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 #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 static void synch_setup(void *dummy); 75 SYSINIT(synch_setup, SI_SUB_KICK_SCHEDULER, SI_ORDER_FIRST, synch_setup, 76 NULL); 77 78 int hogticks; 79 static int pause_wchan; 80 81 static struct callout loadav_callout; 82 83 struct loadavg averunnable = 84 { {0, 0, 0}, FSCALE }; /* load average, of runnable procs */ 85 /* 86 * Constants for averages over 1, 5, and 15 minutes 87 * when sampling at 5 second intervals. 88 */ 89 static fixpt_t cexp[3] = { 90 0.9200444146293232 * FSCALE, /* exp(-1/12) */ 91 0.9834714538216174 * FSCALE, /* exp(-1/60) */ 92 0.9944598480048967 * FSCALE, /* exp(-1/180) */ 93 }; 94 95 /* kernel uses `FSCALE', userland (SHOULD) use kern.fscale */ 96 static int fscale __unused = FSCALE; 97 SYSCTL_INT(_kern, OID_AUTO, fscale, CTLFLAG_RD, 0, FSCALE, ""); 98 99 static void loadav(void *arg); 100 101 void 102 sleepinit(void) 103 { 104 105 hogticks = (hz / 10) * 2; /* Default only. */ 106 init_sleepqueues(); 107 } 108 109 /* 110 * General sleep call. Suspends the current thread until a wakeup is 111 * performed on the specified identifier. The thread will then be made 112 * runnable with the specified priority. Sleeps at most timo/hz seconds 113 * (0 means no timeout). If pri includes PCATCH flag, signals are checked 114 * before and after sleeping, else signals are not checked. Returns 0 if 115 * awakened, EWOULDBLOCK if the timeout expires. If PCATCH is set and a 116 * signal needs to be delivered, ERESTART is returned if the current system 117 * call should be restarted if possible, and EINTR is returned if the system 118 * call should be interrupted by the signal (return EINTR). 119 * 120 * The lock argument is unlocked before the caller is suspended, and 121 * re-locked before _sleep() returns. If priority includes the PDROP 122 * flag the lock is not re-locked before returning. 123 */ 124 int 125 _sleep(void *ident, struct lock_object *lock, int priority, 126 const char *wmesg, int timo) 127 { 128 struct thread *td; 129 struct proc *p; 130 struct lock_class *class; 131 int catch, flags, lock_state, pri, rval; 132 WITNESS_SAVE_DECL(lock_witness); 133 134 td = curthread; 135 p = td->td_proc; 136 #ifdef KTRACE 137 if (KTRPOINT(td, KTR_CSW)) 138 ktrcsw(1, 0); 139 #endif 140 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, lock, 141 "Sleeping on \"%s\"", wmesg); 142 KASSERT(timo != 0 || mtx_owned(&Giant) || lock != NULL, 143 ("sleeping without a lock")); 144 KASSERT(p != NULL, ("msleep1")); 145 KASSERT(ident != NULL && TD_IS_RUNNING(td), ("msleep")); 146 if (priority & PDROP) 147 KASSERT(lock != NULL && lock != &Giant.lock_object, 148 ("PDROP requires a non-Giant lock")); 149 if (lock != NULL) 150 class = LOCK_CLASS(lock); 151 else 152 class = NULL; 153 154 if (cold) { 155 /* 156 * During autoconfiguration, just return; 157 * don't run any other threads or panic below, 158 * in case this is the idle thread and already asleep. 159 * XXX: this used to do "s = splhigh(); splx(safepri); 160 * splx(s);" to give interrupts a chance, but there is 161 * no way to give interrupts a chance now. 162 */ 163 if (lock != NULL && priority & PDROP) 164 class->lc_unlock(lock); 165 return (0); 166 } 167 catch = priority & PCATCH; 168 pri = priority & PRIMASK; 169 rval = 0; 170 171 /* 172 * If we are already on a sleep queue, then remove us from that 173 * sleep queue first. We have to do this to handle recursive 174 * sleeps. 175 */ 176 if (TD_ON_SLEEPQ(td)) 177 sleepq_remove(td, td->td_wchan); 178 179 if (ident == &pause_wchan) 180 flags = SLEEPQ_PAUSE; 181 else 182 flags = SLEEPQ_SLEEP; 183 if (catch) 184 flags |= SLEEPQ_INTERRUPTIBLE; 185 186 sleepq_lock(ident); 187 CTR5(KTR_PROC, "sleep: thread %ld (pid %ld, %s) on %s (%p)", 188 td->td_tid, p->p_pid, td->td_name, wmesg, ident); 189 190 if (lock == &Giant.lock_object) 191 mtx_assert(&Giant, MA_OWNED); 192 DROP_GIANT(); 193 if (lock != NULL && lock != &Giant.lock_object && 194 !(class->lc_flags & LC_SLEEPABLE)) { 195 WITNESS_SAVE(lock, lock_witness); 196 lock_state = class->lc_unlock(lock); 197 } else 198 /* GCC needs to follow the Yellow Brick Road */ 199 lock_state = -1; 200 201 /* 202 * We put ourselves on the sleep queue and start our timeout 203 * before calling thread_suspend_check, as we could stop there, 204 * and a wakeup or a SIGCONT (or both) could occur while we were 205 * stopped without resuming us. Thus, we must be ready for sleep 206 * when cursig() is called. If the wakeup happens while we're 207 * stopped, then td will no longer be on a sleep queue upon 208 * return from cursig(). 209 */ 210 sleepq_add(ident, lock, wmesg, flags, 0); 211 if (timo) 212 sleepq_set_timeout(ident, timo); 213 if (lock != NULL && class->lc_flags & LC_SLEEPABLE) { 214 sleepq_release(ident); 215 WITNESS_SAVE(lock, lock_witness); 216 lock_state = class->lc_unlock(lock); 217 sleepq_lock(ident); 218 } 219 if (timo && catch) 220 rval = sleepq_timedwait_sig(ident, pri); 221 else if (timo) 222 rval = sleepq_timedwait(ident, pri); 223 else if (catch) 224 rval = sleepq_wait_sig(ident, pri); 225 else { 226 sleepq_wait(ident, pri); 227 rval = 0; 228 } 229 #ifdef KTRACE 230 if (KTRPOINT(td, KTR_CSW)) 231 ktrcsw(0, 0); 232 #endif 233 PICKUP_GIANT(); 234 if (lock != NULL && lock != &Giant.lock_object && !(priority & PDROP)) { 235 class->lc_lock(lock, lock_state); 236 WITNESS_RESTORE(lock, lock_witness); 237 } 238 return (rval); 239 } 240 241 int 242 msleep_spin(void *ident, struct mtx *mtx, const char *wmesg, int timo) 243 { 244 struct thread *td; 245 struct proc *p; 246 int rval; 247 WITNESS_SAVE_DECL(mtx); 248 249 td = curthread; 250 p = td->td_proc; 251 KASSERT(mtx != NULL, ("sleeping without a mutex")); 252 KASSERT(p != NULL, ("msleep1")); 253 KASSERT(ident != NULL && TD_IS_RUNNING(td), ("msleep")); 254 255 if (cold) { 256 /* 257 * During autoconfiguration, just return; 258 * don't run any other threads or panic below, 259 * in case this is the idle thread and already asleep. 260 * XXX: this used to do "s = splhigh(); splx(safepri); 261 * splx(s);" to give interrupts a chance, but there is 262 * no way to give interrupts a chance now. 263 */ 264 return (0); 265 } 266 267 sleepq_lock(ident); 268 CTR5(KTR_PROC, "msleep_spin: thread %ld (pid %ld, %s) on %s (%p)", 269 td->td_tid, p->p_pid, td->td_name, wmesg, ident); 270 271 DROP_GIANT(); 272 mtx_assert(mtx, MA_OWNED | MA_NOTRECURSED); 273 WITNESS_SAVE(&mtx->lock_object, mtx); 274 mtx_unlock_spin(mtx); 275 276 /* 277 * We put ourselves on the sleep queue and start our timeout. 278 */ 279 sleepq_add(ident, &mtx->lock_object, wmesg, SLEEPQ_SLEEP, 0); 280 if (timo) 281 sleepq_set_timeout(ident, timo); 282 283 /* 284 * Can't call ktrace with any spin locks held so it can lock the 285 * ktrace_mtx lock, and WITNESS_WARN considers it an error to hold 286 * any spin lock. Thus, we have to drop the sleepq spin lock while 287 * we handle those requests. This is safe since we have placed our 288 * thread on the sleep queue already. 289 */ 290 #ifdef KTRACE 291 if (KTRPOINT(td, KTR_CSW)) { 292 sleepq_release(ident); 293 ktrcsw(1, 0); 294 sleepq_lock(ident); 295 } 296 #endif 297 #ifdef WITNESS 298 sleepq_release(ident); 299 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, "Sleeping on \"%s\"", 300 wmesg); 301 sleepq_lock(ident); 302 #endif 303 if (timo) 304 rval = sleepq_timedwait(ident, 0); 305 else { 306 sleepq_wait(ident, 0); 307 rval = 0; 308 } 309 #ifdef KTRACE 310 if (KTRPOINT(td, KTR_CSW)) 311 ktrcsw(0, 0); 312 #endif 313 PICKUP_GIANT(); 314 mtx_lock_spin(mtx); 315 WITNESS_RESTORE(&mtx->lock_object, mtx); 316 return (rval); 317 } 318 319 /* 320 * pause() is like tsleep() except that the intention is to not be 321 * explicitly woken up by another thread. Instead, the current thread 322 * simply wishes to sleep until the timeout expires. It is 323 * implemented using a dummy wait channel. 324 */ 325 int 326 pause(const char *wmesg, int timo) 327 { 328 329 KASSERT(timo != 0, ("pause: timeout required")); 330 return (tsleep(&pause_wchan, 0, wmesg, timo)); 331 } 332 333 /* 334 * Make all threads sleeping on the specified identifier runnable. 335 */ 336 void 337 wakeup(void *ident) 338 { 339 int wakeup_swapper; 340 341 sleepq_lock(ident); 342 wakeup_swapper = sleepq_broadcast(ident, SLEEPQ_SLEEP, 0, 0); 343 sleepq_release(ident); 344 if (wakeup_swapper) 345 kick_proc0(); 346 } 347 348 /* 349 * Make a thread sleeping on the specified identifier runnable. 350 * May wake more than one thread if a target thread is currently 351 * swapped out. 352 */ 353 void 354 wakeup_one(void *ident) 355 { 356 int wakeup_swapper; 357 358 sleepq_lock(ident); 359 wakeup_swapper = sleepq_signal(ident, SLEEPQ_SLEEP, 0, 0); 360 sleepq_release(ident); 361 if (wakeup_swapper) 362 kick_proc0(); 363 } 364 365 static void 366 kdb_switch(void) 367 { 368 thread_unlock(curthread); 369 kdb_backtrace(); 370 kdb_reenter(); 371 panic("%s: did not reenter debugger", __func__); 372 } 373 374 /* 375 * The machine independent parts of context switching. 376 */ 377 void 378 mi_switch(int flags, struct thread *newtd) 379 { 380 uint64_t runtime, new_switchtime; 381 struct thread *td; 382 struct proc *p; 383 384 td = curthread; /* XXX */ 385 THREAD_LOCK_ASSERT(td, MA_OWNED | MA_NOTRECURSED); 386 p = td->td_proc; /* XXX */ 387 KASSERT(!TD_ON_RUNQ(td), ("mi_switch: called by old code")); 388 #ifdef INVARIANTS 389 if (!TD_ON_LOCK(td) && !TD_IS_RUNNING(td)) 390 mtx_assert(&Giant, MA_NOTOWNED); 391 #endif 392 KASSERT(td->td_critnest == 1 || (td->td_critnest == 2 && 393 (td->td_owepreempt) && (flags & SW_INVOL) != 0 && 394 newtd == NULL) || panicstr, 395 ("mi_switch: switch in a critical section")); 396 KASSERT((flags & (SW_INVOL | SW_VOL)) != 0, 397 ("mi_switch: switch must be voluntary or involuntary")); 398 KASSERT(newtd != curthread, ("mi_switch: preempting back to ourself")); 399 400 /* 401 * Don't perform context switches from the debugger. 402 */ 403 if (kdb_active) 404 kdb_switch(); 405 if (flags & SW_VOL) 406 td->td_ru.ru_nvcsw++; 407 else 408 td->td_ru.ru_nivcsw++; 409 #ifdef SCHED_STATS 410 SCHED_STAT_INC(sched_switch_stats[flags & SW_TYPE_MASK]); 411 #endif 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 (td_sched %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 #ifdef XEN 442 PT_UPDATES_FLUSH(); 443 #endif 444 sched_switch(td, newtd, flags); 445 CTR3(KTR_SCHED, "mi_switch: running %p(%s) prio %d", 446 td, td->td_name, td->td_priority); 447 448 CTR4(KTR_PROC, "mi_switch: new thread %ld (td_sched %p, pid %ld, %s)", 449 td->td_tid, td->td_sched, p->p_pid, td->td_name); 450 451 /* 452 * If the last thread was exiting, finish cleaning it up. 453 */ 454 if ((td = PCPU_GET(deadthread))) { 455 PCPU_SET(deadthread, NULL); 456 thread_stash(td); 457 } 458 } 459 460 /* 461 * Change thread state to be runnable, placing it on the run queue if 462 * it is in memory. If it is swapped out, return true so our caller 463 * will know to awaken the swapper. 464 */ 465 int 466 setrunnable(struct thread *td) 467 { 468 469 THREAD_LOCK_ASSERT(td, MA_OWNED); 470 KASSERT(td->td_proc->p_state != PRS_ZOMBIE, 471 ("setrunnable: pid %d is a zombie", td->td_proc->p_pid)); 472 switch (td->td_state) { 473 case TDS_RUNNING: 474 case TDS_RUNQ: 475 return (0); 476 case TDS_INHIBITED: 477 /* 478 * If we are only inhibited because we are swapped out 479 * then arange to swap in this process. Otherwise just return. 480 */ 481 if (td->td_inhibitors != TDI_SWAPPED) 482 return (0); 483 /* FALLTHROUGH */ 484 case TDS_CAN_RUN: 485 break; 486 default: 487 printf("state is 0x%x", td->td_state); 488 panic("setrunnable(2)"); 489 } 490 if ((td->td_flags & TDF_INMEM) == 0) { 491 if ((td->td_flags & TDF_SWAPINREQ) == 0) { 492 td->td_flags |= TDF_SWAPINREQ; 493 return (1); 494 } 495 } else 496 sched_wakeup(td); 497 return (0); 498 } 499 500 /* 501 * Compute a tenex style load average of a quantity on 502 * 1, 5 and 15 minute intervals. 503 */ 504 static void 505 loadav(void *arg) 506 { 507 int i, nrun; 508 struct loadavg *avg; 509 510 nrun = sched_load(); 511 avg = &averunnable; 512 513 for (i = 0; i < 3; i++) 514 avg->ldavg[i] = (cexp[i] * avg->ldavg[i] + 515 nrun * FSCALE * (FSCALE - cexp[i])) >> FSHIFT; 516 517 /* 518 * Schedule the next update to occur after 5 seconds, but add a 519 * random variation to avoid synchronisation with processes that 520 * run at regular intervals. 521 */ 522 callout_reset(&loadav_callout, hz * 4 + (int)(random() % (hz * 2 + 1)), 523 loadav, NULL); 524 } 525 526 /* ARGSUSED */ 527 static void 528 synch_setup(void *dummy) 529 { 530 callout_init(&loadav_callout, CALLOUT_MPSAFE); 531 532 /* Kick off timeout driven events by calling first time. */ 533 loadav(NULL); 534 } 535 536 /* 537 * General purpose yield system call. 538 */ 539 int 540 yield(struct thread *td, struct yield_args *uap) 541 { 542 543 thread_lock(td); 544 sched_prio(td, PRI_MAX_TIMESHARE); 545 mi_switch(SW_VOL | SWT_RELINQUISH, NULL); 546 thread_unlock(td); 547 td->td_retval[0] = 0; 548 return (0); 549 } 550