92 "Number of CPUs online"); 93 94int smp_topology = 0; /* Which topology we're using. */ 95SYSCTL_INT(_kern_smp, OID_AUTO, topology, CTLFLAG_RD, &smp_topology, 0, 96 "Topology override setting; 0 is default provided by hardware."); 97TUNABLE_INT("kern.smp.topology", &smp_topology); 98 99#ifdef SMP 100/* Enable forwarding of a signal to a process running on a different CPU */ 101static int forward_signal_enabled = 1; 102SYSCTL_INT(_kern_smp, OID_AUTO, forward_signal_enabled, CTLFLAG_RW, 103 &forward_signal_enabled, 0, 104 "Forwarding of a signal to a process on a different CPU"); 105 106/* Variables needed for SMP rendezvous. */ 107static volatile int smp_rv_ncpus; 108static void (*volatile smp_rv_setup_func)(void *arg); 109static void (*volatile smp_rv_action_func)(void *arg); 110static void (*volatile smp_rv_teardown_func)(void *arg); 111static void *volatile smp_rv_func_arg; 112static volatile int smp_rv_waiters[3]; 113static volatile int smp_rv_generation; 114 115/* 116 * Shared mutex to restrict busywaits between smp_rendezvous() and 117 * smp(_targeted)_tlb_shootdown(). A deadlock occurs if both of these 118 * functions trigger at once and cause multiple CPUs to busywait with 119 * interrupts disabled. 120 */ 121struct mtx smp_ipi_mtx; 122 123/* 124 * Let the MD SMP code initialize mp_maxid very early if it can. 125 */ 126static void 127mp_setmaxid(void *dummy) 128{ 129 cpu_mp_setmaxid(); 130} 131SYSINIT(cpu_mp_setmaxid, SI_SUB_TUNABLES, SI_ORDER_FIRST, mp_setmaxid, NULL); 132 133/* 134 * Call the MD SMP initialization code. 135 */ 136static void 137mp_start(void *dummy) 138{ 139 140 mtx_init(&smp_ipi_mtx, "smp rendezvous", NULL, MTX_SPIN); 141 142 /* Probe for MP hardware. */ 143 if (smp_disabled != 0 || cpu_mp_probe() == 0) { 144 mp_ncpus = 1; 145 CPU_SETOF(PCPU_GET(cpuid), &all_cpus); 146 return; 147 } 148 149 cpu_mp_start(); 150 printf("FreeBSD/SMP: Multiprocessor System Detected: %d CPUs\n", 151 mp_ncpus); 152 cpu_mp_announce(); 153} 154SYSINIT(cpu_mp, SI_SUB_CPU, SI_ORDER_THIRD, mp_start, NULL); 155 156void 157forward_signal(struct thread *td) 158{ 159 int id; 160 161 /* 162 * signotify() has already set TDF_ASTPENDING and TDF_NEEDSIGCHECK on 163 * this thread, so all we need to do is poke it if it is currently 164 * executing so that it executes ast(). 165 */ 166 THREAD_LOCK_ASSERT(td, MA_OWNED); 167 KASSERT(TD_IS_RUNNING(td), 168 ("forward_signal: thread is not TDS_RUNNING")); 169 170 CTR1(KTR_SMP, "forward_signal(%p)", td->td_proc); 171 172 if (!smp_started || cold || panicstr) 173 return; 174 if (!forward_signal_enabled) 175 return; 176 177 /* No need to IPI ourself. */ 178 if (td == curthread) 179 return; 180 181 id = td->td_oncpu; 182 if (id == NOCPU) 183 return; 184 ipi_cpu(id, IPI_AST); 185} 186 187/* 188 * When called the executing CPU will send an IPI to all other CPUs 189 * requesting that they halt execution. 190 * 191 * Usually (but not necessarily) called with 'other_cpus' as its arg. 192 * 193 * - Signals all CPUs in map to stop. 194 * - Waits for each to stop. 195 * 196 * Returns: 197 * -1: error 198 * 0: NA 199 * 1: ok 200 * 201 */ 202static int 203generic_stop_cpus(cpuset_t map, u_int type) 204{ 205#ifdef KTR 206 char cpusetbuf[CPUSETBUFSIZ]; 207#endif 208 static volatile u_int stopping_cpu = NOCPU; 209 int i; 210 211 KASSERT( 212#if defined(__amd64__) 213 type == IPI_STOP || type == IPI_STOP_HARD || type == IPI_SUSPEND, 214#else 215 type == IPI_STOP || type == IPI_STOP_HARD, 216#endif 217 ("%s: invalid stop type", __func__)); 218 219 if (!smp_started) 220 return (0); 221 222 CTR2(KTR_SMP, "stop_cpus(%s) with %u type", 223 cpusetobj_strprint(cpusetbuf, &map), type); 224 225 if (stopping_cpu != PCPU_GET(cpuid)) 226 while (atomic_cmpset_int(&stopping_cpu, NOCPU, 227 PCPU_GET(cpuid)) == 0) 228 while (stopping_cpu != NOCPU) 229 cpu_spinwait(); /* spin */ 230 231 /* send the stop IPI to all CPUs in map */ 232 ipi_selected(map, type); 233 234 i = 0; 235 while (!CPU_SUBSET(&stopped_cpus, &map)) { 236 /* spin */ 237 cpu_spinwait(); 238 i++; 239 if (i == 100000000) { 240 printf("timeout stopping cpus\n"); 241 break; 242 } 243 } 244 245 stopping_cpu = NOCPU; 246 return (1); 247} 248 249int 250stop_cpus(cpuset_t map) 251{ 252 253 return (generic_stop_cpus(map, IPI_STOP)); 254} 255 256int 257stop_cpus_hard(cpuset_t map) 258{ 259 260 return (generic_stop_cpus(map, IPI_STOP_HARD)); 261} 262 263#if defined(__amd64__) 264int 265suspend_cpus(cpuset_t map) 266{ 267 268 return (generic_stop_cpus(map, IPI_SUSPEND)); 269} 270#endif 271 272/* 273 * Called by a CPU to restart stopped CPUs. 274 * 275 * Usually (but not necessarily) called with 'stopped_cpus' as its arg. 276 * 277 * - Signals all CPUs in map to restart. 278 * - Waits for each to restart. 279 * 280 * Returns: 281 * -1: error 282 * 0: NA 283 * 1: ok 284 */ 285int 286restart_cpus(cpuset_t map) 287{ 288#ifdef KTR 289 char cpusetbuf[CPUSETBUFSIZ]; 290#endif 291 292 if (!smp_started) 293 return 0; 294 295 CTR1(KTR_SMP, "restart_cpus(%s)", cpusetobj_strprint(cpusetbuf, &map)); 296 297 /* signal other cpus to restart */ 298 CPU_COPY_STORE_REL(&map, &started_cpus); 299 300 /* wait for each to clear its bit */ 301 while (CPU_OVERLAP(&stopped_cpus, &map)) 302 cpu_spinwait(); 303 304 return 1; 305} 306 307/* 308 * All-CPU rendezvous. CPUs are signalled, all execute the setup function 309 * (if specified), rendezvous, execute the action function (if specified), 310 * rendezvous again, execute the teardown function (if specified), and then 311 * resume. 312 * 313 * Note that the supplied external functions _must_ be reentrant and aware 314 * that they are running in parallel and in an unknown lock context. 315 */ 316void 317smp_rendezvous_action(void) 318{ 319 struct thread *td; 320 void *local_func_arg; 321 void (*local_setup_func)(void*); 322 void (*local_action_func)(void*); 323 void (*local_teardown_func)(void*); 324 int generation; 325#ifdef INVARIANTS 326 int owepreempt; 327#endif 328 329 /* Ensure we have up-to-date values. */ 330 atomic_add_acq_int(&smp_rv_waiters[0], 1); 331 while (smp_rv_waiters[0] < smp_rv_ncpus) 332 cpu_spinwait(); 333 334 /* Fetch rendezvous parameters after acquire barrier. */ 335 local_func_arg = smp_rv_func_arg; 336 local_setup_func = smp_rv_setup_func; 337 local_action_func = smp_rv_action_func; 338 local_teardown_func = smp_rv_teardown_func; 339 generation = smp_rv_generation; 340 341 /* 342 * Use a nested critical section to prevent any preemptions 343 * from occurring during a rendezvous action routine. 344 * Specifically, if a rendezvous handler is invoked via an IPI 345 * and the interrupted thread was in the critical_exit() 346 * function after setting td_critnest to 0 but before 347 * performing a deferred preemption, this routine can be 348 * invoked with td_critnest set to 0 and td_owepreempt true. 349 * In that case, a critical_exit() during the rendezvous 350 * action would trigger a preemption which is not permitted in 351 * a rendezvous action. To fix this, wrap all of the 352 * rendezvous action handlers in a critical section. We 353 * cannot use a regular critical section however as having 354 * critical_exit() preempt from this routine would also be 355 * problematic (the preemption must not occur before the IPI 356 * has been acknowledged via an EOI). Instead, we 357 * intentionally ignore td_owepreempt when leaving the 358 * critical section. This should be harmless because we do 359 * not permit rendezvous action routines to schedule threads, 360 * and thus td_owepreempt should never transition from 0 to 1 361 * during this routine. 362 */ 363 td = curthread; 364 td->td_critnest++; 365#ifdef INVARIANTS 366 owepreempt = td->td_owepreempt; 367#endif 368 369 /* 370 * If requested, run a setup function before the main action 371 * function. Ensure all CPUs have completed the setup 372 * function before moving on to the action function. 373 */ 374 if (local_setup_func != smp_no_rendevous_barrier) { 375 if (smp_rv_setup_func != NULL) 376 smp_rv_setup_func(smp_rv_func_arg); 377 atomic_add_int(&smp_rv_waiters[1], 1); 378 while (smp_rv_waiters[1] < smp_rv_ncpus) 379 cpu_spinwait(); 380 } 381 382 if (local_action_func != NULL) 383 local_action_func(local_func_arg); 384 385 /* 386 * Signal that the main action has been completed. If a 387 * full exit rendezvous is requested, then all CPUs will 388 * wait here until all CPUs have finished the main action. 389 * 390 * Note that the write by the last CPU to finish the action 391 * may become visible to different CPUs at different times. 392 * As a result, the CPU that initiated the rendezvous may 393 * exit the rendezvous and drop the lock allowing another 394 * rendezvous to be initiated on the same CPU or a different 395 * CPU. In that case the exit sentinel may be cleared before 396 * all CPUs have noticed causing those CPUs to hang forever. 397 * Workaround this by using a generation count to notice when 398 * this race occurs and to exit the rendezvous in that case. 399 */ 400 MPASS(generation == smp_rv_generation); 401 atomic_add_int(&smp_rv_waiters[2], 1); 402 if (local_teardown_func != smp_no_rendevous_barrier) { 403 while (smp_rv_waiters[2] < smp_rv_ncpus && 404 generation == smp_rv_generation) 405 cpu_spinwait(); 406 407 if (local_teardown_func != NULL) 408 local_teardown_func(local_func_arg); 409 } 410 411 td->td_critnest--; 412 KASSERT(owepreempt == td->td_owepreempt, 413 ("rendezvous action changed td_owepreempt")); 414} 415 416void 417smp_rendezvous_cpus(cpuset_t map, 418 void (* setup_func)(void *), 419 void (* action_func)(void *), 420 void (* teardown_func)(void *), 421 void *arg) 422{ 423 int curcpumap, i, ncpus = 0; 424 425 if (!smp_started) { 426 if (setup_func != NULL) 427 setup_func(arg); 428 if (action_func != NULL) 429 action_func(arg); 430 if (teardown_func != NULL) 431 teardown_func(arg); 432 return; 433 } 434 435 CPU_FOREACH(i) { 436 if (CPU_ISSET(i, &map)) 437 ncpus++; 438 } 439 if (ncpus == 0) 440 panic("ncpus is 0 with non-zero map"); 441 442 mtx_lock_spin(&smp_ipi_mtx); 443 444 atomic_add_acq_int(&smp_rv_generation, 1); 445 446 /* Pass rendezvous parameters via global variables. */ 447 smp_rv_ncpus = ncpus; 448 smp_rv_setup_func = setup_func; 449 smp_rv_action_func = action_func; 450 smp_rv_teardown_func = teardown_func; 451 smp_rv_func_arg = arg; 452 smp_rv_waiters[1] = 0; 453 smp_rv_waiters[2] = 0; 454 atomic_store_rel_int(&smp_rv_waiters[0], 0); 455 456 /* 457 * Signal other processors, which will enter the IPI with 458 * interrupts off. 459 */ 460 curcpumap = CPU_ISSET(curcpu, &map); 461 CPU_CLR(curcpu, &map); 462 ipi_selected(map, IPI_RENDEZVOUS); 463 464 /* Check if the current CPU is in the map */ 465 if (curcpumap != 0) 466 smp_rendezvous_action(); 467 468 /* 469 * If the caller did not request an exit barrier to be enforced 470 * on each CPU, ensure that this CPU waits for all the other 471 * CPUs to finish the rendezvous. 472 */ 473 if (teardown_func == smp_no_rendevous_barrier) 474 while (atomic_load_acq_int(&smp_rv_waiters[2]) < ncpus) 475 cpu_spinwait(); 476 477 mtx_unlock_spin(&smp_ipi_mtx); 478} 479 480void 481smp_rendezvous(void (* setup_func)(void *), 482 void (* action_func)(void *), 483 void (* teardown_func)(void *), 484 void *arg) 485{ 486 smp_rendezvous_cpus(all_cpus, setup_func, action_func, teardown_func, arg); 487} 488 489static struct cpu_group group[MAXCPU]; 490 491struct cpu_group * 492smp_topo(void) 493{ 494 char cpusetbuf[CPUSETBUFSIZ], cpusetbuf2[CPUSETBUFSIZ]; 495 struct cpu_group *top; 496 497 /* 498 * Check for a fake topology request for debugging purposes. 499 */ 500 switch (smp_topology) { 501 case 1: 502 /* Dual core with no sharing. */ 503 top = smp_topo_1level(CG_SHARE_NONE, 2, 0); 504 break; 505 case 2: 506 /* No topology, all cpus are equal. */ 507 top = smp_topo_none(); 508 break; 509 case 3: 510 /* Dual core with shared L2. */ 511 top = smp_topo_1level(CG_SHARE_L2, 2, 0); 512 break; 513 case 4: 514 /* quad core, shared l3 among each package, private l2. */ 515 top = smp_topo_1level(CG_SHARE_L3, 4, 0); 516 break; 517 case 5: 518 /* quad core, 2 dualcore parts on each package share l2. */ 519 top = smp_topo_2level(CG_SHARE_NONE, 2, CG_SHARE_L2, 2, 0); 520 break; 521 case 6: 522 /* Single-core 2xHTT */ 523 top = smp_topo_1level(CG_SHARE_L1, 2, CG_FLAG_HTT); 524 break; 525 case 7: 526 /* quad core with a shared l3, 8 threads sharing L2. */ 527 top = smp_topo_2level(CG_SHARE_L3, 4, CG_SHARE_L2, 8, 528 CG_FLAG_SMT); 529 break; 530 default: 531 /* Default, ask the system what it wants. */ 532 top = cpu_topo(); 533 break; 534 } 535 /* 536 * Verify the returned topology. 537 */ 538 if (top->cg_count != mp_ncpus) 539 panic("Built bad topology at %p. CPU count %d != %d", 540 top, top->cg_count, mp_ncpus); 541 if (CPU_CMP(&top->cg_mask, &all_cpus)) 542 panic("Built bad topology at %p. CPU mask (%s) != (%s)", 543 top, cpusetobj_strprint(cpusetbuf, &top->cg_mask), 544 cpusetobj_strprint(cpusetbuf2, &all_cpus)); 545 return (top); 546} 547 548struct cpu_group * 549smp_topo_none(void) 550{ 551 struct cpu_group *top; 552 553 top = &group[0]; 554 top->cg_parent = NULL; 555 top->cg_child = NULL; 556 top->cg_mask = all_cpus; 557 top->cg_count = mp_ncpus; 558 top->cg_children = 0; 559 top->cg_level = CG_SHARE_NONE; 560 top->cg_flags = 0; 561 562 return (top); 563} 564 565static int 566smp_topo_addleaf(struct cpu_group *parent, struct cpu_group *child, int share, 567 int count, int flags, int start) 568{ 569 char cpusetbuf[CPUSETBUFSIZ], cpusetbuf2[CPUSETBUFSIZ]; 570 cpuset_t mask; 571 int i; 572 573 CPU_ZERO(&mask); 574 for (i = 0; i < count; i++, start++) 575 CPU_SET(start, &mask); 576 child->cg_parent = parent; 577 child->cg_child = NULL; 578 child->cg_children = 0; 579 child->cg_level = share; 580 child->cg_count = count; 581 child->cg_flags = flags; 582 child->cg_mask = mask; 583 parent->cg_children++; 584 for (; parent != NULL; parent = parent->cg_parent) { 585 if (CPU_OVERLAP(&parent->cg_mask, &child->cg_mask)) 586 panic("Duplicate children in %p. mask (%s) child (%s)", 587 parent, 588 cpusetobj_strprint(cpusetbuf, &parent->cg_mask), 589 cpusetobj_strprint(cpusetbuf2, &child->cg_mask)); 590 CPU_OR(&parent->cg_mask, &child->cg_mask); 591 parent->cg_count += child->cg_count; 592 } 593 594 return (start); 595} 596 597struct cpu_group * 598smp_topo_1level(int share, int count, int flags) 599{ 600 struct cpu_group *child; 601 struct cpu_group *top; 602 int packages; 603 int cpu; 604 int i; 605 606 cpu = 0; 607 top = &group[0]; 608 packages = mp_ncpus / count; 609 top->cg_child = child = &group[1]; 610 top->cg_level = CG_SHARE_NONE; 611 for (i = 0; i < packages; i++, child++) 612 cpu = smp_topo_addleaf(top, child, share, count, flags, cpu); 613 return (top); 614} 615 616struct cpu_group * 617smp_topo_2level(int l2share, int l2count, int l1share, int l1count, 618 int l1flags) 619{ 620 struct cpu_group *top; 621 struct cpu_group *l1g; 622 struct cpu_group *l2g; 623 int cpu; 624 int i; 625 int j; 626 627 cpu = 0; 628 top = &group[0]; 629 l2g = &group[1]; 630 top->cg_child = l2g; 631 top->cg_level = CG_SHARE_NONE; 632 top->cg_children = mp_ncpus / (l2count * l1count); 633 l1g = l2g + top->cg_children; 634 for (i = 0; i < top->cg_children; i++, l2g++) { 635 l2g->cg_parent = top; 636 l2g->cg_child = l1g; 637 l2g->cg_level = l2share; 638 for (j = 0; j < l2count; j++, l1g++) 639 cpu = smp_topo_addleaf(l2g, l1g, l1share, l1count, 640 l1flags, cpu); 641 } 642 return (top); 643} 644 645 646struct cpu_group * 647smp_topo_find(struct cpu_group *top, int cpu) 648{ 649 struct cpu_group *cg; 650 cpuset_t mask; 651 int children; 652 int i; 653 654 CPU_SETOF(cpu, &mask); 655 cg = top; 656 for (;;) { 657 if (!CPU_OVERLAP(&cg->cg_mask, &mask)) 658 return (NULL); 659 if (cg->cg_children == 0) 660 return (cg); 661 children = cg->cg_children; 662 for (i = 0, cg = cg->cg_child; i < children; cg++, i++) 663 if (CPU_OVERLAP(&cg->cg_mask, &mask)) 664 break; 665 } 666 return (NULL); 667} 668#else /* !SMP */ 669 670void 671smp_rendezvous_cpus(cpuset_t map, 672 void (*setup_func)(void *), 673 void (*action_func)(void *), 674 void (*teardown_func)(void *), 675 void *arg) 676{ 677 if (setup_func != NULL) 678 setup_func(arg); 679 if (action_func != NULL) 680 action_func(arg); 681 if (teardown_func != NULL) 682 teardown_func(arg); 683} 684 685void 686smp_rendezvous(void (*setup_func)(void *), 687 void (*action_func)(void *), 688 void (*teardown_func)(void *), 689 void *arg) 690{ 691 692 if (setup_func != NULL) 693 setup_func(arg); 694 if (action_func != NULL) 695 action_func(arg); 696 if (teardown_func != NULL) 697 teardown_func(arg); 698} 699 700/* 701 * Provide dummy SMP support for UP kernels. Modules that need to use SMP 702 * APIs will still work using this dummy support. 703 */ 704static void 705mp_setvariables_for_up(void *dummy) 706{ 707 mp_ncpus = 1; 708 mp_maxid = PCPU_GET(cpuid); 709 CPU_SETOF(mp_maxid, &all_cpus); 710 KASSERT(PCPU_GET(cpuid) == 0, ("UP must have a CPU ID of zero")); 711} 712SYSINIT(cpu_mp_setvariables, SI_SUB_TUNABLES, SI_ORDER_FIRST, 713 mp_setvariables_for_up, NULL); 714#endif /* SMP */ 715 716void 717smp_no_rendevous_barrier(void *dummy) 718{ 719#ifdef SMP 720 KASSERT((!smp_started),("smp_no_rendevous called and smp is started")); 721#endif 722}
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