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, 545 thread_reap_callout_cb, NULL); 546 } 547 548 /* 549 * Place an unused thread on the zombie list. 550 */ 551 void 552 thread_zombie(struct thread *td) 553 { 554 struct thread_domain_data *tdd; 555 struct thread *ztd; 556 557 tdd = &thread_domain_data[td->td_allocdomain]; 558 ztd = atomic_load_ptr(&tdd->tdd_zombies); 559 for (;;) { 560 td->td_zombie = ztd; 561 if (atomic_fcmpset_rel_ptr((uintptr_t *)&tdd->tdd_zombies, 562 (uintptr_t *)&ztd, (uintptr_t)td)) 563 break; 564 continue; 565 } 566 } 567 568 /* 569 * Release a thread that has exited after cpu_throw(). 570 */ 571 void 572 thread_stash(struct thread *td) 573 { 574 atomic_subtract_rel_int(&td->td_proc->p_exitthreads, 1); 575 thread_zombie(td); 576 } 577 578 /* 579 * Reap zombies from passed domain. 580 */ 581 static void 582 thread_reap_domain(struct thread_domain_data *tdd) 583 { 584 struct thread *itd, *ntd; 585 struct tidbatch tidbatch; 586 struct credbatch credbatch; 587 int tdcount; 588 struct plimit *lim; 589 int limcount; 590 591 /* 592 * Reading upfront is pessimal if followed by concurrent atomic_swap, 593 * but most of the time the list is empty. 594 */ 595 if (tdd->tdd_zombies == NULL) 596 return; 597 598 itd = (struct thread *)atomic_swap_ptr((uintptr_t *)&tdd->tdd_zombies, 599 (uintptr_t)NULL); 600 if (itd == NULL) 601 return; 602 603 /* 604 * Multiple CPUs can get here, the race is fine as ticks is only 605 * advisory. 606 */ 607 tdd->tdd_reapticks = ticks; 608 609 tidbatch_prep(&tidbatch); 610 credbatch_prep(&credbatch); 611 tdcount = 0; 612 lim = NULL; 613 limcount = 0; 614 615 while (itd != NULL) { 616 ntd = itd->td_zombie; 617 EVENTHANDLER_DIRECT_INVOKE(thread_dtor, itd); 618 tidbatch_add(&tidbatch, itd); 619 credbatch_add(&credbatch, itd); 620 MPASS(itd->td_limit != NULL); 621 if (lim != itd->td_limit) { 622 if (limcount != 0) { 623 lim_freen(lim, limcount); 624 limcount = 0; 625 } 626 } 627 lim = itd->td_limit; 628 limcount++; 629 thread_free_batched(itd); 630 tidbatch_process(&tidbatch); 631 credbatch_process(&credbatch); 632 tdcount++; 633 if (tdcount == 32) { 634 thread_count_sub(tdcount); 635 tdcount = 0; 636 } 637 itd = ntd; 638 } 639 640 tidbatch_final(&tidbatch); 641 credbatch_final(&credbatch); 642 if (tdcount != 0) { 643 thread_count_sub(tdcount); 644 } 645 MPASS(limcount != 0); 646 lim_freen(lim, limcount); 647 } 648 649 /* 650 * Reap zombies from all domains. 651 */ 652 static void 653 thread_reap_all(void) 654 { 655 struct thread_domain_data *tdd; 656 int i, domain; 657 658 domain = PCPU_GET(domain); 659 for (i = 0; i < vm_ndomains; i++) { 660 tdd = &thread_domain_data[(i + domain) % vm_ndomains]; 661 thread_reap_domain(tdd); 662 } 663 } 664 665 /* 666 * Reap zombies from local domain. 667 */ 668 static void 669 thread_reap(void) 670 { 671 struct thread_domain_data *tdd; 672 int domain; 673 674 domain = PCPU_GET(domain); 675 tdd = &thread_domain_data[domain]; 676 677 thread_reap_domain(tdd); 678 } 679 680 static void 681 thread_reap_task_cb(void *arg __unused, int pending __unused) 682 { 683 684 thread_reap_all(); 685 } 686 687 static void 688 thread_reap_callout_cb(void *arg __unused) 689 { 690 struct thread_domain_data *tdd; 691 int i, cticks, lticks; 692 bool wantreap; 693 694 wantreap = false; 695 cticks = atomic_load_int(&ticks); 696 for (i = 0; i < vm_ndomains; i++) { 697 tdd = &thread_domain_data[i]; 698 lticks = tdd->tdd_reapticks; 699 if (tdd->tdd_zombies != NULL && 700 (u_int)(cticks - lticks) > 5 * hz) { 701 wantreap = true; 702 break; 703 } 704 } 705 706 if (wantreap) 707 taskqueue_enqueue(taskqueue_thread, &thread_reap_task); 708 callout_reset(&thread_reap_callout, 5 * hz, 709 thread_reap_callout_cb, NULL); 710 } 711 712 /* 713 * Calling this function guarantees that any thread that exited before 714 * the call is reaped when the function returns. By 'exited' we mean 715 * a thread removed from the process linkage with thread_unlink(). 716 * Practically this means that caller must lock/unlock corresponding 717 * process lock before the call, to synchronize with thread_exit(). 718 */ 719 void 720 thread_reap_barrier(void) 721 { 722 struct task *t; 723 724 /* 725 * First do context switches to each CPU to ensure that all 726 * PCPU pc_deadthreads are moved to zombie list. 727 */ 728 quiesce_all_cpus("", PDROP); 729 730 /* 731 * Second, fire the task in the same thread as normal 732 * thread_reap() is done, to serialize reaping. 733 */ 734 t = malloc(sizeof(*t), M_TEMP, M_WAITOK); 735 TASK_INIT(t, 0, thread_reap_task_cb, t); 736 taskqueue_enqueue(taskqueue_thread, t); 737 taskqueue_drain(taskqueue_thread, t); 738 free(t, M_TEMP); 739 } 740 741 /* 742 * Allocate a thread. 743 */ 744 struct thread * 745 thread_alloc(int pages) 746 { 747 struct thread *td; 748 lwpid_t tid; 749 750 if (!thread_count_inc()) { 751 return (NULL); 752 } 753 754 tid = tid_alloc(); 755 td = uma_zalloc(thread_zone, M_WAITOK); 756 KASSERT(td->td_kstack == 0, ("thread_alloc got thread with kstack")); 757 if (!vm_thread_new(td, pages)) { 758 uma_zfree(thread_zone, td); 759 tid_free(tid); 760 thread_count_dec(); 761 return (NULL); 762 } 763 td->td_tid = tid; 764 cpu_thread_alloc(td); 765 EVENTHANDLER_DIRECT_INVOKE(thread_ctor, td); 766 return (td); 767 } 768 769 int 770 thread_alloc_stack(struct thread *td, int pages) 771 { 772 773 KASSERT(td->td_kstack == 0, 774 ("thread_alloc_stack called on a thread with kstack")); 775 if (!vm_thread_new(td, pages)) 776 return (0); 777 cpu_thread_alloc(td); 778 return (1); 779 } 780 781 /* 782 * Deallocate a thread. 783 */ 784 static void 785 thread_free_batched(struct thread *td) 786 { 787 788 lock_profile_thread_exit(td); 789 if (td->td_cpuset) 790 cpuset_rel(td->td_cpuset); 791 td->td_cpuset = NULL; 792 cpu_thread_free(td); 793 if (td->td_kstack != 0) 794 vm_thread_dispose(td); 795 callout_drain(&td->td_slpcallout); 796 /* 797 * Freeing handled by the caller. 798 */ 799 td->td_tid = -1; 800 uma_zfree(thread_zone, td); 801 } 802 803 void 804 thread_free(struct thread *td) 805 { 806 lwpid_t tid; 807 808 EVENTHANDLER_DIRECT_INVOKE(thread_dtor, td); 809 tid = td->td_tid; 810 thread_free_batched(td); 811 tid_free(tid); 812 thread_count_dec(); 813 } 814 815 void 816 thread_cow_get_proc(struct thread *newtd, struct proc *p) 817 { 818 819 PROC_LOCK_ASSERT(p, MA_OWNED); 820 newtd->td_realucred = crcowget(p->p_ucred); 821 newtd->td_ucred = newtd->td_realucred; 822 newtd->td_limit = lim_hold(p->p_limit); 823 newtd->td_cowgen = p->p_cowgen; 824 } 825 826 void 827 thread_cow_get(struct thread *newtd, struct thread *td) 828 { 829 830 MPASS(td->td_realucred == td->td_ucred); 831 newtd->td_realucred = crcowget(td->td_realucred); 832 newtd->td_ucred = newtd->td_realucred; 833 newtd->td_limit = lim_hold(td->td_limit); 834 newtd->td_cowgen = td->td_cowgen; 835 } 836 837 void 838 thread_cow_free(struct thread *td) 839 { 840 841 if (td->td_realucred != NULL) 842 crcowfree(td); 843 if (td->td_limit != NULL) 844 lim_free(td->td_limit); 845 } 846 847 void 848 thread_cow_update(struct thread *td) 849 { 850 struct proc *p; 851 struct ucred *oldcred; 852 struct plimit *oldlimit; 853 854 p = td->td_proc; 855 oldlimit = NULL; 856 PROC_LOCK(p); 857 oldcred = crcowsync(); 858 if (td->td_limit != p->p_limit) { 859 oldlimit = td->td_limit; 860 td->td_limit = lim_hold(p->p_limit); 861 } 862 td->td_cowgen = p->p_cowgen; 863 PROC_UNLOCK(p); 864 if (oldcred != NULL) 865 crfree(oldcred); 866 if (oldlimit != NULL) 867 lim_free(oldlimit); 868 } 869 870 /* 871 * Discard the current thread and exit from its context. 872 * Always called with scheduler locked. 873 * 874 * Because we can't free a thread while we're operating under its context, 875 * push the current thread into our CPU's deadthread holder. This means 876 * we needn't worry about someone else grabbing our context before we 877 * do a cpu_throw(). 878 */ 879 void 880 thread_exit(void) 881 { 882 uint64_t runtime, new_switchtime; 883 struct thread *td; 884 struct thread *td2; 885 struct proc *p; 886 int wakeup_swapper; 887 888 td = curthread; 889 p = td->td_proc; 890 891 PROC_SLOCK_ASSERT(p, MA_OWNED); 892 mtx_assert(&Giant, MA_NOTOWNED); 893 894 PROC_LOCK_ASSERT(p, MA_OWNED); 895 KASSERT(p != NULL, ("thread exiting without a process")); 896 CTR3(KTR_PROC, "thread_exit: thread %p (pid %ld, %s)", td, 897 (long)p->p_pid, td->td_name); 898 SDT_PROBE0(proc, , , lwp__exit); 899 KASSERT(TAILQ_EMPTY(&td->td_sigqueue.sq_list), ("signal pending")); 900 MPASS(td->td_realucred == td->td_ucred); 901 902 /* 903 * drop FPU & debug register state storage, or any other 904 * architecture specific resources that 905 * would not be on a new untouched process. 906 */ 907 cpu_thread_exit(td); 908 909 /* 910 * The last thread is left attached to the process 911 * So that the whole bundle gets recycled. Skip 912 * all this stuff if we never had threads. 913 * EXIT clears all sign of other threads when 914 * it goes to single threading, so the last thread always 915 * takes the short path. 916 */ 917 if (p->p_flag & P_HADTHREADS) { 918 if (p->p_numthreads > 1) { 919 atomic_add_int(&td->td_proc->p_exitthreads, 1); 920 thread_unlink(td); 921 td2 = FIRST_THREAD_IN_PROC(p); 922 sched_exit_thread(td2, td); 923 924 /* 925 * The test below is NOT true if we are the 926 * sole exiting thread. P_STOPPED_SINGLE is unset 927 * in exit1() after it is the only survivor. 928 */ 929 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) { 930 if (p->p_numthreads == p->p_suspcount) { 931 thread_lock(p->p_singlethread); 932 wakeup_swapper = thread_unsuspend_one( 933 p->p_singlethread, p, false); 934 if (wakeup_swapper) 935 kick_proc0(); 936 } 937 } 938 939 PCPU_SET(deadthread, td); 940 } else { 941 /* 942 * The last thread is exiting.. but not through exit() 943 */ 944 panic ("thread_exit: Last thread exiting on its own"); 945 } 946 } 947 #ifdef HWPMC_HOOKS 948 /* 949 * If this thread is part of a process that is being tracked by hwpmc(4), 950 * inform the module of the thread's impending exit. 951 */ 952 if (PMC_PROC_IS_USING_PMCS(td->td_proc)) { 953 PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_OUT); 954 PMC_CALL_HOOK_UNLOCKED(td, PMC_FN_THR_EXIT, NULL); 955 } else if (PMC_SYSTEM_SAMPLING_ACTIVE()) 956 PMC_CALL_HOOK_UNLOCKED(td, PMC_FN_THR_EXIT_LOG, NULL); 957 #endif 958 PROC_UNLOCK(p); 959 PROC_STATLOCK(p); 960 thread_lock(td); 961 PROC_SUNLOCK(p); 962 963 /* Do the same timestamp bookkeeping that mi_switch() would do. */ 964 new_switchtime = cpu_ticks(); 965 runtime = new_switchtime - PCPU_GET(switchtime); 966 td->td_runtime += runtime; 967 td->td_incruntime += runtime; 968 PCPU_SET(switchtime, new_switchtime); 969 PCPU_SET(switchticks, ticks); 970 VM_CNT_INC(v_swtch); 971 972 /* Save our resource usage in our process. */ 973 td->td_ru.ru_nvcsw++; 974 ruxagg_locked(p, td); 975 rucollect(&p->p_ru, &td->td_ru); 976 PROC_STATUNLOCK(p); 977 978 td->td_state = TDS_INACTIVE; 979 #ifdef WITNESS 980 witness_thread_exit(td); 981 #endif 982 CTR1(KTR_PROC, "thread_exit: cpu_throw() thread %p", td); 983 sched_throw(td); 984 panic("I'm a teapot!"); 985 /* NOTREACHED */ 986 } 987 988 /* 989 * Do any thread specific cleanups that may be needed in wait() 990 * called with Giant, proc and schedlock not held. 991 */ 992 void 993 thread_wait(struct proc *p) 994 { 995 struct thread *td; 996 997 mtx_assert(&Giant, MA_NOTOWNED); 998 KASSERT(p->p_numthreads == 1, ("multiple threads in thread_wait()")); 999 KASSERT(p->p_exitthreads == 0, ("p_exitthreads leaking")); 1000 td = FIRST_THREAD_IN_PROC(p); 1001 /* Lock the last thread so we spin until it exits cpu_throw(). */ 1002 thread_lock(td); 1003 thread_unlock(td); 1004 lock_profile_thread_exit(td); 1005 cpuset_rel(td->td_cpuset); 1006 td->td_cpuset = NULL; 1007 cpu_thread_clean(td); 1008 thread_cow_free(td); 1009 callout_drain(&td->td_slpcallout); 1010 thread_reap(); /* check for zombie threads etc. */ 1011 } 1012 1013 /* 1014 * Link a thread to a process. 1015 * set up anything that needs to be initialized for it to 1016 * be used by the process. 1017 */ 1018 void 1019 thread_link(struct thread *td, struct proc *p) 1020 { 1021 1022 /* 1023 * XXX This can't be enabled because it's called for proc0 before 1024 * its lock has been created. 1025 * PROC_LOCK_ASSERT(p, MA_OWNED); 1026 */ 1027 td->td_state = TDS_INACTIVE; 1028 td->td_proc = p; 1029 td->td_flags = TDF_INMEM; 1030 1031 LIST_INIT(&td->td_contested); 1032 LIST_INIT(&td->td_lprof[0]); 1033 LIST_INIT(&td->td_lprof[1]); 1034 #ifdef EPOCH_TRACE 1035 SLIST_INIT(&td->td_epochs); 1036 #endif 1037 sigqueue_init(&td->td_sigqueue, p); 1038 callout_init(&td->td_slpcallout, 1); 1039 TAILQ_INSERT_TAIL(&p->p_threads, td, td_plist); 1040 p->p_numthreads++; 1041 } 1042 1043 /* 1044 * Called from: 1045 * thread_exit() 1046 */ 1047 void 1048 thread_unlink(struct thread *td) 1049 { 1050 struct proc *p = td->td_proc; 1051 1052 PROC_LOCK_ASSERT(p, MA_OWNED); 1053 #ifdef EPOCH_TRACE 1054 MPASS(SLIST_EMPTY(&td->td_epochs)); 1055 #endif 1056 1057 TAILQ_REMOVE(&p->p_threads, td, td_plist); 1058 p->p_numthreads--; 1059 /* could clear a few other things here */ 1060 /* Must NOT clear links to proc! */ 1061 } 1062 1063 static int 1064 calc_remaining(struct proc *p, int mode) 1065 { 1066 int remaining; 1067 1068 PROC_LOCK_ASSERT(p, MA_OWNED); 1069 PROC_SLOCK_ASSERT(p, MA_OWNED); 1070 if (mode == SINGLE_EXIT) 1071 remaining = p->p_numthreads; 1072 else if (mode == SINGLE_BOUNDARY) 1073 remaining = p->p_numthreads - p->p_boundary_count; 1074 else if (mode == SINGLE_NO_EXIT || mode == SINGLE_ALLPROC) 1075 remaining = p->p_numthreads - p->p_suspcount; 1076 else 1077 panic("calc_remaining: wrong mode %d", mode); 1078 return (remaining); 1079 } 1080 1081 static int 1082 remain_for_mode(int mode) 1083 { 1084 1085 return (mode == SINGLE_ALLPROC ? 0 : 1); 1086 } 1087 1088 static int 1089 weed_inhib(int mode, struct thread *td2, struct proc *p) 1090 { 1091 int wakeup_swapper; 1092 1093 PROC_LOCK_ASSERT(p, MA_OWNED); 1094 PROC_SLOCK_ASSERT(p, MA_OWNED); 1095 THREAD_LOCK_ASSERT(td2, MA_OWNED); 1096 1097 wakeup_swapper = 0; 1098 1099 /* 1100 * Since the thread lock is dropped by the scheduler we have 1101 * to retry to check for races. 1102 */ 1103 restart: 1104 switch (mode) { 1105 case SINGLE_EXIT: 1106 if (TD_IS_SUSPENDED(td2)) { 1107 wakeup_swapper |= thread_unsuspend_one(td2, p, true); 1108 thread_lock(td2); 1109 goto restart; 1110 } 1111 if (TD_CAN_ABORT(td2)) { 1112 wakeup_swapper |= sleepq_abort(td2, EINTR); 1113 return (wakeup_swapper); 1114 } 1115 break; 1116 case SINGLE_BOUNDARY: 1117 case SINGLE_NO_EXIT: 1118 if (TD_IS_SUSPENDED(td2) && 1119 (td2->td_flags & TDF_BOUNDARY) == 0) { 1120 wakeup_swapper |= thread_unsuspend_one(td2, p, false); 1121 thread_lock(td2); 1122 goto restart; 1123 } 1124 if (TD_CAN_ABORT(td2)) { 1125 wakeup_swapper |= sleepq_abort(td2, ERESTART); 1126 return (wakeup_swapper); 1127 } 1128 break; 1129 case SINGLE_ALLPROC: 1130 /* 1131 * ALLPROC suspend tries to avoid spurious EINTR for 1132 * threads sleeping interruptable, by suspending the 1133 * thread directly, similarly to sig_suspend_threads(). 1134 * Since such sleep is not performed at the user 1135 * boundary, TDF_BOUNDARY flag is not set, and TDF_ALLPROCSUSP 1136 * is used to avoid immediate un-suspend. 1137 */ 1138 if (TD_IS_SUSPENDED(td2) && (td2->td_flags & (TDF_BOUNDARY | 1139 TDF_ALLPROCSUSP)) == 0) { 1140 wakeup_swapper |= thread_unsuspend_one(td2, p, false); 1141 thread_lock(td2); 1142 goto restart; 1143 } 1144 if (TD_CAN_ABORT(td2)) { 1145 if ((td2->td_flags & TDF_SBDRY) == 0) { 1146 thread_suspend_one(td2); 1147 td2->td_flags |= TDF_ALLPROCSUSP; 1148 } else { 1149 wakeup_swapper |= sleepq_abort(td2, ERESTART); 1150 return (wakeup_swapper); 1151 } 1152 } 1153 break; 1154 default: 1155 break; 1156 } 1157 thread_unlock(td2); 1158 return (wakeup_swapper); 1159 } 1160 1161 /* 1162 * Enforce single-threading. 1163 * 1164 * Returns 1 if the caller must abort (another thread is waiting to 1165 * exit the process or similar). Process is locked! 1166 * Returns 0 when you are successfully the only thread running. 1167 * A process has successfully single threaded in the suspend mode when 1168 * There are no threads in user mode. Threads in the kernel must be 1169 * allowed to continue until they get to the user boundary. They may even 1170 * copy out their return values and data before suspending. They may however be 1171 * accelerated in reaching the user boundary as we will wake up 1172 * any sleeping threads that are interruptable. (PCATCH). 1173 */ 1174 int 1175 thread_single(struct proc *p, int mode) 1176 { 1177 struct thread *td; 1178 struct thread *td2; 1179 int remaining, wakeup_swapper; 1180 1181 td = curthread; 1182 KASSERT(mode == SINGLE_EXIT || mode == SINGLE_BOUNDARY || 1183 mode == SINGLE_ALLPROC || mode == SINGLE_NO_EXIT, 1184 ("invalid mode %d", mode)); 1185 /* 1186 * If allowing non-ALLPROC singlethreading for non-curproc 1187 * callers, calc_remaining() and remain_for_mode() should be 1188 * adjusted to also account for td->td_proc != p. For now 1189 * this is not implemented because it is not used. 1190 */ 1191 KASSERT((mode == SINGLE_ALLPROC && td->td_proc != p) || 1192 (mode != SINGLE_ALLPROC && td->td_proc == p), 1193 ("mode %d proc %p curproc %p", mode, p, td->td_proc)); 1194 mtx_assert(&Giant, MA_NOTOWNED); 1195 PROC_LOCK_ASSERT(p, MA_OWNED); 1196 1197 if ((p->p_flag & P_HADTHREADS) == 0 && mode != SINGLE_ALLPROC) 1198 return (0); 1199 1200 /* Is someone already single threading? */ 1201 if (p->p_singlethread != NULL && p->p_singlethread != td) 1202 return (1); 1203 1204 if (mode == SINGLE_EXIT) { 1205 p->p_flag |= P_SINGLE_EXIT; 1206 p->p_flag &= ~P_SINGLE_BOUNDARY; 1207 } else { 1208 p->p_flag &= ~P_SINGLE_EXIT; 1209 if (mode == SINGLE_BOUNDARY) 1210 p->p_flag |= P_SINGLE_BOUNDARY; 1211 else 1212 p->p_flag &= ~P_SINGLE_BOUNDARY; 1213 } 1214 if (mode == SINGLE_ALLPROC) 1215 p->p_flag |= P_TOTAL_STOP; 1216 p->p_flag |= P_STOPPED_SINGLE; 1217 PROC_SLOCK(p); 1218 p->p_singlethread = td; 1219 remaining = calc_remaining(p, mode); 1220 while (remaining != remain_for_mode(mode)) { 1221 if (P_SHOULDSTOP(p) != P_STOPPED_SINGLE) 1222 goto stopme; 1223 wakeup_swapper = 0; 1224 FOREACH_THREAD_IN_PROC(p, td2) { 1225 if (td2 == td) 1226 continue; 1227 thread_lock(td2); 1228 td2->td_flags |= TDF_ASTPENDING | TDF_NEEDSUSPCHK; 1229 if (TD_IS_INHIBITED(td2)) { 1230 wakeup_swapper |= weed_inhib(mode, td2, p); 1231 #ifdef SMP 1232 } else if (TD_IS_RUNNING(td2) && td != td2) { 1233 forward_signal(td2); 1234 thread_unlock(td2); 1235 #endif 1236 } else 1237 thread_unlock(td2); 1238 } 1239 if (wakeup_swapper) 1240 kick_proc0(); 1241 remaining = calc_remaining(p, mode); 1242 1243 /* 1244 * Maybe we suspended some threads.. was it enough? 1245 */ 1246 if (remaining == remain_for_mode(mode)) 1247 break; 1248 1249 stopme: 1250 /* 1251 * Wake us up when everyone else has suspended. 1252 * In the mean time we suspend as well. 1253 */ 1254 thread_suspend_switch(td, p); 1255 remaining = calc_remaining(p, mode); 1256 } 1257 if (mode == SINGLE_EXIT) { 1258 /* 1259 * Convert the process to an unthreaded process. The 1260 * SINGLE_EXIT is called by exit1() or execve(), in 1261 * both cases other threads must be retired. 1262 */ 1263 KASSERT(p->p_numthreads == 1, ("Unthreading with >1 threads")); 1264 p->p_singlethread = NULL; 1265 p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT | P_HADTHREADS); 1266 1267 /* 1268 * Wait for any remaining threads to exit cpu_throw(). 1269 */ 1270 while (p->p_exitthreads != 0) { 1271 PROC_SUNLOCK(p); 1272 PROC_UNLOCK(p); 1273 sched_relinquish(td); 1274 PROC_LOCK(p); 1275 PROC_SLOCK(p); 1276 } 1277 } else if (mode == SINGLE_BOUNDARY) { 1278 /* 1279 * Wait until all suspended threads are removed from 1280 * the processors. The thread_suspend_check() 1281 * increments p_boundary_count while it is still 1282 * running, which makes it possible for the execve() 1283 * to destroy vmspace while our other threads are 1284 * still using the address space. 1285 * 1286 * We lock the thread, which is only allowed to 1287 * succeed after context switch code finished using 1288 * the address space. 1289 */ 1290 FOREACH_THREAD_IN_PROC(p, td2) { 1291 if (td2 == td) 1292 continue; 1293 thread_lock(td2); 1294 KASSERT((td2->td_flags & TDF_BOUNDARY) != 0, 1295 ("td %p not on boundary", td2)); 1296 KASSERT(TD_IS_SUSPENDED(td2), 1297 ("td %p is not suspended", td2)); 1298 thread_unlock(td2); 1299 } 1300 } 1301 PROC_SUNLOCK(p); 1302 return (0); 1303 } 1304 1305 bool 1306 thread_suspend_check_needed(void) 1307 { 1308 struct proc *p; 1309 struct thread *td; 1310 1311 td = curthread; 1312 p = td->td_proc; 1313 PROC_LOCK_ASSERT(p, MA_OWNED); 1314 return (P_SHOULDSTOP(p) || ((p->p_flag & P_TRACED) != 0 && 1315 (td->td_dbgflags & TDB_SUSPEND) != 0)); 1316 } 1317 1318 /* 1319 * Called in from locations that can safely check to see 1320 * whether we have to suspend or at least throttle for a 1321 * single-thread event (e.g. fork). 1322 * 1323 * Such locations include userret(). 1324 * If the "return_instead" argument is non zero, the thread must be able to 1325 * accept 0 (caller may continue), or 1 (caller must abort) as a result. 1326 * 1327 * The 'return_instead' argument tells the function if it may do a 1328 * thread_exit() or suspend, or whether the caller must abort and back 1329 * out instead. 1330 * 1331 * If the thread that set the single_threading request has set the 1332 * P_SINGLE_EXIT bit in the process flags then this call will never return 1333 * if 'return_instead' is false, but will exit. 1334 * 1335 * P_SINGLE_EXIT | return_instead == 0| return_instead != 0 1336 *---------------+--------------------+--------------------- 1337 * 0 | returns 0 | returns 0 or 1 1338 * | when ST ends | immediately 1339 *---------------+--------------------+--------------------- 1340 * 1 | thread exits | returns 1 1341 * | | immediately 1342 * 0 = thread_exit() or suspension ok, 1343 * other = return error instead of stopping the thread. 1344 * 1345 * While a full suspension is under effect, even a single threading 1346 * thread would be suspended if it made this call (but it shouldn't). 1347 * This call should only be made from places where 1348 * thread_exit() would be safe as that may be the outcome unless 1349 * return_instead is set. 1350 */ 1351 int 1352 thread_suspend_check(int return_instead) 1353 { 1354 struct thread *td; 1355 struct proc *p; 1356 int wakeup_swapper; 1357 1358 td = curthread; 1359 p = td->td_proc; 1360 mtx_assert(&Giant, MA_NOTOWNED); 1361 PROC_LOCK_ASSERT(p, MA_OWNED); 1362 while (thread_suspend_check_needed()) { 1363 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) { 1364 KASSERT(p->p_singlethread != NULL, 1365 ("singlethread not set")); 1366 /* 1367 * The only suspension in action is a 1368 * single-threading. Single threader need not stop. 1369 * It is safe to access p->p_singlethread unlocked 1370 * because it can only be set to our address by us. 1371 */ 1372 if (p->p_singlethread == td) 1373 return (0); /* Exempt from stopping. */ 1374 } 1375 if ((p->p_flag & P_SINGLE_EXIT) && return_instead) 1376 return (EINTR); 1377 1378 /* Should we goto user boundary if we didn't come from there? */ 1379 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE && 1380 (p->p_flag & P_SINGLE_BOUNDARY) && return_instead) 1381 return (ERESTART); 1382 1383 /* 1384 * Ignore suspend requests if they are deferred. 1385 */ 1386 if ((td->td_flags & TDF_SBDRY) != 0) { 1387 KASSERT(return_instead, 1388 ("TDF_SBDRY set for unsafe thread_suspend_check")); 1389 KASSERT((td->td_flags & (TDF_SEINTR | TDF_SERESTART)) != 1390 (TDF_SEINTR | TDF_SERESTART), 1391 ("both TDF_SEINTR and TDF_SERESTART")); 1392 return (TD_SBDRY_INTR(td) ? TD_SBDRY_ERRNO(td) : 0); 1393 } 1394 1395 /* 1396 * If the process is waiting for us to exit, 1397 * this thread should just suicide. 1398 * Assumes that P_SINGLE_EXIT implies P_STOPPED_SINGLE. 1399 */ 1400 if ((p->p_flag & P_SINGLE_EXIT) && (p->p_singlethread != td)) { 1401 PROC_UNLOCK(p); 1402 1403 /* 1404 * Allow Linux emulation layer to do some work 1405 * before thread suicide. 1406 */ 1407 if (__predict_false(p->p_sysent->sv_thread_detach != NULL)) 1408 (p->p_sysent->sv_thread_detach)(td); 1409 umtx_thread_exit(td); 1410 kern_thr_exit(td); 1411 panic("stopped thread did not exit"); 1412 } 1413 1414 PROC_SLOCK(p); 1415 thread_stopped(p); 1416 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) { 1417 if (p->p_numthreads == p->p_suspcount + 1) { 1418 thread_lock(p->p_singlethread); 1419 wakeup_swapper = thread_unsuspend_one( 1420 p->p_singlethread, p, false); 1421 if (wakeup_swapper) 1422 kick_proc0(); 1423 } 1424 } 1425 PROC_UNLOCK(p); 1426 thread_lock(td); 1427 /* 1428 * When a thread suspends, it just 1429 * gets taken off all queues. 1430 */ 1431 thread_suspend_one(td); 1432 if (return_instead == 0) { 1433 p->p_boundary_count++; 1434 td->td_flags |= TDF_BOUNDARY; 1435 } 1436 PROC_SUNLOCK(p); 1437 mi_switch(SW_INVOL | SWT_SUSPEND); 1438 PROC_LOCK(p); 1439 } 1440 return (0); 1441 } 1442 1443 /* 1444 * Check for possible stops and suspensions while executing a 1445 * casueword or similar transiently failing operation. 1446 * 1447 * The sleep argument controls whether the function can handle a stop 1448 * request itself or it should return ERESTART and the request is 1449 * proceed at the kernel/user boundary in ast. 1450 * 1451 * Typically, when retrying due to casueword(9) failure (rv == 1), we 1452 * should handle the stop requests there, with exception of cases when 1453 * the thread owns a kernel resource, for instance busied the umtx 1454 * key, or when functions return immediately if thread_check_susp() 1455 * returned non-zero. On the other hand, retrying the whole lock 1456 * operation, we better not stop there but delegate the handling to 1457 * ast. 1458 * 1459 * If the request is for thread termination P_SINGLE_EXIT, we cannot 1460 * handle it at all, and simply return EINTR. 1461 */ 1462 int 1463 thread_check_susp(struct thread *td, bool sleep) 1464 { 1465 struct proc *p; 1466 int error; 1467 1468 /* 1469 * The check for TDF_NEEDSUSPCHK is racy, but it is enough to 1470 * eventually break the lockstep loop. 1471 */ 1472 if ((td->td_flags & TDF_NEEDSUSPCHK) == 0) 1473 return (0); 1474 error = 0; 1475 p = td->td_proc; 1476 PROC_LOCK(p); 1477 if (p->p_flag & P_SINGLE_EXIT) 1478 error = EINTR; 1479 else if (P_SHOULDSTOP(p) || 1480 ((p->p_flag & P_TRACED) && (td->td_dbgflags & TDB_SUSPEND))) 1481 error = sleep ? thread_suspend_check(0) : ERESTART; 1482 PROC_UNLOCK(p); 1483 return (error); 1484 } 1485 1486 void 1487 thread_suspend_switch(struct thread *td, struct proc *p) 1488 { 1489 1490 KASSERT(!TD_IS_SUSPENDED(td), ("already suspended")); 1491 PROC_LOCK_ASSERT(p, MA_OWNED); 1492 PROC_SLOCK_ASSERT(p, MA_OWNED); 1493 /* 1494 * We implement thread_suspend_one in stages here to avoid 1495 * dropping the proc lock while the thread lock is owned. 1496 */ 1497 if (p == td->td_proc) { 1498 thread_stopped(p); 1499 p->p_suspcount++; 1500 } 1501 PROC_UNLOCK(p); 1502 thread_lock(td); 1503 td->td_flags &= ~TDF_NEEDSUSPCHK; 1504 TD_SET_SUSPENDED(td); 1505 sched_sleep(td, 0); 1506 PROC_SUNLOCK(p); 1507 DROP_GIANT(); 1508 mi_switch(SW_VOL | SWT_SUSPEND); 1509 PICKUP_GIANT(); 1510 PROC_LOCK(p); 1511 PROC_SLOCK(p); 1512 } 1513 1514 void 1515 thread_suspend_one(struct thread *td) 1516 { 1517 struct proc *p; 1518 1519 p = td->td_proc; 1520 PROC_SLOCK_ASSERT(p, MA_OWNED); 1521 THREAD_LOCK_ASSERT(td, MA_OWNED); 1522 KASSERT(!TD_IS_SUSPENDED(td), ("already suspended")); 1523 p->p_suspcount++; 1524 td->td_flags &= ~TDF_NEEDSUSPCHK; 1525 TD_SET_SUSPENDED(td); 1526 sched_sleep(td, 0); 1527 } 1528 1529 static int 1530 thread_unsuspend_one(struct thread *td, struct proc *p, bool boundary) 1531 { 1532 1533 THREAD_LOCK_ASSERT(td, MA_OWNED); 1534 KASSERT(TD_IS_SUSPENDED(td), ("Thread not suspended")); 1535 TD_CLR_SUSPENDED(td); 1536 td->td_flags &= ~TDF_ALLPROCSUSP; 1537 if (td->td_proc == p) { 1538 PROC_SLOCK_ASSERT(p, MA_OWNED); 1539 p->p_suspcount--; 1540 if (boundary && (td->td_flags & TDF_BOUNDARY) != 0) { 1541 td->td_flags &= ~TDF_BOUNDARY; 1542 p->p_boundary_count--; 1543 } 1544 } 1545 return (setrunnable(td, 0)); 1546 } 1547 1548 void 1549 thread_run_flash(struct thread *td) 1550 { 1551 struct proc *p; 1552 1553 p = td->td_proc; 1554 PROC_LOCK_ASSERT(p, MA_OWNED); 1555 1556 if (TD_ON_SLEEPQ(td)) 1557 sleepq_remove_nested(td); 1558 else 1559 thread_lock(td); 1560 1561 THREAD_LOCK_ASSERT(td, MA_OWNED); 1562 KASSERT(TD_IS_SUSPENDED(td), ("Thread not suspended")); 1563 1564 TD_CLR_SUSPENDED(td); 1565 PROC_SLOCK(p); 1566 MPASS(p->p_suspcount > 0); 1567 p->p_suspcount--; 1568 PROC_SUNLOCK(p); 1569 if (setrunnable(td, 0)) 1570 kick_proc0(); 1571 } 1572 1573 /* 1574 * Allow all threads blocked by single threading to continue running. 1575 */ 1576 void 1577 thread_unsuspend(struct proc *p) 1578 { 1579 struct thread *td; 1580 int wakeup_swapper; 1581 1582 PROC_LOCK_ASSERT(p, MA_OWNED); 1583 PROC_SLOCK_ASSERT(p, MA_OWNED); 1584 wakeup_swapper = 0; 1585 if (!P_SHOULDSTOP(p)) { 1586 FOREACH_THREAD_IN_PROC(p, td) { 1587 thread_lock(td); 1588 if (TD_IS_SUSPENDED(td)) { 1589 wakeup_swapper |= thread_unsuspend_one(td, p, 1590 true); 1591 } else 1592 thread_unlock(td); 1593 } 1594 } else if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE && 1595 p->p_numthreads == p->p_suspcount) { 1596 /* 1597 * Stopping everything also did the job for the single 1598 * threading request. Now we've downgraded to single-threaded, 1599 * let it continue. 1600 */ 1601 if (p->p_singlethread->td_proc == p) { 1602 thread_lock(p->p_singlethread); 1603 wakeup_swapper = thread_unsuspend_one( 1604 p->p_singlethread, p, false); 1605 } 1606 } 1607 if (wakeup_swapper) 1608 kick_proc0(); 1609 } 1610 1611 /* 1612 * End the single threading mode.. 1613 */ 1614 void 1615 thread_single_end(struct proc *p, int mode) 1616 { 1617 struct thread *td; 1618 int wakeup_swapper; 1619 1620 KASSERT(mode == SINGLE_EXIT || mode == SINGLE_BOUNDARY || 1621 mode == SINGLE_ALLPROC || mode == SINGLE_NO_EXIT, 1622 ("invalid mode %d", mode)); 1623 PROC_LOCK_ASSERT(p, MA_OWNED); 1624 KASSERT((mode == SINGLE_ALLPROC && (p->p_flag & P_TOTAL_STOP) != 0) || 1625 (mode != SINGLE_ALLPROC && (p->p_flag & P_TOTAL_STOP) == 0), 1626 ("mode %d does not match P_TOTAL_STOP", mode)); 1627 KASSERT(mode == SINGLE_ALLPROC || p->p_singlethread == curthread, 1628 ("thread_single_end from other thread %p %p", 1629 curthread, p->p_singlethread)); 1630 KASSERT(mode != SINGLE_BOUNDARY || 1631 (p->p_flag & P_SINGLE_BOUNDARY) != 0, 1632 ("mis-matched SINGLE_BOUNDARY flags %x", p->p_flag)); 1633 p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT | P_SINGLE_BOUNDARY | 1634 P_TOTAL_STOP); 1635 PROC_SLOCK(p); 1636 p->p_singlethread = NULL; 1637 wakeup_swapper = 0; 1638 /* 1639 * If there are other threads they may now run, 1640 * unless of course there is a blanket 'stop order' 1641 * on the process. The single threader must be allowed 1642 * to continue however as this is a bad place to stop. 1643 */ 1644 if (p->p_numthreads != remain_for_mode(mode) && !P_SHOULDSTOP(p)) { 1645 FOREACH_THREAD_IN_PROC(p, td) { 1646 thread_lock(td); 1647 if (TD_IS_SUSPENDED(td)) { 1648 wakeup_swapper |= thread_unsuspend_one(td, p, 1649 mode == SINGLE_BOUNDARY); 1650 } else 1651 thread_unlock(td); 1652 } 1653 } 1654 KASSERT(mode != SINGLE_BOUNDARY || p->p_boundary_count == 0, 1655 ("inconsistent boundary count %d", p->p_boundary_count)); 1656 PROC_SUNLOCK(p); 1657 if (wakeup_swapper) 1658 kick_proc0(); 1659 } 1660 1661 /* 1662 * Locate a thread by number and return with proc lock held. 1663 * 1664 * thread exit establishes proc -> tidhash lock ordering, but lookup 1665 * takes tidhash first and needs to return locked proc. 1666 * 1667 * The problem is worked around by relying on type-safety of both 1668 * structures and doing the work in 2 steps: 1669 * - tidhash-locked lookup which saves both thread and proc pointers 1670 * - proc-locked verification that the found thread still matches 1671 */ 1672 static bool 1673 tdfind_hash(lwpid_t tid, pid_t pid, struct proc **pp, struct thread **tdp) 1674 { 1675 #define RUN_THRESH 16 1676 struct proc *p; 1677 struct thread *td; 1678 int run; 1679 bool locked; 1680 1681 run = 0; 1682 rw_rlock(TIDHASHLOCK(tid)); 1683 locked = true; 1684 LIST_FOREACH(td, TIDHASH(tid), td_hash) { 1685 if (td->td_tid != tid) { 1686 run++; 1687 continue; 1688 } 1689 p = td->td_proc; 1690 if (pid != -1 && p->p_pid != pid) { 1691 td = NULL; 1692 break; 1693 } 1694 if (run > RUN_THRESH) { 1695 if (rw_try_upgrade(TIDHASHLOCK(tid))) { 1696 LIST_REMOVE(td, td_hash); 1697 LIST_INSERT_HEAD(TIDHASH(td->td_tid), 1698 td, td_hash); 1699 rw_wunlock(TIDHASHLOCK(tid)); 1700 locked = false; 1701 break; 1702 } 1703 } 1704 break; 1705 } 1706 if (locked) 1707 rw_runlock(TIDHASHLOCK(tid)); 1708 if (td == NULL) 1709 return (false); 1710 *pp = p; 1711 *tdp = td; 1712 return (true); 1713 } 1714 1715 struct thread * 1716 tdfind(lwpid_t tid, pid_t pid) 1717 { 1718 struct proc *p; 1719 struct thread *td; 1720 1721 td = curthread; 1722 if (td->td_tid == tid) { 1723 if (pid != -1 && td->td_proc->p_pid != pid) 1724 return (NULL); 1725 PROC_LOCK(td->td_proc); 1726 return (td); 1727 } 1728 1729 for (;;) { 1730 if (!tdfind_hash(tid, pid, &p, &td)) 1731 return (NULL); 1732 PROC_LOCK(p); 1733 if (td->td_tid != tid) { 1734 PROC_UNLOCK(p); 1735 continue; 1736 } 1737 if (td->td_proc != p) { 1738 PROC_UNLOCK(p); 1739 continue; 1740 } 1741 if (p->p_state == PRS_NEW) { 1742 PROC_UNLOCK(p); 1743 return (NULL); 1744 } 1745 return (td); 1746 } 1747 } 1748 1749 void 1750 tidhash_add(struct thread *td) 1751 { 1752 rw_wlock(TIDHASHLOCK(td->td_tid)); 1753 LIST_INSERT_HEAD(TIDHASH(td->td_tid), td, td_hash); 1754 rw_wunlock(TIDHASHLOCK(td->td_tid)); 1755 } 1756 1757 void 1758 tidhash_remove(struct thread *td) 1759 { 1760 1761 rw_wlock(TIDHASHLOCK(td->td_tid)); 1762 LIST_REMOVE(td, td_hash); 1763 rw_wunlock(TIDHASHLOCK(td->td_tid)); 1764 }
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