kern_synch.c revision 195700
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 195700 2009-07-14 22:50:41Z kib $"); 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/signalvar.h> 55#include <sys/sleepqueue.h> 56#include <sys/smp.h> 57#include <sys/sx.h> 58#include <sys/sysctl.h> 59#include <sys/sysproto.h> 60#include <sys/vmmeter.h> 61#ifdef KTRACE 62#include <sys/uio.h> 63#include <sys/ktrace.h> 64#endif 65 66#include <machine/cpu.h> 67 68#ifdef XEN 69#include <vm/vm.h> 70#include <vm/vm_param.h> 71#include <vm/pmap.h> 72#endif 73 74#define KTDSTATE(td) \ 75 (((td)->td_inhibitors & TDI_SLEEPING) != 0 ? "sleep" : \ 76 ((td)->td_inhibitors & TDI_SUSPENDED) != 0 ? "suspended" : \ 77 ((td)->td_inhibitors & TDI_SWAPPED) != 0 ? "swapped" : \ 78 ((td)->td_inhibitors & TDI_LOCK) != 0 ? "blocked" : \ 79 ((td)->td_inhibitors & TDI_IWAIT) != 0 ? "iwait" : "yielding") 80 81static void synch_setup(void *dummy); 82SYSINIT(synch_setup, SI_SUB_KICK_SCHEDULER, SI_ORDER_FIRST, synch_setup, 83 NULL); 84 85int hogticks; 86static int pause_wchan; 87 88static struct callout loadav_callout; 89 90struct loadavg averunnable = 91 { {0, 0, 0}, FSCALE }; /* load average, of runnable procs */ 92/* 93 * Constants for averages over 1, 5, and 15 minutes 94 * when sampling at 5 second intervals. 95 */ 96static fixpt_t cexp[3] = { 97 0.9200444146293232 * FSCALE, /* exp(-1/12) */ 98 0.9834714538216174 * FSCALE, /* exp(-1/60) */ 99 0.9944598480048967 * FSCALE, /* exp(-1/180) */ 100}; 101 102/* kernel uses `FSCALE', userland (SHOULD) use kern.fscale */ 103static int fscale __unused = FSCALE; 104SYSCTL_INT(_kern, OID_AUTO, fscale, CTLFLAG_RD, 0, FSCALE, ""); 105 106static void loadav(void *arg); 107 108void 109sleepinit(void) 110{ 111 112 hogticks = (hz / 10) * 2; /* Default only. */ 113 init_sleepqueues(); 114} 115 116/* 117 * General sleep call. Suspends the current thread until a wakeup is 118 * performed on the specified identifier. The thread will then be made 119 * runnable with the specified priority. Sleeps at most timo/hz seconds 120 * (0 means no timeout). If pri includes PCATCH flag, signals are checked 121 * before and after sleeping, else signals are not checked. Returns 0 if 122 * awakened, EWOULDBLOCK if the timeout expires. If PCATCH is set and a 123 * signal needs to be delivered, ERESTART is returned if the current system 124 * call should be restarted if possible, and EINTR is returned if the system 125 * call should be interrupted by the signal (return EINTR). 126 * 127 * The lock argument is unlocked before the caller is suspended, and 128 * re-locked before _sleep() returns. If priority includes the PDROP 129 * flag the lock is not re-locked before returning. 130 */ 131int 132_sleep(void *ident, struct lock_object *lock, int priority, 133 const char *wmesg, int timo) 134{ 135 struct thread *td; 136 struct proc *p; 137 struct lock_class *class; 138 int catch, flags, lock_state, pri, rval; 139 WITNESS_SAVE_DECL(lock_witness); 140 141 td = curthread; 142 p = td->td_proc; 143#ifdef KTRACE 144 if (KTRPOINT(td, KTR_CSW)) 145 ktrcsw(1, 0); 146#endif 147 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, lock, 148 "Sleeping on \"%s\"", wmesg); 149 KASSERT(timo != 0 || mtx_owned(&Giant) || lock != NULL, 150 ("sleeping without a lock")); 151 KASSERT(p != NULL, ("msleep1")); 152 KASSERT(ident != NULL && TD_IS_RUNNING(td), ("msleep")); 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 (cold) { 162 /* 163 * During autoconfiguration, just return; 164 * don't run any other threads or panic below, 165 * in case this is the idle thread and already asleep. 166 * XXX: this used to do "s = splhigh(); splx(safepri); 167 * splx(s);" to give interrupts a chance, but there is 168 * no way to give interrupts a chance now. 169 */ 170 if (lock != NULL && priority & PDROP) 171 class->lc_unlock(lock); 172 return (0); 173 } 174 catch = priority & PCATCH; 175 pri = priority & PRIMASK; 176 177 /* 178 * If we are already on a sleep queue, then remove us from that 179 * sleep queue first. We have to do this to handle recursive 180 * sleeps. 181 */ 182 if (TD_ON_SLEEPQ(td)) 183 sleepq_remove(td, td->td_wchan); 184 185 if (ident == &pause_wchan) 186 flags = SLEEPQ_PAUSE; 187 else 188 flags = SLEEPQ_SLEEP; 189 if (catch) 190 flags |= SLEEPQ_INTERRUPTIBLE; 191 192 sleepq_lock(ident); 193 CTR5(KTR_PROC, "sleep: thread %ld (pid %ld, %s) on %s (%p)", 194 td->td_tid, p->p_pid, td->td_name, wmesg, ident); 195 196 if (lock == &Giant.lock_object) 197 mtx_assert(&Giant, MA_OWNED); 198 DROP_GIANT(); 199 if (lock != NULL && lock != &Giant.lock_object && 200 !(class->lc_flags & LC_SLEEPABLE)) { 201 WITNESS_SAVE(lock, lock_witness); 202 lock_state = class->lc_unlock(lock); 203 } else 204 /* GCC needs to follow the Yellow Brick Road */ 205 lock_state = -1; 206 207 /* 208 * We put ourselves on the sleep queue and start our timeout 209 * before calling thread_suspend_check, as we could stop there, 210 * and a wakeup or a SIGCONT (or both) could occur while we were 211 * stopped without resuming us. Thus, we must be ready for sleep 212 * when cursig() is called. If the wakeup happens while we're 213 * stopped, then td will no longer be on a sleep queue upon 214 * return from cursig(). 215 */ 216 sleepq_add(ident, lock, wmesg, flags, 0); 217 if (timo) 218 sleepq_set_timeout(ident, timo); 219 if (lock != NULL && class->lc_flags & LC_SLEEPABLE) { 220 sleepq_release(ident); 221 WITNESS_SAVE(lock, lock_witness); 222 lock_state = class->lc_unlock(lock); 223 sleepq_lock(ident); 224 } 225 if (timo && catch) 226 rval = sleepq_timedwait_sig(ident, pri); 227 else if (timo) 228 rval = sleepq_timedwait(ident, pri); 229 else if (catch) 230 rval = sleepq_wait_sig(ident, pri); 231 else { 232 sleepq_wait(ident, pri); 233 rval = 0; 234 } 235#ifdef KTRACE 236 if (KTRPOINT(td, KTR_CSW)) 237 ktrcsw(0, 0); 238#endif 239 PICKUP_GIANT(); 240 if (lock != NULL && lock != &Giant.lock_object && !(priority & PDROP)) { 241 class->lc_lock(lock, lock_state); 242 WITNESS_RESTORE(lock, lock_witness); 243 } 244 return (rval); 245} 246 247int 248msleep_spin(void *ident, struct mtx *mtx, const char *wmesg, 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, 0); 311 else { 312 sleepq_wait(ident, 0); 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(const char *wmesg, int timo) 333{ 334 335 KASSERT(timo != 0, ("pause: timeout required")); 336 return (tsleep(&pause_wchan, 0, wmesg, timo)); 337} 338 339/* 340 * Make all threads sleeping on the specified identifier runnable. 341 */ 342void 343wakeup(void *ident) 344{ 345 int wakeup_swapper; 346 347 sleepq_lock(ident); 348 wakeup_swapper = sleepq_broadcast(ident, SLEEPQ_SLEEP, 0, 0); 349 sleepq_release(ident); 350 if (wakeup_swapper) { 351 KASSERT(ident != &proc0, 352 ("wakeup and wakeup_swapper and proc0")); 353 kick_proc0(); 354 } 355} 356 357/* 358 * Make a thread sleeping on the specified identifier runnable. 359 * May wake more than one thread if a target thread is currently 360 * swapped out. 361 */ 362void 363wakeup_one(void *ident) 364{ 365 int wakeup_swapper; 366 367 sleepq_lock(ident); 368 wakeup_swapper = sleepq_signal(ident, SLEEPQ_SLEEP, 0, 0); 369 sleepq_release(ident); 370 if (wakeup_swapper) 371 kick_proc0(); 372} 373 374static void 375kdb_switch(void) 376{ 377 thread_unlock(curthread); 378 kdb_backtrace(); 379 kdb_reenter(); 380 panic("%s: did not reenter debugger", __func__); 381} 382 383/* 384 * The machine independent parts of context switching. 385 */ 386void 387mi_switch(int flags, struct thread *newtd) 388{ 389 uint64_t runtime, new_switchtime; 390 struct thread *td; 391 struct proc *p; 392 393 td = curthread; /* XXX */ 394 THREAD_LOCK_ASSERT(td, MA_OWNED | MA_NOTRECURSED); 395 p = td->td_proc; /* XXX */ 396 KASSERT(!TD_ON_RUNQ(td), ("mi_switch: called by old code")); 397#ifdef INVARIANTS 398 if (!TD_ON_LOCK(td) && !TD_IS_RUNNING(td)) 399 mtx_assert(&Giant, MA_NOTOWNED); 400#endif 401 KASSERT(td->td_critnest == 1 || (td->td_critnest == 2 && 402 (td->td_owepreempt) && (flags & SW_INVOL) != 0 && 403 newtd == NULL) || 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 (flags & SW_VOL) 415 td->td_ru.ru_nvcsw++; 416 else 417 td->td_ru.ru_nivcsw++; 418#ifdef SCHED_STATS 419 SCHED_STAT_INC(sched_switch_stats[flags & SW_TYPE_MASK]); 420#endif 421 /* 422 * Compute the amount of time during which the current 423 * thread was running, and add that to its total so far. 424 */ 425 new_switchtime = cpu_ticks(); 426 runtime = new_switchtime - PCPU_GET(switchtime); 427 td->td_runtime += runtime; 428 td->td_incruntime += runtime; 429 PCPU_SET(switchtime, new_switchtime); 430 td->td_generation++; /* bump preempt-detect counter */ 431 PCPU_INC(cnt.v_swtch); 432 PCPU_SET(switchticks, ticks); 433 CTR4(KTR_PROC, "mi_switch: old thread %ld (td_sched %p, pid %ld, %s)", 434 td->td_tid, td->td_sched, p->p_pid, td->td_name); 435#if (KTR_COMPILE & KTR_SCHED) != 0 436 if (TD_IS_IDLETHREAD(td)) 437 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "idle", 438 "prio:%d", td->td_priority); 439 else 440 KTR_STATE3(KTR_SCHED, "thread", sched_tdname(td), KTDSTATE(td), 441 "prio:%d", td->td_priority, "wmesg:\"%s\"", td->td_wmesg, 442 "lockname:\"%s\"", td->td_lockname); 443#endif 444#ifdef XEN 445 PT_UPDATES_FLUSH(); 446#endif 447 sched_switch(td, newtd, flags); 448 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "running", 449 "prio:%d", td->td_priority); 450 451 CTR4(KTR_PROC, "mi_switch: new thread %ld (td_sched %p, pid %ld, %s)", 452 td->td_tid, td->td_sched, p->p_pid, td->td_name); 453 454 /* 455 * If the last thread was exiting, finish cleaning it up. 456 */ 457 if ((td = PCPU_GET(deadthread))) { 458 PCPU_SET(deadthread, NULL); 459 thread_stash(td); 460 } 461} 462 463/* 464 * Change thread state to be runnable, placing it on the run queue if 465 * it is in memory. If it is swapped out, return true so our caller 466 * will know to awaken the swapper. 467 */ 468int 469setrunnable(struct thread *td) 470{ 471 472 THREAD_LOCK_ASSERT(td, MA_OWNED); 473 KASSERT(td->td_proc->p_state != PRS_ZOMBIE, 474 ("setrunnable: pid %d is a zombie", td->td_proc->p_pid)); 475 switch (td->td_state) { 476 case TDS_RUNNING: 477 case TDS_RUNQ: 478 return (0); 479 case TDS_INHIBITED: 480 /* 481 * If we are only inhibited because we are swapped out 482 * then arange to swap in this process. Otherwise just return. 483 */ 484 if (td->td_inhibitors != TDI_SWAPPED) 485 return (0); 486 /* FALLTHROUGH */ 487 case TDS_CAN_RUN: 488 break; 489 default: 490 printf("state is 0x%x", td->td_state); 491 panic("setrunnable(2)"); 492 } 493 if ((td->td_flags & TDF_INMEM) == 0) { 494 if ((td->td_flags & TDF_SWAPINREQ) == 0) { 495 td->td_flags |= TDF_SWAPINREQ; 496 return (1); 497 } 498 } else 499 sched_wakeup(td); 500 return (0); 501} 502 503/* 504 * Compute a tenex style load average of a quantity on 505 * 1, 5 and 15 minute intervals. 506 */ 507static void 508loadav(void *arg) 509{ 510 int i, nrun; 511 struct loadavg *avg; 512 513 nrun = sched_load(); 514 avg = &averunnable; 515 516 for (i = 0; i < 3; i++) 517 avg->ldavg[i] = (cexp[i] * avg->ldavg[i] + 518 nrun * FSCALE * (FSCALE - cexp[i])) >> FSHIFT; 519 520 /* 521 * Schedule the next update to occur after 5 seconds, but add a 522 * random variation to avoid synchronisation with processes that 523 * run at regular intervals. 524 */ 525 callout_reset(&loadav_callout, hz * 4 + (int)(random() % (hz * 2 + 1)), 526 loadav, NULL); 527} 528 529/* ARGSUSED */ 530static void 531synch_setup(void *dummy) 532{ 533 callout_init(&loadav_callout, CALLOUT_MPSAFE); 534 535 /* Kick off timeout driven events by calling first time. */ 536 loadav(NULL); 537} 538 539/* 540 * General purpose yield system call. 541 */ 542int 543yield(struct thread *td, struct yield_args *uap) 544{ 545 546 thread_lock(td); 547 sched_prio(td, PRI_MAX_TIMESHARE); 548 mi_switch(SW_VOL | SWT_RELINQUISH, NULL); 549 thread_unlock(td); 550 td->td_retval[0] = 0; 551 return (0); 552} 553