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/condvar.h> 48 #include <sys/kdb.h> 49 #include <sys/kernel.h> 50 #include <sys/ktr.h> 51 #include <sys/lock.h> 52 #include <sys/mutex.h> 53 #include <sys/proc.h> 54 #include <sys/resourcevar.h> 55 #include <sys/sched.h> 56 #include <sys/sdt.h> 57 #include <sys/signalvar.h> 58 #include <sys/sleepqueue.h> 59 #include <sys/smp.h> 60 #include <sys/sx.h> 61 #include <sys/sysctl.h> 62 #include <sys/sysproto.h> 63 #include <sys/vmmeter.h> 64 #ifdef KTRACE 65 #include <sys/uio.h> 66 #include <sys/ktrace.h> 67 #endif 68 69 #include <machine/cpu.h> 70 71 static void synch_setup(void *dummy); 72 SYSINIT(synch_setup, SI_SUB_KICK_SCHEDULER, SI_ORDER_FIRST, synch_setup, 73 NULL); 74 75 int hogticks; 76 static uint8_t pause_wchan[MAXCPU]; 77 78 static struct callout loadav_callout; 79 80 struct 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 */ 86 static 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 */ 93 SYSCTL_INT(_kern, OID_AUTO, fscale, CTLFLAG_RD, SYSCTL_NULL_INT_PTR, FSCALE, ""); 94 95 static void loadav(void *arg); 96 97 SDT_PROVIDER_DECLARE(sched); 98 SDT_PROBE_DEFINE(sched, , , preempt); 99 100 static void 101 sleepinit(void *unused) 102 { 103 104 hogticks = (hz / 10) * 2; /* Default only. */ 105 init_sleepqueues(); 106 } 107 108 /* 109 * vmem tries to lock the sleepq mutexes when free'ing kva, so make sure 110 * it is available. 111 */ 112 SYSINIT(sleepinit, SI_SUB_KMEM, SI_ORDER_ANY, sleepinit, 0); 113 114 /* 115 * General sleep call. Suspends the current thread until a wakeup is 116 * performed on the specified identifier. The thread will then be made 117 * runnable with the specified priority. Sleeps at most sbt units of time 118 * (0 means no timeout). If pri includes the PCATCH flag, let signals 119 * interrupt the sleep, otherwise ignore them while sleeping. Returns 0 if 120 * awakened, EWOULDBLOCK if the timeout expires. If PCATCH is set and a 121 * signal becomes pending, ERESTART is returned if the current system 122 * call should be restarted if possible, and EINTR is returned if the system 123 * call should be interrupted by the signal (return EINTR). 124 * 125 * The lock argument is unlocked before the caller is suspended, and 126 * re-locked before _sleep() returns. If priority includes the PDROP 127 * flag the lock is not re-locked before returning. 128 */ 129 int 130 _sleep(void *ident, struct lock_object *lock, int priority, 131 const char *wmesg, sbintime_t sbt, sbintime_t pr, int flags) 132 { 133 struct thread *td; 134 struct lock_class *class; 135 uintptr_t lock_state; 136 int catch, pri, rval, sleepq_flags; 137 WITNESS_SAVE_DECL(lock_witness); 138 139 td = curthread; 140 #ifdef KTRACE 141 if (KTRPOINT(td, KTR_CSW)) 142 ktrcsw(1, 0, wmesg); 143 #endif 144 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, lock, 145 "Sleeping on \"%s\"", wmesg); 146 KASSERT(sbt != 0 || mtx_owned(&Giant) || lock != NULL, 147 ("sleeping without a lock")); 148 KASSERT(ident != NULL, ("_sleep: NULL ident")); 149 KASSERT(TD_IS_RUNNING(td), ("_sleep: curthread not running")); 150 if (priority & PDROP) 151 KASSERT(lock != NULL && lock != &Giant.lock_object, 152 ("PDROP requires a non-Giant lock")); 153 if (lock != NULL) 154 class = LOCK_CLASS(lock); 155 else 156 class = NULL; 157 158 if (SCHEDULER_STOPPED_TD(td)) { 159 if (lock != NULL && priority & PDROP) 160 class->lc_unlock(lock); 161 return (0); 162 } 163 catch = priority & PCATCH; 164 pri = priority & PRIMASK; 165 166 KASSERT(!TD_ON_SLEEPQ(td), ("recursive sleep")); 167 168 if ((uint8_t *)ident >= &pause_wchan[0] && 169 (uint8_t *)ident <= &pause_wchan[MAXCPU - 1]) 170 sleepq_flags = SLEEPQ_PAUSE; 171 else 172 sleepq_flags = SLEEPQ_SLEEP; 173 if (catch) 174 sleepq_flags |= SLEEPQ_INTERRUPTIBLE; 175 176 sleepq_lock(ident); 177 CTR5(KTR_PROC, "sleep: thread %ld (pid %ld, %s) on %s (%p)", 178 td->td_tid, td->td_proc->p_pid, td->td_name, wmesg, ident); 179 180 if (lock == &Giant.lock_object) 181 mtx_assert(&Giant, MA_OWNED); 182 DROP_GIANT(); 183 if (lock != NULL && lock != &Giant.lock_object && 184 !(class->lc_flags & LC_SLEEPABLE)) { 185 WITNESS_SAVE(lock, lock_witness); 186 lock_state = class->lc_unlock(lock); 187 } else 188 /* GCC needs to follow the Yellow Brick Road */ 189 lock_state = -1; 190 191 /* 192 * We put ourselves on the sleep queue and start our timeout 193 * before calling thread_suspend_check, as we could stop there, 194 * and a wakeup or a SIGCONT (or both) could occur while we were 195 * stopped without resuming us. Thus, we must be ready for sleep 196 * when cursig() is called. If the wakeup happens while we're 197 * stopped, then td will no longer be on a sleep queue upon 198 * return from cursig(). 199 */ 200 sleepq_add(ident, lock, wmesg, sleepq_flags, 0); 201 if (sbt != 0) 202 sleepq_set_timeout_sbt(ident, sbt, pr, flags); 203 if (lock != NULL && class->lc_flags & LC_SLEEPABLE) { 204 sleepq_release(ident); 205 WITNESS_SAVE(lock, lock_witness); 206 lock_state = class->lc_unlock(lock); 207 sleepq_lock(ident); 208 } 209 if (sbt != 0 && catch) 210 rval = sleepq_timedwait_sig(ident, pri); 211 else if (sbt != 0) 212 rval = sleepq_timedwait(ident, pri); 213 else if (catch) 214 rval = sleepq_wait_sig(ident, pri); 215 else { 216 sleepq_wait(ident, pri); 217 rval = 0; 218 } 219 #ifdef KTRACE 220 if (KTRPOINT(td, KTR_CSW)) 221 ktrcsw(0, 0, wmesg); 222 #endif 223 PICKUP_GIANT(); 224 if (lock != NULL && lock != &Giant.lock_object && !(priority & PDROP)) { 225 class->lc_lock(lock, lock_state); 226 WITNESS_RESTORE(lock, lock_witness); 227 } 228 return (rval); 229 } 230 231 int 232 msleep_spin_sbt(void *ident, struct mtx *mtx, const char *wmesg, 233 sbintime_t sbt, sbintime_t pr, int flags) 234 { 235 struct thread *td; 236 int rval; 237 WITNESS_SAVE_DECL(mtx); 238 239 td = curthread; 240 KASSERT(mtx != NULL, ("sleeping without a mutex")); 241 KASSERT(ident != NULL, ("msleep_spin_sbt: NULL ident")); 242 KASSERT(TD_IS_RUNNING(td), ("msleep_spin_sbt: curthread not running")); 243 244 if (SCHEDULER_STOPPED_TD(td)) 245 return (0); 246 247 sleepq_lock(ident); 248 CTR5(KTR_PROC, "msleep_spin: thread %ld (pid %ld, %s) on %s (%p)", 249 td->td_tid, td->td_proc->p_pid, td->td_name, wmesg, ident); 250 251 DROP_GIANT(); 252 mtx_assert(mtx, MA_OWNED | MA_NOTRECURSED); 253 WITNESS_SAVE(&mtx->lock_object, mtx); 254 mtx_unlock_spin(mtx); 255 256 /* 257 * We put ourselves on the sleep queue and start our timeout. 258 */ 259 sleepq_add(ident, &mtx->lock_object, wmesg, SLEEPQ_SLEEP, 0); 260 if (sbt != 0) 261 sleepq_set_timeout_sbt(ident, sbt, pr, flags); 262 263 /* 264 * Can't call ktrace with any spin locks held so it can lock the 265 * ktrace_mtx lock, and WITNESS_WARN considers it an error to hold 266 * any spin lock. Thus, we have to drop the sleepq spin lock while 267 * we handle those requests. This is safe since we have placed our 268 * thread on the sleep queue already. 269 */ 270 #ifdef KTRACE 271 if (KTRPOINT(td, KTR_CSW)) { 272 sleepq_release(ident); 273 ktrcsw(1, 0, wmesg); 274 sleepq_lock(ident); 275 } 276 #endif 277 #ifdef WITNESS 278 sleepq_release(ident); 279 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, "Sleeping on \"%s\"", 280 wmesg); 281 sleepq_lock(ident); 282 #endif 283 if (sbt != 0) 284 rval = sleepq_timedwait(ident, 0); 285 else { 286 sleepq_wait(ident, 0); 287 rval = 0; 288 } 289 #ifdef KTRACE 290 if (KTRPOINT(td, KTR_CSW)) 291 ktrcsw(0, 0, wmesg); 292 #endif 293 PICKUP_GIANT(); 294 mtx_lock_spin(mtx); 295 WITNESS_RESTORE(&mtx->lock_object, mtx); 296 return (rval); 297 } 298 299 /* 300 * pause_sbt() delays the calling thread by the given signed binary 301 * time. During cold bootup, pause_sbt() uses the DELAY() function 302 * instead of the _sleep() function to do the waiting. The "sbt" 303 * argument must be greater than or equal to zero. A "sbt" value of 304 * zero is equivalent to a "sbt" value of one tick. 305 */ 306 int 307 pause_sbt(const char *wmesg, sbintime_t sbt, sbintime_t pr, int flags) 308 { 309 KASSERT(sbt >= 0, ("pause_sbt: timeout must be >= 0")); 310 311 /* silently convert invalid timeouts */ 312 if (sbt == 0) 313 sbt = tick_sbt; 314 315 if ((cold && curthread == &thread0) || kdb_active || 316 SCHEDULER_STOPPED()) { 317 /* 318 * We delay one second at a time to avoid overflowing the 319 * system specific DELAY() function(s): 320 */ 321 while (sbt >= SBT_1S) { 322 DELAY(1000000); 323 sbt -= SBT_1S; 324 } 325 /* Do the delay remainder, if any */ 326 sbt = howmany(sbt, SBT_1US); 327 if (sbt > 0) 328 DELAY(sbt); 329 return (EWOULDBLOCK); 330 } 331 return (_sleep(&pause_wchan[curcpu], NULL, 332 (flags & C_CATCH) ? PCATCH : 0, wmesg, sbt, pr, flags)); 333 } 334 335 /* 336 * Make all threads sleeping on the specified identifier runnable. 337 */ 338 void 339 wakeup(void *ident) 340 { 341 int wakeup_swapper; 342 343 sleepq_lock(ident); 344 wakeup_swapper = sleepq_broadcast(ident, SLEEPQ_SLEEP, 0, 0); 345 sleepq_release(ident); 346 if (wakeup_swapper) { 347 KASSERT(ident != &proc0, 348 ("wakeup and wakeup_swapper and proc0")); 349 kick_proc0(); 350 } 351 } 352 353 /* 354 * Make a thread sleeping on the specified identifier runnable. 355 * May wake more than one thread if a target thread is currently 356 * swapped out. 357 */ 358 void 359 wakeup_one(void *ident) 360 { 361 int wakeup_swapper; 362 363 sleepq_lock(ident); 364 wakeup_swapper = sleepq_signal(ident, SLEEPQ_SLEEP, 0, 0); 365 sleepq_release(ident); 366 if (wakeup_swapper) 367 kick_proc0(); 368 } 369 370 static void 371 kdb_switch(void) 372 { 373 thread_unlock(curthread); 374 kdb_backtrace(); 375 kdb_reenter(); 376 panic("%s: did not reenter debugger", __func__); 377 } 378 379 /* 380 * The machine independent parts of context switching. 381 */ 382 void 383 mi_switch(int flags, struct thread *newtd) 384 { 385 uint64_t runtime, new_switchtime; 386 struct thread *td; 387 388 td = curthread; /* XXX */ 389 THREAD_LOCK_ASSERT(td, MA_OWNED | MA_NOTRECURSED); 390 KASSERT(!TD_ON_RUNQ(td), ("mi_switch: called by old code")); 391 #ifdef INVARIANTS 392 if (!TD_ON_LOCK(td) && !TD_IS_RUNNING(td)) 393 mtx_assert(&Giant, MA_NOTOWNED); 394 #endif 395 KASSERT(td->td_critnest == 1 || panicstr, 396 ("mi_switch: switch in a critical section")); 397 KASSERT((flags & (SW_INVOL | SW_VOL)) != 0, 398 ("mi_switch: switch must be voluntary or involuntary")); 399 KASSERT(newtd != curthread, ("mi_switch: preempting back to ourself")); 400 401 /* 402 * Don't perform context switches from the debugger. 403 */ 404 if (kdb_active) 405 kdb_switch(); 406 if (SCHEDULER_STOPPED_TD(td)) 407 return; 408 if (flags & SW_VOL) { 409 td->td_ru.ru_nvcsw++; 410 td->td_swvoltick = ticks; 411 } else { 412 td->td_ru.ru_nivcsw++; 413 td->td_swinvoltick = ticks; 414 } 415 #ifdef SCHED_STATS 416 SCHED_STAT_INC(sched_switch_stats[flags & SW_TYPE_MASK]); 417 #endif 418 /* 419 * Compute the amount of time during which the current 420 * thread was running, and add that to its total so far. 421 */ 422 new_switchtime = cpu_ticks(); 423 runtime = new_switchtime - PCPU_GET(switchtime); 424 td->td_runtime += runtime; 425 td->td_incruntime += runtime; 426 PCPU_SET(switchtime, new_switchtime); 427 td->td_generation++; /* bump preempt-detect counter */ 428 VM_CNT_INC(v_swtch); 429 PCPU_SET(switchticks, ticks); 430 CTR4(KTR_PROC, "mi_switch: old thread %ld (td_sched %p, pid %ld, %s)", 431 td->td_tid, td_get_sched(td), td->td_proc->p_pid, td->td_name); 432 #ifdef KDTRACE_HOOKS 433 if ((flags & SW_PREEMPT) != 0 || ((flags & SW_INVOL) != 0 && 434 (flags & SW_TYPE_MASK) == SWT_NEEDRESCHED)) 435 SDT_PROBE0(sched, , , preempt); 436 #endif 437 sched_switch(td, newtd, flags); 438 CTR4(KTR_PROC, "mi_switch: new thread %ld (td_sched %p, pid %ld, %s)", 439 td->td_tid, td_get_sched(td), td->td_proc->p_pid, td->td_name); 440 441 /* 442 * If the last thread was exiting, finish cleaning it up. 443 */ 444 if ((td = PCPU_GET(deadthread))) { 445 PCPU_SET(deadthread, NULL); 446 thread_stash(td); 447 } 448 } 449 450 /* 451 * Change thread state to be runnable, placing it on the run queue if 452 * it is in memory. If it is swapped out, return true so our caller 453 * will know to awaken the swapper. 454 */ 455 int 456 setrunnable(struct thread *td) 457 { 458 459 THREAD_LOCK_ASSERT(td, MA_OWNED); 460 KASSERT(td->td_proc->p_state != PRS_ZOMBIE, 461 ("setrunnable: pid %d is a zombie", td->td_proc->p_pid)); 462 switch (td->td_state) { 463 case TDS_RUNNING: 464 case TDS_RUNQ: 465 return (0); 466 case TDS_INHIBITED: 467 /* 468 * If we are only inhibited because we are swapped out 469 * then arange to swap in this process. Otherwise just return. 470 */ 471 if (td->td_inhibitors != TDI_SWAPPED) 472 return (0); 473 /* FALLTHROUGH */ 474 case TDS_CAN_RUN: 475 break; 476 default: 477 printf("state is 0x%x", td->td_state); 478 panic("setrunnable(2)"); 479 } 480 if ((td->td_flags & TDF_INMEM) == 0) { 481 if ((td->td_flags & TDF_SWAPINREQ) == 0) { 482 td->td_flags |= TDF_SWAPINREQ; 483 return (1); 484 } 485 } else 486 sched_wakeup(td); 487 return (0); 488 } 489 490 /* 491 * Compute a tenex style load average of a quantity on 492 * 1, 5 and 15 minute intervals. 493 */ 494 static void 495 loadav(void *arg) 496 { 497 int i, nrun; 498 struct loadavg *avg; 499 500 nrun = sched_load(); 501 avg = &averunnable; 502 503 for (i = 0; i < 3; i++) 504 avg->ldavg[i] = (cexp[i] * avg->ldavg[i] + 505 nrun * FSCALE * (FSCALE - cexp[i])) >> FSHIFT; 506 507 /* 508 * Schedule the next update to occur after 5 seconds, but add a 509 * random variation to avoid synchronisation with processes that 510 * run at regular intervals. 511 */ 512 callout_reset_sbt(&loadav_callout, 513 SBT_1US * (4000000 + (int)(random() % 2000001)), SBT_1US, 514 loadav, NULL, C_DIRECT_EXEC | C_PREL(32)); 515 } 516 517 /* ARGSUSED */ 518 static void 519 synch_setup(void *dummy) 520 { 521 callout_init(&loadav_callout, 1); 522 523 /* Kick off timeout driven events by calling first time. */ 524 loadav(NULL); 525 } 526 527 int 528 should_yield(void) 529 { 530 531 return ((u_int)ticks - (u_int)curthread->td_swvoltick >= hogticks); 532 } 533 534 void 535 maybe_yield(void) 536 { 537 538 if (should_yield()) 539 kern_yield(PRI_USER); 540 } 541 542 void 543 kern_yield(int prio) 544 { 545 struct thread *td; 546 547 td = curthread; 548 DROP_GIANT(); 549 thread_lock(td); 550 if (prio == PRI_USER) 551 prio = td->td_user_pri; 552 if (prio >= 0) 553 sched_prio(td, prio); 554 mi_switch(SW_VOL | SWT_RELINQUISH, NULL); 555 thread_unlock(td); 556 PICKUP_GIANT(); 557 } 558 559 /* 560 * General purpose yield system call. 561 */ 562 int 563 sys_yield(struct thread *td, struct yield_args *uap) 564 { 565 566 thread_lock(td); 567 if (PRI_BASE(td->td_pri_class) == PRI_TIMESHARE) 568 sched_prio(td, PRI_MAX_TIMESHARE); 569 mi_switch(SW_VOL | SWT_RELINQUISH, NULL); 570 thread_unlock(td); 571 td->td_retval[0] = 0; 572 return (0); 573 } 574