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. 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(ident != NULL, ("_sleep: NULL ident")); 156 KASSERT(TD_IS_RUNNING(td), ("_sleep: curthread not running")); 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 (SCHEDULER_STOPPED_TD(td)) { 166 if (lock != NULL && priority & PDROP) 167 class->lc_unlock(lock); 168 return (0); 169 } 170 catch = priority & PCATCH; 171 pri = priority & PRIMASK; 172 173 KASSERT(!TD_ON_SLEEPQ(td), ("recursive sleep")); 174 175 if ((uint8_t *)ident >= &pause_wchan[0] && 176 (uint8_t *)ident <= &pause_wchan[MAXCPU - 1]) 177 sleepq_flags = SLEEPQ_PAUSE; 178 else 179 sleepq_flags = SLEEPQ_SLEEP; 180 if (catch) 181 sleepq_flags |= SLEEPQ_INTERRUPTIBLE; 182 183 sleepq_lock(ident); 184 CTR5(KTR_PROC, "sleep: thread %ld (pid %ld, %s) on %s (%p)", 185 td->td_tid, p->p_pid, td->td_name, wmesg, ident); 186 187 if (lock == &Giant.lock_object) 188 mtx_assert(&Giant, MA_OWNED); 189 DROP_GIANT(); 190 if (lock != NULL && lock != &Giant.lock_object && 191 !(class->lc_flags & LC_SLEEPABLE)) { 192 WITNESS_SAVE(lock, lock_witness); 193 lock_state = class->lc_unlock(lock); 194 } else 195 /* GCC needs to follow the Yellow Brick Road */ 196 lock_state = -1; 197 198 /* 199 * We put ourselves on the sleep queue and start our timeout 200 * before calling thread_suspend_check, as we could stop there, 201 * and a wakeup or a SIGCONT (or both) could occur while we were 202 * stopped without resuming us. Thus, we must be ready for sleep 203 * when cursig() is called. If the wakeup happens while we're 204 * stopped, then td will no longer be on a sleep queue upon 205 * return from cursig(). 206 */ 207 sleepq_add(ident, lock, wmesg, sleepq_flags, 0); 208 if (sbt != 0) 209 sleepq_set_timeout_sbt(ident, sbt, pr, flags); 210 if (lock != NULL && class->lc_flags & LC_SLEEPABLE) { 211 sleepq_release(ident); 212 WITNESS_SAVE(lock, lock_witness); 213 lock_state = class->lc_unlock(lock); 214 sleepq_lock(ident); 215 } 216 if (sbt != 0 && catch) 217 rval = sleepq_timedwait_sig(ident, pri); 218 else if (sbt != 0) 219 rval = sleepq_timedwait(ident, pri); 220 else if (catch) 221 rval = sleepq_wait_sig(ident, pri); 222 else { 223 sleepq_wait(ident, pri); 224 rval = 0; 225 } 226 #ifdef KTRACE 227 if (KTRPOINT(td, KTR_CSW)) 228 ktrcsw(0, 0, wmesg); 229 #endif 230 PICKUP_GIANT(); 231 if (lock != NULL && lock != &Giant.lock_object && !(priority & PDROP)) { 232 class->lc_lock(lock, lock_state); 233 WITNESS_RESTORE(lock, lock_witness); 234 } 235 return (rval); 236 } 237 238 int 239 msleep_spin_sbt(void *ident, struct mtx *mtx, const char *wmesg, 240 sbintime_t sbt, sbintime_t pr, int flags) 241 { 242 struct thread *td; 243 struct proc *p; 244 int rval; 245 WITNESS_SAVE_DECL(mtx); 246 247 td = curthread; 248 p = td->td_proc; 249 KASSERT(mtx != NULL, ("sleeping without a mutex")); 250 KASSERT(ident != NULL, ("msleep_spin_sbt: NULL ident")); 251 KASSERT(TD_IS_RUNNING(td), ("msleep_spin_sbt: curthread not running")); 252 253 if (SCHEDULER_STOPPED_TD(td)) 254 return (0); 255 256 sleepq_lock(ident); 257 CTR5(KTR_PROC, "msleep_spin: thread %ld (pid %ld, %s) on %s (%p)", 258 td->td_tid, p->p_pid, td->td_name, wmesg, ident); 259 260 DROP_GIANT(); 261 mtx_assert(mtx, MA_OWNED | MA_NOTRECURSED); 262 WITNESS_SAVE(&mtx->lock_object, mtx); 263 mtx_unlock_spin(mtx); 264 265 /* 266 * We put ourselves on the sleep queue and start our timeout. 267 */ 268 sleepq_add(ident, &mtx->lock_object, wmesg, SLEEPQ_SLEEP, 0); 269 if (sbt != 0) 270 sleepq_set_timeout_sbt(ident, sbt, pr, flags); 271 272 /* 273 * Can't call ktrace with any spin locks held so it can lock the 274 * ktrace_mtx lock, and WITNESS_WARN considers it an error to hold 275 * any spin lock. Thus, we have to drop the sleepq spin lock while 276 * we handle those requests. This is safe since we have placed our 277 * thread on the sleep queue already. 278 */ 279 #ifdef KTRACE 280 if (KTRPOINT(td, KTR_CSW)) { 281 sleepq_release(ident); 282 ktrcsw(1, 0, wmesg); 283 sleepq_lock(ident); 284 } 285 #endif 286 #ifdef WITNESS 287 sleepq_release(ident); 288 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, "Sleeping on \"%s\"", 289 wmesg); 290 sleepq_lock(ident); 291 #endif 292 if (sbt != 0) 293 rval = sleepq_timedwait(ident, 0); 294 else { 295 sleepq_wait(ident, 0); 296 rval = 0; 297 } 298 #ifdef KTRACE 299 if (KTRPOINT(td, KTR_CSW)) 300 ktrcsw(0, 0, wmesg); 301 #endif 302 PICKUP_GIANT(); 303 mtx_lock_spin(mtx); 304 WITNESS_RESTORE(&mtx->lock_object, mtx); 305 return (rval); 306 } 307 308 /* 309 * pause() delays the calling thread by the given number of system ticks. 310 * During cold bootup, pause() uses the DELAY() function instead of 311 * the tsleep() function to do the waiting. The "timo" argument must be 312 * greater than or equal to zero. A "timo" value of zero is equivalent 313 * to a "timo" value of one. 314 */ 315 int 316 pause_sbt(const char *wmesg, sbintime_t sbt, sbintime_t pr, int flags) 317 { 318 KASSERT(sbt >= 0, ("pause: timeout must be >= 0")); 319 320 /* silently convert invalid timeouts */ 321 if (sbt == 0) 322 sbt = tick_sbt; 323 324 if ((cold && curthread == &thread0) || kdb_active || 325 SCHEDULER_STOPPED()) { 326 /* 327 * We delay one second at a time to avoid overflowing the 328 * system specific DELAY() function(s): 329 */ 330 while (sbt >= SBT_1S) { 331 DELAY(1000000); 332 sbt -= SBT_1S; 333 } 334 /* Do the delay remainder, if any */ 335 sbt = howmany(sbt, SBT_1US); 336 if (sbt > 0) 337 DELAY(sbt); 338 return (0); 339 } 340 return (_sleep(&pause_wchan[curcpu], NULL, 0, wmesg, sbt, pr, flags)); 341 } 342 343 /* 344 * Make all threads sleeping on the specified identifier runnable. 345 */ 346 void 347 wakeup(void *ident) 348 { 349 int wakeup_swapper; 350 351 sleepq_lock(ident); 352 wakeup_swapper = sleepq_broadcast(ident, SLEEPQ_SLEEP, 0, 0); 353 sleepq_release(ident); 354 if (wakeup_swapper) { 355 KASSERT(ident != &proc0, 356 ("wakeup and wakeup_swapper and proc0")); 357 kick_proc0(); 358 } 359 } 360 361 /* 362 * Make a thread sleeping on the specified identifier runnable. 363 * May wake more than one thread if a target thread is currently 364 * swapped out. 365 */ 366 void 367 wakeup_one(void *ident) 368 { 369 int wakeup_swapper; 370 371 sleepq_lock(ident); 372 wakeup_swapper = sleepq_signal(ident, SLEEPQ_SLEEP, 0, 0); 373 sleepq_release(ident); 374 if (wakeup_swapper) 375 kick_proc0(); 376 } 377 378 static void 379 kdb_switch(void) 380 { 381 thread_unlock(curthread); 382 kdb_backtrace(); 383 kdb_reenter(); 384 panic("%s: did not reenter debugger", __func__); 385 } 386 387 /* 388 * The machine independent parts of context switching. 389 */ 390 void 391 mi_switch(int flags, struct thread *newtd) 392 { 393 uint64_t runtime, new_switchtime; 394 struct thread *td; 395 396 td = curthread; /* XXX */ 397 THREAD_LOCK_ASSERT(td, MA_OWNED | MA_NOTRECURSED); 398 KASSERT(!TD_ON_RUNQ(td), ("mi_switch: called by old code")); 399 #ifdef INVARIANTS 400 if (!TD_ON_LOCK(td) && !TD_IS_RUNNING(td)) 401 mtx_assert(&Giant, MA_NOTOWNED); 402 #endif 403 KASSERT(td->td_critnest == 1 || panicstr, 404 ("mi_switch: switch in a critical section")); 405 KASSERT((flags & (SW_INVOL | SW_VOL)) != 0, 406 ("mi_switch: switch must be voluntary or involuntary")); 407 KASSERT(newtd != curthread, ("mi_switch: preempting back to ourself")); 408 409 /* 410 * Don't perform context switches from the debugger. 411 */ 412 if (kdb_active) 413 kdb_switch(); 414 if (SCHEDULER_STOPPED_TD(td)) 415 return; 416 if (flags & SW_VOL) { 417 td->td_ru.ru_nvcsw++; 418 td->td_swvoltick = ticks; 419 } else { 420 td->td_ru.ru_nivcsw++; 421 td->td_swinvoltick = ticks; 422 } 423 #ifdef SCHED_STATS 424 SCHED_STAT_INC(sched_switch_stats[flags & SW_TYPE_MASK]); 425 #endif 426 /* 427 * Compute the amount of time during which the current 428 * thread was running, and add that to its total so far. 429 */ 430 new_switchtime = cpu_ticks(); 431 runtime = new_switchtime - PCPU_GET(switchtime); 432 td->td_runtime += runtime; 433 td->td_incruntime += runtime; 434 PCPU_SET(switchtime, new_switchtime); 435 td->td_generation++; /* bump preempt-detect counter */ 436 PCPU_INC(cnt.v_swtch); 437 PCPU_SET(switchticks, ticks); 438 CTR4(KTR_PROC, "mi_switch: old thread %ld (td_sched %p, pid %ld, %s)", 439 td->td_tid, td_get_sched(td), td->td_proc->p_pid, td->td_name); 440 #if (KTR_COMPILE & KTR_SCHED) != 0 441 if (TD_IS_IDLETHREAD(td)) 442 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "idle", 443 "prio:%d", td->td_priority); 444 else 445 KTR_STATE3(KTR_SCHED, "thread", sched_tdname(td), KTDSTATE(td), 446 "prio:%d", td->td_priority, "wmesg:\"%s\"", td->td_wmesg, 447 "lockname:\"%s\"", td->td_lockname); 448 #endif 449 SDT_PROBE0(sched, , , preempt); 450 sched_switch(td, newtd, flags); 451 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "running", 452 "prio:%d", td->td_priority); 453 454 CTR4(KTR_PROC, "mi_switch: new thread %ld (td_sched %p, pid %ld, %s)", 455 td->td_tid, td_get_sched(td), td->td_proc->p_pid, td->td_name); 456 457 /* 458 * If the last thread was exiting, finish cleaning it up. 459 */ 460 if ((td = PCPU_GET(deadthread))) { 461 PCPU_SET(deadthread, NULL); 462 thread_stash(td); 463 } 464 } 465 466 /* 467 * Change thread state to be runnable, placing it on the run queue if 468 * it is in memory. If it is swapped out, return true so our caller 469 * will know to awaken the swapper. 470 */ 471 int 472 setrunnable(struct thread *td) 473 { 474 475 THREAD_LOCK_ASSERT(td, MA_OWNED); 476 KASSERT(td->td_proc->p_state != PRS_ZOMBIE, 477 ("setrunnable: pid %d is a zombie", td->td_proc->p_pid)); 478 switch (td->td_state) { 479 case TDS_RUNNING: 480 case TDS_RUNQ: 481 return (0); 482 case TDS_INHIBITED: 483 /* 484 * If we are only inhibited because we are swapped out 485 * then arange to swap in this process. Otherwise just return. 486 */ 487 if (td->td_inhibitors != TDI_SWAPPED) 488 return (0); 489 /* FALLTHROUGH */ 490 case TDS_CAN_RUN: 491 break; 492 default: 493 printf("state is 0x%x", td->td_state); 494 panic("setrunnable(2)"); 495 } 496 if ((td->td_flags & TDF_INMEM) == 0) { 497 if ((td->td_flags & TDF_SWAPINREQ) == 0) { 498 td->td_flags |= TDF_SWAPINREQ; 499 return (1); 500 } 501 } else 502 sched_wakeup(td); 503 return (0); 504 } 505 506 /* 507 * Compute a tenex style load average of a quantity on 508 * 1, 5 and 15 minute intervals. 509 */ 510 static void 511 loadav(void *arg) 512 { 513 int i, nrun; 514 struct loadavg *avg; 515 516 nrun = sched_load(); 517 avg = &averunnable; 518 519 for (i = 0; i < 3; i++) 520 avg->ldavg[i] = (cexp[i] * avg->ldavg[i] + 521 nrun * FSCALE * (FSCALE - cexp[i])) >> FSHIFT; 522 523 /* 524 * Schedule the next update to occur after 5 seconds, but add a 525 * random variation to avoid synchronisation with processes that 526 * run at regular intervals. 527 */ 528 callout_reset_sbt(&loadav_callout, 529 SBT_1US * (4000000 + (int)(random() % 2000001)), SBT_1US, 530 loadav, NULL, C_DIRECT_EXEC | C_PREL(32)); 531 } 532 533 /* ARGSUSED */ 534 static void 535 synch_setup(void *dummy) 536 { 537 callout_init(&loadav_callout, 1); 538 539 /* Kick off timeout driven events by calling first time. */ 540 loadav(NULL); 541 } 542 543 int 544 should_yield(void) 545 { 546 547 return ((u_int)ticks - (u_int)curthread->td_swvoltick >= hogticks); 548 } 549 550 void 551 maybe_yield(void) 552 { 553 554 if (should_yield()) 555 kern_yield(PRI_USER); 556 } 557 558 void 559 kern_yield(int prio) 560 { 561 struct thread *td; 562 563 td = curthread; 564 DROP_GIANT(); 565 thread_lock(td); 566 if (prio == PRI_USER) 567 prio = td->td_user_pri; 568 if (prio >= 0) 569 sched_prio(td, prio); 570 mi_switch(SW_VOL | SWT_RELINQUISH, NULL); 571 thread_unlock(td); 572 PICKUP_GIANT(); 573 } 574 575 /* 576 * General purpose yield system call. 577 */ 578 int 579 sys_yield(struct thread *td, struct yield_args *uap) 580 { 581 582 thread_lock(td); 583 if (PRI_BASE(td->td_pri_class) == PRI_TIMESHARE) 584 sched_prio(td, PRI_MAX_TIMESHARE); 585 mi_switch(SW_VOL | SWT_RELINQUISH, NULL); 586 thread_unlock(td); 587 td->td_retval[0] = 0; 588 return (0); 589 } 590