Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
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FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_thread.c
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1 /*- 2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD 3 * 4 * Copyright (C) 2001 Julian Elischer <julian@freebsd.org>. 5 * All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice(s), this list of conditions and the following disclaimer as 12 * the first lines of this file unmodified other than the possible 13 * addition of one or more copyright notices. 14 * 2. Redistributions in binary form must reproduce the above copyright 15 * notice(s), this list of conditions and the following disclaimer in the 16 * documentation and/or other materials provided with the distribution. 17 * 18 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY 19 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 20 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 21 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE LIABLE FOR ANY 22 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES 23 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR 24 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER 25 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH 28 * DAMAGE. 29 */ 30 31 #include "opt_witness.h" 32 #include "opt_hwpmc_hooks.h" 33 34 #include <sys/cdefs.h> 35 __FBSDID("$FreeBSD$"); 36 37 #include <sys/param.h> 38 #include <sys/systm.h> 39 #include <sys/kernel.h> 40 #include <sys/lock.h> 41 #include <sys/mutex.h> 42 #include <sys/proc.h> 43 #include <sys/bitstring.h> 44 #include <sys/epoch.h> 45 #include <sys/rangelock.h> 46 #include <sys/resourcevar.h> 47 #include <sys/sdt.h> 48 #include <sys/smp.h> 49 #include <sys/sched.h> 50 #include <sys/sleepqueue.h> 51 #include <sys/selinfo.h> 52 #include <sys/syscallsubr.h> 53 #include <sys/dtrace_bsd.h> 54 #include <sys/sysent.h> 55 #include <sys/turnstile.h> 56 #include <sys/taskqueue.h> 57 #include <sys/ktr.h> 58 #include <sys/rwlock.h> 59 #include <sys/umtx.h> 60 #include <sys/vmmeter.h> 61 #include <sys/cpuset.h> 62 #ifdef HWPMC_HOOKS 63 #include <sys/pmckern.h> 64 #endif 65 #include <sys/priv.h> 66 67 #include <security/audit/audit.h> 68 69 #include <vm/pmap.h> 70 #include <vm/vm.h> 71 #include <vm/vm_extern.h> 72 #include <vm/uma.h> 73 #include <vm/vm_phys.h> 74 #include <sys/eventhandler.h> 75 76 /* 77 * Asserts below verify the stability of struct thread and struct proc 78 * layout, as exposed by KBI to modules. On head, the KBI is allowed 79 * to drift, change to the structures must be accompanied by the 80 * assert update. 81 * 82 * On the stable branches after KBI freeze, conditions must not be 83 * violated. Typically new fields are moved to the end of the 84 * structures. 85 */ 86 #ifdef __amd64__ 87 _Static_assert(offsetof(struct thread, td_flags) == 0xfc, 88 "struct thread KBI td_flags"); 89 _Static_assert(offsetof(struct thread, td_pflags) == 0x104, 90 "struct thread KBI td_pflags"); 91 _Static_assert(offsetof(struct thread, td_frame) == 0x4a0, 92 "struct thread KBI td_frame"); 93 _Static_assert(offsetof(struct thread, td_emuldata) == 0x6b0, 94 "struct thread KBI td_emuldata"); 95 _Static_assert(offsetof(struct proc, p_flag) == 0xb8, 96 "struct proc KBI p_flag"); 97 _Static_assert(offsetof(struct proc, p_pid) == 0xc4, 98 "struct proc KBI p_pid"); 99 _Static_assert(offsetof(struct proc, p_filemon) == 0x3c0, 100 "struct proc KBI p_filemon"); 101 _Static_assert(offsetof(struct proc, p_comm) == 0x3d8, 102 "struct proc KBI p_comm"); 103 _Static_assert(offsetof(struct proc, p_emuldata) == 0x4b8, 104 "struct proc KBI p_emuldata"); 105 #endif 106 #ifdef __i386__ 107 _Static_assert(offsetof(struct thread, td_flags) == 0x98, 108 "struct thread KBI td_flags"); 109 _Static_assert(offsetof(struct thread, td_pflags) == 0xa0, 110 "struct thread KBI td_pflags"); 111 _Static_assert(offsetof(struct thread, td_frame) == 0x300, 112 "struct thread KBI td_frame"); 113 _Static_assert(offsetof(struct thread, td_emuldata) == 0x344, 114 "struct thread KBI td_emuldata"); 115 _Static_assert(offsetof(struct proc, p_flag) == 0x6c, 116 "struct proc KBI p_flag"); 117 _Static_assert(offsetof(struct proc, p_pid) == 0x78, 118 "struct proc KBI p_pid"); 119 _Static_assert(offsetof(struct proc, p_filemon) == 0x26c, 120 "struct proc KBI p_filemon"); 121 _Static_assert(offsetof(struct proc, p_comm) == 0x280, 122 "struct proc KBI p_comm"); 123 _Static_assert(offsetof(struct proc, p_emuldata) == 0x30c, 124 "struct proc KBI p_emuldata"); 125 #endif 126 127 SDT_PROVIDER_DECLARE(proc); 128 SDT_PROBE_DEFINE(proc, , , lwp__exit); 129 130 /* 131 * thread related storage. 132 */ 133 static uma_zone_t thread_zone; 134 135 struct thread_domain_data { 136 struct thread *tdd_zombies; 137 int tdd_reapticks; 138 } __aligned(CACHE_LINE_SIZE); 139 140 static struct thread_domain_data thread_domain_data[MAXMEMDOM]; 141 142 static struct task thread_reap_task; 143 static struct callout thread_reap_callout; 144 145 static void thread_zombie(struct thread *); 146 static void thread_reap(void); 147 static void thread_reap_all(void); 148 static void thread_reap_task_cb(void *, int); 149 static void thread_reap_callout_cb(void *); 150 static int thread_unsuspend_one(struct thread *td, struct proc *p, 151 bool boundary); 152 static void thread_free_batched(struct thread *td); 153 154 static __exclusive_cache_line struct mtx tid_lock; 155 static bitstr_t *tid_bitmap; 156 157 static MALLOC_DEFINE(M_TIDHASH, "tidhash", "thread hash"); 158 159 static int maxthread; 160 SYSCTL_INT(_kern, OID_AUTO, maxthread, CTLFLAG_RDTUN, 161 &maxthread, 0, "Maximum number of threads"); 162 163 static __exclusive_cache_line int nthreads; 164 165 static LIST_HEAD(tidhashhead, thread) *tidhashtbl; 166 static u_long tidhash; 167 static u_long tidhashlock; 168 static struct rwlock *tidhashtbl_lock; 169 #define TIDHASH(tid) (&tidhashtbl[(tid) & tidhash]) 170 #define TIDHASHLOCK(tid) (&tidhashtbl_lock[(tid) & tidhashlock]) 171 172 EVENTHANDLER_LIST_DEFINE(thread_ctor); 173 EVENTHANDLER_LIST_DEFINE(thread_dtor); 174 EVENTHANDLER_LIST_DEFINE(thread_init); 175 EVENTHANDLER_LIST_DEFINE(thread_fini); 176 177 static bool 178 thread_count_inc_try(void) 179 { 180 int nthreads_new; 181 182 nthreads_new = atomic_fetchadd_int(&nthreads, 1) + 1; 183 if (nthreads_new >= maxthread - 100) { 184 if (priv_check_cred(curthread->td_ucred, PRIV_MAXPROC) != 0 || 185 nthreads_new >= maxthread) { 186 atomic_subtract_int(&nthreads, 1); 187 return (false); 188 } 189 } 190 return (true); 191 } 192 193 static bool 194 thread_count_inc(void) 195 { 196 static struct timeval lastfail; 197 static int curfail; 198 199 thread_reap(); 200 if (thread_count_inc_try()) { 201 return (true); 202 } 203 204 thread_reap_all(); 205 if (thread_count_inc_try()) { 206 return (true); 207 } 208 209 if (ppsratecheck(&lastfail, &curfail, 1)) { 210 printf("maxthread limit exceeded by uid %u " 211 "(pid %d); consider increasing kern.maxthread\n", 212 curthread->td_ucred->cr_ruid, curproc->p_pid); 213 } 214 return (false); 215 } 216 217 static void 218 thread_count_sub(int n) 219 { 220 221 atomic_subtract_int(&nthreads, n); 222 } 223 224 static void 225 thread_count_dec(void) 226 { 227 228 thread_count_sub(1); 229 } 230 231 static lwpid_t 232 tid_alloc(void) 233 { 234 static lwpid_t trytid; 235 lwpid_t tid; 236 237 mtx_lock(&tid_lock); 238 /* 239 * It is an invariant that the bitmap is big enough to hold maxthread 240 * IDs. If we got to this point there has to be at least one free. 241 */ 242 if (trytid >= maxthread) 243 trytid = 0; 244 bit_ffc_at(tid_bitmap, trytid, maxthread, &tid); 245 if (tid == -1) { 246 KASSERT(trytid != 0, ("unexpectedly ran out of IDs")); 247 trytid = 0; 248 bit_ffc_at(tid_bitmap, trytid, maxthread, &tid); 249 KASSERT(tid != -1, ("unexpectedly ran out of IDs")); 250 } 251 bit_set(tid_bitmap, tid); 252 trytid = tid + 1; 253 mtx_unlock(&tid_lock); 254 return (tid + NO_PID); 255 } 256 257 static void 258 tid_free_locked(lwpid_t rtid) 259 { 260 lwpid_t tid; 261 262 mtx_assert(&tid_lock, MA_OWNED); 263 KASSERT(rtid >= NO_PID, 264 ("%s: invalid tid %d\n", __func__, rtid)); 265 tid = rtid - NO_PID; 266 KASSERT(bit_test(tid_bitmap, tid) != 0, 267 ("thread ID %d not allocated\n", rtid)); 268 bit_clear(tid_bitmap, tid); 269 } 270 271 static void 272 tid_free(lwpid_t rtid) 273 { 274 275 mtx_lock(&tid_lock); 276 tid_free_locked(rtid); 277 mtx_unlock(&tid_lock); 278 } 279 280 static void 281 tid_free_batch(lwpid_t *batch, int n) 282 { 283 int i; 284 285 mtx_lock(&tid_lock); 286 for (i = 0; i < n; i++) { 287 tid_free_locked(batch[i]); 288 } 289 mtx_unlock(&tid_lock); 290 } 291 292 /* 293 * Batching for thread reapping. 294 */ 295 struct tidbatch { 296 lwpid_t tab[16]; 297 int n; 298 }; 299 300 static void 301 tidbatch_prep(struct tidbatch *tb) 302 { 303 304 tb->n = 0; 305 } 306 307 static void 308 tidbatch_add(struct tidbatch *tb, struct thread *td) 309 { 310 311 KASSERT(tb->n < nitems(tb->tab), 312 ("%s: count too high %d", __func__, tb->n)); 313 tb->tab[tb->n] = td->td_tid; 314 tb->n++; 315 } 316 317 static void 318 tidbatch_process(struct tidbatch *tb) 319 { 320 321 KASSERT(tb->n <= nitems(tb->tab), 322 ("%s: count too high %d", __func__, tb->n)); 323 if (tb->n == nitems(tb->tab)) { 324 tid_free_batch(tb->tab, tb->n); 325 tb->n = 0; 326 } 327 } 328 329 static void 330 tidbatch_final(struct tidbatch *tb) 331 { 332 333 KASSERT(tb->n <= nitems(tb->tab), 334 ("%s: count too high %d", __func__, tb->n)); 335 if (tb->n != 0) { 336 tid_free_batch(tb->tab, tb->n); 337 } 338 } 339 340 /* 341 * Prepare a thread for use. 342 */ 343 static int 344 thread_ctor(void *mem, int size, void *arg, int flags) 345 { 346 struct thread *td; 347 348 td = (struct thread *)mem; 349 td->td_state = TDS_INACTIVE; 350 td->td_lastcpu = td->td_oncpu = NOCPU; 351 352 /* 353 * Note that td_critnest begins life as 1 because the thread is not 354 * running and is thereby implicitly waiting to be on the receiving 355 * end of a context switch. 356 */ 357 td->td_critnest = 1; 358 td->td_lend_user_pri = PRI_MAX; 359 #ifdef AUDIT 360 audit_thread_alloc(td); 361 #endif 362 #ifdef KDTRACE_HOOKS 363 kdtrace_thread_ctor(td); 364 #endif 365 umtx_thread_alloc(td); 366 MPASS(td->td_sel == NULL); 367 return (0); 368 } 369 370 /* 371 * Reclaim a thread after use. 372 */ 373 static void 374 thread_dtor(void *mem, int size, void *arg) 375 { 376 struct thread *td; 377 378 td = (struct thread *)mem; 379 380 #ifdef INVARIANTS 381 /* Verify that this thread is in a safe state to free. */ 382 switch (td->td_state) { 383 case TDS_INHIBITED: 384 case TDS_RUNNING: 385 case TDS_CAN_RUN: 386 case TDS_RUNQ: 387 /* 388 * We must never unlink a thread that is in one of 389 * these states, because it is currently active. 390 */ 391 panic("bad state for thread unlinking"); 392 /* NOTREACHED */ 393 case TDS_INACTIVE: 394 break; 395 default: 396 panic("bad thread state"); 397 /* NOTREACHED */ 398 } 399 #endif 400 #ifdef AUDIT 401 audit_thread_free(td); 402 #endif 403 #ifdef KDTRACE_HOOKS 404 kdtrace_thread_dtor(td); 405 #endif 406 /* Free all OSD associated to this thread. */ 407 osd_thread_exit(td); 408 td_softdep_cleanup(td); 409 MPASS(td->td_su == NULL); 410 seltdfini(td); 411 } 412 413 /* 414 * Initialize type-stable parts of a thread (when newly created). 415 */ 416 static int 417 thread_init(void *mem, int size, int flags) 418 { 419 struct thread *td; 420 421 td = (struct thread *)mem; 422 423 td->td_allocdomain = vm_phys_domain(vtophys(td)); 424 td->td_sleepqueue = sleepq_alloc(); 425 td->td_turnstile = turnstile_alloc(); 426 td->td_rlqe = NULL; 427 EVENTHANDLER_DIRECT_INVOKE(thread_init, td); 428 umtx_thread_init(td); 429 td->td_kstack = 0; 430 td->td_sel = NULL; 431 return (0); 432 } 433 434 /* 435 * Tear down type-stable parts of a thread (just before being discarded). 436 */ 437 static void 438 thread_fini(void *mem, int size) 439 { 440 struct thread *td; 441 442 td = (struct thread *)mem; 443 EVENTHANDLER_DIRECT_INVOKE(thread_fini, td); 444 rlqentry_free(td->td_rlqe); 445 turnstile_free(td->td_turnstile); 446 sleepq_free(td->td_sleepqueue); 447 umtx_thread_fini(td); 448 MPASS(td->td_sel == NULL); 449 } 450 451 /* 452 * For a newly created process, 453 * link up all the structures and its initial threads etc. 454 * called from: 455 * {arch}/{arch}/machdep.c {arch}_init(), init386() etc. 456 * proc_dtor() (should go away) 457 * proc_init() 458 */ 459 void 460 proc_linkup0(struct proc *p, struct thread *td) 461 { 462 TAILQ_INIT(&p->p_threads); /* all threads in proc */ 463 proc_linkup(p, td); 464 } 465 466 void 467 proc_linkup(struct proc *p, struct thread *td) 468 { 469 470 sigqueue_init(&p->p_sigqueue, p); 471 p->p_ksi = ksiginfo_alloc(1); 472 if (p->p_ksi != NULL) { 473 /* XXX p_ksi may be null if ksiginfo zone is not ready */ 474 p->p_ksi->ksi_flags = KSI_EXT | KSI_INS; 475 } 476 LIST_INIT(&p->p_mqnotifier); 477 p->p_numthreads = 0; 478 thread_link(td, p); 479 } 480 481 extern int max_threads_per_proc; 482 483 /* 484 * Initialize global thread allocation resources. 485 */ 486 void 487 threadinit(void) 488 { 489 u_long i; 490 lwpid_t tid0; 491 uint32_t flags; 492 493 /* 494 * Place an upper limit on threads which can be allocated. 495 * 496 * Note that other factors may make the de facto limit much lower. 497 * 498 * Platform limits are somewhat arbitrary but deemed "more than good 499 * enough" for the foreseable future. 500 */ 501 if (maxthread == 0) { 502 #ifdef _LP64 503 maxthread = MIN(maxproc * max_threads_per_proc, 1000000); 504 #else 505 maxthread = MIN(maxproc * max_threads_per_proc, 100000); 506 #endif 507 } 508 509 mtx_init(&tid_lock, "TID lock", NULL, MTX_DEF); 510 tid_bitmap = bit_alloc(maxthread, M_TIDHASH, M_WAITOK); 511 /* 512 * Handle thread0. 513 */ 514 thread_count_inc(); 515 tid0 = tid_alloc(); 516 if (tid0 != THREAD0_TID) 517 panic("tid0 %d != %d\n", tid0, THREAD0_TID); 518 519 flags = UMA_ZONE_NOFREE; 520 #ifdef __aarch64__ 521 /* 522 * Force thread structures to be allocated from the direct map. 523 * Otherwise, superpage promotions and demotions may temporarily 524 * invalidate thread structure mappings. For most dynamically allocated 525 * structures this is not a problem, but translation faults cannot be 526 * handled without accessing curthread. 527 */ 528 flags |= UMA_ZONE_CONTIG; 529 #endif 530 thread_zone = uma_zcreate("THREAD", sched_sizeof_thread(), 531 thread_ctor, thread_dtor, thread_init, thread_fini, 532 32 - 1, flags); 533 tidhashtbl = hashinit(maxproc / 2, M_TIDHASH, &tidhash); 534 tidhashlock = (tidhash + 1) / 64; 535 if (tidhashlock > 0) 536 tidhashlock--; 537 tidhashtbl_lock = malloc(sizeof(*tidhashtbl_lock) * (tidhashlock + 1), 538 M_TIDHASH, M_WAITOK | M_ZERO); 539 for (i = 0; i < tidhashlock + 1; i++) 540 rw_init(&tidhashtbl_lock[i], "tidhash"); 541 542 TASK_INIT(&thread_reap_task, 0, thread_reap_task_cb, NULL); 543 callout_init(&thread_reap_callout, 1); 544 callout_reset(&thread_reap_callout, 5 * hz, thread_reap_callout_cb, NULL); 545 } 546 547 /* 548 * Place an unused thread on the zombie list. 549 */ 550 void 551 thread_zombie(struct thread *td) 552 { 553 struct thread_domain_data *tdd; 554 struct thread *ztd; 555 556 tdd = &thread_domain_data[td->td_allocdomain]; 557 ztd = atomic_load_ptr(&tdd->tdd_zombies); 558 for (;;) { 559 td->td_zombie = ztd; 560 if (atomic_fcmpset_rel_ptr((uintptr_t *)&tdd->tdd_zombies, 561 (uintptr_t *)&ztd, (uintptr_t)td)) 562 break; 563 continue; 564 } 565 } 566 567 /* 568 * Release a thread that has exited after cpu_throw(). 569 */ 570 void 571 thread_stash(struct thread *td) 572 { 573 atomic_subtract_rel_int(&td->td_proc->p_exitthreads, 1); 574 thread_zombie(td); 575 } 576 577 /* 578 * Reap zombies from passed domain. 579 */ 580 static void 581 thread_reap_domain(struct thread_domain_data *tdd) 582 { 583 struct thread *itd, *ntd; 584 struct tidbatch tidbatch; 585 struct credbatch credbatch; 586 int tdcount; 587 struct plimit *lim; 588 int limcount; 589 590 /* 591 * Reading upfront is pessimal if followed by concurrent atomic_swap, 592 * but most of the time the list is empty. 593 */ 594 if (tdd->tdd_zombies == NULL) 595 return; 596 597 itd = (struct thread *)atomic_swap_ptr((uintptr_t *)&tdd->tdd_zombies, 598 (uintptr_t)NULL); 599 if (itd == NULL) 600 return; 601 602 /* 603 * Multiple CPUs can get here, the race is fine as ticks is only 604 * advisory. 605 */ 606 tdd->tdd_reapticks = ticks; 607 608 tidbatch_prep(&tidbatch); 609 credbatch_prep(&credbatch); 610 tdcount = 0; 611 lim = NULL; 612 limcount = 0; 613 614 while (itd != NULL) { 615 ntd = itd->td_zombie; 616 EVENTHANDLER_DIRECT_INVOKE(thread_dtor, itd); 617 tidbatch_add(&tidbatch, itd); 618 credbatch_add(&credbatch, itd); 619 MPASS(itd->td_limit != NULL); 620 if (lim != itd->td_limit) { 621 if (limcount != 0) { 622 lim_freen(lim, limcount); 623 limcount = 0; 624 } 625 } 626 lim = itd->td_limit; 627 limcount++; 628 thread_free_batched(itd); 629 tidbatch_process(&tidbatch); 630 credbatch_process(&credbatch); 631 tdcount++; 632 if (tdcount == 32) { 633 thread_count_sub(tdcount); 634 tdcount = 0; 635 } 636 itd = ntd; 637 } 638 639 tidbatch_final(&tidbatch); 640 credbatch_final(&credbatch); 641 if (tdcount != 0) { 642 thread_count_sub(tdcount); 643 } 644 MPASS(limcount != 0); 645 lim_freen(lim, limcount); 646 } 647 648 /* 649 * Reap zombies from all domains. 650 */ 651 static void 652 thread_reap_all(void) 653 { 654 struct thread_domain_data *tdd; 655 int i, domain; 656 657 domain = PCPU_GET(domain); 658 for (i = 0; i < vm_ndomains; i++) { 659 tdd = &thread_domain_data[(i + domain) % vm_ndomains]; 660 thread_reap_domain(tdd); 661 } 662 } 663 664 /* 665 * Reap zombies from local domain. 666 */ 667 static void 668 thread_reap(void) 669 { 670 struct thread_domain_data *tdd; 671 int domain; 672 673 domain = PCPU_GET(domain); 674 tdd = &thread_domain_data[domain]; 675 676 thread_reap_domain(tdd); 677 } 678 679 static void 680 thread_reap_task_cb(void *arg __unused, int pending __unused) 681 { 682 683 thread_reap_all(); 684 } 685 686 static void 687 thread_reap_callout_cb(void *arg __unused) 688 { 689 struct thread_domain_data *tdd; 690 int i, cticks, lticks; 691 bool wantreap; 692 693 wantreap = false; 694 cticks = atomic_load_int(&ticks); 695 for (i = 0; i < vm_ndomains; i++) { 696 tdd = &thread_domain_data[i]; 697 lticks = tdd->tdd_reapticks; 698 if (tdd->tdd_zombies != NULL && 699 (u_int)(cticks - lticks) > 5 * hz) { 700 wantreap = true; 701 break; 702 } 703 } 704 705 if (wantreap) 706 taskqueue_enqueue(taskqueue_thread, &thread_reap_task); 707 callout_reset(&thread_reap_callout, 5 * hz, thread_reap_callout_cb, NULL); 708 } 709 710 /* 711 * Allocate a thread. 712 */ 713 struct thread * 714 thread_alloc(int pages) 715 { 716 struct thread *td; 717 lwpid_t tid; 718 719 if (!thread_count_inc()) { 720 return (NULL); 721 } 722 723 tid = tid_alloc(); 724 td = uma_zalloc(thread_zone, M_WAITOK); 725 KASSERT(td->td_kstack == 0, ("thread_alloc got thread with kstack")); 726 if (!vm_thread_new(td, pages)) { 727 uma_zfree(thread_zone, td); 728 tid_free(tid); 729 thread_count_dec(); 730 return (NULL); 731 } 732 td->td_tid = tid; 733 cpu_thread_alloc(td); 734 EVENTHANDLER_DIRECT_INVOKE(thread_ctor, td); 735 return (td); 736 } 737 738 int 739 thread_alloc_stack(struct thread *td, int pages) 740 { 741 742 KASSERT(td->td_kstack == 0, 743 ("thread_alloc_stack called on a thread with kstack")); 744 if (!vm_thread_new(td, pages)) 745 return (0); 746 cpu_thread_alloc(td); 747 return (1); 748 } 749 750 /* 751 * Deallocate a thread. 752 */ 753 static void 754 thread_free_batched(struct thread *td) 755 { 756 757 lock_profile_thread_exit(td); 758 if (td->td_cpuset) 759 cpuset_rel(td->td_cpuset); 760 td->td_cpuset = NULL; 761 cpu_thread_free(td); 762 if (td->td_kstack != 0) 763 vm_thread_dispose(td); 764 callout_drain(&td->td_slpcallout); 765 /* 766 * Freeing handled by the caller. 767 */ 768 td->td_tid = -1; 769 uma_zfree(thread_zone, td); 770 } 771 772 void 773 thread_free(struct thread *td) 774 { 775 lwpid_t tid; 776 777 EVENTHANDLER_DIRECT_INVOKE(thread_dtor, td); 778 tid = td->td_tid; 779 thread_free_batched(td); 780 tid_free(tid); 781 thread_count_dec(); 782 } 783 784 void 785 thread_cow_get_proc(struct thread *newtd, struct proc *p) 786 { 787 788 PROC_LOCK_ASSERT(p, MA_OWNED); 789 newtd->td_realucred = crcowget(p->p_ucred); 790 newtd->td_ucred = newtd->td_realucred; 791 newtd->td_limit = lim_hold(p->p_limit); 792 newtd->td_cowgen = p->p_cowgen; 793 } 794 795 void 796 thread_cow_get(struct thread *newtd, struct thread *td) 797 { 798 799 MPASS(td->td_realucred == td->td_ucred); 800 newtd->td_realucred = crcowget(td->td_realucred); 801 newtd->td_ucred = newtd->td_realucred; 802 newtd->td_limit = lim_hold(td->td_limit); 803 newtd->td_cowgen = td->td_cowgen; 804 } 805 806 void 807 thread_cow_free(struct thread *td) 808 { 809 810 if (td->td_realucred != NULL) 811 crcowfree(td); 812 if (td->td_limit != NULL) 813 lim_free(td->td_limit); 814 } 815 816 void 817 thread_cow_update(struct thread *td) 818 { 819 struct proc *p; 820 struct ucred *oldcred; 821 struct plimit *oldlimit; 822 823 p = td->td_proc; 824 oldlimit = NULL; 825 PROC_LOCK(p); 826 oldcred = crcowsync(); 827 if (td->td_limit != p->p_limit) { 828 oldlimit = td->td_limit; 829 td->td_limit = lim_hold(p->p_limit); 830 } 831 td->td_cowgen = p->p_cowgen; 832 PROC_UNLOCK(p); 833 if (oldcred != NULL) 834 crfree(oldcred); 835 if (oldlimit != NULL) 836 lim_free(oldlimit); 837 } 838 839 /* 840 * Discard the current thread and exit from its context. 841 * Always called with scheduler locked. 842 * 843 * Because we can't free a thread while we're operating under its context, 844 * push the current thread into our CPU's deadthread holder. This means 845 * we needn't worry about someone else grabbing our context before we 846 * do a cpu_throw(). 847 */ 848 void 849 thread_exit(void) 850 { 851 uint64_t runtime, new_switchtime; 852 struct thread *td; 853 struct thread *td2; 854 struct proc *p; 855 int wakeup_swapper; 856 857 td = curthread; 858 p = td->td_proc; 859 860 PROC_SLOCK_ASSERT(p, MA_OWNED); 861 mtx_assert(&Giant, MA_NOTOWNED); 862 863 PROC_LOCK_ASSERT(p, MA_OWNED); 864 KASSERT(p != NULL, ("thread exiting without a process")); 865 CTR3(KTR_PROC, "thread_exit: thread %p (pid %ld, %s)", td, 866 (long)p->p_pid, td->td_name); 867 SDT_PROBE0(proc, , , lwp__exit); 868 KASSERT(TAILQ_EMPTY(&td->td_sigqueue.sq_list), ("signal pending")); 869 MPASS(td->td_realucred == td->td_ucred); 870 871 /* 872 * drop FPU & debug register state storage, or any other 873 * architecture specific resources that 874 * would not be on a new untouched process. 875 */ 876 cpu_thread_exit(td); 877 878 /* 879 * The last thread is left attached to the process 880 * So that the whole bundle gets recycled. Skip 881 * all this stuff if we never had threads. 882 * EXIT clears all sign of other threads when 883 * it goes to single threading, so the last thread always 884 * takes the short path. 885 */ 886 if (p->p_flag & P_HADTHREADS) { 887 if (p->p_numthreads > 1) { 888 atomic_add_int(&td->td_proc->p_exitthreads, 1); 889 thread_unlink(td); 890 td2 = FIRST_THREAD_IN_PROC(p); 891 sched_exit_thread(td2, td); 892 893 /* 894 * The test below is NOT true if we are the 895 * sole exiting thread. P_STOPPED_SINGLE is unset 896 * in exit1() after it is the only survivor. 897 */ 898 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) { 899 if (p->p_numthreads == p->p_suspcount) { 900 thread_lock(p->p_singlethread); 901 wakeup_swapper = thread_unsuspend_one( 902 p->p_singlethread, p, false); 903 if (wakeup_swapper) 904 kick_proc0(); 905 } 906 } 907 908 PCPU_SET(deadthread, td); 909 } else { 910 /* 911 * The last thread is exiting.. but not through exit() 912 */ 913 panic ("thread_exit: Last thread exiting on its own"); 914 } 915 } 916 #ifdef HWPMC_HOOKS 917 /* 918 * If this thread is part of a process that is being tracked by hwpmc(4), 919 * inform the module of the thread's impending exit. 920 */ 921 if (PMC_PROC_IS_USING_PMCS(td->td_proc)) { 922 PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_OUT); 923 PMC_CALL_HOOK_UNLOCKED(td, PMC_FN_THR_EXIT, NULL); 924 } else if (PMC_SYSTEM_SAMPLING_ACTIVE()) 925 PMC_CALL_HOOK_UNLOCKED(td, PMC_FN_THR_EXIT_LOG, NULL); 926 #endif 927 PROC_UNLOCK(p); 928 PROC_STATLOCK(p); 929 thread_lock(td); 930 PROC_SUNLOCK(p); 931 932 /* Do the same timestamp bookkeeping that mi_switch() would do. */ 933 new_switchtime = cpu_ticks(); 934 runtime = new_switchtime - PCPU_GET(switchtime); 935 td->td_runtime += runtime; 936 td->td_incruntime += runtime; 937 PCPU_SET(switchtime, new_switchtime); 938 PCPU_SET(switchticks, ticks); 939 VM_CNT_INC(v_swtch); 940 941 /* Save our resource usage in our process. */ 942 td->td_ru.ru_nvcsw++; 943 ruxagg_locked(p, td); 944 rucollect(&p->p_ru, &td->td_ru); 945 PROC_STATUNLOCK(p); 946 947 td->td_state = TDS_INACTIVE; 948 #ifdef WITNESS 949 witness_thread_exit(td); 950 #endif 951 CTR1(KTR_PROC, "thread_exit: cpu_throw() thread %p", td); 952 sched_throw(td); 953 panic("I'm a teapot!"); 954 /* NOTREACHED */ 955 } 956 957 /* 958 * Do any thread specific cleanups that may be needed in wait() 959 * called with Giant, proc and schedlock not held. 960 */ 961 void 962 thread_wait(struct proc *p) 963 { 964 struct thread *td; 965 966 mtx_assert(&Giant, MA_NOTOWNED); 967 KASSERT(p->p_numthreads == 1, ("multiple threads in thread_wait()")); 968 KASSERT(p->p_exitthreads == 0, ("p_exitthreads leaking")); 969 td = FIRST_THREAD_IN_PROC(p); 970 /* Lock the last thread so we spin until it exits cpu_throw(). */ 971 thread_lock(td); 972 thread_unlock(td); 973 lock_profile_thread_exit(td); 974 cpuset_rel(td->td_cpuset); 975 td->td_cpuset = NULL; 976 cpu_thread_clean(td); 977 thread_cow_free(td); 978 callout_drain(&td->td_slpcallout); 979 thread_reap(); /* check for zombie threads etc. */ 980 } 981 982 /* 983 * Link a thread to a process. 984 * set up anything that needs to be initialized for it to 985 * be used by the process. 986 */ 987 void 988 thread_link(struct thread *td, struct proc *p) 989 { 990 991 /* 992 * XXX This can't be enabled because it's called for proc0 before 993 * its lock has been created. 994 * PROC_LOCK_ASSERT(p, MA_OWNED); 995 */ 996 td->td_state = TDS_INACTIVE; 997 td->td_proc = p; 998 td->td_flags = TDF_INMEM; 999 1000 LIST_INIT(&td->td_contested); 1001 LIST_INIT(&td->td_lprof[0]); 1002 LIST_INIT(&td->td_lprof[1]); 1003 #ifdef EPOCH_TRACE 1004 SLIST_INIT(&td->td_epochs); 1005 #endif 1006 sigqueue_init(&td->td_sigqueue, p); 1007 callout_init(&td->td_slpcallout, 1); 1008 TAILQ_INSERT_TAIL(&p->p_threads, td, td_plist); 1009 p->p_numthreads++; 1010 } 1011 1012 /* 1013 * Called from: 1014 * thread_exit() 1015 */ 1016 void 1017 thread_unlink(struct thread *td) 1018 { 1019 struct proc *p = td->td_proc; 1020 1021 PROC_LOCK_ASSERT(p, MA_OWNED); 1022 #ifdef EPOCH_TRACE 1023 MPASS(SLIST_EMPTY(&td->td_epochs)); 1024 #endif 1025 1026 TAILQ_REMOVE(&p->p_threads, td, td_plist); 1027 p->p_numthreads--; 1028 /* could clear a few other things here */ 1029 /* Must NOT clear links to proc! */ 1030 } 1031 1032 static int 1033 calc_remaining(struct proc *p, int mode) 1034 { 1035 int remaining; 1036 1037 PROC_LOCK_ASSERT(p, MA_OWNED); 1038 PROC_SLOCK_ASSERT(p, MA_OWNED); 1039 if (mode == SINGLE_EXIT) 1040 remaining = p->p_numthreads; 1041 else if (mode == SINGLE_BOUNDARY) 1042 remaining = p->p_numthreads - p->p_boundary_count; 1043 else if (mode == SINGLE_NO_EXIT || mode == SINGLE_ALLPROC) 1044 remaining = p->p_numthreads - p->p_suspcount; 1045 else 1046 panic("calc_remaining: wrong mode %d", mode); 1047 return (remaining); 1048 } 1049 1050 static int 1051 remain_for_mode(int mode) 1052 { 1053 1054 return (mode == SINGLE_ALLPROC ? 0 : 1); 1055 } 1056 1057 static int 1058 weed_inhib(int mode, struct thread *td2, struct proc *p) 1059 { 1060 int wakeup_swapper; 1061 1062 PROC_LOCK_ASSERT(p, MA_OWNED); 1063 PROC_SLOCK_ASSERT(p, MA_OWNED); 1064 THREAD_LOCK_ASSERT(td2, MA_OWNED); 1065 1066 wakeup_swapper = 0; 1067 1068 /* 1069 * Since the thread lock is dropped by the scheduler we have 1070 * to retry to check for races. 1071 */ 1072 restart: 1073 switch (mode) { 1074 case SINGLE_EXIT: 1075 if (TD_IS_SUSPENDED(td2)) { 1076 wakeup_swapper |= thread_unsuspend_one(td2, p, true); 1077 thread_lock(td2); 1078 goto restart; 1079 } 1080 if (TD_CAN_ABORT(td2)) { 1081 wakeup_swapper |= sleepq_abort(td2, EINTR); 1082 return (wakeup_swapper); 1083 } 1084 break; 1085 case SINGLE_BOUNDARY: 1086 case SINGLE_NO_EXIT: 1087 if (TD_IS_SUSPENDED(td2) && 1088 (td2->td_flags & TDF_BOUNDARY) == 0) { 1089 wakeup_swapper |= thread_unsuspend_one(td2, p, false); 1090 thread_lock(td2); 1091 goto restart; 1092 } 1093 if (TD_CAN_ABORT(td2)) { 1094 wakeup_swapper |= sleepq_abort(td2, ERESTART); 1095 return (wakeup_swapper); 1096 } 1097 break; 1098 case SINGLE_ALLPROC: 1099 /* 1100 * ALLPROC suspend tries to avoid spurious EINTR for 1101 * threads sleeping interruptable, by suspending the 1102 * thread directly, similarly to sig_suspend_threads(). 1103 * Since such sleep is not performed at the user 1104 * boundary, TDF_BOUNDARY flag is not set, and TDF_ALLPROCSUSP 1105 * is used to avoid immediate un-suspend. 1106 */ 1107 if (TD_IS_SUSPENDED(td2) && (td2->td_flags & (TDF_BOUNDARY | 1108 TDF_ALLPROCSUSP)) == 0) { 1109 wakeup_swapper |= thread_unsuspend_one(td2, p, false); 1110 thread_lock(td2); 1111 goto restart; 1112 } 1113 if (TD_CAN_ABORT(td2)) { 1114 if ((td2->td_flags & TDF_SBDRY) == 0) { 1115 thread_suspend_one(td2); 1116 td2->td_flags |= TDF_ALLPROCSUSP; 1117 } else { 1118 wakeup_swapper |= sleepq_abort(td2, ERESTART); 1119 return (wakeup_swapper); 1120 } 1121 } 1122 break; 1123 default: 1124 break; 1125 } 1126 thread_unlock(td2); 1127 return (wakeup_swapper); 1128 } 1129 1130 /* 1131 * Enforce single-threading. 1132 * 1133 * Returns 1 if the caller must abort (another thread is waiting to 1134 * exit the process or similar). Process is locked! 1135 * Returns 0 when you are successfully the only thread running. 1136 * A process has successfully single threaded in the suspend mode when 1137 * There are no threads in user mode. Threads in the kernel must be 1138 * allowed to continue until they get to the user boundary. They may even 1139 * copy out their return values and data before suspending. They may however be 1140 * accelerated in reaching the user boundary as we will wake up 1141 * any sleeping threads that are interruptable. (PCATCH). 1142 */ 1143 int 1144 thread_single(struct proc *p, int mode) 1145 { 1146 struct thread *td; 1147 struct thread *td2; 1148 int remaining, wakeup_swapper; 1149 1150 td = curthread; 1151 KASSERT(mode == SINGLE_EXIT || mode == SINGLE_BOUNDARY || 1152 mode == SINGLE_ALLPROC || mode == SINGLE_NO_EXIT, 1153 ("invalid mode %d", mode)); 1154 /* 1155 * If allowing non-ALLPROC singlethreading for non-curproc 1156 * callers, calc_remaining() and remain_for_mode() should be 1157 * adjusted to also account for td->td_proc != p. For now 1158 * this is not implemented because it is not used. 1159 */ 1160 KASSERT((mode == SINGLE_ALLPROC && td->td_proc != p) || 1161 (mode != SINGLE_ALLPROC && td->td_proc == p), 1162 ("mode %d proc %p curproc %p", mode, p, td->td_proc)); 1163 mtx_assert(&Giant, MA_NOTOWNED); 1164 PROC_LOCK_ASSERT(p, MA_OWNED); 1165 1166 if ((p->p_flag & P_HADTHREADS) == 0 && mode != SINGLE_ALLPROC) 1167 return (0); 1168 1169 /* Is someone already single threading? */ 1170 if (p->p_singlethread != NULL && p->p_singlethread != td) 1171 return (1); 1172 1173 if (mode == SINGLE_EXIT) { 1174 p->p_flag |= P_SINGLE_EXIT; 1175 p->p_flag &= ~P_SINGLE_BOUNDARY; 1176 } else { 1177 p->p_flag &= ~P_SINGLE_EXIT; 1178 if (mode == SINGLE_BOUNDARY) 1179 p->p_flag |= P_SINGLE_BOUNDARY; 1180 else 1181 p->p_flag &= ~P_SINGLE_BOUNDARY; 1182 } 1183 if (mode == SINGLE_ALLPROC) 1184 p->p_flag |= P_TOTAL_STOP; 1185 p->p_flag |= P_STOPPED_SINGLE; 1186 PROC_SLOCK(p); 1187 p->p_singlethread = td; 1188 remaining = calc_remaining(p, mode); 1189 while (remaining != remain_for_mode(mode)) { 1190 if (P_SHOULDSTOP(p) != P_STOPPED_SINGLE) 1191 goto stopme; 1192 wakeup_swapper = 0; 1193 FOREACH_THREAD_IN_PROC(p, td2) { 1194 if (td2 == td) 1195 continue; 1196 thread_lock(td2); 1197 td2->td_flags |= TDF_ASTPENDING | TDF_NEEDSUSPCHK; 1198 if (TD_IS_INHIBITED(td2)) { 1199 wakeup_swapper |= weed_inhib(mode, td2, p); 1200 #ifdef SMP 1201 } else if (TD_IS_RUNNING(td2) && td != td2) { 1202 forward_signal(td2); 1203 thread_unlock(td2); 1204 #endif 1205 } else 1206 thread_unlock(td2); 1207 } 1208 if (wakeup_swapper) 1209 kick_proc0(); 1210 remaining = calc_remaining(p, mode); 1211 1212 /* 1213 * Maybe we suspended some threads.. was it enough? 1214 */ 1215 if (remaining == remain_for_mode(mode)) 1216 break; 1217 1218 stopme: 1219 /* 1220 * Wake us up when everyone else has suspended. 1221 * In the mean time we suspend as well. 1222 */ 1223 thread_suspend_switch(td, p); 1224 remaining = calc_remaining(p, mode); 1225 } 1226 if (mode == SINGLE_EXIT) { 1227 /* 1228 * Convert the process to an unthreaded process. The 1229 * SINGLE_EXIT is called by exit1() or execve(), in 1230 * both cases other threads must be retired. 1231 */ 1232 KASSERT(p->p_numthreads == 1, ("Unthreading with >1 threads")); 1233 p->p_singlethread = NULL; 1234 p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT | P_HADTHREADS); 1235 1236 /* 1237 * Wait for any remaining threads to exit cpu_throw(). 1238 */ 1239 while (p->p_exitthreads != 0) { 1240 PROC_SUNLOCK(p); 1241 PROC_UNLOCK(p); 1242 sched_relinquish(td); 1243 PROC_LOCK(p); 1244 PROC_SLOCK(p); 1245 } 1246 } else if (mode == SINGLE_BOUNDARY) { 1247 /* 1248 * Wait until all suspended threads are removed from 1249 * the processors. The thread_suspend_check() 1250 * increments p_boundary_count while it is still 1251 * running, which makes it possible for the execve() 1252 * to destroy vmspace while our other threads are 1253 * still using the address space. 1254 * 1255 * We lock the thread, which is only allowed to 1256 * succeed after context switch code finished using 1257 * the address space. 1258 */ 1259 FOREACH_THREAD_IN_PROC(p, td2) { 1260 if (td2 == td) 1261 continue; 1262 thread_lock(td2); 1263 KASSERT((td2->td_flags & TDF_BOUNDARY) != 0, 1264 ("td %p not on boundary", td2)); 1265 KASSERT(TD_IS_SUSPENDED(td2), 1266 ("td %p is not suspended", td2)); 1267 thread_unlock(td2); 1268 } 1269 } 1270 PROC_SUNLOCK(p); 1271 return (0); 1272 } 1273 1274 bool 1275 thread_suspend_check_needed(void) 1276 { 1277 struct proc *p; 1278 struct thread *td; 1279 1280 td = curthread; 1281 p = td->td_proc; 1282 PROC_LOCK_ASSERT(p, MA_OWNED); 1283 return (P_SHOULDSTOP(p) || ((p->p_flag & P_TRACED) != 0 && 1284 (td->td_dbgflags & TDB_SUSPEND) != 0)); 1285 } 1286 1287 /* 1288 * Called in from locations that can safely check to see 1289 * whether we have to suspend or at least throttle for a 1290 * single-thread event (e.g. fork). 1291 * 1292 * Such locations include userret(). 1293 * If the "return_instead" argument is non zero, the thread must be able to 1294 * accept 0 (caller may continue), or 1 (caller must abort) as a result. 1295 * 1296 * The 'return_instead' argument tells the function if it may do a 1297 * thread_exit() or suspend, or whether the caller must abort and back 1298 * out instead. 1299 * 1300 * If the thread that set the single_threading request has set the 1301 * P_SINGLE_EXIT bit in the process flags then this call will never return 1302 * if 'return_instead' is false, but will exit. 1303 * 1304 * P_SINGLE_EXIT | return_instead == 0| return_instead != 0 1305 *---------------+--------------------+--------------------- 1306 * 0 | returns 0 | returns 0 or 1 1307 * | when ST ends | immediately 1308 *---------------+--------------------+--------------------- 1309 * 1 | thread exits | returns 1 1310 * | | immediately 1311 * 0 = thread_exit() or suspension ok, 1312 * other = return error instead of stopping the thread. 1313 * 1314 * While a full suspension is under effect, even a single threading 1315 * thread would be suspended if it made this call (but it shouldn't). 1316 * This call should only be made from places where 1317 * thread_exit() would be safe as that may be the outcome unless 1318 * return_instead is set. 1319 */ 1320 int 1321 thread_suspend_check(int return_instead) 1322 { 1323 struct thread *td; 1324 struct proc *p; 1325 int wakeup_swapper; 1326 1327 td = curthread; 1328 p = td->td_proc; 1329 mtx_assert(&Giant, MA_NOTOWNED); 1330 PROC_LOCK_ASSERT(p, MA_OWNED); 1331 while (thread_suspend_check_needed()) { 1332 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) { 1333 KASSERT(p->p_singlethread != NULL, 1334 ("singlethread not set")); 1335 /* 1336 * The only suspension in action is a 1337 * single-threading. Single threader need not stop. 1338 * It is safe to access p->p_singlethread unlocked 1339 * because it can only be set to our address by us. 1340 */ 1341 if (p->p_singlethread == td) 1342 return (0); /* Exempt from stopping. */ 1343 } 1344 if ((p->p_flag & P_SINGLE_EXIT) && return_instead) 1345 return (EINTR); 1346 1347 /* Should we goto user boundary if we didn't come from there? */ 1348 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE && 1349 (p->p_flag & P_SINGLE_BOUNDARY) && return_instead) 1350 return (ERESTART); 1351 1352 /* 1353 * Ignore suspend requests if they are deferred. 1354 */ 1355 if ((td->td_flags & TDF_SBDRY) != 0) { 1356 KASSERT(return_instead, 1357 ("TDF_SBDRY set for unsafe thread_suspend_check")); 1358 KASSERT((td->td_flags & (TDF_SEINTR | TDF_SERESTART)) != 1359 (TDF_SEINTR | TDF_SERESTART), 1360 ("both TDF_SEINTR and TDF_SERESTART")); 1361 return (TD_SBDRY_INTR(td) ? TD_SBDRY_ERRNO(td) : 0); 1362 } 1363 1364 /* 1365 * If the process is waiting for us to exit, 1366 * this thread should just suicide. 1367 * Assumes that P_SINGLE_EXIT implies P_STOPPED_SINGLE. 1368 */ 1369 if ((p->p_flag & P_SINGLE_EXIT) && (p->p_singlethread != td)) { 1370 PROC_UNLOCK(p); 1371 1372 /* 1373 * Allow Linux emulation layer to do some work 1374 * before thread suicide. 1375 */ 1376 if (__predict_false(p->p_sysent->sv_thread_detach != NULL)) 1377 (p->p_sysent->sv_thread_detach)(td); 1378 umtx_thread_exit(td); 1379 kern_thr_exit(td); 1380 panic("stopped thread did not exit"); 1381 } 1382 1383 PROC_SLOCK(p); 1384 thread_stopped(p); 1385 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) { 1386 if (p->p_numthreads == p->p_suspcount + 1) { 1387 thread_lock(p->p_singlethread); 1388 wakeup_swapper = thread_unsuspend_one( 1389 p->p_singlethread, p, false); 1390 if (wakeup_swapper) 1391 kick_proc0(); 1392 } 1393 } 1394 PROC_UNLOCK(p); 1395 thread_lock(td); 1396 /* 1397 * When a thread suspends, it just 1398 * gets taken off all queues. 1399 */ 1400 thread_suspend_one(td); 1401 if (return_instead == 0) { 1402 p->p_boundary_count++; 1403 td->td_flags |= TDF_BOUNDARY; 1404 } 1405 PROC_SUNLOCK(p); 1406 mi_switch(SW_INVOL | SWT_SUSPEND); 1407 PROC_LOCK(p); 1408 } 1409 return (0); 1410 } 1411 1412 /* 1413 * Check for possible stops and suspensions while executing a 1414 * casueword or similar transiently failing operation. 1415 * 1416 * The sleep argument controls whether the function can handle a stop 1417 * request itself or it should return ERESTART and the request is 1418 * proceed at the kernel/user boundary in ast. 1419 * 1420 * Typically, when retrying due to casueword(9) failure (rv == 1), we 1421 * should handle the stop requests there, with exception of cases when 1422 * the thread owns a kernel resource, for instance busied the umtx 1423 * key, or when functions return immediately if thread_check_susp() 1424 * returned non-zero. On the other hand, retrying the whole lock 1425 * operation, we better not stop there but delegate the handling to 1426 * ast. 1427 * 1428 * If the request is for thread termination P_SINGLE_EXIT, we cannot 1429 * handle it at all, and simply return EINTR. 1430 */ 1431 int 1432 thread_check_susp(struct thread *td, bool sleep) 1433 { 1434 struct proc *p; 1435 int error; 1436 1437 /* 1438 * The check for TDF_NEEDSUSPCHK is racy, but it is enough to 1439 * eventually break the lockstep loop. 1440 */ 1441 if ((td->td_flags & TDF_NEEDSUSPCHK) == 0) 1442 return (0); 1443 error = 0; 1444 p = td->td_proc; 1445 PROC_LOCK(p); 1446 if (p->p_flag & P_SINGLE_EXIT) 1447 error = EINTR; 1448 else if (P_SHOULDSTOP(p) || 1449 ((p->p_flag & P_TRACED) && (td->td_dbgflags & TDB_SUSPEND))) 1450 error = sleep ? thread_suspend_check(0) : ERESTART; 1451 PROC_UNLOCK(p); 1452 return (error); 1453 } 1454 1455 void 1456 thread_suspend_switch(struct thread *td, struct proc *p) 1457 { 1458 1459 KASSERT(!TD_IS_SUSPENDED(td), ("already suspended")); 1460 PROC_LOCK_ASSERT(p, MA_OWNED); 1461 PROC_SLOCK_ASSERT(p, MA_OWNED); 1462 /* 1463 * We implement thread_suspend_one in stages here to avoid 1464 * dropping the proc lock while the thread lock is owned. 1465 */ 1466 if (p == td->td_proc) { 1467 thread_stopped(p); 1468 p->p_suspcount++; 1469 } 1470 PROC_UNLOCK(p); 1471 thread_lock(td); 1472 td->td_flags &= ~TDF_NEEDSUSPCHK; 1473 TD_SET_SUSPENDED(td); 1474 sched_sleep(td, 0); 1475 PROC_SUNLOCK(p); 1476 DROP_GIANT(); 1477 mi_switch(SW_VOL | SWT_SUSPEND); 1478 PICKUP_GIANT(); 1479 PROC_LOCK(p); 1480 PROC_SLOCK(p); 1481 } 1482 1483 void 1484 thread_suspend_one(struct thread *td) 1485 { 1486 struct proc *p; 1487 1488 p = td->td_proc; 1489 PROC_SLOCK_ASSERT(p, MA_OWNED); 1490 THREAD_LOCK_ASSERT(td, MA_OWNED); 1491 KASSERT(!TD_IS_SUSPENDED(td), ("already suspended")); 1492 p->p_suspcount++; 1493 td->td_flags &= ~TDF_NEEDSUSPCHK; 1494 TD_SET_SUSPENDED(td); 1495 sched_sleep(td, 0); 1496 } 1497 1498 static int 1499 thread_unsuspend_one(struct thread *td, struct proc *p, bool boundary) 1500 { 1501 1502 THREAD_LOCK_ASSERT(td, MA_OWNED); 1503 KASSERT(TD_IS_SUSPENDED(td), ("Thread not suspended")); 1504 TD_CLR_SUSPENDED(td); 1505 td->td_flags &= ~TDF_ALLPROCSUSP; 1506 if (td->td_proc == p) { 1507 PROC_SLOCK_ASSERT(p, MA_OWNED); 1508 p->p_suspcount--; 1509 if (boundary && (td->td_flags & TDF_BOUNDARY) != 0) { 1510 td->td_flags &= ~TDF_BOUNDARY; 1511 p->p_boundary_count--; 1512 } 1513 } 1514 return (setrunnable(td, 0)); 1515 } 1516 1517 /* 1518 * Allow all threads blocked by single threading to continue running. 1519 */ 1520 void 1521 thread_unsuspend(struct proc *p) 1522 { 1523 struct thread *td; 1524 int wakeup_swapper; 1525 1526 PROC_LOCK_ASSERT(p, MA_OWNED); 1527 PROC_SLOCK_ASSERT(p, MA_OWNED); 1528 wakeup_swapper = 0; 1529 if (!P_SHOULDSTOP(p)) { 1530 FOREACH_THREAD_IN_PROC(p, td) { 1531 thread_lock(td); 1532 if (TD_IS_SUSPENDED(td)) { 1533 wakeup_swapper |= thread_unsuspend_one(td, p, 1534 true); 1535 } else 1536 thread_unlock(td); 1537 } 1538 } else if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE && 1539 p->p_numthreads == p->p_suspcount) { 1540 /* 1541 * Stopping everything also did the job for the single 1542 * threading request. Now we've downgraded to single-threaded, 1543 * let it continue. 1544 */ 1545 if (p->p_singlethread->td_proc == p) { 1546 thread_lock(p->p_singlethread); 1547 wakeup_swapper = thread_unsuspend_one( 1548 p->p_singlethread, p, false); 1549 } 1550 } 1551 if (wakeup_swapper) 1552 kick_proc0(); 1553 } 1554 1555 /* 1556 * End the single threading mode.. 1557 */ 1558 void 1559 thread_single_end(struct proc *p, int mode) 1560 { 1561 struct thread *td; 1562 int wakeup_swapper; 1563 1564 KASSERT(mode == SINGLE_EXIT || mode == SINGLE_BOUNDARY || 1565 mode == SINGLE_ALLPROC || mode == SINGLE_NO_EXIT, 1566 ("invalid mode %d", mode)); 1567 PROC_LOCK_ASSERT(p, MA_OWNED); 1568 KASSERT((mode == SINGLE_ALLPROC && (p->p_flag & P_TOTAL_STOP) != 0) || 1569 (mode != SINGLE_ALLPROC && (p->p_flag & P_TOTAL_STOP) == 0), 1570 ("mode %d does not match P_TOTAL_STOP", mode)); 1571 KASSERT(mode == SINGLE_ALLPROC || p->p_singlethread == curthread, 1572 ("thread_single_end from other thread %p %p", 1573 curthread, p->p_singlethread)); 1574 KASSERT(mode != SINGLE_BOUNDARY || 1575 (p->p_flag & P_SINGLE_BOUNDARY) != 0, 1576 ("mis-matched SINGLE_BOUNDARY flags %x", p->p_flag)); 1577 p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT | P_SINGLE_BOUNDARY | 1578 P_TOTAL_STOP); 1579 PROC_SLOCK(p); 1580 p->p_singlethread = NULL; 1581 wakeup_swapper = 0; 1582 /* 1583 * If there are other threads they may now run, 1584 * unless of course there is a blanket 'stop order' 1585 * on the process. The single threader must be allowed 1586 * to continue however as this is a bad place to stop. 1587 */ 1588 if (p->p_numthreads != remain_for_mode(mode) && !P_SHOULDSTOP(p)) { 1589 FOREACH_THREAD_IN_PROC(p, td) { 1590 thread_lock(td); 1591 if (TD_IS_SUSPENDED(td)) { 1592 wakeup_swapper |= thread_unsuspend_one(td, p, 1593 mode == SINGLE_BOUNDARY); 1594 } else 1595 thread_unlock(td); 1596 } 1597 } 1598 KASSERT(mode != SINGLE_BOUNDARY || p->p_boundary_count == 0, 1599 ("inconsistent boundary count %d", p->p_boundary_count)); 1600 PROC_SUNLOCK(p); 1601 if (wakeup_swapper) 1602 kick_proc0(); 1603 } 1604 1605 /* 1606 * Locate a thread by number and return with proc lock held. 1607 * 1608 * thread exit establishes proc -> tidhash lock ordering, but lookup 1609 * takes tidhash first and needs to return locked proc. 1610 * 1611 * The problem is worked around by relying on type-safety of both 1612 * structures and doing the work in 2 steps: 1613 * - tidhash-locked lookup which saves both thread and proc pointers 1614 * - proc-locked verification that the found thread still matches 1615 */ 1616 static bool 1617 tdfind_hash(lwpid_t tid, pid_t pid, struct proc **pp, struct thread **tdp) 1618 { 1619 #define RUN_THRESH 16 1620 struct proc *p; 1621 struct thread *td; 1622 int run; 1623 bool locked; 1624 1625 run = 0; 1626 rw_rlock(TIDHASHLOCK(tid)); 1627 locked = true; 1628 LIST_FOREACH(td, TIDHASH(tid), td_hash) { 1629 if (td->td_tid != tid) { 1630 run++; 1631 continue; 1632 } 1633 p = td->td_proc; 1634 if (pid != -1 && p->p_pid != pid) { 1635 td = NULL; 1636 break; 1637 } 1638 if (run > RUN_THRESH) { 1639 if (rw_try_upgrade(TIDHASHLOCK(tid))) { 1640 LIST_REMOVE(td, td_hash); 1641 LIST_INSERT_HEAD(TIDHASH(td->td_tid), 1642 td, td_hash); 1643 rw_wunlock(TIDHASHLOCK(tid)); 1644 locked = false; 1645 break; 1646 } 1647 } 1648 break; 1649 } 1650 if (locked) 1651 rw_runlock(TIDHASHLOCK(tid)); 1652 if (td == NULL) 1653 return (false); 1654 *pp = p; 1655 *tdp = td; 1656 return (true); 1657 } 1658 1659 struct thread * 1660 tdfind(lwpid_t tid, pid_t pid) 1661 { 1662 struct proc *p; 1663 struct thread *td; 1664 1665 td = curthread; 1666 if (td->td_tid == tid) { 1667 if (pid != -1 && td->td_proc->p_pid != pid) 1668 return (NULL); 1669 PROC_LOCK(td->td_proc); 1670 return (td); 1671 } 1672 1673 for (;;) { 1674 if (!tdfind_hash(tid, pid, &p, &td)) 1675 return (NULL); 1676 PROC_LOCK(p); 1677 if (td->td_tid != tid) { 1678 PROC_UNLOCK(p); 1679 continue; 1680 } 1681 if (td->td_proc != p) { 1682 PROC_UNLOCK(p); 1683 continue; 1684 } 1685 if (p->p_state == PRS_NEW) { 1686 PROC_UNLOCK(p); 1687 return (NULL); 1688 } 1689 return (td); 1690 } 1691 } 1692 1693 void 1694 tidhash_add(struct thread *td) 1695 { 1696 rw_wlock(TIDHASHLOCK(td->td_tid)); 1697 LIST_INSERT_HEAD(TIDHASH(td->td_tid), td, td_hash); 1698 rw_wunlock(TIDHASHLOCK(td->td_tid)); 1699 } 1700 1701 void 1702 tidhash_remove(struct thread *td) 1703 { 1704 1705 rw_wlock(TIDHASHLOCK(td->td_tid)); 1706 LIST_REMOVE(td, td_hash); 1707 rw_wunlock(TIDHASHLOCK(td->td_tid)); 1708 }
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