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 * 4. Neither the name of the University nor the names of its contributors 19 * may be used to endorse or promote products derived from this software 20 * without specific prior written permission. 21 * 22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32 * SUCH DAMAGE. 33 * 34 * @(#)kern_synch.c 8.9 (Berkeley) 5/19/95 35 */ 36 37 #include <sys/cdefs.h> 38 __FBSDID("$FreeBSD$"); 39 40 #include "opt_ktrace.h" 41 #include "opt_sched.h" 42 43 #include <sys/param.h> 44 #include <sys/systm.h> 45 #include <sys/condvar.h> 46 #include <sys/kdb.h> 47 #include <sys/kernel.h> 48 #include <sys/ktr.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 #include <sys/ktrace.h> 65 #endif 66 67 #include <machine/cpu.h> 68 69 #define KTDSTATE(td) \ 70 (((td)->td_inhibitors & TDI_SLEEPING) != 0 ? "sleep" : \ 71 ((td)->td_inhibitors & TDI_SUSPENDED) != 0 ? "suspended" : \ 72 ((td)->td_inhibitors & TDI_SWAPPED) != 0 ? "swapped" : \ 73 ((td)->td_inhibitors & TDI_LOCK) != 0 ? "blocked" : \ 74 ((td)->td_inhibitors & TDI_IWAIT) != 0 ? "iwait" : "yielding") 75 76 static void synch_setup(void *dummy); 77 SYSINIT(synch_setup, SI_SUB_KICK_SCHEDULER, SI_ORDER_FIRST, synch_setup, 78 NULL); 79 80 int hogticks; 81 static uint8_t pause_wchan[MAXCPU]; 82 83 static struct callout loadav_callout; 84 85 struct loadavg averunnable = 86 { {0, 0, 0}, FSCALE }; /* load average, of runnable procs */ 87 /* 88 * Constants for averages over 1, 5, and 15 minutes 89 * when sampling at 5 second intervals. 90 */ 91 static fixpt_t cexp[3] = { 92 0.9200444146293232 * FSCALE, /* exp(-1/12) */ 93 0.9834714538216174 * FSCALE, /* exp(-1/60) */ 94 0.9944598480048967 * FSCALE, /* exp(-1/180) */ 95 }; 96 97 /* kernel uses `FSCALE', userland (SHOULD) use kern.fscale */ 98 SYSCTL_INT(_kern, OID_AUTO, fscale, CTLFLAG_RD, SYSCTL_NULL_INT_PTR, FSCALE, ""); 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, 0); 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(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 proc *p; 140 struct lock_class *class; 141 uintptr_t lock_state; 142 int catch, pri, rval, sleepq_flags; 143 WITNESS_SAVE_DECL(lock_witness); 144 145 td = curthread; 146 p = td->td_proc; 147 #ifdef KTRACE 148 if (KTRPOINT(td, KTR_CSW)) 149 ktrcsw(1, 0, wmesg); 150 #endif 151 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, lock, 152 "Sleeping on \"%s\"", wmesg); 153 KASSERT(sbt != 0 || mtx_owned(&Giant) || lock != NULL, 154 ("sleeping without a lock")); 155 KASSERT(p != NULL, ("msleep1")); 156 KASSERT(ident != NULL && TD_IS_RUNNING(td), ("msleep")); 157 if (priority & PDROP) 158 KASSERT(lock != NULL && lock != &Giant.lock_object, 159 ("PDROP requires a non-Giant lock")); 160 if (lock != NULL) 161 class = LOCK_CLASS(lock); 162 else 163 class = NULL; 164 165 if (cold || SCHEDULER_STOPPED()) { 166 /* 167 * During autoconfiguration, just return; 168 * don't run any other threads or panic below, 169 * in case this is the idle thread and already asleep. 170 * XXX: this used to do "s = splhigh(); splx(safepri); 171 * splx(s);" to give interrupts a chance, but there is 172 * no way to give interrupts a chance now. 173 */ 174 if (lock != NULL && priority & PDROP) 175 class->lc_unlock(lock); 176 return (0); 177 } 178 catch = priority & PCATCH; 179 pri = priority & PRIMASK; 180 181 /* 182 * If we are already on a sleep queue, then remove us from that 183 * sleep queue first. We have to do this to handle recursive 184 * sleeps. 185 */ 186 if (TD_ON_SLEEPQ(td)) 187 sleepq_remove(td, td->td_wchan); 188 189 if ((uint8_t *)ident >= &pause_wchan[0] && 190 (uint8_t *)ident <= &pause_wchan[MAXCPU - 1]) 191 sleepq_flags = SLEEPQ_PAUSE; 192 else 193 sleepq_flags = SLEEPQ_SLEEP; 194 if (catch) 195 sleepq_flags |= SLEEPQ_INTERRUPTIBLE; 196 197 sleepq_lock(ident); 198 CTR5(KTR_PROC, "sleep: thread %ld (pid %ld, %s) on %s (%p)", 199 td->td_tid, p->p_pid, td->td_name, wmesg, ident); 200 201 if (lock == &Giant.lock_object) 202 mtx_assert(&Giant, MA_OWNED); 203 DROP_GIANT(); 204 if (lock != NULL && lock != &Giant.lock_object && 205 !(class->lc_flags & LC_SLEEPABLE)) { 206 WITNESS_SAVE(lock, lock_witness); 207 lock_state = class->lc_unlock(lock); 208 } else 209 /* GCC needs to follow the Yellow Brick Road */ 210 lock_state = -1; 211 212 /* 213 * We put ourselves on the sleep queue and start our timeout 214 * before calling thread_suspend_check, as we could stop there, 215 * and a wakeup or a SIGCONT (or both) could occur while we were 216 * stopped without resuming us. Thus, we must be ready for sleep 217 * when cursig() is called. If the wakeup happens while we're 218 * stopped, then td will no longer be on a sleep queue upon 219 * return from cursig(). 220 */ 221 sleepq_add(ident, lock, wmesg, sleepq_flags, 0); 222 if (sbt != 0) 223 sleepq_set_timeout_sbt(ident, sbt, pr, flags); 224 if (lock != NULL && class->lc_flags & LC_SLEEPABLE) { 225 sleepq_release(ident); 226 WITNESS_SAVE(lock, lock_witness); 227 lock_state = class->lc_unlock(lock); 228 sleepq_lock(ident); 229 } 230 if (sbt != 0 && catch) 231 rval = sleepq_timedwait_sig(ident, pri); 232 else if (sbt != 0) 233 rval = sleepq_timedwait(ident, pri); 234 else if (catch) 235 rval = sleepq_wait_sig(ident, pri); 236 else { 237 sleepq_wait(ident, pri); 238 rval = 0; 239 } 240 #ifdef KTRACE 241 if (KTRPOINT(td, KTR_CSW)) 242 ktrcsw(0, 0, wmesg); 243 #endif 244 PICKUP_GIANT(); 245 if (lock != NULL && lock != &Giant.lock_object && !(priority & PDROP)) { 246 class->lc_lock(lock, lock_state); 247 WITNESS_RESTORE(lock, lock_witness); 248 } 249 return (rval); 250 } 251 252 int 253 msleep_spin_sbt(void *ident, struct mtx *mtx, const char *wmesg, 254 sbintime_t sbt, sbintime_t pr, int flags) 255 { 256 struct thread *td; 257 struct proc *p; 258 int rval; 259 WITNESS_SAVE_DECL(mtx); 260 261 td = curthread; 262 p = td->td_proc; 263 KASSERT(mtx != NULL, ("sleeping without a mutex")); 264 KASSERT(p != NULL, ("msleep1")); 265 KASSERT(ident != NULL && TD_IS_RUNNING(td), ("msleep")); 266 267 if (cold || SCHEDULER_STOPPED()) { 268 /* 269 * During autoconfiguration, just return; 270 * don't run any other threads or panic below, 271 * in case this is the idle thread and already asleep. 272 * XXX: this used to do "s = splhigh(); splx(safepri); 273 * splx(s);" to give interrupts a chance, but there is 274 * no way to give interrupts a chance now. 275 */ 276 return (0); 277 } 278 279 sleepq_lock(ident); 280 CTR5(KTR_PROC, "msleep_spin: thread %ld (pid %ld, %s) on %s (%p)", 281 td->td_tid, p->p_pid, td->td_name, wmesg, ident); 282 283 DROP_GIANT(); 284 mtx_assert(mtx, MA_OWNED | MA_NOTRECURSED); 285 WITNESS_SAVE(&mtx->lock_object, mtx); 286 mtx_unlock_spin(mtx); 287 288 /* 289 * We put ourselves on the sleep queue and start our timeout. 290 */ 291 sleepq_add(ident, &mtx->lock_object, wmesg, SLEEPQ_SLEEP, 0); 292 if (sbt != 0) 293 sleepq_set_timeout_sbt(ident, sbt, pr, flags); 294 295 /* 296 * Can't call ktrace with any spin locks held so it can lock the 297 * ktrace_mtx lock, and WITNESS_WARN considers it an error to hold 298 * any spin lock. Thus, we have to drop the sleepq spin lock while 299 * we handle those requests. This is safe since we have placed our 300 * thread on the sleep queue already. 301 */ 302 #ifdef KTRACE 303 if (KTRPOINT(td, KTR_CSW)) { 304 sleepq_release(ident); 305 ktrcsw(1, 0, wmesg); 306 sleepq_lock(ident); 307 } 308 #endif 309 #ifdef WITNESS 310 sleepq_release(ident); 311 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, "Sleeping on \"%s\"", 312 wmesg); 313 sleepq_lock(ident); 314 #endif 315 if (sbt != 0) 316 rval = sleepq_timedwait(ident, 0); 317 else { 318 sleepq_wait(ident, 0); 319 rval = 0; 320 } 321 #ifdef KTRACE 322 if (KTRPOINT(td, KTR_CSW)) 323 ktrcsw(0, 0, wmesg); 324 #endif 325 PICKUP_GIANT(); 326 mtx_lock_spin(mtx); 327 WITNESS_RESTORE(&mtx->lock_object, mtx); 328 return (rval); 329 } 330 331 /* 332 * pause() delays the calling thread by the given number of system ticks. 333 * During cold bootup, pause() uses the DELAY() function instead of 334 * the tsleep() function to do the waiting. The "timo" argument must be 335 * greater than or equal to zero. A "timo" value of zero is equivalent 336 * to a "timo" value of one. 337 */ 338 int 339 pause_sbt(const char *wmesg, sbintime_t sbt, sbintime_t pr, int flags) 340 { 341 KASSERT(sbt >= 0, ("pause: timeout must be >= 0")); 342 343 /* silently convert invalid timeouts */ 344 if (sbt == 0) 345 sbt = tick_sbt; 346 347 if (cold || kdb_active) { 348 /* 349 * We delay one second at a time to avoid overflowing the 350 * system specific DELAY() function(s): 351 */ 352 while (sbt >= SBT_1S) { 353 DELAY(1000000); 354 sbt -= SBT_1S; 355 } 356 /* Do the delay remainder, if any */ 357 sbt = (sbt + SBT_1US - 1) / SBT_1US; 358 if (sbt > 0) 359 DELAY(sbt); 360 return (0); 361 } 362 return (_sleep(&pause_wchan[curcpu], NULL, 0, wmesg, sbt, pr, flags)); 363 } 364 365 /* 366 * Make all threads sleeping on the specified identifier runnable. 367 */ 368 void 369 wakeup(void *ident) 370 { 371 int wakeup_swapper; 372 373 sleepq_lock(ident); 374 wakeup_swapper = sleepq_broadcast(ident, SLEEPQ_SLEEP, 0, 0); 375 sleepq_release(ident); 376 if (wakeup_swapper) { 377 KASSERT(ident != &proc0, 378 ("wakeup and wakeup_swapper and proc0")); 379 kick_proc0(); 380 } 381 } 382 383 /* 384 * Make a thread sleeping on the specified identifier runnable. 385 * May wake more than one thread if a target thread is currently 386 * swapped out. 387 */ 388 void 389 wakeup_one(void *ident) 390 { 391 int wakeup_swapper; 392 393 sleepq_lock(ident); 394 wakeup_swapper = sleepq_signal(ident, SLEEPQ_SLEEP, 0, 0); 395 sleepq_release(ident); 396 if (wakeup_swapper) 397 kick_proc0(); 398 } 399 400 static void 401 kdb_switch(void) 402 { 403 thread_unlock(curthread); 404 kdb_backtrace(); 405 kdb_reenter(); 406 panic("%s: did not reenter debugger", __func__); 407 } 408 409 /* 410 * The machine independent parts of context switching. 411 */ 412 void 413 mi_switch(int flags, struct thread *newtd) 414 { 415 uint64_t runtime, new_switchtime; 416 struct thread *td; 417 418 td = curthread; /* XXX */ 419 THREAD_LOCK_ASSERT(td, MA_OWNED | MA_NOTRECURSED); 420 KASSERT(!TD_ON_RUNQ(td), ("mi_switch: called by old code")); 421 #ifdef INVARIANTS 422 if (!TD_ON_LOCK(td) && !TD_IS_RUNNING(td)) 423 mtx_assert(&Giant, MA_NOTOWNED); 424 #endif 425 KASSERT(td->td_critnest == 1 || panicstr, 426 ("mi_switch: switch in a critical section")); 427 KASSERT((flags & (SW_INVOL | SW_VOL)) != 0, 428 ("mi_switch: switch must be voluntary or involuntary")); 429 KASSERT(newtd != curthread, ("mi_switch: preempting back to ourself")); 430 431 /* 432 * Don't perform context switches from the debugger. 433 */ 434 if (kdb_active) 435 kdb_switch(); 436 if (SCHEDULER_STOPPED()) 437 return; 438 if (flags & SW_VOL) { 439 td->td_ru.ru_nvcsw++; 440 td->td_swvoltick = ticks; 441 } else 442 td->td_ru.ru_nivcsw++; 443 #ifdef SCHED_STATS 444 SCHED_STAT_INC(sched_switch_stats[flags & SW_TYPE_MASK]); 445 #endif 446 /* 447 * Compute the amount of time during which the current 448 * thread was running, and add that to its total so far. 449 */ 450 new_switchtime = cpu_ticks(); 451 runtime = new_switchtime - PCPU_GET(switchtime); 452 td->td_runtime += runtime; 453 td->td_incruntime += runtime; 454 PCPU_SET(switchtime, new_switchtime); 455 td->td_generation++; /* bump preempt-detect counter */ 456 PCPU_INC(cnt.v_swtch); 457 PCPU_SET(switchticks, ticks); 458 CTR4(KTR_PROC, "mi_switch: old thread %ld (td_sched %p, pid %ld, %s)", 459 td->td_tid, td->td_sched, td->td_proc->p_pid, td->td_name); 460 #if (KTR_COMPILE & KTR_SCHED) != 0 461 if (TD_IS_IDLETHREAD(td)) 462 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "idle", 463 "prio:%d", td->td_priority); 464 else 465 KTR_STATE3(KTR_SCHED, "thread", sched_tdname(td), KTDSTATE(td), 466 "prio:%d", td->td_priority, "wmesg:\"%s\"", td->td_wmesg, 467 "lockname:\"%s\"", td->td_lockname); 468 #endif 469 SDT_PROBE0(sched, , , preempt); 470 sched_switch(td, newtd, flags); 471 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "running", 472 "prio:%d", td->td_priority); 473 474 CTR4(KTR_PROC, "mi_switch: new thread %ld (td_sched %p, pid %ld, %s)", 475 td->td_tid, td->td_sched, td->td_proc->p_pid, td->td_name); 476 477 /* 478 * If the last thread was exiting, finish cleaning it up. 479 */ 480 if ((td = PCPU_GET(deadthread))) { 481 PCPU_SET(deadthread, NULL); 482 thread_stash(td); 483 } 484 } 485 486 /* 487 * Change thread state to be runnable, placing it on the run queue if 488 * it is in memory. If it is swapped out, return true so our caller 489 * will know to awaken the swapper. 490 */ 491 int 492 setrunnable(struct thread *td) 493 { 494 495 THREAD_LOCK_ASSERT(td, MA_OWNED); 496 KASSERT(td->td_proc->p_state != PRS_ZOMBIE, 497 ("setrunnable: pid %d is a zombie", td->td_proc->p_pid)); 498 switch (td->td_state) { 499 case TDS_RUNNING: 500 case TDS_RUNQ: 501 return (0); 502 case TDS_INHIBITED: 503 /* 504 * If we are only inhibited because we are swapped out 505 * then arange to swap in this process. Otherwise just return. 506 */ 507 if (td->td_inhibitors != TDI_SWAPPED) 508 return (0); 509 /* FALLTHROUGH */ 510 case TDS_CAN_RUN: 511 break; 512 default: 513 printf("state is 0x%x", td->td_state); 514 panic("setrunnable(2)"); 515 } 516 if ((td->td_flags & TDF_INMEM) == 0) { 517 if ((td->td_flags & TDF_SWAPINREQ) == 0) { 518 td->td_flags |= TDF_SWAPINREQ; 519 return (1); 520 } 521 } else 522 sched_wakeup(td); 523 return (0); 524 } 525 526 /* 527 * Compute a tenex style load average of a quantity on 528 * 1, 5 and 15 minute intervals. 529 */ 530 static void 531 loadav(void *arg) 532 { 533 int i, nrun; 534 struct loadavg *avg; 535 536 nrun = sched_load(); 537 avg = &averunnable; 538 539 for (i = 0; i < 3; i++) 540 avg->ldavg[i] = (cexp[i] * avg->ldavg[i] + 541 nrun * FSCALE * (FSCALE - cexp[i])) >> FSHIFT; 542 543 /* 544 * Schedule the next update to occur after 5 seconds, but add a 545 * random variation to avoid synchronisation with processes that 546 * run at regular intervals. 547 */ 548 callout_reset_sbt(&loadav_callout, 549 SBT_1US * (4000000 + (int)(random() % 2000001)), SBT_1US, 550 loadav, NULL, C_DIRECT_EXEC | C_PREL(32)); 551 } 552 553 /* ARGSUSED */ 554 static void 555 synch_setup(void *dummy) 556 { 557 callout_init(&loadav_callout, 1); 558 559 /* Kick off timeout driven events by calling first time. */ 560 loadav(NULL); 561 } 562 563 int 564 should_yield(void) 565 { 566 567 return ((u_int)ticks - (u_int)curthread->td_swvoltick >= hogticks); 568 } 569 570 void 571 maybe_yield(void) 572 { 573 574 if (should_yield()) 575 kern_yield(PRI_USER); 576 } 577 578 void 579 kern_yield(int prio) 580 { 581 struct thread *td; 582 583 td = curthread; 584 DROP_GIANT(); 585 thread_lock(td); 586 if (prio == PRI_USER) 587 prio = td->td_user_pri; 588 if (prio >= 0) 589 sched_prio(td, prio); 590 mi_switch(SW_VOL | SWT_RELINQUISH, NULL); 591 thread_unlock(td); 592 PICKUP_GIANT(); 593 } 594 595 /* 596 * General purpose yield system call. 597 */ 598 int 599 sys_yield(struct thread *td, struct yield_args *uap) 600 { 601 602 thread_lock(td); 603 if (PRI_BASE(td->td_pri_class) == PRI_TIMESHARE) 604 sched_prio(td, PRI_MAX_TIMESHARE); 605 mi_switch(SW_VOL | SWT_RELINQUISH, NULL); 606 thread_unlock(td); 607 td->td_retval[0] = 0; 608 return (0); 609 } 610