kern_synch.c revision 177010
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: head/sys/kern/kern_synch.c 177010 2008-03-10 03:16:51Z jeff $"); 39 40#include "opt_ktrace.h" 41 42#include <sys/param.h> 43#include <sys/systm.h> 44#include <sys/condvar.h> 45#include <sys/kdb.h> 46#include <sys/kernel.h> 47#include <sys/ktr.h> 48#include <sys/lock.h> 49#include <sys/mutex.h> 50#include <sys/proc.h> 51#include <sys/resourcevar.h> 52#include <sys/sched.h> 53#include <sys/signalvar.h> 54#include <sys/sleepqueue.h> 55#include <sys/smp.h> 56#include <sys/sx.h> 57#include <sys/sysctl.h> 58#include <sys/sysproto.h> 59#include <sys/vmmeter.h> 60#ifdef KTRACE 61#include <sys/uio.h> 62#include <sys/ktrace.h> 63#endif 64 65#include <machine/cpu.h> 66 67static void synch_setup(void *dummy); 68SYSINIT(synch_setup, SI_SUB_KICK_SCHEDULER, SI_ORDER_FIRST, synch_setup, NULL) 69 70int hogticks; 71int lbolt; 72static int pause_wchan; 73 74static struct callout loadav_callout; 75static struct callout lbolt_callout; 76 77struct loadavg averunnable = 78 { {0, 0, 0}, FSCALE }; /* load average, of runnable procs */ 79/* 80 * Constants for averages over 1, 5, and 15 minutes 81 * when sampling at 5 second intervals. 82 */ 83static fixpt_t cexp[3] = { 84 0.9200444146293232 * FSCALE, /* exp(-1/12) */ 85 0.9834714538216174 * FSCALE, /* exp(-1/60) */ 86 0.9944598480048967 * FSCALE, /* exp(-1/180) */ 87}; 88 89/* kernel uses `FSCALE', userland (SHOULD) use kern.fscale */ 90static int fscale __unused = FSCALE; 91SYSCTL_INT(_kern, OID_AUTO, fscale, CTLFLAG_RD, 0, FSCALE, ""); 92 93static void loadav(void *arg); 94static void lboltcb(void *arg); 95 96void 97sleepinit(void) 98{ 99 100 hogticks = (hz / 10) * 2; /* Default only. */ 101 init_sleepqueues(); 102} 103 104/* 105 * General sleep call. Suspends the current thread until a wakeup is 106 * performed on the specified identifier. The thread will then be made 107 * runnable with the specified priority. Sleeps at most timo/hz seconds 108 * (0 means no timeout). If pri includes PCATCH flag, signals are checked 109 * before and after sleeping, else signals are not checked. Returns 0 if 110 * awakened, EWOULDBLOCK if the timeout expires. If PCATCH is set and a 111 * signal needs to be delivered, ERESTART is returned if the current system 112 * call should be restarted if possible, and EINTR is returned if the system 113 * call should be interrupted by the signal (return EINTR). 114 * 115 * The lock argument is unlocked before the caller is suspended, and 116 * re-locked before _sleep() returns. If priority includes the PDROP 117 * flag the lock is not re-locked before returning. 118 */ 119int 120_sleep(ident, lock, priority, wmesg, timo) 121 void *ident; 122 struct lock_object *lock; 123 int priority, timo; 124 const char *wmesg; 125{ 126 struct thread *td; 127 struct proc *p; 128 struct lock_class *class; 129 int catch, flags, lock_state, pri, rval; 130 WITNESS_SAVE_DECL(lock_witness); 131 132 td = curthread; 133 p = td->td_proc; 134#ifdef KTRACE 135 if (KTRPOINT(td, KTR_CSW)) 136 ktrcsw(1, 0); 137#endif 138 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, lock, 139 "Sleeping on \"%s\"", wmesg); 140 KASSERT(timo != 0 || mtx_owned(&Giant) || lock != NULL || 141 ident == &lbolt, ("sleeping without a lock")); 142 KASSERT(p != NULL, ("msleep1")); 143 KASSERT(ident != NULL && TD_IS_RUNNING(td), ("msleep")); 144 if (lock != NULL) 145 class = LOCK_CLASS(lock); 146 else 147 class = NULL; 148 149 if (cold) { 150 /* 151 * During autoconfiguration, just return; 152 * don't run any other threads or panic below, 153 * in case this is the idle thread and already asleep. 154 * XXX: this used to do "s = splhigh(); splx(safepri); 155 * splx(s);" to give interrupts a chance, but there is 156 * no way to give interrupts a chance now. 157 */ 158 if (lock != NULL && priority & PDROP) 159 class->lc_unlock(lock); 160 return (0); 161 } 162 catch = priority & PCATCH; 163 rval = 0; 164 165 /* 166 * If we are already on a sleep queue, then remove us from that 167 * sleep queue first. We have to do this to handle recursive 168 * sleeps. 169 */ 170 if (TD_ON_SLEEPQ(td)) 171 sleepq_remove(td, td->td_wchan); 172 173 if (ident == &pause_wchan) 174 flags = SLEEPQ_PAUSE; 175 else 176 flags = SLEEPQ_SLEEP; 177 if (catch) 178 flags |= SLEEPQ_INTERRUPTIBLE; 179 180 sleepq_lock(ident); 181 CTR5(KTR_PROC, "sleep: thread %ld (pid %ld, %s) on %s (%p)", 182 td->td_tid, p->p_pid, td->td_name, wmesg, ident); 183 184 DROP_GIANT(); 185 if (lock != NULL && !(class->lc_flags & LC_SLEEPABLE)) { 186 WITNESS_SAVE(lock, lock_witness); 187 lock_state = class->lc_unlock(lock); 188 } else 189 /* GCC needs to follow the Yellow Brick Road */ 190 lock_state = -1; 191 192 /* 193 * We put ourselves on the sleep queue and start our timeout 194 * before calling thread_suspend_check, as we could stop there, 195 * and a wakeup or a SIGCONT (or both) could occur while we were 196 * stopped without resuming us. Thus, we must be ready for sleep 197 * when cursig() is called. If the wakeup happens while we're 198 * stopped, then td will no longer be on a sleep queue upon 199 * return from cursig(). 200 */ 201 sleepq_add(ident, ident == &lbolt ? NULL : lock, wmesg, flags, 0); 202 if (timo) 203 sleepq_set_timeout(ident, timo); 204 if (lock != NULL && class->lc_flags & LC_SLEEPABLE) { 205 sleepq_release(ident); 206 WITNESS_SAVE(lock, lock_witness); 207 lock_state = class->lc_unlock(lock); 208 sleepq_lock(ident); 209 } 210 211 /* 212 * Adjust this thread's priority, if necessary. 213 */ 214 pri = priority & PRIMASK; 215 if (pri != 0 && pri != td->td_priority) { 216 thread_lock(td); 217 sched_prio(td, pri); 218 thread_unlock(td); 219 } 220 221 if (timo && catch) 222 rval = sleepq_timedwait_sig(ident); 223 else if (timo) 224 rval = sleepq_timedwait(ident); 225 else if (catch) 226 rval = sleepq_wait_sig(ident); 227 else { 228 sleepq_wait(ident); 229 rval = 0; 230 } 231#ifdef KTRACE 232 if (KTRPOINT(td, KTR_CSW)) 233 ktrcsw(0, 0); 234#endif 235 PICKUP_GIANT(); 236 if (lock != NULL && !(priority & PDROP)) { 237 class->lc_lock(lock, lock_state); 238 WITNESS_RESTORE(lock, lock_witness); 239 } 240 return (rval); 241} 242 243int 244msleep_spin(ident, mtx, wmesg, timo) 245 void *ident; 246 struct mtx *mtx; 247 const char *wmesg; 248 int timo; 249{ 250 struct thread *td; 251 struct proc *p; 252 int rval; 253 WITNESS_SAVE_DECL(mtx); 254 255 td = curthread; 256 p = td->td_proc; 257 KASSERT(mtx != NULL, ("sleeping without a mutex")); 258 KASSERT(p != NULL, ("msleep1")); 259 KASSERT(ident != NULL && TD_IS_RUNNING(td), ("msleep")); 260 261 if (cold) { 262 /* 263 * During autoconfiguration, just return; 264 * don't run any other threads or panic below, 265 * in case this is the idle thread and already asleep. 266 * XXX: this used to do "s = splhigh(); splx(safepri); 267 * splx(s);" to give interrupts a chance, but there is 268 * no way to give interrupts a chance now. 269 */ 270 return (0); 271 } 272 273 sleepq_lock(ident); 274 CTR5(KTR_PROC, "msleep_spin: thread %ld (pid %ld, %s) on %s (%p)", 275 td->td_tid, p->p_pid, td->td_name, wmesg, ident); 276 277 DROP_GIANT(); 278 mtx_assert(mtx, MA_OWNED | MA_NOTRECURSED); 279 WITNESS_SAVE(&mtx->lock_object, mtx); 280 mtx_unlock_spin(mtx); 281 282 /* 283 * We put ourselves on the sleep queue and start our timeout. 284 */ 285 sleepq_add(ident, &mtx->lock_object, wmesg, SLEEPQ_SLEEP, 0); 286 if (timo) 287 sleepq_set_timeout(ident, timo); 288 289 /* 290 * Can't call ktrace with any spin locks held so it can lock the 291 * ktrace_mtx lock, and WITNESS_WARN considers it an error to hold 292 * any spin lock. Thus, we have to drop the sleepq spin lock while 293 * we handle those requests. This is safe since we have placed our 294 * thread on the sleep queue already. 295 */ 296#ifdef KTRACE 297 if (KTRPOINT(td, KTR_CSW)) { 298 sleepq_release(ident); 299 ktrcsw(1, 0); 300 sleepq_lock(ident); 301 } 302#endif 303#ifdef WITNESS 304 sleepq_release(ident); 305 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, "Sleeping on \"%s\"", 306 wmesg); 307 sleepq_lock(ident); 308#endif 309 if (timo) 310 rval = sleepq_timedwait(ident); 311 else { 312 sleepq_wait(ident); 313 rval = 0; 314 } 315#ifdef KTRACE 316 if (KTRPOINT(td, KTR_CSW)) 317 ktrcsw(0, 0); 318#endif 319 PICKUP_GIANT(); 320 mtx_lock_spin(mtx); 321 WITNESS_RESTORE(&mtx->lock_object, mtx); 322 return (rval); 323} 324 325/* 326 * pause() is like tsleep() except that the intention is to not be 327 * explicitly woken up by another thread. Instead, the current thread 328 * simply wishes to sleep until the timeout expires. It is 329 * implemented using a dummy wait channel. 330 */ 331int 332pause(wmesg, timo) 333 const char *wmesg; 334 int timo; 335{ 336 337 KASSERT(timo != 0, ("pause: timeout required")); 338 return (tsleep(&pause_wchan, 0, wmesg, timo)); 339} 340 341/* 342 * Make all threads sleeping on the specified identifier runnable. 343 */ 344void 345wakeup(ident) 346 register void *ident; 347{ 348 349 sleepq_lock(ident); 350 sleepq_broadcast(ident, SLEEPQ_SLEEP, -1, 0); 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 */ 358void 359wakeup_one(ident) 360 register void *ident; 361{ 362 363 sleepq_lock(ident); 364 sleepq_signal(ident, SLEEPQ_SLEEP, -1, 0); 365 sleepq_release(ident); 366} 367 368static void 369kdb_switch(void) 370{ 371 thread_unlock(curthread); 372 kdb_backtrace(); 373 kdb_reenter(); 374 panic("%s: did not reenter debugger", __func__); 375} 376 377/* 378 * The machine independent parts of context switching. 379 */ 380void 381mi_switch(int flags, struct thread *newtd) 382{ 383 uint64_t runtime, new_switchtime; 384 struct thread *td; 385 struct proc *p; 386 387 td = curthread; /* XXX */ 388 THREAD_LOCK_ASSERT(td, MA_OWNED | MA_NOTRECURSED); 389 p = td->td_proc; /* XXX */ 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 || (td->td_critnest == 2 && 396 (td->td_owepreempt) && (flags & SW_INVOL) != 0 && 397 newtd == NULL) || panicstr, 398 ("mi_switch: switch in a critical section")); 399 KASSERT((flags & (SW_INVOL | SW_VOL)) != 0, 400 ("mi_switch: switch must be voluntary or involuntary")); 401 KASSERT(newtd != curthread, ("mi_switch: preempting back to ourself")); 402 403 /* 404 * Don't perform context switches from the debugger. 405 */ 406 if (kdb_active) 407 kdb_switch(); 408 if (flags & SW_VOL) 409 td->td_ru.ru_nvcsw++; 410 else 411 td->td_ru.ru_nivcsw++; 412 /* 413 * Compute the amount of time during which the current 414 * thread was running, and add that to its total so far. 415 */ 416 new_switchtime = cpu_ticks(); 417 runtime = new_switchtime - PCPU_GET(switchtime); 418 td->td_runtime += runtime; 419 td->td_incruntime += runtime; 420 PCPU_SET(switchtime, new_switchtime); 421 td->td_generation++; /* bump preempt-detect counter */ 422 PCPU_INC(cnt.v_swtch); 423 PCPU_SET(switchticks, ticks); 424 CTR4(KTR_PROC, "mi_switch: old thread %ld (kse %p, pid %ld, %s)", 425 td->td_tid, td->td_sched, p->p_pid, td->td_name); 426#if (KTR_COMPILE & KTR_SCHED) != 0 427 if (TD_IS_IDLETHREAD(td)) 428 CTR3(KTR_SCHED, "mi_switch: %p(%s) prio %d idle", 429 td, td->td_name, td->td_priority); 430 else if (newtd != NULL) 431 CTR5(KTR_SCHED, 432 "mi_switch: %p(%s) prio %d preempted by %p(%s)", 433 td, td->td_name, td->td_priority, newtd, 434 newtd->td_name); 435 else 436 CTR6(KTR_SCHED, 437 "mi_switch: %p(%s) prio %d inhibit %d wmesg %s lock %s", 438 td, td->td_name, td->td_priority, 439 td->td_inhibitors, td->td_wmesg, td->td_lockname); 440#endif 441 /* 442 * We call thread_switchout after the KTR_SCHED prints above so kse 443 * selecting a new thread to run does not show up as a preemption. 444 */ 445#ifdef KSE 446 if ((flags & SW_VOL) && (td->td_proc->p_flag & P_SA)) 447 newtd = thread_switchout(td, flags, newtd); 448#endif 449 sched_switch(td, newtd, flags); 450 CTR3(KTR_SCHED, "mi_switch: running %p(%s) prio %d", 451 td, td->td_name, td->td_priority); 452 453 CTR4(KTR_PROC, "mi_switch: new thread %ld (kse %p, pid %ld, %s)", 454 td->td_tid, td->td_sched, p->p_pid, td->td_name); 455 456 /* 457 * If the last thread was exiting, finish cleaning it up. 458 */ 459 if ((td = PCPU_GET(deadthread))) { 460 PCPU_SET(deadthread, NULL); 461 thread_stash(td); 462 } 463} 464 465/* 466 * Change process state to be runnable, 467 * placing it on the run queue if it is in memory, 468 * and awakening the swapper if it isn't in memory. 469 */ 470void 471setrunnable(struct thread *td) 472{ 473 474 THREAD_LOCK_ASSERT(td, MA_OWNED); 475 KASSERT(td->td_proc->p_state != PRS_ZOMBIE, 476 ("setrunnable: pid %d is a zombie", td->td_proc->p_pid)); 477 switch (td->td_state) { 478 case TDS_RUNNING: 479 case TDS_RUNQ: 480 return; 481 case TDS_INHIBITED: 482 /* 483 * If we are only inhibited because we are swapped out 484 * then arange to swap in this process. Otherwise just return. 485 */ 486 if (td->td_inhibitors != TDI_SWAPPED) 487 return; 488 /* XXX: intentional fall-through ? */ 489 case TDS_CAN_RUN: 490 break; 491 default: 492 printf("state is 0x%x", td->td_state); 493 panic("setrunnable(2)"); 494 } 495 if ((td->td_flags & TDF_INMEM) == 0) { 496 if ((td->td_flags & TDF_SWAPINREQ) == 0) { 497 td->td_flags |= TDF_SWAPINREQ; 498 /* 499 * due to a LOR between the thread lock and 500 * the sleepqueue chain locks, use 501 * lower level scheduling functions. 502 */ 503 kick_proc0(); 504 } 505 } else 506 sched_wakeup(td); 507} 508 509/* 510 * Compute a tenex style load average of a quantity on 511 * 1, 5 and 15 minute intervals. 512 * XXXKSE Needs complete rewrite when correct info is available. 513 * Completely Bogus.. only works with 1:1 (but compiles ok now :-) 514 */ 515static void 516loadav(void *arg) 517{ 518 int i, nrun; 519 struct loadavg *avg; 520 521 nrun = sched_load(); 522 avg = &averunnable; 523 524 for (i = 0; i < 3; i++) 525 avg->ldavg[i] = (cexp[i] * avg->ldavg[i] + 526 nrun * FSCALE * (FSCALE - cexp[i])) >> FSHIFT; 527 528 /* 529 * Schedule the next update to occur after 5 seconds, but add a 530 * random variation to avoid synchronisation with processes that 531 * run at regular intervals. 532 */ 533 callout_reset(&loadav_callout, hz * 4 + (int)(random() % (hz * 2 + 1)), 534 loadav, NULL); 535} 536 537static void 538lboltcb(void *arg) 539{ 540 wakeup(&lbolt); 541 callout_reset(&lbolt_callout, hz, lboltcb, NULL); 542} 543 544/* ARGSUSED */ 545static void 546synch_setup(dummy) 547 void *dummy; 548{ 549 callout_init(&loadav_callout, CALLOUT_MPSAFE); 550 callout_init(&lbolt_callout, CALLOUT_MPSAFE); 551 552 /* Kick off timeout driven events by calling first time. */ 553 loadav(NULL); 554 lboltcb(NULL); 555} 556 557/* 558 * General purpose yield system call. 559 */ 560int 561yield(struct thread *td, struct yield_args *uap) 562{ 563 564 thread_lock(td); 565 sched_prio(td, PRI_MAX_TIMESHARE); 566 mi_switch(SW_VOL, NULL); 567 thread_unlock(td); 568 td->td_retval[0] = 0; 569 return (0); 570} 571