298 #endif 299 PICKUP_GIANT(); 300 mtx_lock_spin(mtx); 301 WITNESS_RESTORE(&mtx->lock_object, mtx); 302 return (rval); 303 } 304 305 /* 306 * pause_sbt() delays the calling thread by the given signed binary 307 * time. During cold bootup, pause_sbt() uses the DELAY() function 308 * instead of the _sleep() function to do the waiting. The "sbt" 309 * argument must be greater than or equal to zero. A "sbt" value of 310 * zero is equivalent to a "sbt" value of one tick. 311 */ 312 int 313 pause_sbt(const char *wmesg, sbintime_t sbt, sbintime_t pr, int flags) 314 { 315 KASSERT(sbt >= 0, ("pause_sbt: timeout must be >= 0")); 316 317 /* silently convert invalid timeouts */ 318 if (sbt == 0) 319 sbt = tick_sbt; 320 321 if ((cold && curthread == &thread0) || kdb_active || 322 SCHEDULER_STOPPED()) { 323 /* 324 * We delay one second at a time to avoid overflowing the 325 * system specific DELAY() function(s): 326 */ 327 while (sbt >= SBT_1S) { 328 DELAY(1000000); 329 sbt -= SBT_1S; 330 } 331 /* Do the delay remainder, if any */ 332 sbt = howmany(sbt, SBT_1US); 333 if (sbt > 0) 334 DELAY(sbt); 335 return (EWOULDBLOCK); 336 } 337 return (_sleep(&pause_wchan[curcpu], NULL, 338 (flags & C_CATCH) ? PCATCH : 0, wmesg, sbt, pr, flags)); 339 } 340 341 /* 342 * Make all threads sleeping on the specified identifier runnable. 343 */ 344 void 345 wakeup(const void *ident) 346 { 347 int wakeup_swapper; 348 349 sleepq_lock(ident); 350 wakeup_swapper = sleepq_broadcast(ident, SLEEPQ_SLEEP, 0, 0); 351 sleepq_release(ident); 352 if (wakeup_swapper) { 353 KASSERT(ident != &proc0, 354 ("wakeup and wakeup_swapper and proc0")); 355 kick_proc0(); 356 } 357 } 358 359 /* 360 * Make a thread sleeping on the specified identifier runnable. 361 * May wake more than one thread if a target thread is currently 362 * swapped out. 363 */ 364 void 365 wakeup_one(const void *ident) 366 { 367 int wakeup_swapper; 368 369 sleepq_lock(ident); 370 wakeup_swapper = sleepq_signal(ident, SLEEPQ_SLEEP | SLEEPQ_DROP, 0, 0); 371 if (wakeup_swapper) 372 kick_proc0(); 373 } 374 375 void 376 wakeup_any(const void *ident) 377 { 378 int wakeup_swapper; 379 380 sleepq_lock(ident); 381 wakeup_swapper = sleepq_signal(ident, SLEEPQ_SLEEP | SLEEPQ_UNFAIR | 382 SLEEPQ_DROP, 0, 0); 383 if (wakeup_swapper) 384 kick_proc0(); 385 } 386 387 /* 388 * Signal sleeping waiters after the counter has reached zero. 389 */ 390 void 391 _blockcount_wakeup(blockcount_t *bc, u_int old) 392 { 393 394 KASSERT(_BLOCKCOUNT_WAITERS(old), 395 ("%s: no waiters on %p", __func__, bc)); 396 397 if (atomic_cmpset_int(&bc->__count, _BLOCKCOUNT_WAITERS_FLAG, 0)) 398 wakeup(bc); 399 } 400 401 /* 402 * Wait for a wakeup or a signal. This does not guarantee that the count is 403 * still zero on return. Callers wanting a precise answer should use 404 * blockcount_wait() with an interlock. 405 * 406 * If there is no work to wait for, return 0. If the sleep was interrupted by a 407 * signal, return EINTR or ERESTART, and return EAGAIN otherwise. 408 */ 409 int 410 _blockcount_sleep(blockcount_t *bc, struct lock_object *lock, const char *wmesg, 411 int prio) 412 { 413 void *wchan; 414 uintptr_t lock_state; 415 u_int old; 416 int ret; 417 bool catch, drop; 418 419 KASSERT(lock != &Giant.lock_object, 420 ("%s: cannot use Giant as the interlock", __func__)); 421 422 catch = (prio & PCATCH) != 0; 423 drop = (prio & PDROP) != 0; 424 prio &= PRIMASK; 425 426 /* 427 * Synchronize with the fence in blockcount_release(). If we end up 428 * waiting, the sleepqueue lock acquisition will provide the required 429 * side effects. 430 * 431 * If there is no work to wait for, but waiters are present, try to put 432 * ourselves to sleep to avoid jumping ahead. 433 */ 434 if (atomic_load_acq_int(&bc->__count) == 0) { 435 if (lock != NULL && drop) 436 LOCK_CLASS(lock)->lc_unlock(lock); 437 return (0); 438 } 439 lock_state = 0; 440 wchan = bc; 441 sleepq_lock(wchan); 442 DROP_GIANT(); 443 if (lock != NULL) 444 lock_state = LOCK_CLASS(lock)->lc_unlock(lock); 445 old = blockcount_read(bc); 446 ret = 0; 447 do { 448 if (_BLOCKCOUNT_COUNT(old) == 0) { 449 sleepq_release(wchan); 450 goto out; 451 } 452 if (_BLOCKCOUNT_WAITERS(old)) 453 break; 454 } while (!atomic_fcmpset_int(&bc->__count, &old, 455 old | _BLOCKCOUNT_WAITERS_FLAG)); 456 sleepq_add(wchan, NULL, wmesg, catch ? SLEEPQ_INTERRUPTIBLE : 0, 0); 457 if (catch) 458 ret = sleepq_wait_sig(wchan, prio); 459 else 460 sleepq_wait(wchan, prio); 461 if (ret == 0) 462 ret = EAGAIN; 463 464 out: 465 PICKUP_GIANT(); 466 if (lock != NULL && !drop) 467 LOCK_CLASS(lock)->lc_lock(lock, lock_state); 468 469 return (ret); 470 } 471 472 static void 473 kdb_switch(void) 474 { 475 thread_unlock(curthread); 476 kdb_backtrace(); 477 kdb_reenter(); 478 panic("%s: did not reenter debugger", __func__); 479 } 480 481 /* 482 * The machine independent parts of context switching. 483 * 484 * The thread lock is required on entry and is no longer held on return. 485 */ 486 void 487 mi_switch(int flags) 488 { 489 uint64_t runtime, new_switchtime; 490 struct thread *td; 491 492 td = curthread; /* XXX */ 493 THREAD_LOCK_ASSERT(td, MA_OWNED | MA_NOTRECURSED); 494 KASSERT(!TD_ON_RUNQ(td), ("mi_switch: called by old code")); 495 #ifdef INVARIANTS 496 if (!TD_ON_LOCK(td) && !TD_IS_RUNNING(td)) 497 mtx_assert(&Giant, MA_NOTOWNED); 498 #endif 499 KASSERT(td->td_critnest == 1 || KERNEL_PANICKED(), 500 ("mi_switch: switch in a critical section")); 501 KASSERT((flags & (SW_INVOL | SW_VOL)) != 0, 502 ("mi_switch: switch must be voluntary or involuntary")); 503 504 /* 505 * Don't perform context switches from the debugger. 506 */ 507 if (kdb_active) 508 kdb_switch(); 509 if (SCHEDULER_STOPPED_TD(td)) 510 return; 511 if (flags & SW_VOL) { 512 td->td_ru.ru_nvcsw++; 513 td->td_swvoltick = ticks; 514 } else { 515 td->td_ru.ru_nivcsw++; 516 td->td_swinvoltick = ticks; 517 } 518 #ifdef SCHED_STATS 519 SCHED_STAT_INC(sched_switch_stats[flags & SW_TYPE_MASK]); 520 #endif 521 /* 522 * Compute the amount of time during which the current 523 * thread was running, and add that to its total so far. 524 */ 525 new_switchtime = cpu_ticks(); 526 runtime = new_switchtime - PCPU_GET(switchtime); 527 td->td_runtime += runtime; 528 td->td_incruntime += runtime; 529 PCPU_SET(switchtime, new_switchtime); 530 td->td_generation++; /* bump preempt-detect counter */ 531 VM_CNT_INC(v_swtch); 532 PCPU_SET(switchticks, ticks); 533 CTR4(KTR_PROC, "mi_switch: old thread %ld (td_sched %p, pid %ld, %s)", 534 td->td_tid, td_get_sched(td), td->td_proc->p_pid, td->td_name); 535 #ifdef KDTRACE_HOOKS 536 if (SDT_PROBES_ENABLED() && 537 ((flags & SW_PREEMPT) != 0 || ((flags & SW_INVOL) != 0 && 538 (flags & SW_TYPE_MASK) == SWT_NEEDRESCHED))) 539 SDT_PROBE0(sched, , , preempt); 540 #endif 541 sched_switch(td, flags); 542 CTR4(KTR_PROC, "mi_switch: new thread %ld (td_sched %p, pid %ld, %s)", 543 td->td_tid, td_get_sched(td), td->td_proc->p_pid, td->td_name); 544 545 /* 546 * If the last thread was exiting, finish cleaning it up. 547 */ 548 if ((td = PCPU_GET(deadthread))) { 549 PCPU_SET(deadthread, NULL); 550 thread_stash(td); 551 } 552 spinlock_exit(); 553 } 554 555 /* 556 * Change thread state to be runnable, placing it on the run queue if 557 * it is in memory. If it is swapped out, return true so our caller 558 * will know to awaken the swapper. 559 * 560 * Requires the thread lock on entry, drops on exit. 561 */ 562 int 563 setrunnable(struct thread *td, int srqflags) 564 { 565 int swapin; 566 567 THREAD_LOCK_ASSERT(td, MA_OWNED); 568 KASSERT(td->td_proc->p_state != PRS_ZOMBIE, 569 ("setrunnable: pid %d is a zombie", td->td_proc->p_pid)); 570 571 swapin = 0; 572 switch (TD_GET_STATE(td)) { 573 case TDS_RUNNING: 574 case TDS_RUNQ: 575 break; 576 case TDS_CAN_RUN: 577 KASSERT((td->td_flags & TDF_INMEM) != 0, 578 ("setrunnable: td %p not in mem, flags 0x%X inhibit 0x%X", 579 td, td->td_flags, td->td_inhibitors)); 580 /* unlocks thread lock according to flags */ 581 sched_wakeup(td, srqflags); 582 return (0); 583 case TDS_INHIBITED: 584 /* 585 * If we are only inhibited because we are swapped out 586 * arrange to swap in this process. 587 */ 588 if (td->td_inhibitors == TDI_SWAPPED && 589 (td->td_flags & TDF_SWAPINREQ) == 0) { 590 td->td_flags |= TDF_SWAPINREQ; 591 swapin = 1; 592 } 593 break; 594 default: 595 panic("setrunnable: state 0x%x", TD_GET_STATE(td)); 596 } 597 if ((srqflags & (SRQ_HOLD | SRQ_HOLDTD)) == 0) 598 thread_unlock(td); 599 600 return (swapin); 601 } 602 603 /* 604 * Compute a tenex style load average of a quantity on 605 * 1, 5 and 15 minute intervals. 606 */ 607 static void 608 loadav(void *arg) 609 { 610 int i, nrun; 611 struct loadavg *avg; 612 613 nrun = sched_load(); 614 avg = &averunnable; 615 616 for (i = 0; i < 3; i++) 617 avg->ldavg[i] = (cexp[i] * avg->ldavg[i] + 618 nrun * FSCALE * (FSCALE - cexp[i])) >> FSHIFT; 619 620 /* 621 * Schedule the next update to occur after 5 seconds, but add a 622 * random variation to avoid synchronisation with processes that 623 * run at regular intervals. 624 */ 625 callout_reset_sbt(&loadav_callout, 626 SBT_1US * (4000000 + (int)(random() % 2000001)), SBT_1US, 627 loadav, NULL, C_DIRECT_EXEC | C_PREL(32)); 628 } 629 630 /* ARGSUSED */ 631 static void 632 synch_setup(void *dummy) 633 { 634 callout_init(&loadav_callout, 1); 635 636 /* Kick off timeout driven events by calling first time. */ 637 loadav(NULL); 638 } 639 640 int 641 should_yield(void) 642 { 643 644 return ((u_int)ticks - (u_int)curthread->td_swvoltick >= hogticks); 645 } 646 647 void 648 maybe_yield(void) 649 { 650 651 if (should_yield()) 652 kern_yield(PRI_USER); 653 } 654 655 void 656 kern_yield(int prio) 657 { 658 struct thread *td; 659 660 td = curthread; 661 DROP_GIANT(); 662 thread_lock(td); 663 if (prio == PRI_USER) 664 prio = td->td_user_pri; 665 if (prio >= 0) 666 sched_prio(td, prio); 667 mi_switch(SW_VOL | SWT_RELINQUISH); 668 PICKUP_GIANT(); 669 } 670 671 /* 672 * General purpose yield system call. 673 */ 674 int 675 sys_yield(struct thread *td, struct yield_args *uap) 676 { 677 678 thread_lock(td); 679 if (PRI_BASE(td->td_pri_class) == PRI_TIMESHARE) 680 sched_prio(td, PRI_MAX_TIMESHARE); 681 mi_switch(SW_VOL | SWT_RELINQUISH); 682 td->td_retval[0] = 0; 683 return (0); 684 } 685