kern_synch.c revision 187357
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 187357 2009-01-17 07:17:57Z jeff $"); 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 rval = 0; 177 178 /* 179 * If we are already on a sleep queue, then remove us from that 180 * sleep queue first. We have to do this to handle recursive 181 * sleeps. 182 */ 183 if (TD_ON_SLEEPQ(td)) 184 sleepq_remove(td, td->td_wchan); 185 186 if (ident == &pause_wchan) 187 flags = SLEEPQ_PAUSE; 188 else 189 flags = SLEEPQ_SLEEP; 190 if (catch) 191 flags |= SLEEPQ_INTERRUPTIBLE; 192 193 sleepq_lock(ident); 194 CTR5(KTR_PROC, "sleep: thread %ld (pid %ld, %s) on %s (%p)", 195 td->td_tid, p->p_pid, td->td_name, wmesg, ident); 196 197 if (lock == &Giant.lock_object) 198 mtx_assert(&Giant, MA_OWNED); 199 DROP_GIANT(); 200 if (lock != NULL && lock != &Giant.lock_object && 201 !(class->lc_flags & LC_SLEEPABLE)) { 202 WITNESS_SAVE(lock, lock_witness); 203 lock_state = class->lc_unlock(lock); 204 } else 205 /* GCC needs to follow the Yellow Brick Road */ 206 lock_state = -1; 207 208 /* 209 * We put ourselves on the sleep queue and start our timeout 210 * before calling thread_suspend_check, as we could stop there, 211 * and a wakeup or a SIGCONT (or both) could occur while we were 212 * stopped without resuming us. Thus, we must be ready for sleep 213 * when cursig() is called. If the wakeup happens while we're 214 * stopped, then td will no longer be on a sleep queue upon 215 * return from cursig(). 216 */ 217 sleepq_add(ident, lock, wmesg, flags, 0); 218 if (timo) 219 sleepq_set_timeout(ident, timo); 220 if (lock != NULL && class->lc_flags & LC_SLEEPABLE) { 221 sleepq_release(ident); 222 WITNESS_SAVE(lock, lock_witness); 223 lock_state = class->lc_unlock(lock); 224 sleepq_lock(ident); 225 } 226 if (timo && catch) 227 rval = sleepq_timedwait_sig(ident, pri); 228 else if (timo) 229 rval = sleepq_timedwait(ident, pri); 230 else if (catch) 231 rval = sleepq_wait_sig(ident, pri); 232 else { 233 sleepq_wait(ident, pri); 234 rval = 0; 235 } 236#ifdef KTRACE 237 if (KTRPOINT(td, KTR_CSW)) 238 ktrcsw(0, 0); 239#endif 240 PICKUP_GIANT(); 241 if (lock != NULL && lock != &Giant.lock_object && !(priority & PDROP)) { 242 class->lc_lock(lock, lock_state); 243 WITNESS_RESTORE(lock, lock_witness); 244 } 245 return (rval); 246} 247 248int 249msleep_spin(void *ident, struct mtx *mtx, const char *wmesg, int timo) 250{ 251 struct thread *td; 252 struct proc *p; 253 int rval; 254 WITNESS_SAVE_DECL(mtx); 255 256 td = curthread; 257 p = td->td_proc; 258 KASSERT(mtx != NULL, ("sleeping without a mutex")); 259 KASSERT(p != NULL, ("msleep1")); 260 KASSERT(ident != NULL && TD_IS_RUNNING(td), ("msleep")); 261 262 if (cold) { 263 /* 264 * During autoconfiguration, just return; 265 * don't run any other threads or panic below, 266 * in case this is the idle thread and already asleep. 267 * XXX: this used to do "s = splhigh(); splx(safepri); 268 * splx(s);" to give interrupts a chance, but there is 269 * no way to give interrupts a chance now. 270 */ 271 return (0); 272 } 273 274 sleepq_lock(ident); 275 CTR5(KTR_PROC, "msleep_spin: thread %ld (pid %ld, %s) on %s (%p)", 276 td->td_tid, p->p_pid, td->td_name, wmesg, ident); 277 278 DROP_GIANT(); 279 mtx_assert(mtx, MA_OWNED | MA_NOTRECURSED); 280 WITNESS_SAVE(&mtx->lock_object, mtx); 281 mtx_unlock_spin(mtx); 282 283 /* 284 * We put ourselves on the sleep queue and start our timeout. 285 */ 286 sleepq_add(ident, &mtx->lock_object, wmesg, SLEEPQ_SLEEP, 0); 287 if (timo) 288 sleepq_set_timeout(ident, timo); 289 290 /* 291 * Can't call ktrace with any spin locks held so it can lock the 292 * ktrace_mtx lock, and WITNESS_WARN considers it an error to hold 293 * any spin lock. Thus, we have to drop the sleepq spin lock while 294 * we handle those requests. This is safe since we have placed our 295 * thread on the sleep queue already. 296 */ 297#ifdef KTRACE 298 if (KTRPOINT(td, KTR_CSW)) { 299 sleepq_release(ident); 300 ktrcsw(1, 0); 301 sleepq_lock(ident); 302 } 303#endif 304#ifdef WITNESS 305 sleepq_release(ident); 306 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, "Sleeping on \"%s\"", 307 wmesg); 308 sleepq_lock(ident); 309#endif 310 if (timo) 311 rval = sleepq_timedwait(ident, 0); 312 else { 313 sleepq_wait(ident, 0); 314 rval = 0; 315 } 316#ifdef KTRACE 317 if (KTRPOINT(td, KTR_CSW)) 318 ktrcsw(0, 0); 319#endif 320 PICKUP_GIANT(); 321 mtx_lock_spin(mtx); 322 WITNESS_RESTORE(&mtx->lock_object, mtx); 323 return (rval); 324} 325 326/* 327 * pause() is like tsleep() except that the intention is to not be 328 * explicitly woken up by another thread. Instead, the current thread 329 * simply wishes to sleep until the timeout expires. It is 330 * implemented using a dummy wait channel. 331 */ 332int 333pause(const char *wmesg, int timo) 334{ 335 336 KASSERT(timo != 0, ("pause: timeout required")); 337 return (tsleep(&pause_wchan, 0, wmesg, timo)); 338} 339 340/* 341 * Make all threads sleeping on the specified identifier runnable. 342 */ 343void 344wakeup(void *ident) 345{ 346 int wakeup_swapper; 347 348 sleepq_lock(ident); 349 wakeup_swapper = sleepq_broadcast(ident, SLEEPQ_SLEEP, 0, 0); 350 sleepq_release(ident); 351 if (wakeup_swapper) 352 kick_proc0(); 353} 354 355/* 356 * Make a thread sleeping on the specified identifier runnable. 357 * May wake more than one thread if a target thread is currently 358 * swapped out. 359 */ 360void 361wakeup_one(void *ident) 362{ 363 int wakeup_swapper; 364 365 sleepq_lock(ident); 366 wakeup_swapper = sleepq_signal(ident, SLEEPQ_SLEEP, 0, 0); 367 sleepq_release(ident); 368 if (wakeup_swapper) 369 kick_proc0(); 370} 371 372static void 373kdb_switch(void) 374{ 375 thread_unlock(curthread); 376 kdb_backtrace(); 377 kdb_reenter(); 378 panic("%s: did not reenter debugger", __func__); 379} 380 381/* 382 * The machine independent parts of context switching. 383 */ 384void 385mi_switch(int flags, struct thread *newtd) 386{ 387 uint64_t runtime, new_switchtime; 388 struct thread *td; 389 struct proc *p; 390 391 td = curthread; /* XXX */ 392 THREAD_LOCK_ASSERT(td, MA_OWNED | MA_NOTRECURSED); 393 p = td->td_proc; /* XXX */ 394 KASSERT(!TD_ON_RUNQ(td), ("mi_switch: called by old code")); 395#ifdef INVARIANTS 396 if (!TD_ON_LOCK(td) && !TD_IS_RUNNING(td)) 397 mtx_assert(&Giant, MA_NOTOWNED); 398#endif 399 KASSERT(td->td_critnest == 1 || (td->td_critnest == 2 && 400 (td->td_owepreempt) && (flags & SW_INVOL) != 0 && 401 newtd == NULL) || panicstr, 402 ("mi_switch: switch in a critical section")); 403 KASSERT((flags & (SW_INVOL | SW_VOL)) != 0, 404 ("mi_switch: switch must be voluntary or involuntary")); 405 KASSERT(newtd != curthread, ("mi_switch: preempting back to ourself")); 406 407 /* 408 * Don't perform context switches from the debugger. 409 */ 410 if (kdb_active) 411 kdb_switch(); 412 if (flags & SW_VOL) 413 td->td_ru.ru_nvcsw++; 414 else 415 td->td_ru.ru_nivcsw++; 416#ifdef SCHED_STATS 417 SCHED_STAT_INC(sched_switch_stats[flags & SW_TYPE_MASK]); 418#endif 419 /* 420 * Compute the amount of time during which the current 421 * thread was running, and add that to its total so far. 422 */ 423 new_switchtime = cpu_ticks(); 424 runtime = new_switchtime - PCPU_GET(switchtime); 425 td->td_runtime += runtime; 426 td->td_incruntime += runtime; 427 PCPU_SET(switchtime, new_switchtime); 428 td->td_generation++; /* bump preempt-detect counter */ 429 PCPU_INC(cnt.v_swtch); 430 PCPU_SET(switchticks, ticks); 431 CTR4(KTR_PROC, "mi_switch: old thread %ld (td_sched %p, pid %ld, %s)", 432 td->td_tid, td->td_sched, p->p_pid, td->td_name); 433#if (KTR_COMPILE & KTR_SCHED) != 0 434 if (TD_IS_IDLETHREAD(td)) 435 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "idle", 436 "prio:%d", td->td_priority); 437 else 438 KTR_STATE3(KTR_SCHED, "thread", sched_tdname(td), KTDSTATE(td), 439 "prio:%d", td->td_priority, "wmesg:\"%s\"", td->td_wmesg, 440 "lockname:\"%s\"", td->td_lockname); 441#endif 442#ifdef XEN 443 PT_UPDATES_FLUSH(); 444#endif 445 sched_switch(td, newtd, flags); 446 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "running", 447 "prio:%d", td->td_priority); 448 449 CTR4(KTR_PROC, "mi_switch: new thread %ld (td_sched %p, pid %ld, %s)", 450 td->td_tid, td->td_sched, p->p_pid, td->td_name); 451 452 /* 453 * If the last thread was exiting, finish cleaning it up. 454 */ 455 if ((td = PCPU_GET(deadthread))) { 456 PCPU_SET(deadthread, NULL); 457 thread_stash(td); 458 } 459} 460 461/* 462 * Change thread state to be runnable, placing it on the run queue if 463 * it is in memory. If it is swapped out, return true so our caller 464 * will know to awaken the swapper. 465 */ 466int 467setrunnable(struct thread *td) 468{ 469 470 THREAD_LOCK_ASSERT(td, MA_OWNED); 471 KASSERT(td->td_proc->p_state != PRS_ZOMBIE, 472 ("setrunnable: pid %d is a zombie", td->td_proc->p_pid)); 473 switch (td->td_state) { 474 case TDS_RUNNING: 475 case TDS_RUNQ: 476 return (0); 477 case TDS_INHIBITED: 478 /* 479 * If we are only inhibited because we are swapped out 480 * then arange to swap in this process. Otherwise just return. 481 */ 482 if (td->td_inhibitors != TDI_SWAPPED) 483 return (0); 484 /* FALLTHROUGH */ 485 case TDS_CAN_RUN: 486 break; 487 default: 488 printf("state is 0x%x", td->td_state); 489 panic("setrunnable(2)"); 490 } 491 if ((td->td_flags & TDF_INMEM) == 0) { 492 if ((td->td_flags & TDF_SWAPINREQ) == 0) { 493 td->td_flags |= TDF_SWAPINREQ; 494 return (1); 495 } 496 } else 497 sched_wakeup(td); 498 return (0); 499} 500 501/* 502 * Compute a tenex style load average of a quantity on 503 * 1, 5 and 15 minute intervals. 504 */ 505static void 506loadav(void *arg) 507{ 508 int i, nrun; 509 struct loadavg *avg; 510 511 nrun = sched_load(); 512 avg = &averunnable; 513 514 for (i = 0; i < 3; i++) 515 avg->ldavg[i] = (cexp[i] * avg->ldavg[i] + 516 nrun * FSCALE * (FSCALE - cexp[i])) >> FSHIFT; 517 518 /* 519 * Schedule the next update to occur after 5 seconds, but add a 520 * random variation to avoid synchronisation with processes that 521 * run at regular intervals. 522 */ 523 callout_reset(&loadav_callout, hz * 4 + (int)(random() % (hz * 2 + 1)), 524 loadav, NULL); 525} 526 527/* ARGSUSED */ 528static void 529synch_setup(void *dummy) 530{ 531 callout_init(&loadav_callout, CALLOUT_MPSAFE); 532 533 /* Kick off timeout driven events by calling first time. */ 534 loadav(NULL); 535} 536 537/* 538 * General purpose yield system call. 539 */ 540int 541yield(struct thread *td, struct yield_args *uap) 542{ 543 544 thread_lock(td); 545 sched_prio(td, PRI_MAX_TIMESHARE); 546 mi_switch(SW_VOL | SWT_RELINQUISH, NULL); 547 thread_unlock(td); 548 td->td_retval[0] = 0; 549 return (0); 550} 551