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 37#include <sys/cdefs.h> 38#include "opt_ktrace.h" 39#include "opt_sched.h" 40 41#include <sys/param.h> 42#include <sys/systm.h> 43#include <sys/blockcount.h> 44#include <sys/condvar.h> 45#include <sys/kdb.h> 46#include <sys/kernel.h> 47#include <sys/ktr.h> 48#include <sys/ktrace.h> 49#include <sys/lock.h> 50#include <sys/mutex.h> 51#include <sys/proc.h> 52#include <sys/resourcevar.h> 53#include <sys/sched.h> 54#include <sys/sdt.h> 55#include <sys/signalvar.h> 56#include <sys/sleepqueue.h> 57#include <sys/smp.h> 58#include <sys/sx.h> 59#include <sys/sysctl.h> 60#include <sys/sysproto.h> 61#include <sys/vmmeter.h> 62#ifdef KTRACE 63#include <sys/uio.h> 64#endif 65#ifdef EPOCH_TRACE 66#include <sys/epoch.h> 67#endif 68 69#include <machine/cpu.h> 70 71static void synch_setup(void *dummy); 72SYSINIT(synch_setup, SI_SUB_KICK_SCHEDULER, SI_ORDER_FIRST, synch_setup, 73 NULL); 74 75int hogticks; 76static const char pause_wchan[MAXCPU]; 77 78static struct callout loadav_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 uint64_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 */ 93SYSCTL_INT(_kern, OID_AUTO, fscale, CTLFLAG_RD, SYSCTL_NULL_INT_PTR, FSCALE, 94 "Fixed-point scale factor used for calculating load average values"); 95 96static void loadav(void *arg); 97 98SDT_PROVIDER_DECLARE(sched); 99SDT_PROBE_DEFINE(sched, , , preempt); 100 101static void 102sleepinit(void *unused) 103{ 104 105 hogticks = (hz / 10) * 2; /* Default only. */ 106 init_sleepqueues(); 107} 108 109/* 110 * vmem tries to lock the sleepq mutexes when free'ing kva, so make sure 111 * it is available. 112 */ 113SYSINIT(sleepinit, SI_SUB_KMEM, SI_ORDER_ANY, sleepinit, NULL); 114 115/* 116 * General sleep call. Suspends the current thread until a wakeup is 117 * performed on the specified identifier. The thread will then be made 118 * runnable with the specified priority. Sleeps at most sbt units of time 119 * (0 means no timeout). If pri includes the PCATCH flag, let signals 120 * interrupt the sleep, otherwise ignore them while sleeping. Returns 0 if 121 * awakened, EWOULDBLOCK if the timeout expires. If PCATCH is set and a 122 * signal becomes pending, ERESTART is returned if the current system 123 * call should be restarted if possible, and EINTR is returned if the system 124 * call should be interrupted by the signal (return EINTR). 125 * 126 * The lock argument is unlocked before the caller is suspended, and 127 * re-locked before _sleep() returns. If priority includes the PDROP 128 * flag the lock is not re-locked before returning. 129 */ 130int 131_sleep(const void *ident, struct lock_object *lock, int priority, 132 const char *wmesg, sbintime_t sbt, sbintime_t pr, int flags) 133{ 134 struct thread *td __ktrace_used; 135 struct lock_class *class; 136 uintptr_t lock_state; 137 int catch, pri, rval, sleepq_flags; 138 WITNESS_SAVE_DECL(lock_witness); 139 140 TSENTER(); 141 td = curthread; 142#ifdef KTRACE 143 if (KTRPOINT(td, KTR_CSW)) 144 ktrcsw(1, 0, wmesg); 145#endif 146 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, lock, 147 "Sleeping on \"%s\"", wmesg); 148 KASSERT(sbt != 0 || mtx_owned(&Giant) || lock != NULL || 149 (priority & PNOLOCK) != 0, 150 ("sleeping without a lock")); 151 KASSERT(ident != NULL, ("_sleep: NULL ident")); 152 KASSERT(TD_IS_RUNNING(td), ("_sleep: curthread not running")); 153 if (priority & PDROP) 154 KASSERT(lock != NULL && lock != &Giant.lock_object, 155 ("PDROP requires a non-Giant lock")); 156 if (lock != NULL) 157 class = LOCK_CLASS(lock); 158 else 159 class = NULL; 160 161 if (SCHEDULER_STOPPED()) { 162 if (lock != NULL && priority & PDROP) 163 class->lc_unlock(lock); 164 return (0); 165 } 166 catch = priority & PCATCH; 167 pri = priority & PRIMASK; 168 169 KASSERT(!TD_ON_SLEEPQ(td), ("recursive sleep")); 170 171 if ((uintptr_t)ident >= (uintptr_t)&pause_wchan[0] && 172 (uintptr_t)ident <= (uintptr_t)&pause_wchan[MAXCPU - 1]) 173 sleepq_flags = SLEEPQ_PAUSE; 174 else 175 sleepq_flags = SLEEPQ_SLEEP; 176 if (catch) 177 sleepq_flags |= SLEEPQ_INTERRUPTIBLE; 178 179 sleepq_lock(ident); 180 CTR5(KTR_PROC, "sleep: thread %ld (pid %ld, %s) on %s (%p)", 181 td->td_tid, td->td_proc->p_pid, td->td_name, wmesg, ident); 182 183 if (lock == &Giant.lock_object) 184 mtx_assert(&Giant, MA_OWNED); 185 DROP_GIANT(); 186 if (lock != NULL && lock != &Giant.lock_object && 187 !(class->lc_flags & LC_SLEEPABLE)) { 188 KASSERT(!(class->lc_flags & LC_SPINLOCK), 189 ("spin locks can only use msleep_spin")); 190 WITNESS_SAVE(lock, lock_witness); 191 lock_state = class->lc_unlock(lock); 192 } else 193 /* GCC needs to follow the Yellow Brick Road */ 194 lock_state = -1; 195 196 /* 197 * We put ourselves on the sleep queue and start our timeout 198 * before calling thread_suspend_check, as we could stop there, 199 * and a wakeup or a SIGCONT (or both) could occur while we were 200 * stopped without resuming us. Thus, we must be ready for sleep 201 * when cursig() is called. If the wakeup happens while we're 202 * stopped, then td will no longer be on a sleep queue upon 203 * return from cursig(). 204 */ 205 sleepq_add(ident, lock, wmesg, sleepq_flags, 0); 206 if (sbt != 0) 207 sleepq_set_timeout_sbt(ident, sbt, pr, flags); 208 if (lock != NULL && class->lc_flags & LC_SLEEPABLE) { 209 sleepq_release(ident); 210 WITNESS_SAVE(lock, lock_witness); 211 lock_state = class->lc_unlock(lock); 212 sleepq_lock(ident); 213 } 214 if (sbt != 0 && catch) 215 rval = sleepq_timedwait_sig(ident, pri); 216 else if (sbt != 0) 217 rval = sleepq_timedwait(ident, pri); 218 else if (catch) 219 rval = sleepq_wait_sig(ident, pri); 220 else { 221 sleepq_wait(ident, pri); 222 rval = 0; 223 } 224#ifdef KTRACE 225 if (KTRPOINT(td, KTR_CSW)) 226 ktrcsw(0, 0, wmesg); 227#endif 228 PICKUP_GIANT(); 229 if (lock != NULL && lock != &Giant.lock_object && !(priority & PDROP)) { 230 class->lc_lock(lock, lock_state); 231 WITNESS_RESTORE(lock, lock_witness); 232 } 233 TSEXIT(); 234 return (rval); 235} 236 237int 238msleep_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 __ktrace_used; 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()) 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 */ 312int 313pause_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 */ 344void 345wakeup(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 */ 364void 365wakeup_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 375void 376wakeup_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 */ 390void 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 */ 409int 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 464out: 465 PICKUP_GIANT(); 466 if (lock != NULL && !drop) 467 LOCK_CLASS(lock)->lc_lock(lock, lock_state); 468 469 return (ret); 470} 471 472static void 473kdb_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 * mi_switch(9): The machine-independent parts of context switching. 483 * 484 * The thread lock is required on entry and is no longer held on return. 485 */ 486void 487mi_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 /* thread_lock() performs spinlock_enter(). */ 500 KASSERT(td->td_critnest == 1 || KERNEL_PANICKED(), 501 ("mi_switch: switch in a critical section")); 502 KASSERT((flags & (SW_INVOL | SW_VOL)) != 0, 503 ("mi_switch: switch must be voluntary or involuntary")); 504 KASSERT((flags & SW_TYPE_MASK) != 0, 505 ("mi_switch: a switch reason (type) must be specified")); 506 KASSERT((flags & SW_TYPE_MASK) < SWT_COUNT, 507 ("mi_switch: invalid switch reason %d", (flags & SW_TYPE_MASK))); 508 509 /* 510 * Don't perform context switches from the debugger. 511 */ 512 if (kdb_active) 513 kdb_switch(); 514 if (SCHEDULER_STOPPED()) 515 return; 516 if (flags & SW_VOL) { 517 td->td_ru.ru_nvcsw++; 518 td->td_swvoltick = ticks; 519 } else { 520 td->td_ru.ru_nivcsw++; 521 td->td_swinvoltick = ticks; 522 } 523#ifdef SCHED_STATS 524 SCHED_STAT_INC(sched_switch_stats[flags & SW_TYPE_MASK]); 525#endif 526 /* 527 * Compute the amount of time during which the current 528 * thread was running, and add that to its total so far. 529 */ 530 new_switchtime = cpu_ticks(); 531 runtime = new_switchtime - PCPU_GET(switchtime); 532 td->td_runtime += runtime; 533 td->td_incruntime += runtime; 534 PCPU_SET(switchtime, new_switchtime); 535 td->td_generation++; /* bump preempt-detect counter */ 536 VM_CNT_INC(v_swtch); 537 PCPU_SET(switchticks, ticks); 538 CTR4(KTR_PROC, "mi_switch: old thread %ld (td_sched %p, pid %ld, %s)", 539 td->td_tid, td_get_sched(td), td->td_proc->p_pid, td->td_name); 540#ifdef KDTRACE_HOOKS 541 if (SDT_PROBES_ENABLED() && 542 ((flags & SW_PREEMPT) != 0 || ((flags & SW_INVOL) != 0 && 543 (flags & SW_TYPE_MASK) == SWT_NEEDRESCHED))) 544 SDT_PROBE0(sched, , , preempt); 545#endif 546 sched_switch(td, flags); 547 CTR4(KTR_PROC, "mi_switch: new thread %ld (td_sched %p, pid %ld, %s)", 548 td->td_tid, td_get_sched(td), td->td_proc->p_pid, td->td_name); 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 spinlock_exit(); 558} 559 560/* 561 * Change thread state to be runnable, placing it on the run queue if 562 * it is in memory. If it is swapped out, return true so our caller 563 * will know to awaken the swapper. 564 * 565 * Requires the thread lock on entry, drops on exit. 566 */ 567int 568setrunnable(struct thread *td, int srqflags) 569{ 570 int swapin; 571 572 THREAD_LOCK_ASSERT(td, MA_OWNED); 573 KASSERT(td->td_proc->p_state != PRS_ZOMBIE, 574 ("setrunnable: pid %d is a zombie", td->td_proc->p_pid)); 575 576 swapin = 0; 577 switch (TD_GET_STATE(td)) { 578 case TDS_RUNNING: 579 case TDS_RUNQ: 580 break; 581 case TDS_CAN_RUN: 582 KASSERT((td->td_flags & TDF_INMEM) != 0, 583 ("setrunnable: td %p not in mem, flags 0x%X inhibit 0x%X", 584 td, td->td_flags, td->td_inhibitors)); 585 /* unlocks thread lock according to flags */ 586 sched_wakeup(td, srqflags); 587 return (0); 588 case TDS_INHIBITED: 589 /* 590 * If we are only inhibited because we are swapped out 591 * arrange to swap in this process. 592 */ 593 if (td->td_inhibitors == TDI_SWAPPED && 594 (td->td_flags & TDF_SWAPINREQ) == 0) { 595 td->td_flags |= TDF_SWAPINREQ; 596 swapin = 1; 597 } 598 break; 599 default: 600 panic("setrunnable: state 0x%x", TD_GET_STATE(td)); 601 } 602 if ((srqflags & (SRQ_HOLD | SRQ_HOLDTD)) == 0) 603 thread_unlock(td); 604 605 return (swapin); 606} 607 608/* 609 * Compute a tenex style load average of a quantity on 610 * 1, 5 and 15 minute intervals. 611 */ 612static void 613loadav(void *arg) 614{ 615 int i; 616 uint64_t nrun; 617 struct loadavg *avg; 618 619 nrun = (uint64_t)sched_load(); 620 avg = &averunnable; 621 622 for (i = 0; i < 3; i++) 623 avg->ldavg[i] = (cexp[i] * (uint64_t)avg->ldavg[i] + 624 nrun * FSCALE * (FSCALE - cexp[i])) >> FSHIFT; 625 626 /* 627 * Schedule the next update to occur after 5 seconds, but add a 628 * random variation to avoid synchronisation with processes that 629 * run at regular intervals. 630 */ 631 callout_reset_sbt(&loadav_callout, 632 SBT_1US * (4000000 + (int)(random() % 2000001)), SBT_1US, 633 loadav, NULL, C_DIRECT_EXEC | C_PREL(32)); 634} 635 636static void 637ast_scheduler(struct thread *td, int tda __unused) 638{ 639#ifdef KTRACE 640 if (KTRPOINT(td, KTR_CSW)) 641 ktrcsw(1, 1, __func__); 642#endif 643 thread_lock(td); 644 sched_prio(td, td->td_user_pri); 645 mi_switch(SW_INVOL | SWT_NEEDRESCHED); 646#ifdef KTRACE 647 if (KTRPOINT(td, KTR_CSW)) 648 ktrcsw(0, 1, __func__); 649#endif 650} 651 652static void 653synch_setup(void *dummy __unused) 654{ 655 callout_init(&loadav_callout, 1); 656 ast_register(TDA_SCHED, ASTR_ASTF_REQUIRED, 0, ast_scheduler); 657 658 /* Kick off timeout driven events by calling first time. */ 659 loadav(NULL); 660} 661 662bool 663should_yield(void) 664{ 665 666 return ((u_int)ticks - (u_int)curthread->td_swvoltick >= hogticks); 667} 668 669void 670maybe_yield(void) 671{ 672 673 if (should_yield()) 674 kern_yield(PRI_USER); 675} 676 677void 678kern_yield(int prio) 679{ 680 struct thread *td; 681 682 td = curthread; 683 DROP_GIANT(); 684 thread_lock(td); 685 if (prio == PRI_USER) 686 prio = td->td_user_pri; 687 if (prio >= 0) 688 sched_prio(td, prio); 689 mi_switch(SW_VOL | SWT_RELINQUISH); 690 PICKUP_GIANT(); 691} 692 693/* 694 * General purpose yield system call. 695 */ 696int 697sys_yield(struct thread *td, struct yield_args *uap) 698{ 699 700 thread_lock(td); 701 if (PRI_BASE(td->td_pri_class) == PRI_TIMESHARE) 702 sched_prio(td, PRI_MAX_TIMESHARE); 703 mi_switch(SW_VOL | SWT_RELINQUISH); 704 td->td_retval[0] = 0; 705 return (0); 706} 707 708int 709sys_sched_getcpu(struct thread *td, struct sched_getcpu_args *uap) 710{ 711 td->td_retval[0] = td->td_oncpu; 712 return (0); 713} 714