kern_synch.c revision 110858
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. All advertising materials mentioning features or use of this software 19 * must display the following acknowledgement: 20 * This product includes software developed by the University of 21 * California, Berkeley and its contributors. 22 * 4. Neither the name of the University nor the names of its contributors 23 * may be used to endorse or promote products derived from this software 24 * without specific prior written permission. 25 * 26 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 27 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 28 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 29 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 30 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 31 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 32 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 33 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 34 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 35 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 36 * SUCH DAMAGE. 37 * 38 * @(#)kern_synch.c 8.9 (Berkeley) 5/19/95 39 * $FreeBSD: head/sys/kern/kern_synch.c 110858 2003-02-14 12:44:07Z alfred $ 40 */ 41 42#include "opt_ddb.h" 43#include "opt_ktrace.h" 44 45#include <sys/param.h> 46#include <sys/systm.h> 47#include <sys/condvar.h> 48#include <sys/kernel.h> 49#include <sys/ktr.h> 50#include <sys/lock.h> 51#include <sys/mutex.h> 52#include <sys/proc.h> 53#include <sys/resourcevar.h> 54#include <sys/sched.h> 55#include <sys/signalvar.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 DDB 62#include <ddb/ddb.h> 63#endif 64#ifdef KTRACE 65#include <sys/uio.h> 66#include <sys/ktrace.h> 67#endif 68 69#include <machine/cpu.h> 70 71static void sched_setup(void *dummy); 72SYSINIT(sched_setup, SI_SUB_KICK_SCHEDULER, SI_ORDER_FIRST, sched_setup, NULL) 73 74int hogticks; 75int lbolt; 76 77static struct callout loadav_callout; 78static struct callout lbolt_callout; 79 80struct 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 */ 86static 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 */ 93static int fscale __unused = FSCALE; 94SYSCTL_INT(_kern, OID_AUTO, fscale, CTLFLAG_RD, 0, FSCALE, ""); 95 96static void endtsleep(void *); 97static void loadav(void *arg); 98static void lboltcb(void *arg); 99 100/* 101 * We're only looking at 7 bits of the address; everything is 102 * aligned to 4, lots of things are aligned to greater powers 103 * of 2. Shift right by 8, i.e. drop the bottom 256 worth. 104 */ 105#define TABLESIZE 128 106static TAILQ_HEAD(slpquehead, thread) slpque[TABLESIZE]; 107#define LOOKUP(x) (((intptr_t)(x) >> 8) & (TABLESIZE - 1)) 108 109void 110sleepinit(void) 111{ 112 int i; 113 114 hogticks = (hz / 10) * 2; /* Default only. */ 115 for (i = 0; i < TABLESIZE; i++) 116 TAILQ_INIT(&slpque[i]); 117} 118 119/* 120 * General sleep call. Suspends the current process until a wakeup is 121 * performed on the specified identifier. The process will then be made 122 * runnable with the specified priority. Sleeps at most timo/hz seconds 123 * (0 means no timeout). If pri includes PCATCH flag, signals are checked 124 * before and after sleeping, else signals are not checked. Returns 0 if 125 * awakened, EWOULDBLOCK if the timeout expires. If PCATCH is set and a 126 * signal needs to be delivered, 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 mutex argument is exited before the caller is suspended, and 131 * entered before msleep returns. If priority includes the PDROP 132 * flag the mutex is not entered before returning. 133 */ 134 135int 136msleep(ident, mtx, priority, wmesg, timo) 137 void *ident; 138 struct mtx *mtx; 139 int priority, timo; 140 const char *wmesg; 141{ 142 struct thread *td = curthread; 143 struct proc *p = td->td_proc; 144 int sig, catch = priority & PCATCH; 145 int rval = 0; 146 WITNESS_SAVE_DECL(mtx); 147 148#ifdef KTRACE 149 if (KTRPOINT(td, KTR_CSW)) 150 ktrcsw(1, 0); 151#endif 152 WITNESS_SLEEP(0, &mtx->mtx_object); 153 KASSERT(timo != 0 || mtx_owned(&Giant) || mtx != NULL, 154 ("sleeping without a mutex")); 155 /* 156 * If we are capable of async syscalls and there isn't already 157 * another one ready to return, start a new thread 158 * and queue it as ready to run. Note that there is danger here 159 * because we need to make sure that we don't sleep allocating 160 * the thread (recursion here might be bad). 161 * Hence the TDF_INMSLEEP flag. 162 */ 163 if (p->p_flag & P_KSES) { 164 /* 165 * Just don't bother if we are exiting 166 * and not the exiting thread or thread was marked as 167 * interrupted. 168 */ 169 if (catch && 170 (((p->p_flag & P_WEXIT) && (p->p_singlethread != td)) || 171 (td->td_flags & TDF_INTERRUPT))) { 172 td->td_flags &= ~TDF_INTERRUPT; 173 return (EINTR); 174 } 175 } 176 mtx_lock_spin(&sched_lock); 177 if (cold ) { 178 /* 179 * During autoconfiguration, just give interrupts 180 * a chance, then just return. 181 * Don't run any other procs or panic below, 182 * in case this is the idle process and already asleep. 183 */ 184 if (mtx != NULL && priority & PDROP) 185 mtx_unlock(mtx); 186 mtx_unlock_spin(&sched_lock); 187 return (0); 188 } 189 190 DROP_GIANT(); 191 192 if (mtx != NULL) { 193 mtx_assert(mtx, MA_OWNED | MA_NOTRECURSED); 194 WITNESS_SAVE(&mtx->mtx_object, mtx); 195 mtx_unlock(mtx); 196 if (priority & PDROP) 197 mtx = NULL; 198 } 199 200 KASSERT(p != NULL, ("msleep1")); 201 KASSERT(ident != NULL && TD_IS_RUNNING(td), ("msleep")); 202 203 CTR5(KTR_PROC, "msleep: thread %p (pid %d, %s) on %s (%p)", 204 td, p->p_pid, p->p_comm, wmesg, ident); 205 206 td->td_wchan = ident; 207 td->td_wmesg = wmesg; 208 TAILQ_INSERT_TAIL(&slpque[LOOKUP(ident)], td, td_slpq); 209 TD_SET_ON_SLEEPQ(td); 210 if (timo) 211 callout_reset(&td->td_slpcallout, timo, endtsleep, td); 212 /* 213 * We put ourselves on the sleep queue and start our timeout 214 * before calling thread_suspend_check, as we could stop there, and 215 * a wakeup or a SIGCONT (or both) could occur while we were stopped. 216 * without resuming us, thus we must be ready for sleep 217 * when cursig is called. If the wakeup happens while we're 218 * stopped, td->td_wchan will be 0 upon return from cursig. 219 */ 220 if (catch) { 221 CTR3(KTR_PROC, "msleep caught: thread %p (pid %d, %s)", td, 222 p->p_pid, p->p_comm); 223 td->td_flags |= TDF_SINTR; 224 mtx_unlock_spin(&sched_lock); 225 PROC_LOCK(p); 226 sig = cursig(td); 227 if (sig == 0 && thread_suspend_check(1)) 228 sig = SIGSTOP; 229 mtx_lock_spin(&sched_lock); 230 PROC_UNLOCK(p); 231 if (sig != 0) { 232 if (TD_ON_SLEEPQ(td)) 233 unsleep(td); 234 } else if (!TD_ON_SLEEPQ(td)) 235 catch = 0; 236 } else 237 sig = 0; 238 239 /* 240 * Let the scheduler know we're about to voluntarily go to sleep. 241 */ 242 sched_sleep(td, priority & PRIMASK); 243 244 if (TD_ON_SLEEPQ(td)) { 245 p->p_stats->p_ru.ru_nvcsw++; 246 TD_SET_SLEEPING(td); 247 mi_switch(); 248 } 249 /* 250 * We're awake from voluntary sleep. 251 */ 252 CTR3(KTR_PROC, "msleep resume: thread %p (pid %d, %s)", td, p->p_pid, 253 p->p_comm); 254 KASSERT(TD_IS_RUNNING(td), ("running but not TDS_RUNNING")); 255 td->td_flags &= ~TDF_SINTR; 256 if (td->td_flags & TDF_TIMEOUT) { 257 td->td_flags &= ~TDF_TIMEOUT; 258 if (sig == 0) 259 rval = EWOULDBLOCK; 260 } else if (td->td_flags & TDF_TIMOFAIL) { 261 td->td_flags &= ~TDF_TIMOFAIL; 262 } else if (timo && callout_stop(&td->td_slpcallout) == 0) { 263 /* 264 * This isn't supposed to be pretty. If we are here, then 265 * the endtsleep() callout is currently executing on another 266 * CPU and is either spinning on the sched_lock or will be 267 * soon. If we don't synchronize here, there is a chance 268 * that this process may msleep() again before the callout 269 * has a chance to run and the callout may end up waking up 270 * the wrong msleep(). Yuck. 271 */ 272 TD_SET_SLEEPING(td); 273 p->p_stats->p_ru.ru_nivcsw++; 274 mi_switch(); 275 td->td_flags &= ~TDF_TIMOFAIL; 276 } 277 if ((td->td_flags & TDF_INTERRUPT) && (priority & PCATCH) && 278 (rval == 0)) { 279 td->td_flags &= ~TDF_INTERRUPT; 280 rval = EINTR; 281 } 282 mtx_unlock_spin(&sched_lock); 283 284 if (rval == 0 && catch) { 285 PROC_LOCK(p); 286 /* XXX: shouldn't we always be calling cursig() */ 287 if (sig != 0 || (sig = cursig(td))) { 288 if (SIGISMEMBER(p->p_sigacts->ps_sigintr, sig)) 289 rval = EINTR; 290 else 291 rval = ERESTART; 292 } 293 PROC_UNLOCK(p); 294 } 295#ifdef KTRACE 296 if (KTRPOINT(td, KTR_CSW)) 297 ktrcsw(0, 0); 298#endif 299 PICKUP_GIANT(); 300 if (mtx != NULL) { 301 mtx_lock(mtx); 302 WITNESS_RESTORE(&mtx->mtx_object, mtx); 303 } 304 return (rval); 305} 306 307/* 308 * Implement timeout for msleep() 309 * 310 * If process hasn't been awakened (wchan non-zero), 311 * set timeout flag and undo the sleep. If proc 312 * is stopped, just unsleep so it will remain stopped. 313 * MP-safe, called without the Giant mutex. 314 */ 315static void 316endtsleep(arg) 317 void *arg; 318{ 319 register struct thread *td = arg; 320 321 CTR3(KTR_PROC, "endtsleep: thread %p (pid %d, %s)", 322 td, td->td_proc->p_pid, td->td_proc->p_comm); 323 mtx_lock_spin(&sched_lock); 324 /* 325 * This is the other half of the synchronization with msleep() 326 * described above. If the TDS_TIMEOUT flag is set, we lost the 327 * race and just need to put the process back on the runqueue. 328 */ 329 if (TD_ON_SLEEPQ(td)) { 330 TAILQ_REMOVE(&slpque[LOOKUP(td->td_wchan)], td, td_slpq); 331 TD_CLR_ON_SLEEPQ(td); 332 td->td_flags |= TDF_TIMEOUT; 333 } else { 334 td->td_flags |= TDF_TIMOFAIL; 335 } 336 TD_CLR_SLEEPING(td); 337 setrunnable(td); 338 mtx_unlock_spin(&sched_lock); 339} 340 341/* 342 * Abort a thread, as if an interrupt had occured. Only abort 343 * interruptable waits (unfortunatly it isn't only safe to abort others). 344 * This is about identical to cv_abort(). 345 * Think about merging them? 346 * Also, whatever the signal code does... 347 */ 348void 349abortsleep(struct thread *td) 350{ 351 352 mtx_assert(&sched_lock, MA_OWNED); 353 /* 354 * If the TDF_TIMEOUT flag is set, just leave. A 355 * timeout is scheduled anyhow. 356 */ 357 if ((td->td_flags & (TDF_TIMEOUT | TDF_SINTR)) == TDF_SINTR) { 358 if (TD_ON_SLEEPQ(td)) { 359 unsleep(td); 360 TD_CLR_SLEEPING(td); 361 setrunnable(td); 362 } 363 } 364} 365 366/* 367 * Remove a process from its wait queue 368 */ 369void 370unsleep(struct thread *td) 371{ 372 373 mtx_lock_spin(&sched_lock); 374 if (TD_ON_SLEEPQ(td)) { 375 TAILQ_REMOVE(&slpque[LOOKUP(td->td_wchan)], td, td_slpq); 376 TD_CLR_ON_SLEEPQ(td); 377 } 378 mtx_unlock_spin(&sched_lock); 379} 380 381/* 382 * Make all processes sleeping on the specified identifier runnable. 383 */ 384void 385wakeup(ident) 386 register void *ident; 387{ 388 register struct slpquehead *qp; 389 register struct thread *td; 390 struct thread *ntd; 391 struct proc *p; 392 393 mtx_lock_spin(&sched_lock); 394 qp = &slpque[LOOKUP(ident)]; 395restart: 396 for (td = TAILQ_FIRST(qp); td != NULL; td = ntd) { 397 ntd = TAILQ_NEXT(td, td_slpq); 398 if (td->td_wchan == ident) { 399 unsleep(td); 400 TD_CLR_SLEEPING(td); 401 setrunnable(td); 402 p = td->td_proc; 403 CTR3(KTR_PROC,"wakeup: thread %p (pid %d, %s)", 404 td, p->p_pid, p->p_comm); 405 goto restart; 406 } 407 } 408 mtx_unlock_spin(&sched_lock); 409} 410 411/* 412 * Make a process sleeping on the specified identifier runnable. 413 * May wake more than one process if a target process is currently 414 * swapped out. 415 */ 416void 417wakeup_one(ident) 418 register void *ident; 419{ 420 register struct slpquehead *qp; 421 register struct thread *td; 422 register struct proc *p; 423 struct thread *ntd; 424 425 mtx_lock_spin(&sched_lock); 426 qp = &slpque[LOOKUP(ident)]; 427 for (td = TAILQ_FIRST(qp); td != NULL; td = ntd) { 428 ntd = TAILQ_NEXT(td, td_slpq); 429 if (td->td_wchan == ident) { 430 unsleep(td); 431 TD_CLR_SLEEPING(td); 432 setrunnable(td); 433 p = td->td_proc; 434 CTR3(KTR_PROC,"wakeup1: thread %p (pid %d, %s)", 435 td, p->p_pid, p->p_comm); 436 break; 437 } 438 } 439 mtx_unlock_spin(&sched_lock); 440} 441 442/* 443 * The machine independent parts of mi_switch(). 444 */ 445void 446mi_switch(void) 447{ 448 struct bintime new_switchtime; 449 struct thread *td = curthread; /* XXX */ 450 struct proc *p = td->td_proc; /* XXX */ 451 struct kse *ke = td->td_kse; 452 u_int sched_nest; 453 454 mtx_assert(&sched_lock, MA_OWNED | MA_NOTRECURSED); 455 456 KASSERT(!TD_ON_RUNQ(td), ("mi_switch: called by old code")); 457#ifdef INVARIANTS 458 if (!TD_ON_LOCK(td) && 459 !TD_ON_RUNQ(td) && 460 !TD_IS_RUNNING(td)) 461 mtx_assert(&Giant, MA_NOTOWNED); 462#endif 463 KASSERT(td->td_critnest == 1, 464 ("mi_switch: switch in a critical section")); 465 466 /* 467 * Compute the amount of time during which the current 468 * process was running, and add that to its total so far. 469 */ 470 binuptime(&new_switchtime); 471 bintime_add(&p->p_runtime, &new_switchtime); 472 bintime_sub(&p->p_runtime, PCPU_PTR(switchtime)); 473 474#ifdef DDB 475 /* 476 * Don't perform context switches from the debugger. 477 */ 478 if (db_active) { 479 mtx_unlock_spin(&sched_lock); 480 db_print_backtrace(); 481 db_error("Context switches not allowed in the debugger."); 482 } 483#endif 484 485 /* 486 * Check if the process exceeds its cpu resource allocation. If 487 * over max, arrange to kill the process in ast(). 488 */ 489 if (p->p_cpulimit != RLIM_INFINITY && 490 p->p_runtime.sec > p->p_cpulimit) { 491 p->p_sflag |= PS_XCPU; 492 ke->ke_flags |= KEF_ASTPENDING; 493 } 494 495 /* 496 * Finish up stats for outgoing thread. 497 */ 498 cnt.v_swtch++; 499 PCPU_SET(switchtime, new_switchtime); 500 CTR3(KTR_PROC, "mi_switch: old thread %p (pid %d, %s)", td, p->p_pid, 501 p->p_comm); 502 503 sched_nest = sched_lock.mtx_recurse; 504 sched_switchout(td); 505 506 cpu_switch(); /* SHAZAM!!*/ 507 508 sched_lock.mtx_recurse = sched_nest; 509 sched_lock.mtx_lock = (uintptr_t)td; 510 sched_switchin(td); 511 512 /* 513 * Start setting up stats etc. for the incoming thread. 514 * Similar code in fork_exit() is returned to by cpu_switch() 515 * in the case of a new thread/process. 516 */ 517 CTR3(KTR_PROC, "mi_switch: new thread %p (pid %d, %s)", td, p->p_pid, 518 p->p_comm); 519 if (PCPU_GET(switchtime.sec) == 0) 520 binuptime(PCPU_PTR(switchtime)); 521 PCPU_SET(switchticks, ticks); 522 523 /* 524 * Call the switchin function while still holding the scheduler lock 525 * (used by the idlezero code and the general page-zeroing code) 526 */ 527 if (td->td_switchin) 528 td->td_switchin(); 529 530 /* 531 * If the last thread was exiting, finish cleaning it up. 532 */ 533 if ((td = PCPU_GET(deadthread))) { 534 PCPU_SET(deadthread, NULL); 535 thread_stash(td); 536 } 537} 538 539/* 540 * Change process state to be runnable, 541 * placing it on the run queue if it is in memory, 542 * and awakening the swapper if it isn't in memory. 543 */ 544void 545setrunnable(struct thread *td) 546{ 547 struct proc *p = td->td_proc; 548 549 mtx_assert(&sched_lock, MA_OWNED); 550 switch (p->p_state) { 551 case PRS_ZOMBIE: 552 panic("setrunnable(1)"); 553 default: 554 break; 555 } 556 switch (td->td_state) { 557 case TDS_RUNNING: 558 case TDS_RUNQ: 559 return; 560 case TDS_INHIBITED: 561 /* 562 * If we are only inhibited because we are swapped out 563 * then arange to swap in this process. Otherwise just return. 564 */ 565 if (td->td_inhibitors != TDI_SWAPPED) 566 return; 567 case TDS_CAN_RUN: 568 break; 569 default: 570 printf("state is 0x%x", td->td_state); 571 panic("setrunnable(2)"); 572 } 573 if ((p->p_sflag & PS_INMEM) == 0) { 574 if ((p->p_sflag & PS_SWAPPINGIN) == 0) { 575 p->p_sflag |= PS_SWAPINREQ; 576 wakeup(&proc0); 577 } 578 } else 579 sched_wakeup(td); 580} 581 582/* 583 * Compute a tenex style load average of a quantity on 584 * 1, 5 and 15 minute intervals. 585 * XXXKSE Needs complete rewrite when correct info is available. 586 * Completely Bogus.. only works with 1:1 (but compiles ok now :-) 587 */ 588static void 589loadav(void *arg) 590{ 591 int i, nrun; 592 struct loadavg *avg; 593 struct proc *p; 594 struct thread *td; 595 596 avg = &averunnable; 597 sx_slock(&allproc_lock); 598 nrun = 0; 599 FOREACH_PROC_IN_SYSTEM(p) { 600 FOREACH_THREAD_IN_PROC(p, td) { 601 switch (td->td_state) { 602 case TDS_RUNQ: 603 case TDS_RUNNING: 604 if ((p->p_flag & P_NOLOAD) != 0) 605 goto nextproc; 606 nrun++; /* XXXKSE */ 607 default: 608 break; 609 } 610nextproc: 611 continue; 612 } 613 } 614 sx_sunlock(&allproc_lock); 615 for (i = 0; i < 3; i++) 616 avg->ldavg[i] = (cexp[i] * avg->ldavg[i] + 617 nrun * FSCALE * (FSCALE - cexp[i])) >> FSHIFT; 618 619 /* 620 * Schedule the next update to occur after 5 seconds, but add a 621 * random variation to avoid synchronisation with processes that 622 * run at regular intervals. 623 */ 624 callout_reset(&loadav_callout, hz * 4 + (int)(random() % (hz * 2 + 1)), 625 loadav, NULL); 626} 627 628static void 629lboltcb(void *arg) 630{ 631 wakeup(&lbolt); 632 callout_reset(&lbolt_callout, hz, lboltcb, NULL); 633} 634 635/* ARGSUSED */ 636static void 637sched_setup(dummy) 638 void *dummy; 639{ 640 callout_init(&loadav_callout, 0); 641 callout_init(&lbolt_callout, 1); 642 643 /* Kick off timeout driven events by calling first time. */ 644 loadav(NULL); 645 lboltcb(NULL); 646} 647 648/* 649 * General purpose yield system call 650 */ 651int 652yield(struct thread *td, struct yield_args *uap) 653{ 654 struct ksegrp *kg = td->td_ksegrp; 655 656 mtx_assert(&Giant, MA_NOTOWNED); 657 mtx_lock_spin(&sched_lock); 658 kg->kg_proc->p_stats->p_ru.ru_nvcsw++; 659 sched_prio(td, PRI_MAX_TIMESHARE); 660 mi_switch(); 661 mtx_unlock_spin(&sched_lock); 662 td->td_retval[0] = 0; 663 664 return (0); 665} 666 667