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("$FreeBSD$"); 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 67 static void synch_setup(void *dummy); 68 SYSINIT(synch_setup, SI_SUB_KICK_SCHEDULER, SI_ORDER_FIRST, synch_setup, 69 NULL); 70 71 int hogticks; 72 int lbolt; 73 static int pause_wchan; 74 75 static struct callout loadav_callout; 76 static struct callout lbolt_callout; 77 78 struct loadavg averunnable = 79 { {0, 0, 0}, FSCALE }; /* load average, of runnable procs */ 80 /* 81 * Constants for averages over 1, 5, and 15 minutes 82 * when sampling at 5 second intervals. 83 */ 84 static fixpt_t cexp[3] = { 85 0.9200444146293232 * FSCALE, /* exp(-1/12) */ 86 0.9834714538216174 * FSCALE, /* exp(-1/60) */ 87 0.9944598480048967 * FSCALE, /* exp(-1/180) */ 88 }; 89 90 /* kernel uses `FSCALE', userland (SHOULD) use kern.fscale */ 91 static int fscale __unused = FSCALE; 92 SYSCTL_INT(_kern, OID_AUTO, fscale, CTLFLAG_RD, 0, FSCALE, ""); 93 94 static void loadav(void *arg); 95 static void lboltcb(void *arg); 96 97 void 98 sleepinit(void) 99 { 100 101 hogticks = (hz / 10) * 2; /* Default only. */ 102 init_sleepqueues(); 103 } 104 105 /* 106 * General sleep call. Suspends the current thread until a wakeup is 107 * performed on the specified identifier. The thread will then be made 108 * runnable with the specified priority. Sleeps at most timo/hz seconds 109 * (0 means no timeout). If pri includes PCATCH flag, signals are checked 110 * before and after sleeping, else signals are not checked. Returns 0 if 111 * awakened, EWOULDBLOCK if the timeout expires. If PCATCH is set and a 112 * signal needs to be delivered, ERESTART is returned if the current system 113 * call should be restarted if possible, and EINTR is returned if the system 114 * call should be interrupted by the signal (return EINTR). 115 * 116 * The lock argument is unlocked before the caller is suspended, and 117 * re-locked before _sleep() returns. If priority includes the PDROP 118 * flag the lock is not re-locked before returning. 119 */ 120 int 121 _sleep(void *ident, struct lock_object *lock, int priority, 122 const char *wmesg, int timo) 123 { 124 struct thread *td; 125 struct proc *p; 126 struct lock_class *class; 127 int catch, flags, lock_state, pri, rval; 128 WITNESS_SAVE_DECL(lock_witness); 129 130 td = curthread; 131 p = td->td_proc; 132 #ifdef KTRACE 133 if (KTRPOINT(td, KTR_CSW)) 134 ktrcsw(1, 0); 135 #endif 136 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, lock, 137 "Sleeping on \"%s\"", wmesg); 138 KASSERT(timo != 0 || mtx_owned(&Giant) || lock != NULL || 139 ident == &lbolt, ("sleeping without a lock")); 140 KASSERT(p != NULL, ("msleep1")); 141 KASSERT(ident != NULL && TD_IS_RUNNING(td), ("msleep")); 142 if (lock != NULL) 143 class = LOCK_CLASS(lock); 144 else 145 class = NULL; 146 147 if (cold) { 148 /* 149 * During autoconfiguration, just return; 150 * don't run any other threads or panic below, 151 * in case this is the idle thread and already asleep. 152 * XXX: this used to do "s = splhigh(); splx(safepri); 153 * splx(s);" to give interrupts a chance, but there is 154 * no way to give interrupts a chance now. 155 */ 156 if (lock != NULL && priority & PDROP) 157 class->lc_unlock(lock); 158 return (0); 159 } 160 catch = priority & PCATCH; 161 pri = priority & PRIMASK; 162 rval = 0; 163 164 /* 165 * If we are already on a sleep queue, then remove us from that 166 * sleep queue first. We have to do this to handle recursive 167 * sleeps. 168 */ 169 if (TD_ON_SLEEPQ(td)) 170 sleepq_remove(td, td->td_wchan); 171 172 if (ident == &pause_wchan) 173 flags = SLEEPQ_PAUSE; 174 else 175 flags = SLEEPQ_SLEEP; 176 if (catch) 177 flags |= SLEEPQ_INTERRUPTIBLE; 178 179 sleepq_lock(ident); 180 CTR5(KTR_PROC, "sleep: thread %ld (pid %ld, %s) on %s (%p)", 181 td->td_tid, p->p_pid, td->td_name, wmesg, ident); 182 183 DROP_GIANT(); 184 if (lock != NULL && !(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, ident == &lbolt ? NULL : lock, wmesg, flags, 0); 201 if (timo) 202 sleepq_set_timeout(ident, timo); 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 (timo && catch) 210 rval = sleepq_timedwait_sig(ident, pri); 211 else if (timo) 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); 222 #endif 223 PICKUP_GIANT(); 224 if (lock != NULL && !(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(void *ident, struct mtx *mtx, const char *wmesg, int timo) 233 { 234 struct thread *td; 235 struct proc *p; 236 int rval; 237 WITNESS_SAVE_DECL(mtx); 238 239 td = curthread; 240 p = td->td_proc; 241 KASSERT(mtx != NULL, ("sleeping without a mutex")); 242 KASSERT(p != NULL, ("msleep1")); 243 KASSERT(ident != NULL && TD_IS_RUNNING(td), ("msleep")); 244 245 if (cold) { 246 /* 247 * During autoconfiguration, just return; 248 * don't run any other threads or panic below, 249 * in case this is the idle thread and already asleep. 250 * XXX: this used to do "s = splhigh(); splx(safepri); 251 * splx(s);" to give interrupts a chance, but there is 252 * no way to give interrupts a chance now. 253 */ 254 return (0); 255 } 256 257 sleepq_lock(ident); 258 CTR5(KTR_PROC, "msleep_spin: thread %ld (pid %ld, %s) on %s (%p)", 259 td->td_tid, p->p_pid, td->td_name, wmesg, ident); 260 261 DROP_GIANT(); 262 mtx_assert(mtx, MA_OWNED | MA_NOTRECURSED); 263 WITNESS_SAVE(&mtx->lock_object, mtx); 264 mtx_unlock_spin(mtx); 265 266 /* 267 * We put ourselves on the sleep queue and start our timeout. 268 */ 269 sleepq_add(ident, &mtx->lock_object, wmesg, SLEEPQ_SLEEP, 0); 270 if (timo) 271 sleepq_set_timeout(ident, timo); 272 273 /* 274 * Can't call ktrace with any spin locks held so it can lock the 275 * ktrace_mtx lock, and WITNESS_WARN considers it an error to hold 276 * any spin lock. Thus, we have to drop the sleepq spin lock while 277 * we handle those requests. This is safe since we have placed our 278 * thread on the sleep queue already. 279 */ 280 #ifdef KTRACE 281 if (KTRPOINT(td, KTR_CSW)) { 282 sleepq_release(ident); 283 ktrcsw(1, 0); 284 sleepq_lock(ident); 285 } 286 #endif 287 #ifdef WITNESS 288 sleepq_release(ident); 289 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, "Sleeping on \"%s\"", 290 wmesg); 291 sleepq_lock(ident); 292 #endif 293 if (timo) 294 rval = sleepq_timedwait(ident, 0); 295 else { 296 sleepq_wait(ident, 0); 297 rval = 0; 298 } 299 #ifdef KTRACE 300 if (KTRPOINT(td, KTR_CSW)) 301 ktrcsw(0, 0); 302 #endif 303 PICKUP_GIANT(); 304 mtx_lock_spin(mtx); 305 WITNESS_RESTORE(&mtx->lock_object, mtx); 306 return (rval); 307 } 308 309 /* 310 * pause() is like tsleep() except that the intention is to not be 311 * explicitly woken up by another thread. Instead, the current thread 312 * simply wishes to sleep until the timeout expires. It is 313 * implemented using a dummy wait channel. 314 */ 315 int 316 pause(const char *wmesg, int timo) 317 { 318 319 KASSERT(timo != 0, ("pause: timeout required")); 320 return (tsleep(&pause_wchan, 0, wmesg, timo)); 321 } 322 323 /* 324 * Make all threads sleeping on the specified identifier runnable. 325 */ 326 void 327 wakeup(void *ident) 328 { 329 330 sleepq_lock(ident); 331 sleepq_broadcast(ident, SLEEPQ_SLEEP, 0, 0); 332 sleepq_release(ident); 333 } 334 335 /* 336 * Make a thread sleeping on the specified identifier runnable. 337 * May wake more than one thread if a target thread is currently 338 * swapped out. 339 */ 340 void 341 wakeup_one(void *ident) 342 { 343 344 sleepq_lock(ident); 345 sleepq_signal(ident, SLEEPQ_SLEEP, 0, 0); 346 sleepq_release(ident); 347 } 348 349 static void 350 kdb_switch(void) 351 { 352 thread_unlock(curthread); 353 kdb_backtrace(); 354 kdb_reenter(); 355 panic("%s: did not reenter debugger", __func__); 356 } 357 358 /* 359 * The machine independent parts of context switching. 360 */ 361 void 362 mi_switch(int flags, struct thread *newtd) 363 { 364 uint64_t runtime, new_switchtime; 365 struct thread *td; 366 struct proc *p; 367 368 td = curthread; /* XXX */ 369 THREAD_LOCK_ASSERT(td, MA_OWNED | MA_NOTRECURSED); 370 p = td->td_proc; /* XXX */ 371 KASSERT(!TD_ON_RUNQ(td), ("mi_switch: called by old code")); 372 #ifdef INVARIANTS 373 if (!TD_ON_LOCK(td) && !TD_IS_RUNNING(td)) 374 mtx_assert(&Giant, MA_NOTOWNED); 375 #endif 376 KASSERT(td->td_critnest == 1 || (td->td_critnest == 2 && 377 (td->td_owepreempt) && (flags & SW_INVOL) != 0 && 378 newtd == NULL) || panicstr, 379 ("mi_switch: switch in a critical section")); 380 KASSERT((flags & (SW_INVOL | SW_VOL)) != 0, 381 ("mi_switch: switch must be voluntary or involuntary")); 382 KASSERT(newtd != curthread, ("mi_switch: preempting back to ourself")); 383 384 /* 385 * Don't perform context switches from the debugger. 386 */ 387 if (kdb_active) 388 kdb_switch(); 389 if (flags & SW_VOL) 390 td->td_ru.ru_nvcsw++; 391 else 392 td->td_ru.ru_nivcsw++; 393 /* 394 * Compute the amount of time during which the current 395 * thread was running, and add that to its total so far. 396 */ 397 new_switchtime = cpu_ticks(); 398 runtime = new_switchtime - PCPU_GET(switchtime); 399 td->td_runtime += runtime; 400 td->td_incruntime += runtime; 401 PCPU_SET(switchtime, new_switchtime); 402 td->td_generation++; /* bump preempt-detect counter */ 403 PCPU_INC(cnt.v_swtch); 404 PCPU_SET(switchticks, ticks); 405 CTR4(KTR_PROC, "mi_switch: old thread %ld (td_sched %p, pid %ld, %s)", 406 td->td_tid, td->td_sched, p->p_pid, td->td_name); 407 #if (KTR_COMPILE & KTR_SCHED) != 0 408 if (TD_IS_IDLETHREAD(td)) 409 CTR3(KTR_SCHED, "mi_switch: %p(%s) prio %d idle", 410 td, td->td_name, td->td_priority); 411 else if (newtd != NULL) 412 CTR5(KTR_SCHED, 413 "mi_switch: %p(%s) prio %d preempted by %p(%s)", 414 td, td->td_name, td->td_priority, newtd, 415 newtd->td_name); 416 else 417 CTR6(KTR_SCHED, 418 "mi_switch: %p(%s) prio %d inhibit %d wmesg %s lock %s", 419 td, td->td_name, td->td_priority, 420 td->td_inhibitors, td->td_wmesg, td->td_lockname); 421 #endif 422 sched_switch(td, newtd, flags); 423 CTR3(KTR_SCHED, "mi_switch: running %p(%s) prio %d", 424 td, td->td_name, td->td_priority); 425 426 CTR4(KTR_PROC, "mi_switch: new thread %ld (td_sched %p, pid %ld, %s)", 427 td->td_tid, td->td_sched, p->p_pid, td->td_name); 428 429 /* 430 * If the last thread was exiting, finish cleaning it up. 431 */ 432 if ((td = PCPU_GET(deadthread))) { 433 PCPU_SET(deadthread, NULL); 434 thread_stash(td); 435 } 436 } 437 438 /* 439 * Change process state to be runnable, 440 * placing it on the run queue if it is in memory, 441 * and awakening the swapper if it isn't in memory. 442 */ 443 void 444 setrunnable(struct thread *td) 445 { 446 447 THREAD_LOCK_ASSERT(td, MA_OWNED); 448 KASSERT(td->td_proc->p_state != PRS_ZOMBIE, 449 ("setrunnable: pid %d is a zombie", td->td_proc->p_pid)); 450 switch (td->td_state) { 451 case TDS_RUNNING: 452 case TDS_RUNQ: 453 return; 454 case TDS_INHIBITED: 455 /* 456 * If we are only inhibited because we are swapped out 457 * then arange to swap in this process. Otherwise just return. 458 */ 459 if (td->td_inhibitors != TDI_SWAPPED) 460 return; 461 /* XXX: intentional fall-through ? */ 462 case TDS_CAN_RUN: 463 break; 464 default: 465 printf("state is 0x%x", td->td_state); 466 panic("setrunnable(2)"); 467 } 468 if ((td->td_flags & TDF_INMEM) == 0) { 469 if ((td->td_flags & TDF_SWAPINREQ) == 0) { 470 td->td_flags |= TDF_SWAPINREQ; 471 /* 472 * due to a LOR between the thread lock and 473 * the sleepqueue chain locks, use 474 * lower level scheduling functions. 475 */ 476 kick_proc0(); 477 } 478 } else 479 sched_wakeup(td); 480 } 481 482 /* 483 * Compute a tenex style load average of a quantity on 484 * 1, 5 and 15 minute intervals. 485 */ 486 static void 487 loadav(void *arg) 488 { 489 int i, nrun; 490 struct loadavg *avg; 491 492 nrun = sched_load(); 493 avg = &averunnable; 494 495 for (i = 0; i < 3; i++) 496 avg->ldavg[i] = (cexp[i] * avg->ldavg[i] + 497 nrun * FSCALE * (FSCALE - cexp[i])) >> FSHIFT; 498 499 /* 500 * Schedule the next update to occur after 5 seconds, but add a 501 * random variation to avoid synchronisation with processes that 502 * run at regular intervals. 503 */ 504 callout_reset(&loadav_callout, hz * 4 + (int)(random() % (hz * 2 + 1)), 505 loadav, NULL); 506 } 507 508 static void 509 lboltcb(void *arg) 510 { 511 wakeup(&lbolt); 512 callout_reset(&lbolt_callout, hz, lboltcb, NULL); 513 } 514 515 /* ARGSUSED */ 516 static void 517 synch_setup(void *dummy) 518 { 519 callout_init(&loadav_callout, CALLOUT_MPSAFE); 520 callout_init(&lbolt_callout, CALLOUT_MPSAFE); 521 522 /* Kick off timeout driven events by calling first time. */ 523 loadav(NULL); 524 lboltcb(NULL); 525 } 526 527 /* 528 * General purpose yield system call. 529 */ 530 int 531 yield(struct thread *td, struct yield_args *uap) 532 { 533 534 thread_lock(td); 535 sched_prio(td, PRI_MAX_TIMESHARE); 536 mi_switch(SW_VOL, NULL); 537 thread_unlock(td); 538 td->td_retval[0] = 0; 539 return (0); 540 } 541