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/msan.h> 42 #include <sys/mutex.h> 43 #include <sys/proc.h> 44 #include <sys/bitstring.h> 45 #include <sys/epoch.h> 46 #include <sys/rangelock.h> 47 #include <sys/resourcevar.h> 48 #include <sys/sdt.h> 49 #include <sys/smp.h> 50 #include <sys/sched.h> 51 #include <sys/sleepqueue.h> 52 #include <sys/selinfo.h> 53 #include <sys/syscallsubr.h> 54 #include <sys/dtrace_bsd.h> 55 #include <sys/sysent.h> 56 #include <sys/turnstile.h> 57 #include <sys/taskqueue.h> 58 #include <sys/ktr.h> 59 #include <sys/rwlock.h> 60 #include <sys/umtxvar.h> 61 #include <sys/vmmeter.h> 62 #include <sys/cpuset.h> 63 #ifdef HWPMC_HOOKS 64 #include <sys/pmckern.h> 65 #endif 66 #include <sys/priv.h> 67 68 #include <security/audit/audit.h> 69 70 #include <vm/pmap.h> 71 #include <vm/vm.h> 72 #include <vm/vm_extern.h> 73 #include <vm/uma.h> 74 #include <vm/vm_phys.h> 75 #include <sys/eventhandler.h> 76 77 /* 78 * Asserts below verify the stability of struct thread and struct proc 79 * layout, as exposed by KBI to modules. On head, the KBI is allowed 80 * to drift, change to the structures must be accompanied by the 81 * assert update. 82 * 83 * On the stable branches after KBI freeze, conditions must not be 84 * violated. Typically new fields are moved to the end of the 85 * structures. 86 */ 87 #ifdef __amd64__ 88 _Static_assert(offsetof(struct thread, td_flags) == 0x108, 89 "struct thread KBI td_flags"); 90 _Static_assert(offsetof(struct thread, td_pflags) == 0x114, 91 "struct thread KBI td_pflags"); 92 _Static_assert(offsetof(struct thread, td_frame) == 0x4b0, 93 "struct thread KBI td_frame"); 94 _Static_assert(offsetof(struct thread, td_emuldata) == 0x6c0, 95 "struct thread KBI td_emuldata"); 96 _Static_assert(offsetof(struct proc, p_flag) == 0xb8, 97 "struct proc KBI p_flag"); 98 _Static_assert(offsetof(struct proc, p_pid) == 0xc4, 99 "struct proc KBI p_pid"); 100 _Static_assert(offsetof(struct proc, p_filemon) == 0x3c8, 101 "struct proc KBI p_filemon"); 102 _Static_assert(offsetof(struct proc, p_comm) == 0x3e0, 103 "struct proc KBI p_comm"); 104 _Static_assert(offsetof(struct proc, p_emuldata) == 0x4c8, 105 "struct proc KBI p_emuldata"); 106 #endif 107 #ifdef __i386__ 108 _Static_assert(offsetof(struct thread, td_flags) == 0x9c, 109 "struct thread KBI td_flags"); 110 _Static_assert(offsetof(struct thread, td_pflags) == 0xa8, 111 "struct thread KBI td_pflags"); 112 _Static_assert(offsetof(struct thread, td_frame) == 0x30c, 113 "struct thread KBI td_frame"); 114 _Static_assert(offsetof(struct thread, td_emuldata) == 0x350, 115 "struct thread KBI td_emuldata"); 116 _Static_assert(offsetof(struct proc, p_flag) == 0x6c, 117 "struct proc KBI p_flag"); 118 _Static_assert(offsetof(struct proc, p_pid) == 0x78, 119 "struct proc KBI p_pid"); 120 _Static_assert(offsetof(struct proc, p_filemon) == 0x270, 121 "struct proc KBI p_filemon"); 122 _Static_assert(offsetof(struct proc, p_comm) == 0x284, 123 "struct proc KBI p_comm"); 124 _Static_assert(offsetof(struct proc, p_emuldata) == 0x310, 125 "struct proc KBI p_emuldata"); 126 #endif 127 128 SDT_PROVIDER_DECLARE(proc); 129 SDT_PROBE_DEFINE(proc, , , lwp__exit); 130 131 /* 132 * thread related storage. 133 */ 134 static uma_zone_t thread_zone; 135 136 struct thread_domain_data { 137 struct thread *tdd_zombies; 138 int tdd_reapticks; 139 } __aligned(CACHE_LINE_SIZE); 140 141 static struct thread_domain_data thread_domain_data[MAXMEMDOM]; 142 143 static struct task thread_reap_task; 144 static struct callout thread_reap_callout; 145 146 static void thread_zombie(struct thread *); 147 static void thread_reap(void); 148 static void thread_reap_all(void); 149 static void thread_reap_task_cb(void *, int); 150 static void thread_reap_callout_cb(void *); 151 static int thread_unsuspend_one(struct thread *td, struct proc *p, 152 bool boundary); 153 static void thread_free_batched(struct thread *td); 154 155 static __exclusive_cache_line struct mtx tid_lock; 156 static bitstr_t *tid_bitmap; 157 158 static MALLOC_DEFINE(M_TIDHASH, "tidhash", "thread hash"); 159 160 static int maxthread; 161 SYSCTL_INT(_kern, OID_AUTO, maxthread, CTLFLAG_RDTUN, 162 &maxthread, 0, "Maximum number of threads"); 163 164 static __exclusive_cache_line int nthreads; 165 166 static LIST_HEAD(tidhashhead, thread) *tidhashtbl; 167 static u_long tidhash; 168 static u_long tidhashlock; 169 static struct rwlock *tidhashtbl_lock; 170 #define TIDHASH(tid) (&tidhashtbl[(tid) & tidhash]) 171 #define TIDHASHLOCK(tid) (&tidhashtbl_lock[(tid) & tidhashlock]) 172 173 EVENTHANDLER_LIST_DEFINE(thread_ctor); 174 EVENTHANDLER_LIST_DEFINE(thread_dtor); 175 EVENTHANDLER_LIST_DEFINE(thread_init); 176 EVENTHANDLER_LIST_DEFINE(thread_fini); 177 178 static bool 179 thread_count_inc_try(void) 180 { 181 int nthreads_new; 182 183 nthreads_new = atomic_fetchadd_int(&nthreads, 1) + 1; 184 if (nthreads_new >= maxthread - 100) { 185 if (priv_check_cred(curthread->td_ucred, PRIV_MAXPROC) != 0 || 186 nthreads_new >= maxthread) { 187 atomic_subtract_int(&nthreads, 1); 188 return (false); 189 } 190 } 191 return (true); 192 } 193 194 static bool 195 thread_count_inc(void) 196 { 197 static struct timeval lastfail; 198 static int curfail; 199 200 thread_reap(); 201 if (thread_count_inc_try()) { 202 return (true); 203 } 204 205 thread_reap_all(); 206 if (thread_count_inc_try()) { 207 return (true); 208 } 209 210 if (ppsratecheck(&lastfail, &curfail, 1)) { 211 printf("maxthread limit exceeded by uid %u " 212 "(pid %d); consider increasing kern.maxthread\n", 213 curthread->td_ucred->cr_ruid, curproc->p_pid); 214 } 215 return (false); 216 } 217 218 static void 219 thread_count_sub(int n) 220 { 221 222 atomic_subtract_int(&nthreads, n); 223 } 224 225 static void 226 thread_count_dec(void) 227 { 228 229 thread_count_sub(1); 230 } 231 232 static lwpid_t 233 tid_alloc(void) 234 { 235 static lwpid_t trytid; 236 lwpid_t tid; 237 238 mtx_lock(&tid_lock); 239 /* 240 * It is an invariant that the bitmap is big enough to hold maxthread 241 * IDs. If we got to this point there has to be at least one free. 242 */ 243 if (trytid >= maxthread) 244 trytid = 0; 245 bit_ffc_at(tid_bitmap, trytid, maxthread, &tid); 246 if (tid == -1) { 247 KASSERT(trytid != 0, ("unexpectedly ran out of IDs")); 248 trytid = 0; 249 bit_ffc_at(tid_bitmap, trytid, maxthread, &tid); 250 KASSERT(tid != -1, ("unexpectedly ran out of IDs")); 251 } 252 bit_set(tid_bitmap, tid); 253 trytid = tid + 1; 254 mtx_unlock(&tid_lock); 255 return (tid + NO_PID); 256 } 257 258 static void 259 tid_free_locked(lwpid_t rtid) 260 { 261 lwpid_t tid; 262 263 mtx_assert(&tid_lock, MA_OWNED); 264 KASSERT(rtid >= NO_PID, 265 ("%s: invalid tid %d\n", __func__, rtid)); 266 tid = rtid - NO_PID; 267 KASSERT(bit_test(tid_bitmap, tid) != 0, 268 ("thread ID %d not allocated\n", rtid)); 269 bit_clear(tid_bitmap, tid); 270 } 271 272 static void 273 tid_free(lwpid_t rtid) 274 { 275 276 mtx_lock(&tid_lock); 277 tid_free_locked(rtid); 278 mtx_unlock(&tid_lock); 279 } 280 281 static void 282 tid_free_batch(lwpid_t *batch, int n) 283 { 284 int i; 285 286 mtx_lock(&tid_lock); 287 for (i = 0; i < n; i++) { 288 tid_free_locked(batch[i]); 289 } 290 mtx_unlock(&tid_lock); 291 } 292 293 /* 294 * Batching for thread reapping. 295 */ 296 struct tidbatch { 297 lwpid_t tab[16]; 298 int n; 299 }; 300 301 static void 302 tidbatch_prep(struct tidbatch *tb) 303 { 304 305 tb->n = 0; 306 } 307 308 static void 309 tidbatch_add(struct tidbatch *tb, struct thread *td) 310 { 311 312 KASSERT(tb->n < nitems(tb->tab), 313 ("%s: count too high %d", __func__, tb->n)); 314 tb->tab[tb->n] = td->td_tid; 315 tb->n++; 316 } 317 318 static void 319 tidbatch_process(struct tidbatch *tb) 320 { 321 322 KASSERT(tb->n <= nitems(tb->tab), 323 ("%s: count too high %d", __func__, tb->n)); 324 if (tb->n == nitems(tb->tab)) { 325 tid_free_batch(tb->tab, tb->n); 326 tb->n = 0; 327 } 328 } 329 330 static void 331 tidbatch_final(struct tidbatch *tb) 332 { 333 334 KASSERT(tb->n <= nitems(tb->tab), 335 ("%s: count too high %d", __func__, tb->n)); 336 if (tb->n != 0) { 337 tid_free_batch(tb->tab, tb->n); 338 } 339 } 340 341 /* 342 * Prepare a thread for use. 343 */ 344 static int 345 thread_ctor(void *mem, int size, void *arg, int flags) 346 { 347 struct thread *td; 348 349 td = (struct thread *)mem; 350 TD_SET_STATE(td, TDS_INACTIVE); 351 td->td_lastcpu = td->td_oncpu = NOCPU; 352 353 /* 354 * Note that td_critnest begins life as 1 because the thread is not 355 * running and is thereby implicitly waiting to be on the receiving 356 * end of a context switch. 357 */ 358 td->td_critnest = 1; 359 td->td_lend_user_pri = PRI_MAX; 360 #ifdef AUDIT 361 audit_thread_alloc(td); 362 #endif 363 #ifdef KDTRACE_HOOKS 364 kdtrace_thread_ctor(td); 365 #endif 366 umtx_thread_alloc(td); 367 MPASS(td->td_sel == NULL); 368 return (0); 369 } 370 371 /* 372 * Reclaim a thread after use. 373 */ 374 static void 375 thread_dtor(void *mem, int size, void *arg) 376 { 377 struct thread *td; 378 379 td = (struct thread *)mem; 380 381 #ifdef INVARIANTS 382 /* Verify that this thread is in a safe state to free. */ 383 switch (TD_GET_STATE(td)) { 384 case TDS_INHIBITED: 385 case TDS_RUNNING: 386 case TDS_CAN_RUN: 387 case TDS_RUNQ: 388 /* 389 * We must never unlink a thread that is in one of 390 * these states, because it is currently active. 391 */ 392 panic("bad state for thread unlinking"); 393 /* NOTREACHED */ 394 case TDS_INACTIVE: 395 break; 396 default: 397 panic("bad thread state"); 398 /* NOTREACHED */ 399 } 400 #endif 401 #ifdef AUDIT 402 audit_thread_free(td); 403 #endif 404 #ifdef KDTRACE_HOOKS 405 kdtrace_thread_dtor(td); 406 #endif 407 /* Free all OSD associated to this thread. */ 408 osd_thread_exit(td); 409 ast_kclear(td); 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(M_WAITOK); 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 static void 482 ast_suspend(struct thread *td, int tda __unused) 483 { 484 struct proc *p; 485 486 p = td->td_proc; 487 /* 488 * We need to check to see if we have to exit or wait due to a 489 * single threading requirement or some other STOP condition. 490 */ 491 PROC_LOCK(p); 492 thread_suspend_check(0); 493 PROC_UNLOCK(p); 494 } 495 496 extern int max_threads_per_proc; 497 498 /* 499 * Initialize global thread allocation resources. 500 */ 501 void 502 threadinit(void) 503 { 504 u_long i; 505 lwpid_t tid0; 506 507 /* 508 * Place an upper limit on threads which can be allocated. 509 * 510 * Note that other factors may make the de facto limit much lower. 511 * 512 * Platform limits are somewhat arbitrary but deemed "more than good 513 * enough" for the foreseable future. 514 */ 515 if (maxthread == 0) { 516 #ifdef _LP64 517 maxthread = MIN(maxproc * max_threads_per_proc, 1000000); 518 #else 519 maxthread = MIN(maxproc * max_threads_per_proc, 100000); 520 #endif 521 } 522 523 mtx_init(&tid_lock, "TID lock", NULL, MTX_DEF); 524 tid_bitmap = bit_alloc(maxthread, M_TIDHASH, M_WAITOK); 525 /* 526 * Handle thread0. 527 */ 528 thread_count_inc(); 529 tid0 = tid_alloc(); 530 if (tid0 != THREAD0_TID) 531 panic("tid0 %d != %d\n", tid0, THREAD0_TID); 532 533 thread_zone = uma_zcreate("THREAD", sched_sizeof_thread(), 534 thread_ctor, thread_dtor, thread_init, thread_fini, 535 32 - 1, UMA_ZONE_NOFREE); 536 tidhashtbl = hashinit(maxproc / 2, M_TIDHASH, &tidhash); 537 tidhashlock = (tidhash + 1) / 64; 538 if (tidhashlock > 0) 539 tidhashlock--; 540 tidhashtbl_lock = malloc(sizeof(*tidhashtbl_lock) * (tidhashlock + 1), 541 M_TIDHASH, M_WAITOK | M_ZERO); 542 for (i = 0; i < tidhashlock + 1; i++) 543 rw_init(&tidhashtbl_lock[i], "tidhash"); 544 545 TASK_INIT(&thread_reap_task, 0, thread_reap_task_cb, NULL); 546 callout_init(&thread_reap_callout, 1); 547 callout_reset(&thread_reap_callout, 5 * hz, 548 thread_reap_callout_cb, NULL); 549 ast_register(TDA_SUSPEND, ASTR_ASTF_REQUIRED, 0, ast_suspend); 550 } 551 552 /* 553 * Place an unused thread on the zombie list. 554 */ 555 void 556 thread_zombie(struct thread *td) 557 { 558 struct thread_domain_data *tdd; 559 struct thread *ztd; 560 561 tdd = &thread_domain_data[td->td_allocdomain]; 562 ztd = atomic_load_ptr(&tdd->tdd_zombies); 563 for (;;) { 564 td->td_zombie = ztd; 565 if (atomic_fcmpset_rel_ptr((uintptr_t *)&tdd->tdd_zombies, 566 (uintptr_t *)&ztd, (uintptr_t)td)) 567 break; 568 continue; 569 } 570 } 571 572 /* 573 * Release a thread that has exited after cpu_throw(). 574 */ 575 void 576 thread_stash(struct thread *td) 577 { 578 atomic_subtract_rel_int(&td->td_proc->p_exitthreads, 1); 579 thread_zombie(td); 580 } 581 582 /* 583 * Reap zombies from passed domain. 584 */ 585 static void 586 thread_reap_domain(struct thread_domain_data *tdd) 587 { 588 struct thread *itd, *ntd; 589 struct tidbatch tidbatch; 590 struct credbatch credbatch; 591 int tdcount; 592 struct plimit *lim; 593 int limcount; 594 595 /* 596 * Reading upfront is pessimal if followed by concurrent atomic_swap, 597 * but most of the time the list is empty. 598 */ 599 if (tdd->tdd_zombies == NULL) 600 return; 601 602 itd = (struct thread *)atomic_swap_ptr((uintptr_t *)&tdd->tdd_zombies, 603 (uintptr_t)NULL); 604 if (itd == NULL) 605 return; 606 607 /* 608 * Multiple CPUs can get here, the race is fine as ticks is only 609 * advisory. 610 */ 611 tdd->tdd_reapticks = ticks; 612 613 tidbatch_prep(&tidbatch); 614 credbatch_prep(&credbatch); 615 tdcount = 0; 616 lim = NULL; 617 limcount = 0; 618 619 while (itd != NULL) { 620 ntd = itd->td_zombie; 621 EVENTHANDLER_DIRECT_INVOKE(thread_dtor, itd); 622 tidbatch_add(&tidbatch, itd); 623 credbatch_add(&credbatch, itd); 624 MPASS(itd->td_limit != NULL); 625 if (lim != itd->td_limit) { 626 if (limcount != 0) { 627 lim_freen(lim, limcount); 628 limcount = 0; 629 } 630 } 631 lim = itd->td_limit; 632 limcount++; 633 thread_free_batched(itd); 634 tidbatch_process(&tidbatch); 635 credbatch_process(&credbatch); 636 tdcount++; 637 if (tdcount == 32) { 638 thread_count_sub(tdcount); 639 tdcount = 0; 640 } 641 itd = ntd; 642 } 643 644 tidbatch_final(&tidbatch); 645 credbatch_final(&credbatch); 646 if (tdcount != 0) { 647 thread_count_sub(tdcount); 648 } 649 MPASS(limcount != 0); 650 lim_freen(lim, limcount); 651 } 652 653 /* 654 * Reap zombies from all domains. 655 */ 656 static void 657 thread_reap_all(void) 658 { 659 struct thread_domain_data *tdd; 660 int i, domain; 661 662 domain = PCPU_GET(domain); 663 for (i = 0; i < vm_ndomains; i++) { 664 tdd = &thread_domain_data[(i + domain) % vm_ndomains]; 665 thread_reap_domain(tdd); 666 } 667 } 668 669 /* 670 * Reap zombies from local domain. 671 */ 672 static void 673 thread_reap(void) 674 { 675 struct thread_domain_data *tdd; 676 int domain; 677 678 domain = PCPU_GET(domain); 679 tdd = &thread_domain_data[domain]; 680 681 thread_reap_domain(tdd); 682 } 683 684 static void 685 thread_reap_task_cb(void *arg __unused, int pending __unused) 686 { 687 688 thread_reap_all(); 689 } 690 691 static void 692 thread_reap_callout_cb(void *arg __unused) 693 { 694 struct thread_domain_data *tdd; 695 int i, cticks, lticks; 696 bool wantreap; 697 698 wantreap = false; 699 cticks = atomic_load_int(&ticks); 700 for (i = 0; i < vm_ndomains; i++) { 701 tdd = &thread_domain_data[i]; 702 lticks = tdd->tdd_reapticks; 703 if (tdd->tdd_zombies != NULL && 704 (u_int)(cticks - lticks) > 5 * hz) { 705 wantreap = true; 706 break; 707 } 708 } 709 710 if (wantreap) 711 taskqueue_enqueue(taskqueue_thread, &thread_reap_task); 712 callout_reset(&thread_reap_callout, 5 * hz, 713 thread_reap_callout_cb, NULL); 714 } 715 716 /* 717 * Calling this function guarantees that any thread that exited before 718 * the call is reaped when the function returns. By 'exited' we mean 719 * a thread removed from the process linkage with thread_unlink(). 720 * Practically this means that caller must lock/unlock corresponding 721 * process lock before the call, to synchronize with thread_exit(). 722 */ 723 void 724 thread_reap_barrier(void) 725 { 726 struct task *t; 727 728 /* 729 * First do context switches to each CPU to ensure that all 730 * PCPU pc_deadthreads are moved to zombie list. 731 */ 732 quiesce_all_cpus("", PDROP); 733 734 /* 735 * Second, fire the task in the same thread as normal 736 * thread_reap() is done, to serialize reaping. 737 */ 738 t = malloc(sizeof(*t), M_TEMP, M_WAITOK); 739 TASK_INIT(t, 0, thread_reap_task_cb, t); 740 taskqueue_enqueue(taskqueue_thread, t); 741 taskqueue_drain(taskqueue_thread, t); 742 free(t, M_TEMP); 743 } 744 745 /* 746 * Allocate a thread. 747 */ 748 struct thread * 749 thread_alloc(int pages) 750 { 751 struct thread *td; 752 lwpid_t tid; 753 754 if (!thread_count_inc()) { 755 return (NULL); 756 } 757 758 tid = tid_alloc(); 759 td = uma_zalloc(thread_zone, M_WAITOK); 760 KASSERT(td->td_kstack == 0, ("thread_alloc got thread with kstack")); 761 if (!vm_thread_new(td, pages)) { 762 uma_zfree(thread_zone, td); 763 tid_free(tid); 764 thread_count_dec(); 765 return (NULL); 766 } 767 td->td_tid = tid; 768 bzero(&td->td_sa.args, sizeof(td->td_sa.args)); 769 kmsan_thread_alloc(td); 770 cpu_thread_alloc(td); 771 EVENTHANDLER_DIRECT_INVOKE(thread_ctor, td); 772 return (td); 773 } 774 775 int 776 thread_alloc_stack(struct thread *td, int pages) 777 { 778 779 KASSERT(td->td_kstack == 0, 780 ("thread_alloc_stack called on a thread with kstack")); 781 if (!vm_thread_new(td, pages)) 782 return (0); 783 cpu_thread_alloc(td); 784 return (1); 785 } 786 787 /* 788 * Deallocate a thread. 789 */ 790 static void 791 thread_free_batched(struct thread *td) 792 { 793 794 lock_profile_thread_exit(td); 795 if (td->td_cpuset) 796 cpuset_rel(td->td_cpuset); 797 td->td_cpuset = NULL; 798 cpu_thread_free(td); 799 if (td->td_kstack != 0) 800 vm_thread_dispose(td); 801 callout_drain(&td->td_slpcallout); 802 /* 803 * Freeing handled by the caller. 804 */ 805 td->td_tid = -1; 806 kmsan_thread_free(td); 807 uma_zfree(thread_zone, td); 808 } 809 810 void 811 thread_free(struct thread *td) 812 { 813 lwpid_t tid; 814 815 EVENTHANDLER_DIRECT_INVOKE(thread_dtor, td); 816 tid = td->td_tid; 817 thread_free_batched(td); 818 tid_free(tid); 819 thread_count_dec(); 820 } 821 822 void 823 thread_cow_get_proc(struct thread *newtd, struct proc *p) 824 { 825 826 PROC_LOCK_ASSERT(p, MA_OWNED); 827 newtd->td_realucred = crcowget(p->p_ucred); 828 newtd->td_ucred = newtd->td_realucred; 829 newtd->td_limit = lim_hold(p->p_limit); 830 newtd->td_cowgen = p->p_cowgen; 831 } 832 833 void 834 thread_cow_get(struct thread *newtd, struct thread *td) 835 { 836 837 MPASS(td->td_realucred == td->td_ucred); 838 newtd->td_realucred = crcowget(td->td_realucred); 839 newtd->td_ucred = newtd->td_realucred; 840 newtd->td_limit = lim_hold(td->td_limit); 841 newtd->td_cowgen = td->td_cowgen; 842 } 843 844 void 845 thread_cow_free(struct thread *td) 846 { 847 848 if (td->td_realucred != NULL) 849 crcowfree(td); 850 if (td->td_limit != NULL) 851 lim_free(td->td_limit); 852 } 853 854 void 855 thread_cow_update(struct thread *td) 856 { 857 struct proc *p; 858 struct ucred *oldcred; 859 struct plimit *oldlimit; 860 861 p = td->td_proc; 862 PROC_LOCK(p); 863 oldcred = crcowsync(); 864 oldlimit = lim_cowsync(); 865 td->td_cowgen = p->p_cowgen; 866 PROC_UNLOCK(p); 867 if (oldcred != NULL) 868 crfree(oldcred); 869 if (oldlimit != NULL) 870 lim_free(oldlimit); 871 } 872 873 void 874 thread_cow_synced(struct thread *td) 875 { 876 struct proc *p; 877 878 p = td->td_proc; 879 PROC_LOCK_ASSERT(p, MA_OWNED); 880 MPASS(td->td_cowgen != p->p_cowgen); 881 MPASS(td->td_ucred == p->p_ucred); 882 MPASS(td->td_limit == p->p_limit); 883 td->td_cowgen = p->p_cowgen; 884 } 885 886 /* 887 * Discard the current thread and exit from its context. 888 * Always called with scheduler locked. 889 * 890 * Because we can't free a thread while we're operating under its context, 891 * push the current thread into our CPU's deadthread holder. This means 892 * we needn't worry about someone else grabbing our context before we 893 * do a cpu_throw(). 894 */ 895 void 896 thread_exit(void) 897 { 898 uint64_t runtime, new_switchtime; 899 struct thread *td; 900 struct thread *td2; 901 struct proc *p; 902 int wakeup_swapper; 903 904 td = curthread; 905 p = td->td_proc; 906 907 PROC_SLOCK_ASSERT(p, MA_OWNED); 908 mtx_assert(&Giant, MA_NOTOWNED); 909 910 PROC_LOCK_ASSERT(p, MA_OWNED); 911 KASSERT(p != NULL, ("thread exiting without a process")); 912 CTR3(KTR_PROC, "thread_exit: thread %p (pid %ld, %s)", td, 913 (long)p->p_pid, td->td_name); 914 SDT_PROBE0(proc, , , lwp__exit); 915 KASSERT(TAILQ_EMPTY(&td->td_sigqueue.sq_list), ("signal pending")); 916 MPASS(td->td_realucred == td->td_ucred); 917 918 /* 919 * drop FPU & debug register state storage, or any other 920 * architecture specific resources that 921 * would not be on a new untouched process. 922 */ 923 cpu_thread_exit(td); 924 925 /* 926 * The last thread is left attached to the process 927 * So that the whole bundle gets recycled. Skip 928 * all this stuff if we never had threads. 929 * EXIT clears all sign of other threads when 930 * it goes to single threading, so the last thread always 931 * takes the short path. 932 */ 933 if (p->p_flag & P_HADTHREADS) { 934 if (p->p_numthreads > 1) { 935 atomic_add_int(&td->td_proc->p_exitthreads, 1); 936 thread_unlink(td); 937 td2 = FIRST_THREAD_IN_PROC(p); 938 sched_exit_thread(td2, td); 939 940 /* 941 * The test below is NOT true if we are the 942 * sole exiting thread. P_STOPPED_SINGLE is unset 943 * in exit1() after it is the only survivor. 944 */ 945 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) { 946 if (p->p_numthreads == p->p_suspcount) { 947 thread_lock(p->p_singlethread); 948 wakeup_swapper = thread_unsuspend_one( 949 p->p_singlethread, p, false); 950 if (wakeup_swapper) 951 kick_proc0(); 952 } 953 } 954 955 PCPU_SET(deadthread, td); 956 } else { 957 /* 958 * The last thread is exiting.. but not through exit() 959 */ 960 panic ("thread_exit: Last thread exiting on its own"); 961 } 962 } 963 #ifdef HWPMC_HOOKS 964 /* 965 * If this thread is part of a process that is being tracked by hwpmc(4), 966 * inform the module of the thread's impending exit. 967 */ 968 if (PMC_PROC_IS_USING_PMCS(td->td_proc)) { 969 PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_OUT); 970 PMC_CALL_HOOK_UNLOCKED(td, PMC_FN_THR_EXIT, NULL); 971 } else if (PMC_SYSTEM_SAMPLING_ACTIVE()) 972 PMC_CALL_HOOK_UNLOCKED(td, PMC_FN_THR_EXIT_LOG, NULL); 973 #endif 974 PROC_UNLOCK(p); 975 PROC_STATLOCK(p); 976 thread_lock(td); 977 PROC_SUNLOCK(p); 978 979 /* Do the same timestamp bookkeeping that mi_switch() would do. */ 980 new_switchtime = cpu_ticks(); 981 runtime = new_switchtime - PCPU_GET(switchtime); 982 td->td_runtime += runtime; 983 td->td_incruntime += runtime; 984 PCPU_SET(switchtime, new_switchtime); 985 PCPU_SET(switchticks, ticks); 986 VM_CNT_INC(v_swtch); 987 988 /* Save our resource usage in our process. */ 989 td->td_ru.ru_nvcsw++; 990 ruxagg_locked(p, td); 991 rucollect(&p->p_ru, &td->td_ru); 992 PROC_STATUNLOCK(p); 993 994 TD_SET_STATE(td, TDS_INACTIVE); 995 #ifdef WITNESS 996 witness_thread_exit(td); 997 #endif 998 CTR1(KTR_PROC, "thread_exit: cpu_throw() thread %p", td); 999 sched_throw(td); 1000 panic("I'm a teapot!"); 1001 /* NOTREACHED */ 1002 } 1003 1004 /* 1005 * Do any thread specific cleanups that may be needed in wait() 1006 * called with Giant, proc and schedlock not held. 1007 */ 1008 void 1009 thread_wait(struct proc *p) 1010 { 1011 struct thread *td; 1012 1013 mtx_assert(&Giant, MA_NOTOWNED); 1014 KASSERT(p->p_numthreads == 1, ("multiple threads in thread_wait()")); 1015 KASSERT(p->p_exitthreads == 0, ("p_exitthreads leaking")); 1016 td = FIRST_THREAD_IN_PROC(p); 1017 /* Lock the last thread so we spin until it exits cpu_throw(). */ 1018 thread_lock(td); 1019 thread_unlock(td); 1020 lock_profile_thread_exit(td); 1021 cpuset_rel(td->td_cpuset); 1022 td->td_cpuset = NULL; 1023 cpu_thread_clean(td); 1024 thread_cow_free(td); 1025 callout_drain(&td->td_slpcallout); 1026 thread_reap(); /* check for zombie threads etc. */ 1027 } 1028 1029 /* 1030 * Link a thread to a process. 1031 * set up anything that needs to be initialized for it to 1032 * be used by the process. 1033 */ 1034 void 1035 thread_link(struct thread *td, struct proc *p) 1036 { 1037 1038 /* 1039 * XXX This can't be enabled because it's called for proc0 before 1040 * its lock has been created. 1041 * PROC_LOCK_ASSERT(p, MA_OWNED); 1042 */ 1043 TD_SET_STATE(td, TDS_INACTIVE); 1044 td->td_proc = p; 1045 td->td_flags = TDF_INMEM; 1046 1047 LIST_INIT(&td->td_contested); 1048 LIST_INIT(&td->td_lprof[0]); 1049 LIST_INIT(&td->td_lprof[1]); 1050 #ifdef EPOCH_TRACE 1051 SLIST_INIT(&td->td_epochs); 1052 #endif 1053 sigqueue_init(&td->td_sigqueue, p); 1054 callout_init(&td->td_slpcallout, 1); 1055 TAILQ_INSERT_TAIL(&p->p_threads, td, td_plist); 1056 p->p_numthreads++; 1057 } 1058 1059 /* 1060 * Called from: 1061 * thread_exit() 1062 */ 1063 void 1064 thread_unlink(struct thread *td) 1065 { 1066 struct proc *p = td->td_proc; 1067 1068 PROC_LOCK_ASSERT(p, MA_OWNED); 1069 #ifdef EPOCH_TRACE 1070 MPASS(SLIST_EMPTY(&td->td_epochs)); 1071 #endif 1072 1073 TAILQ_REMOVE(&p->p_threads, td, td_plist); 1074 p->p_numthreads--; 1075 /* could clear a few other things here */ 1076 /* Must NOT clear links to proc! */ 1077 } 1078 1079 static int 1080 calc_remaining(struct proc *p, int mode) 1081 { 1082 int remaining; 1083 1084 PROC_LOCK_ASSERT(p, MA_OWNED); 1085 PROC_SLOCK_ASSERT(p, MA_OWNED); 1086 if (mode == SINGLE_EXIT) 1087 remaining = p->p_numthreads; 1088 else if (mode == SINGLE_BOUNDARY) 1089 remaining = p->p_numthreads - p->p_boundary_count; 1090 else if (mode == SINGLE_NO_EXIT || mode == SINGLE_ALLPROC) 1091 remaining = p->p_numthreads - p->p_suspcount; 1092 else 1093 panic("calc_remaining: wrong mode %d", mode); 1094 return (remaining); 1095 } 1096 1097 static int 1098 remain_for_mode(int mode) 1099 { 1100 1101 return (mode == SINGLE_ALLPROC ? 0 : 1); 1102 } 1103 1104 static int 1105 weed_inhib(int mode, struct thread *td2, struct proc *p) 1106 { 1107 int wakeup_swapper; 1108 1109 PROC_LOCK_ASSERT(p, MA_OWNED); 1110 PROC_SLOCK_ASSERT(p, MA_OWNED); 1111 THREAD_LOCK_ASSERT(td2, MA_OWNED); 1112 1113 wakeup_swapper = 0; 1114 1115 /* 1116 * Since the thread lock is dropped by the scheduler we have 1117 * to retry to check for races. 1118 */ 1119 restart: 1120 switch (mode) { 1121 case SINGLE_EXIT: 1122 if (TD_IS_SUSPENDED(td2)) { 1123 wakeup_swapper |= thread_unsuspend_one(td2, p, true); 1124 thread_lock(td2); 1125 goto restart; 1126 } 1127 if (TD_CAN_ABORT(td2)) { 1128 wakeup_swapper |= sleepq_abort(td2, EINTR); 1129 return (wakeup_swapper); 1130 } 1131 break; 1132 case SINGLE_BOUNDARY: 1133 case SINGLE_NO_EXIT: 1134 if (TD_IS_SUSPENDED(td2) && 1135 (td2->td_flags & TDF_BOUNDARY) == 0) { 1136 wakeup_swapper |= thread_unsuspend_one(td2, p, false); 1137 thread_lock(td2); 1138 goto restart; 1139 } 1140 if (TD_CAN_ABORT(td2)) { 1141 wakeup_swapper |= sleepq_abort(td2, ERESTART); 1142 return (wakeup_swapper); 1143 } 1144 break; 1145 case SINGLE_ALLPROC: 1146 /* 1147 * ALLPROC suspend tries to avoid spurious EINTR for 1148 * threads sleeping interruptable, by suspending the 1149 * thread directly, similarly to sig_suspend_threads(). 1150 * Since such sleep is not neccessary performed at the user 1151 * boundary, TDF_ALLPROCSUSP is used to avoid immediate 1152 * un-suspend. 1153 */ 1154 if (TD_IS_SUSPENDED(td2) && (td2->td_flags & 1155 TDF_ALLPROCSUSP) == 0) { 1156 wakeup_swapper |= thread_unsuspend_one(td2, p, false); 1157 thread_lock(td2); 1158 goto restart; 1159 } 1160 if (TD_CAN_ABORT(td2)) { 1161 td2->td_flags |= TDF_ALLPROCSUSP; 1162 wakeup_swapper |= sleepq_abort(td2, ERESTART); 1163 return (wakeup_swapper); 1164 } 1165 break; 1166 default: 1167 break; 1168 } 1169 thread_unlock(td2); 1170 return (wakeup_swapper); 1171 } 1172 1173 /* 1174 * Enforce single-threading. 1175 * 1176 * Returns 1 if the caller must abort (another thread is waiting to 1177 * exit the process or similar). Process is locked! 1178 * Returns 0 when you are successfully the only thread running. 1179 * A process has successfully single threaded in the suspend mode when 1180 * There are no threads in user mode. Threads in the kernel must be 1181 * allowed to continue until they get to the user boundary. They may even 1182 * copy out their return values and data before suspending. They may however be 1183 * accelerated in reaching the user boundary as we will wake up 1184 * any sleeping threads that are interruptable. (PCATCH). 1185 */ 1186 int 1187 thread_single(struct proc *p, int mode) 1188 { 1189 struct thread *td; 1190 struct thread *td2; 1191 int remaining, wakeup_swapper; 1192 1193 td = curthread; 1194 KASSERT(mode == SINGLE_EXIT || mode == SINGLE_BOUNDARY || 1195 mode == SINGLE_ALLPROC || mode == SINGLE_NO_EXIT, 1196 ("invalid mode %d", mode)); 1197 /* 1198 * If allowing non-ALLPROC singlethreading for non-curproc 1199 * callers, calc_remaining() and remain_for_mode() should be 1200 * adjusted to also account for td->td_proc != p. For now 1201 * this is not implemented because it is not used. 1202 */ 1203 KASSERT((mode == SINGLE_ALLPROC && td->td_proc != p) || 1204 (mode != SINGLE_ALLPROC && td->td_proc == p), 1205 ("mode %d proc %p curproc %p", mode, p, td->td_proc)); 1206 mtx_assert(&Giant, MA_NOTOWNED); 1207 PROC_LOCK_ASSERT(p, MA_OWNED); 1208 1209 /* 1210 * Is someone already single threading? 1211 * Or may be singlethreading is not needed at all. 1212 */ 1213 if (mode == SINGLE_ALLPROC) { 1214 while ((p->p_flag & P_STOPPED_SINGLE) != 0) { 1215 if ((p->p_flag2 & P2_WEXIT) != 0) 1216 return (1); 1217 msleep(&p->p_flag, &p->p_mtx, PCATCH, "thrsgl", 0); 1218 } 1219 } else if ((p->p_flag & P_HADTHREADS) == 0) 1220 return (0); 1221 if (p->p_singlethread != NULL && p->p_singlethread != td) 1222 return (1); 1223 1224 if (mode == SINGLE_EXIT) { 1225 p->p_flag |= P_SINGLE_EXIT; 1226 p->p_flag &= ~P_SINGLE_BOUNDARY; 1227 } else { 1228 p->p_flag &= ~P_SINGLE_EXIT; 1229 if (mode == SINGLE_BOUNDARY) 1230 p->p_flag |= P_SINGLE_BOUNDARY; 1231 else 1232 p->p_flag &= ~P_SINGLE_BOUNDARY; 1233 } 1234 if (mode == SINGLE_ALLPROC) 1235 p->p_flag |= P_TOTAL_STOP; 1236 p->p_flag |= P_STOPPED_SINGLE; 1237 PROC_SLOCK(p); 1238 p->p_singlethread = td; 1239 remaining = calc_remaining(p, mode); 1240 while (remaining != remain_for_mode(mode)) { 1241 if (P_SHOULDSTOP(p) != P_STOPPED_SINGLE) 1242 goto stopme; 1243 wakeup_swapper = 0; 1244 FOREACH_THREAD_IN_PROC(p, td2) { 1245 if (td2 == td) 1246 continue; 1247 thread_lock(td2); 1248 ast_sched_locked(td2, TDA_SUSPEND); 1249 if (TD_IS_INHIBITED(td2)) { 1250 wakeup_swapper |= weed_inhib(mode, td2, p); 1251 #ifdef SMP 1252 } else if (TD_IS_RUNNING(td2)) { 1253 forward_signal(td2); 1254 thread_unlock(td2); 1255 #endif 1256 } else 1257 thread_unlock(td2); 1258 } 1259 if (wakeup_swapper) 1260 kick_proc0(); 1261 remaining = calc_remaining(p, mode); 1262 1263 /* 1264 * Maybe we suspended some threads.. was it enough? 1265 */ 1266 if (remaining == remain_for_mode(mode)) 1267 break; 1268 1269 stopme: 1270 /* 1271 * Wake us up when everyone else has suspended. 1272 * In the mean time we suspend as well. 1273 */ 1274 thread_suspend_switch(td, p); 1275 remaining = calc_remaining(p, mode); 1276 } 1277 if (mode == SINGLE_EXIT) { 1278 /* 1279 * Convert the process to an unthreaded process. The 1280 * SINGLE_EXIT is called by exit1() or execve(), in 1281 * both cases other threads must be retired. 1282 */ 1283 KASSERT(p->p_numthreads == 1, ("Unthreading with >1 threads")); 1284 p->p_singlethread = NULL; 1285 p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT | P_HADTHREADS); 1286 1287 /* 1288 * Wait for any remaining threads to exit cpu_throw(). 1289 */ 1290 while (p->p_exitthreads != 0) { 1291 PROC_SUNLOCK(p); 1292 PROC_UNLOCK(p); 1293 sched_relinquish(td); 1294 PROC_LOCK(p); 1295 PROC_SLOCK(p); 1296 } 1297 } else if (mode == SINGLE_BOUNDARY) { 1298 /* 1299 * Wait until all suspended threads are removed from 1300 * the processors. The thread_suspend_check() 1301 * increments p_boundary_count while it is still 1302 * running, which makes it possible for the execve() 1303 * to destroy vmspace while our other threads are 1304 * still using the address space. 1305 * 1306 * We lock the thread, which is only allowed to 1307 * succeed after context switch code finished using 1308 * the address space. 1309 */ 1310 FOREACH_THREAD_IN_PROC(p, td2) { 1311 if (td2 == td) 1312 continue; 1313 thread_lock(td2); 1314 KASSERT((td2->td_flags & TDF_BOUNDARY) != 0, 1315 ("td %p not on boundary", td2)); 1316 KASSERT(TD_IS_SUSPENDED(td2), 1317 ("td %p is not suspended", td2)); 1318 thread_unlock(td2); 1319 } 1320 } 1321 PROC_SUNLOCK(p); 1322 return (0); 1323 } 1324 1325 bool 1326 thread_suspend_check_needed(void) 1327 { 1328 struct proc *p; 1329 struct thread *td; 1330 1331 td = curthread; 1332 p = td->td_proc; 1333 PROC_LOCK_ASSERT(p, MA_OWNED); 1334 return (P_SHOULDSTOP(p) || ((p->p_flag & P_TRACED) != 0 && 1335 (td->td_dbgflags & TDB_SUSPEND) != 0)); 1336 } 1337 1338 /* 1339 * Called in from locations that can safely check to see 1340 * whether we have to suspend or at least throttle for a 1341 * single-thread event (e.g. fork). 1342 * 1343 * Such locations include userret(). 1344 * If the "return_instead" argument is non zero, the thread must be able to 1345 * accept 0 (caller may continue), or 1 (caller must abort) as a result. 1346 * 1347 * The 'return_instead' argument tells the function if it may do a 1348 * thread_exit() or suspend, or whether the caller must abort and back 1349 * out instead. 1350 * 1351 * If the thread that set the single_threading request has set the 1352 * P_SINGLE_EXIT bit in the process flags then this call will never return 1353 * if 'return_instead' is false, but will exit. 1354 * 1355 * P_SINGLE_EXIT | return_instead == 0| return_instead != 0 1356 *---------------+--------------------+--------------------- 1357 * 0 | returns 0 | returns 0 or 1 1358 * | when ST ends | immediately 1359 *---------------+--------------------+--------------------- 1360 * 1 | thread exits | returns 1 1361 * | | immediately 1362 * 0 = thread_exit() or suspension ok, 1363 * other = return error instead of stopping the thread. 1364 * 1365 * While a full suspension is under effect, even a single threading 1366 * thread would be suspended if it made this call (but it shouldn't). 1367 * This call should only be made from places where 1368 * thread_exit() would be safe as that may be the outcome unless 1369 * return_instead is set. 1370 */ 1371 int 1372 thread_suspend_check(int return_instead) 1373 { 1374 struct thread *td; 1375 struct proc *p; 1376 int wakeup_swapper; 1377 1378 td = curthread; 1379 p = td->td_proc; 1380 mtx_assert(&Giant, MA_NOTOWNED); 1381 PROC_LOCK_ASSERT(p, MA_OWNED); 1382 while (thread_suspend_check_needed()) { 1383 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) { 1384 KASSERT(p->p_singlethread != NULL, 1385 ("singlethread not set")); 1386 /* 1387 * The only suspension in action is a 1388 * single-threading. Single threader need not stop. 1389 * It is safe to access p->p_singlethread unlocked 1390 * because it can only be set to our address by us. 1391 */ 1392 if (p->p_singlethread == td) 1393 return (0); /* Exempt from stopping. */ 1394 } 1395 if ((p->p_flag & P_SINGLE_EXIT) && return_instead) 1396 return (EINTR); 1397 1398 /* Should we goto user boundary if we didn't come from there? */ 1399 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE && 1400 (p->p_flag & P_SINGLE_BOUNDARY) && return_instead) 1401 return (ERESTART); 1402 1403 /* 1404 * Ignore suspend requests if they are deferred. 1405 */ 1406 if ((td->td_flags & TDF_SBDRY) != 0) { 1407 KASSERT(return_instead, 1408 ("TDF_SBDRY set for unsafe thread_suspend_check")); 1409 KASSERT((td->td_flags & (TDF_SEINTR | TDF_SERESTART)) != 1410 (TDF_SEINTR | TDF_SERESTART), 1411 ("both TDF_SEINTR and TDF_SERESTART")); 1412 return (TD_SBDRY_INTR(td) ? TD_SBDRY_ERRNO(td) : 0); 1413 } 1414 1415 /* 1416 * If the process is waiting for us to exit, 1417 * this thread should just suicide. 1418 * Assumes that P_SINGLE_EXIT implies P_STOPPED_SINGLE. 1419 */ 1420 if ((p->p_flag & P_SINGLE_EXIT) && (p->p_singlethread != td)) { 1421 PROC_UNLOCK(p); 1422 1423 /* 1424 * Allow Linux emulation layer to do some work 1425 * before thread suicide. 1426 */ 1427 if (__predict_false(p->p_sysent->sv_thread_detach != NULL)) 1428 (p->p_sysent->sv_thread_detach)(td); 1429 umtx_thread_exit(td); 1430 kern_thr_exit(td); 1431 panic("stopped thread did not exit"); 1432 } 1433 1434 PROC_SLOCK(p); 1435 thread_stopped(p); 1436 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) { 1437 if (p->p_numthreads == p->p_suspcount + 1) { 1438 thread_lock(p->p_singlethread); 1439 wakeup_swapper = thread_unsuspend_one( 1440 p->p_singlethread, p, false); 1441 if (wakeup_swapper) 1442 kick_proc0(); 1443 } 1444 } 1445 PROC_UNLOCK(p); 1446 thread_lock(td); 1447 /* 1448 * When a thread suspends, it just 1449 * gets taken off all queues. 1450 */ 1451 thread_suspend_one(td); 1452 if (return_instead == 0) { 1453 p->p_boundary_count++; 1454 td->td_flags |= TDF_BOUNDARY; 1455 } 1456 PROC_SUNLOCK(p); 1457 mi_switch(SW_INVOL | SWT_SUSPEND); 1458 PROC_LOCK(p); 1459 } 1460 return (0); 1461 } 1462 1463 /* 1464 * Check for possible stops and suspensions while executing a 1465 * casueword or similar transiently failing operation. 1466 * 1467 * The sleep argument controls whether the function can handle a stop 1468 * request itself or it should return ERESTART and the request is 1469 * proceed at the kernel/user boundary in ast. 1470 * 1471 * Typically, when retrying due to casueword(9) failure (rv == 1), we 1472 * should handle the stop requests there, with exception of cases when 1473 * the thread owns a kernel resource, for instance busied the umtx 1474 * key, or when functions return immediately if thread_check_susp() 1475 * returned non-zero. On the other hand, retrying the whole lock 1476 * operation, we better not stop there but delegate the handling to 1477 * ast. 1478 * 1479 * If the request is for thread termination P_SINGLE_EXIT, we cannot 1480 * handle it at all, and simply return EINTR. 1481 */ 1482 int 1483 thread_check_susp(struct thread *td, bool sleep) 1484 { 1485 struct proc *p; 1486 int error; 1487 1488 /* 1489 * The check for TDA_SUSPEND is racy, but it is enough to 1490 * eventually break the lockstep loop. 1491 */ 1492 if (!td_ast_pending(td, TDA_SUSPEND)) 1493 return (0); 1494 error = 0; 1495 p = td->td_proc; 1496 PROC_LOCK(p); 1497 if (p->p_flag & P_SINGLE_EXIT) 1498 error = EINTR; 1499 else if (P_SHOULDSTOP(p) || 1500 ((p->p_flag & P_TRACED) && (td->td_dbgflags & TDB_SUSPEND))) 1501 error = sleep ? thread_suspend_check(0) : ERESTART; 1502 PROC_UNLOCK(p); 1503 return (error); 1504 } 1505 1506 void 1507 thread_suspend_switch(struct thread *td, struct proc *p) 1508 { 1509 1510 KASSERT(!TD_IS_SUSPENDED(td), ("already suspended")); 1511 PROC_LOCK_ASSERT(p, MA_OWNED); 1512 PROC_SLOCK_ASSERT(p, MA_OWNED); 1513 /* 1514 * We implement thread_suspend_one in stages here to avoid 1515 * dropping the proc lock while the thread lock is owned. 1516 */ 1517 if (p == td->td_proc) { 1518 thread_stopped(p); 1519 p->p_suspcount++; 1520 } 1521 PROC_UNLOCK(p); 1522 thread_lock(td); 1523 ast_unsched_locked(td, TDA_SUSPEND); 1524 TD_SET_SUSPENDED(td); 1525 sched_sleep(td, 0); 1526 PROC_SUNLOCK(p); 1527 DROP_GIANT(); 1528 mi_switch(SW_VOL | SWT_SUSPEND); 1529 PICKUP_GIANT(); 1530 PROC_LOCK(p); 1531 PROC_SLOCK(p); 1532 } 1533 1534 void 1535 thread_suspend_one(struct thread *td) 1536 { 1537 struct proc *p; 1538 1539 p = td->td_proc; 1540 PROC_SLOCK_ASSERT(p, MA_OWNED); 1541 THREAD_LOCK_ASSERT(td, MA_OWNED); 1542 KASSERT(!TD_IS_SUSPENDED(td), ("already suspended")); 1543 p->p_suspcount++; 1544 ast_unsched_locked(td, TDA_SUSPEND); 1545 TD_SET_SUSPENDED(td); 1546 sched_sleep(td, 0); 1547 } 1548 1549 static int 1550 thread_unsuspend_one(struct thread *td, struct proc *p, bool boundary) 1551 { 1552 1553 THREAD_LOCK_ASSERT(td, MA_OWNED); 1554 KASSERT(TD_IS_SUSPENDED(td), ("Thread not suspended")); 1555 TD_CLR_SUSPENDED(td); 1556 td->td_flags &= ~TDF_ALLPROCSUSP; 1557 if (td->td_proc == p) { 1558 PROC_SLOCK_ASSERT(p, MA_OWNED); 1559 p->p_suspcount--; 1560 if (boundary && (td->td_flags & TDF_BOUNDARY) != 0) { 1561 td->td_flags &= ~TDF_BOUNDARY; 1562 p->p_boundary_count--; 1563 } 1564 } 1565 return (setrunnable(td, 0)); 1566 } 1567 1568 void 1569 thread_run_flash(struct thread *td) 1570 { 1571 struct proc *p; 1572 1573 p = td->td_proc; 1574 PROC_LOCK_ASSERT(p, MA_OWNED); 1575 1576 if (TD_ON_SLEEPQ(td)) 1577 sleepq_remove_nested(td); 1578 else 1579 thread_lock(td); 1580 1581 THREAD_LOCK_ASSERT(td, MA_OWNED); 1582 KASSERT(TD_IS_SUSPENDED(td), ("Thread not suspended")); 1583 1584 TD_CLR_SUSPENDED(td); 1585 PROC_SLOCK(p); 1586 MPASS(p->p_suspcount > 0); 1587 p->p_suspcount--; 1588 PROC_SUNLOCK(p); 1589 if (setrunnable(td, 0)) 1590 kick_proc0(); 1591 } 1592 1593 /* 1594 * Allow all threads blocked by single threading to continue running. 1595 */ 1596 void 1597 thread_unsuspend(struct proc *p) 1598 { 1599 struct thread *td; 1600 int wakeup_swapper; 1601 1602 PROC_LOCK_ASSERT(p, MA_OWNED); 1603 PROC_SLOCK_ASSERT(p, MA_OWNED); 1604 wakeup_swapper = 0; 1605 if (!P_SHOULDSTOP(p)) { 1606 FOREACH_THREAD_IN_PROC(p, td) { 1607 thread_lock(td); 1608 if (TD_IS_SUSPENDED(td)) 1609 wakeup_swapper |= thread_unsuspend_one(td, p, 1610 true); 1611 else 1612 thread_unlock(td); 1613 } 1614 } else if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE && 1615 p->p_numthreads == p->p_suspcount) { 1616 /* 1617 * Stopping everything also did the job for the single 1618 * threading request. Now we've downgraded to single-threaded, 1619 * let it continue. 1620 */ 1621 if (p->p_singlethread->td_proc == p) { 1622 thread_lock(p->p_singlethread); 1623 wakeup_swapper = thread_unsuspend_one( 1624 p->p_singlethread, p, false); 1625 } 1626 } 1627 if (wakeup_swapper) 1628 kick_proc0(); 1629 } 1630 1631 /* 1632 * End the single threading mode.. 1633 */ 1634 void 1635 thread_single_end(struct proc *p, int mode) 1636 { 1637 struct thread *td; 1638 int wakeup_swapper; 1639 1640 KASSERT(mode == SINGLE_EXIT || mode == SINGLE_BOUNDARY || 1641 mode == SINGLE_ALLPROC || mode == SINGLE_NO_EXIT, 1642 ("invalid mode %d", mode)); 1643 PROC_LOCK_ASSERT(p, MA_OWNED); 1644 KASSERT((mode == SINGLE_ALLPROC && (p->p_flag & P_TOTAL_STOP) != 0) || 1645 (mode != SINGLE_ALLPROC && (p->p_flag & P_TOTAL_STOP) == 0), 1646 ("mode %d does not match P_TOTAL_STOP", mode)); 1647 KASSERT(mode == SINGLE_ALLPROC || p->p_singlethread == curthread, 1648 ("thread_single_end from other thread %p %p", 1649 curthread, p->p_singlethread)); 1650 KASSERT(mode != SINGLE_BOUNDARY || 1651 (p->p_flag & P_SINGLE_BOUNDARY) != 0, 1652 ("mis-matched SINGLE_BOUNDARY flags %x", p->p_flag)); 1653 p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT | P_SINGLE_BOUNDARY | 1654 P_TOTAL_STOP); 1655 PROC_SLOCK(p); 1656 p->p_singlethread = NULL; 1657 wakeup_swapper = 0; 1658 /* 1659 * If there are other threads they may now run, 1660 * unless of course there is a blanket 'stop order' 1661 * on the process. The single threader must be allowed 1662 * to continue however as this is a bad place to stop. 1663 */ 1664 if (p->p_numthreads != remain_for_mode(mode) && !P_SHOULDSTOP(p)) { 1665 FOREACH_THREAD_IN_PROC(p, td) { 1666 thread_lock(td); 1667 if (TD_IS_SUSPENDED(td)) { 1668 wakeup_swapper |= thread_unsuspend_one(td, p, 1669 true); 1670 } else 1671 thread_unlock(td); 1672 } 1673 } 1674 KASSERT(mode != SINGLE_BOUNDARY || p->p_boundary_count == 0, 1675 ("inconsistent boundary count %d", p->p_boundary_count)); 1676 PROC_SUNLOCK(p); 1677 if (wakeup_swapper) 1678 kick_proc0(); 1679 wakeup(&p->p_flag); 1680 } 1681 1682 /* 1683 * Locate a thread by number and return with proc lock held. 1684 * 1685 * thread exit establishes proc -> tidhash lock ordering, but lookup 1686 * takes tidhash first and needs to return locked proc. 1687 * 1688 * The problem is worked around by relying on type-safety of both 1689 * structures and doing the work in 2 steps: 1690 * - tidhash-locked lookup which saves both thread and proc pointers 1691 * - proc-locked verification that the found thread still matches 1692 */ 1693 static bool 1694 tdfind_hash(lwpid_t tid, pid_t pid, struct proc **pp, struct thread **tdp) 1695 { 1696 #define RUN_THRESH 16 1697 struct proc *p; 1698 struct thread *td; 1699 int run; 1700 bool locked; 1701 1702 run = 0; 1703 rw_rlock(TIDHASHLOCK(tid)); 1704 locked = true; 1705 LIST_FOREACH(td, TIDHASH(tid), td_hash) { 1706 if (td->td_tid != tid) { 1707 run++; 1708 continue; 1709 } 1710 p = td->td_proc; 1711 if (pid != -1 && p->p_pid != pid) { 1712 td = NULL; 1713 break; 1714 } 1715 if (run > RUN_THRESH) { 1716 if (rw_try_upgrade(TIDHASHLOCK(tid))) { 1717 LIST_REMOVE(td, td_hash); 1718 LIST_INSERT_HEAD(TIDHASH(td->td_tid), 1719 td, td_hash); 1720 rw_wunlock(TIDHASHLOCK(tid)); 1721 locked = false; 1722 break; 1723 } 1724 } 1725 break; 1726 } 1727 if (locked) 1728 rw_runlock(TIDHASHLOCK(tid)); 1729 if (td == NULL) 1730 return (false); 1731 *pp = p; 1732 *tdp = td; 1733 return (true); 1734 } 1735 1736 struct thread * 1737 tdfind(lwpid_t tid, pid_t pid) 1738 { 1739 struct proc *p; 1740 struct thread *td; 1741 1742 td = curthread; 1743 if (td->td_tid == tid) { 1744 if (pid != -1 && td->td_proc->p_pid != pid) 1745 return (NULL); 1746 PROC_LOCK(td->td_proc); 1747 return (td); 1748 } 1749 1750 for (;;) { 1751 if (!tdfind_hash(tid, pid, &p, &td)) 1752 return (NULL); 1753 PROC_LOCK(p); 1754 if (td->td_tid != tid) { 1755 PROC_UNLOCK(p); 1756 continue; 1757 } 1758 if (td->td_proc != p) { 1759 PROC_UNLOCK(p); 1760 continue; 1761 } 1762 if (p->p_state == PRS_NEW) { 1763 PROC_UNLOCK(p); 1764 return (NULL); 1765 } 1766 return (td); 1767 } 1768 } 1769 1770 void 1771 tidhash_add(struct thread *td) 1772 { 1773 rw_wlock(TIDHASHLOCK(td->td_tid)); 1774 LIST_INSERT_HEAD(TIDHASH(td->td_tid), td, td_hash); 1775 rw_wunlock(TIDHASHLOCK(td->td_tid)); 1776 } 1777 1778 void 1779 tidhash_remove(struct thread *td) 1780 { 1781 1782 rw_wlock(TIDHASHLOCK(td->td_tid)); 1783 LIST_REMOVE(td, td_hash); 1784 rw_wunlock(TIDHASHLOCK(td->td_tid)); 1785 }
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