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/umtxvar.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(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 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 bzero(&td->td_sa.args, sizeof(td->td_sa.args)); 765 cpu_thread_alloc(td); 766 EVENTHANDLER_DIRECT_INVOKE(thread_ctor, td); 767 return (td); 768 } 769 770 int 771 thread_alloc_stack(struct thread *td, int pages) 772 { 773 774 KASSERT(td->td_kstack == 0, 775 ("thread_alloc_stack called on a thread with kstack")); 776 if (!vm_thread_new(td, pages)) 777 return (0); 778 cpu_thread_alloc(td); 779 return (1); 780 } 781 782 /* 783 * Deallocate a thread. 784 */ 785 static void 786 thread_free_batched(struct thread *td) 787 { 788 789 lock_profile_thread_exit(td); 790 if (td->td_cpuset) 791 cpuset_rel(td->td_cpuset); 792 td->td_cpuset = NULL; 793 cpu_thread_free(td); 794 if (td->td_kstack != 0) 795 vm_thread_dispose(td); 796 callout_drain(&td->td_slpcallout); 797 /* 798 * Freeing handled by the caller. 799 */ 800 td->td_tid = -1; 801 uma_zfree(thread_zone, td); 802 } 803 804 void 805 thread_free(struct thread *td) 806 { 807 lwpid_t tid; 808 809 EVENTHANDLER_DIRECT_INVOKE(thread_dtor, td); 810 tid = td->td_tid; 811 thread_free_batched(td); 812 tid_free(tid); 813 thread_count_dec(); 814 } 815 816 void 817 thread_cow_get_proc(struct thread *newtd, struct proc *p) 818 { 819 820 PROC_LOCK_ASSERT(p, MA_OWNED); 821 newtd->td_realucred = crcowget(p->p_ucred); 822 newtd->td_ucred = newtd->td_realucred; 823 newtd->td_limit = lim_hold(p->p_limit); 824 newtd->td_cowgen = p->p_cowgen; 825 } 826 827 void 828 thread_cow_get(struct thread *newtd, struct thread *td) 829 { 830 831 MPASS(td->td_realucred == td->td_ucred); 832 newtd->td_realucred = crcowget(td->td_realucred); 833 newtd->td_ucred = newtd->td_realucred; 834 newtd->td_limit = lim_hold(td->td_limit); 835 newtd->td_cowgen = td->td_cowgen; 836 } 837 838 void 839 thread_cow_free(struct thread *td) 840 { 841 842 if (td->td_realucred != NULL) 843 crcowfree(td); 844 if (td->td_limit != NULL) 845 lim_free(td->td_limit); 846 } 847 848 void 849 thread_cow_update(struct thread *td) 850 { 851 struct proc *p; 852 struct ucred *oldcred; 853 struct plimit *oldlimit; 854 855 p = td->td_proc; 856 oldlimit = NULL; 857 PROC_LOCK(p); 858 oldcred = crcowsync(); 859 if (td->td_limit != p->p_limit) { 860 oldlimit = td->td_limit; 861 td->td_limit = lim_hold(p->p_limit); 862 } 863 td->td_cowgen = p->p_cowgen; 864 PROC_UNLOCK(p); 865 if (oldcred != NULL) 866 crfree(oldcred); 867 if (oldlimit != NULL) 868 lim_free(oldlimit); 869 } 870 871 /* 872 * Discard the current thread and exit from its context. 873 * Always called with scheduler locked. 874 * 875 * Because we can't free a thread while we're operating under its context, 876 * push the current thread into our CPU's deadthread holder. This means 877 * we needn't worry about someone else grabbing our context before we 878 * do a cpu_throw(). 879 */ 880 void 881 thread_exit(void) 882 { 883 uint64_t runtime, new_switchtime; 884 struct thread *td; 885 struct thread *td2; 886 struct proc *p; 887 int wakeup_swapper; 888 889 td = curthread; 890 p = td->td_proc; 891 892 PROC_SLOCK_ASSERT(p, MA_OWNED); 893 mtx_assert(&Giant, MA_NOTOWNED); 894 895 PROC_LOCK_ASSERT(p, MA_OWNED); 896 KASSERT(p != NULL, ("thread exiting without a process")); 897 CTR3(KTR_PROC, "thread_exit: thread %p (pid %ld, %s)", td, 898 (long)p->p_pid, td->td_name); 899 SDT_PROBE0(proc, , , lwp__exit); 900 KASSERT(TAILQ_EMPTY(&td->td_sigqueue.sq_list), ("signal pending")); 901 MPASS(td->td_realucred == td->td_ucred); 902 903 /* 904 * drop FPU & debug register state storage, or any other 905 * architecture specific resources that 906 * would not be on a new untouched process. 907 */ 908 cpu_thread_exit(td); 909 910 /* 911 * The last thread is left attached to the process 912 * So that the whole bundle gets recycled. Skip 913 * all this stuff if we never had threads. 914 * EXIT clears all sign of other threads when 915 * it goes to single threading, so the last thread always 916 * takes the short path. 917 */ 918 if (p->p_flag & P_HADTHREADS) { 919 if (p->p_numthreads > 1) { 920 atomic_add_int(&td->td_proc->p_exitthreads, 1); 921 thread_unlink(td); 922 td2 = FIRST_THREAD_IN_PROC(p); 923 sched_exit_thread(td2, td); 924 925 /* 926 * The test below is NOT true if we are the 927 * sole exiting thread. P_STOPPED_SINGLE is unset 928 * in exit1() after it is the only survivor. 929 */ 930 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) { 931 if (p->p_numthreads == p->p_suspcount) { 932 thread_lock(p->p_singlethread); 933 wakeup_swapper = thread_unsuspend_one( 934 p->p_singlethread, p, false); 935 if (wakeup_swapper) 936 kick_proc0(); 937 } 938 } 939 940 PCPU_SET(deadthread, td); 941 } else { 942 /* 943 * The last thread is exiting.. but not through exit() 944 */ 945 panic ("thread_exit: Last thread exiting on its own"); 946 } 947 } 948 #ifdef HWPMC_HOOKS 949 /* 950 * If this thread is part of a process that is being tracked by hwpmc(4), 951 * inform the module of the thread's impending exit. 952 */ 953 if (PMC_PROC_IS_USING_PMCS(td->td_proc)) { 954 PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_OUT); 955 PMC_CALL_HOOK_UNLOCKED(td, PMC_FN_THR_EXIT, NULL); 956 } else if (PMC_SYSTEM_SAMPLING_ACTIVE()) 957 PMC_CALL_HOOK_UNLOCKED(td, PMC_FN_THR_EXIT_LOG, NULL); 958 #endif 959 PROC_UNLOCK(p); 960 PROC_STATLOCK(p); 961 thread_lock(td); 962 PROC_SUNLOCK(p); 963 964 /* Do the same timestamp bookkeeping that mi_switch() would do. */ 965 new_switchtime = cpu_ticks(); 966 runtime = new_switchtime - PCPU_GET(switchtime); 967 td->td_runtime += runtime; 968 td->td_incruntime += runtime; 969 PCPU_SET(switchtime, new_switchtime); 970 PCPU_SET(switchticks, ticks); 971 VM_CNT_INC(v_swtch); 972 973 /* Save our resource usage in our process. */ 974 td->td_ru.ru_nvcsw++; 975 ruxagg_locked(p, td); 976 rucollect(&p->p_ru, &td->td_ru); 977 PROC_STATUNLOCK(p); 978 979 td->td_state = TDS_INACTIVE; 980 #ifdef WITNESS 981 witness_thread_exit(td); 982 #endif 983 CTR1(KTR_PROC, "thread_exit: cpu_throw() thread %p", td); 984 sched_throw(td); 985 panic("I'm a teapot!"); 986 /* NOTREACHED */ 987 } 988 989 /* 990 * Do any thread specific cleanups that may be needed in wait() 991 * called with Giant, proc and schedlock not held. 992 */ 993 void 994 thread_wait(struct proc *p) 995 { 996 struct thread *td; 997 998 mtx_assert(&Giant, MA_NOTOWNED); 999 KASSERT(p->p_numthreads == 1, ("multiple threads in thread_wait()")); 1000 KASSERT(p->p_exitthreads == 0, ("p_exitthreads leaking")); 1001 td = FIRST_THREAD_IN_PROC(p); 1002 /* Lock the last thread so we spin until it exits cpu_throw(). */ 1003 thread_lock(td); 1004 thread_unlock(td); 1005 lock_profile_thread_exit(td); 1006 cpuset_rel(td->td_cpuset); 1007 td->td_cpuset = NULL; 1008 cpu_thread_clean(td); 1009 thread_cow_free(td); 1010 callout_drain(&td->td_slpcallout); 1011 thread_reap(); /* check for zombie threads etc. */ 1012 } 1013 1014 /* 1015 * Link a thread to a process. 1016 * set up anything that needs to be initialized for it to 1017 * be used by the process. 1018 */ 1019 void 1020 thread_link(struct thread *td, struct proc *p) 1021 { 1022 1023 /* 1024 * XXX This can't be enabled because it's called for proc0 before 1025 * its lock has been created. 1026 * PROC_LOCK_ASSERT(p, MA_OWNED); 1027 */ 1028 td->td_state = TDS_INACTIVE; 1029 td->td_proc = p; 1030 td->td_flags = TDF_INMEM; 1031 1032 LIST_INIT(&td->td_contested); 1033 LIST_INIT(&td->td_lprof[0]); 1034 LIST_INIT(&td->td_lprof[1]); 1035 #ifdef EPOCH_TRACE 1036 SLIST_INIT(&td->td_epochs); 1037 #endif 1038 sigqueue_init(&td->td_sigqueue, p); 1039 callout_init(&td->td_slpcallout, 1); 1040 TAILQ_INSERT_TAIL(&p->p_threads, td, td_plist); 1041 p->p_numthreads++; 1042 } 1043 1044 /* 1045 * Called from: 1046 * thread_exit() 1047 */ 1048 void 1049 thread_unlink(struct thread *td) 1050 { 1051 struct proc *p = td->td_proc; 1052 1053 PROC_LOCK_ASSERT(p, MA_OWNED); 1054 #ifdef EPOCH_TRACE 1055 MPASS(SLIST_EMPTY(&td->td_epochs)); 1056 #endif 1057 1058 TAILQ_REMOVE(&p->p_threads, td, td_plist); 1059 p->p_numthreads--; 1060 /* could clear a few other things here */ 1061 /* Must NOT clear links to proc! */ 1062 } 1063 1064 static int 1065 calc_remaining(struct proc *p, int mode) 1066 { 1067 int remaining; 1068 1069 PROC_LOCK_ASSERT(p, MA_OWNED); 1070 PROC_SLOCK_ASSERT(p, MA_OWNED); 1071 if (mode == SINGLE_EXIT) 1072 remaining = p->p_numthreads; 1073 else if (mode == SINGLE_BOUNDARY) 1074 remaining = p->p_numthreads - p->p_boundary_count; 1075 else if (mode == SINGLE_NO_EXIT || mode == SINGLE_ALLPROC) 1076 remaining = p->p_numthreads - p->p_suspcount; 1077 else 1078 panic("calc_remaining: wrong mode %d", mode); 1079 return (remaining); 1080 } 1081 1082 static int 1083 remain_for_mode(int mode) 1084 { 1085 1086 return (mode == SINGLE_ALLPROC ? 0 : 1); 1087 } 1088 1089 static int 1090 weed_inhib(int mode, struct thread *td2, struct proc *p) 1091 { 1092 int wakeup_swapper; 1093 1094 PROC_LOCK_ASSERT(p, MA_OWNED); 1095 PROC_SLOCK_ASSERT(p, MA_OWNED); 1096 THREAD_LOCK_ASSERT(td2, MA_OWNED); 1097 1098 wakeup_swapper = 0; 1099 1100 /* 1101 * Since the thread lock is dropped by the scheduler we have 1102 * to retry to check for races. 1103 */ 1104 restart: 1105 switch (mode) { 1106 case SINGLE_EXIT: 1107 if (TD_IS_SUSPENDED(td2)) { 1108 wakeup_swapper |= thread_unsuspend_one(td2, p, true); 1109 thread_lock(td2); 1110 goto restart; 1111 } 1112 if (TD_CAN_ABORT(td2)) { 1113 wakeup_swapper |= sleepq_abort(td2, EINTR); 1114 return (wakeup_swapper); 1115 } 1116 break; 1117 case SINGLE_BOUNDARY: 1118 case SINGLE_NO_EXIT: 1119 if (TD_IS_SUSPENDED(td2) && 1120 (td2->td_flags & TDF_BOUNDARY) == 0) { 1121 wakeup_swapper |= thread_unsuspend_one(td2, p, false); 1122 thread_lock(td2); 1123 goto restart; 1124 } 1125 if (TD_CAN_ABORT(td2)) { 1126 wakeup_swapper |= sleepq_abort(td2, ERESTART); 1127 return (wakeup_swapper); 1128 } 1129 break; 1130 case SINGLE_ALLPROC: 1131 /* 1132 * ALLPROC suspend tries to avoid spurious EINTR for 1133 * threads sleeping interruptable, by suspending the 1134 * thread directly, similarly to sig_suspend_threads(). 1135 * Since such sleep is not neccessary performed at the user 1136 * boundary, TDF_ALLPROCSUSP is used to avoid immediate 1137 * un-suspend. 1138 */ 1139 if (TD_IS_SUSPENDED(td2) && (td2->td_flags & 1140 TDF_ALLPROCSUSP) == 0) { 1141 wakeup_swapper |= thread_unsuspend_one(td2, p, false); 1142 thread_lock(td2); 1143 goto restart; 1144 } 1145 if (TD_CAN_ABORT(td2)) { 1146 td2->td_flags |= TDF_ALLPROCSUSP; 1147 wakeup_swapper |= sleepq_abort(td2, ERESTART); 1148 return (wakeup_swapper); 1149 } 1150 break; 1151 default: 1152 break; 1153 } 1154 thread_unlock(td2); 1155 return (wakeup_swapper); 1156 } 1157 1158 /* 1159 * Enforce single-threading. 1160 * 1161 * Returns 1 if the caller must abort (another thread is waiting to 1162 * exit the process or similar). Process is locked! 1163 * Returns 0 when you are successfully the only thread running. 1164 * A process has successfully single threaded in the suspend mode when 1165 * There are no threads in user mode. Threads in the kernel must be 1166 * allowed to continue until they get to the user boundary. They may even 1167 * copy out their return values and data before suspending. They may however be 1168 * accelerated in reaching the user boundary as we will wake up 1169 * any sleeping threads that are interruptable. (PCATCH). 1170 */ 1171 int 1172 thread_single(struct proc *p, int mode) 1173 { 1174 struct thread *td; 1175 struct thread *td2; 1176 int remaining, wakeup_swapper; 1177 1178 td = curthread; 1179 KASSERT(mode == SINGLE_EXIT || mode == SINGLE_BOUNDARY || 1180 mode == SINGLE_ALLPROC || mode == SINGLE_NO_EXIT, 1181 ("invalid mode %d", mode)); 1182 /* 1183 * If allowing non-ALLPROC singlethreading for non-curproc 1184 * callers, calc_remaining() and remain_for_mode() should be 1185 * adjusted to also account for td->td_proc != p. For now 1186 * this is not implemented because it is not used. 1187 */ 1188 KASSERT((mode == SINGLE_ALLPROC && td->td_proc != p) || 1189 (mode != SINGLE_ALLPROC && td->td_proc == p), 1190 ("mode %d proc %p curproc %p", mode, p, td->td_proc)); 1191 mtx_assert(&Giant, MA_NOTOWNED); 1192 PROC_LOCK_ASSERT(p, MA_OWNED); 1193 1194 /* 1195 * Is someone already single threading? 1196 * Or may be singlethreading is not needed at all. 1197 */ 1198 if (mode == SINGLE_ALLPROC) { 1199 while ((p->p_flag & P_STOPPED_SINGLE) != 0) { 1200 if ((p->p_flag2 & P2_WEXIT) != 0) 1201 return (1); 1202 msleep(&p->p_flag, &p->p_mtx, PCATCH, "thrsgl", 0); 1203 } 1204 } else if ((p->p_flag & P_HADTHREADS) == 0) 1205 return (0); 1206 if (p->p_singlethread != NULL && p->p_singlethread != td) 1207 return (1); 1208 1209 if (mode == SINGLE_EXIT) { 1210 p->p_flag |= P_SINGLE_EXIT; 1211 p->p_flag &= ~P_SINGLE_BOUNDARY; 1212 } else { 1213 p->p_flag &= ~P_SINGLE_EXIT; 1214 if (mode == SINGLE_BOUNDARY) 1215 p->p_flag |= P_SINGLE_BOUNDARY; 1216 else 1217 p->p_flag &= ~P_SINGLE_BOUNDARY; 1218 } 1219 if (mode == SINGLE_ALLPROC) 1220 p->p_flag |= P_TOTAL_STOP; 1221 p->p_flag |= P_STOPPED_SINGLE; 1222 PROC_SLOCK(p); 1223 p->p_singlethread = td; 1224 remaining = calc_remaining(p, mode); 1225 while (remaining != remain_for_mode(mode)) { 1226 if (P_SHOULDSTOP(p) != P_STOPPED_SINGLE) 1227 goto stopme; 1228 wakeup_swapper = 0; 1229 FOREACH_THREAD_IN_PROC(p, td2) { 1230 if (td2 == td) 1231 continue; 1232 thread_lock(td2); 1233 td2->td_flags |= TDF_ASTPENDING | TDF_NEEDSUSPCHK; 1234 if (TD_IS_INHIBITED(td2)) { 1235 wakeup_swapper |= weed_inhib(mode, td2, p); 1236 #ifdef SMP 1237 } else if (TD_IS_RUNNING(td2)) { 1238 forward_signal(td2); 1239 thread_unlock(td2); 1240 #endif 1241 } else 1242 thread_unlock(td2); 1243 } 1244 if (wakeup_swapper) 1245 kick_proc0(); 1246 remaining = calc_remaining(p, mode); 1247 1248 /* 1249 * Maybe we suspended some threads.. was it enough? 1250 */ 1251 if (remaining == remain_for_mode(mode)) 1252 break; 1253 1254 stopme: 1255 /* 1256 * Wake us up when everyone else has suspended. 1257 * In the mean time we suspend as well. 1258 */ 1259 thread_suspend_switch(td, p); 1260 remaining = calc_remaining(p, mode); 1261 } 1262 if (mode == SINGLE_EXIT) { 1263 /* 1264 * Convert the process to an unthreaded process. The 1265 * SINGLE_EXIT is called by exit1() or execve(), in 1266 * both cases other threads must be retired. 1267 */ 1268 KASSERT(p->p_numthreads == 1, ("Unthreading with >1 threads")); 1269 p->p_singlethread = NULL; 1270 p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT | P_HADTHREADS); 1271 1272 /* 1273 * Wait for any remaining threads to exit cpu_throw(). 1274 */ 1275 while (p->p_exitthreads != 0) { 1276 PROC_SUNLOCK(p); 1277 PROC_UNLOCK(p); 1278 sched_relinquish(td); 1279 PROC_LOCK(p); 1280 PROC_SLOCK(p); 1281 } 1282 } else if (mode == SINGLE_BOUNDARY) { 1283 /* 1284 * Wait until all suspended threads are removed from 1285 * the processors. The thread_suspend_check() 1286 * increments p_boundary_count while it is still 1287 * running, which makes it possible for the execve() 1288 * to destroy vmspace while our other threads are 1289 * still using the address space. 1290 * 1291 * We lock the thread, which is only allowed to 1292 * succeed after context switch code finished using 1293 * the address space. 1294 */ 1295 FOREACH_THREAD_IN_PROC(p, td2) { 1296 if (td2 == td) 1297 continue; 1298 thread_lock(td2); 1299 KASSERT((td2->td_flags & TDF_BOUNDARY) != 0, 1300 ("td %p not on boundary", td2)); 1301 KASSERT(TD_IS_SUSPENDED(td2), 1302 ("td %p is not suspended", td2)); 1303 thread_unlock(td2); 1304 } 1305 } 1306 PROC_SUNLOCK(p); 1307 return (0); 1308 } 1309 1310 bool 1311 thread_suspend_check_needed(void) 1312 { 1313 struct proc *p; 1314 struct thread *td; 1315 1316 td = curthread; 1317 p = td->td_proc; 1318 PROC_LOCK_ASSERT(p, MA_OWNED); 1319 return (P_SHOULDSTOP(p) || ((p->p_flag & P_TRACED) != 0 && 1320 (td->td_dbgflags & TDB_SUSPEND) != 0)); 1321 } 1322 1323 /* 1324 * Called in from locations that can safely check to see 1325 * whether we have to suspend or at least throttle for a 1326 * single-thread event (e.g. fork). 1327 * 1328 * Such locations include userret(). 1329 * If the "return_instead" argument is non zero, the thread must be able to 1330 * accept 0 (caller may continue), or 1 (caller must abort) as a result. 1331 * 1332 * The 'return_instead' argument tells the function if it may do a 1333 * thread_exit() or suspend, or whether the caller must abort and back 1334 * out instead. 1335 * 1336 * If the thread that set the single_threading request has set the 1337 * P_SINGLE_EXIT bit in the process flags then this call will never return 1338 * if 'return_instead' is false, but will exit. 1339 * 1340 * P_SINGLE_EXIT | return_instead == 0| return_instead != 0 1341 *---------------+--------------------+--------------------- 1342 * 0 | returns 0 | returns 0 or 1 1343 * | when ST ends | immediately 1344 *---------------+--------------------+--------------------- 1345 * 1 | thread exits | returns 1 1346 * | | immediately 1347 * 0 = thread_exit() or suspension ok, 1348 * other = return error instead of stopping the thread. 1349 * 1350 * While a full suspension is under effect, even a single threading 1351 * thread would be suspended if it made this call (but it shouldn't). 1352 * This call should only be made from places where 1353 * thread_exit() would be safe as that may be the outcome unless 1354 * return_instead is set. 1355 */ 1356 int 1357 thread_suspend_check(int return_instead) 1358 { 1359 struct thread *td; 1360 struct proc *p; 1361 int wakeup_swapper; 1362 1363 td = curthread; 1364 p = td->td_proc; 1365 mtx_assert(&Giant, MA_NOTOWNED); 1366 PROC_LOCK_ASSERT(p, MA_OWNED); 1367 while (thread_suspend_check_needed()) { 1368 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) { 1369 KASSERT(p->p_singlethread != NULL, 1370 ("singlethread not set")); 1371 /* 1372 * The only suspension in action is a 1373 * single-threading. Single threader need not stop. 1374 * It is safe to access p->p_singlethread unlocked 1375 * because it can only be set to our address by us. 1376 */ 1377 if (p->p_singlethread == td) 1378 return (0); /* Exempt from stopping. */ 1379 } 1380 if ((p->p_flag & P_SINGLE_EXIT) && return_instead) 1381 return (EINTR); 1382 1383 /* Should we goto user boundary if we didn't come from there? */ 1384 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE && 1385 (p->p_flag & P_SINGLE_BOUNDARY) && return_instead) 1386 return (ERESTART); 1387 1388 /* 1389 * Ignore suspend requests if they are deferred. 1390 */ 1391 if ((td->td_flags & TDF_SBDRY) != 0) { 1392 KASSERT(return_instead, 1393 ("TDF_SBDRY set for unsafe thread_suspend_check")); 1394 KASSERT((td->td_flags & (TDF_SEINTR | TDF_SERESTART)) != 1395 (TDF_SEINTR | TDF_SERESTART), 1396 ("both TDF_SEINTR and TDF_SERESTART")); 1397 return (TD_SBDRY_INTR(td) ? TD_SBDRY_ERRNO(td) : 0); 1398 } 1399 1400 /* 1401 * If the process is waiting for us to exit, 1402 * this thread should just suicide. 1403 * Assumes that P_SINGLE_EXIT implies P_STOPPED_SINGLE. 1404 */ 1405 if ((p->p_flag & P_SINGLE_EXIT) && (p->p_singlethread != td)) { 1406 PROC_UNLOCK(p); 1407 1408 /* 1409 * Allow Linux emulation layer to do some work 1410 * before thread suicide. 1411 */ 1412 if (__predict_false(p->p_sysent->sv_thread_detach != NULL)) 1413 (p->p_sysent->sv_thread_detach)(td); 1414 umtx_thread_exit(td); 1415 kern_thr_exit(td); 1416 panic("stopped thread did not exit"); 1417 } 1418 1419 PROC_SLOCK(p); 1420 thread_stopped(p); 1421 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) { 1422 if (p->p_numthreads == p->p_suspcount + 1) { 1423 thread_lock(p->p_singlethread); 1424 wakeup_swapper = thread_unsuspend_one( 1425 p->p_singlethread, p, false); 1426 if (wakeup_swapper) 1427 kick_proc0(); 1428 } 1429 } 1430 PROC_UNLOCK(p); 1431 thread_lock(td); 1432 /* 1433 * When a thread suspends, it just 1434 * gets taken off all queues. 1435 */ 1436 thread_suspend_one(td); 1437 if (return_instead == 0) { 1438 p->p_boundary_count++; 1439 td->td_flags |= TDF_BOUNDARY; 1440 } 1441 PROC_SUNLOCK(p); 1442 mi_switch(SW_INVOL | SWT_SUSPEND); 1443 PROC_LOCK(p); 1444 } 1445 return (0); 1446 } 1447 1448 /* 1449 * Check for possible stops and suspensions while executing a 1450 * casueword or similar transiently failing operation. 1451 * 1452 * The sleep argument controls whether the function can handle a stop 1453 * request itself or it should return ERESTART and the request is 1454 * proceed at the kernel/user boundary in ast. 1455 * 1456 * Typically, when retrying due to casueword(9) failure (rv == 1), we 1457 * should handle the stop requests there, with exception of cases when 1458 * the thread owns a kernel resource, for instance busied the umtx 1459 * key, or when functions return immediately if thread_check_susp() 1460 * returned non-zero. On the other hand, retrying the whole lock 1461 * operation, we better not stop there but delegate the handling to 1462 * ast. 1463 * 1464 * If the request is for thread termination P_SINGLE_EXIT, we cannot 1465 * handle it at all, and simply return EINTR. 1466 */ 1467 int 1468 thread_check_susp(struct thread *td, bool sleep) 1469 { 1470 struct proc *p; 1471 int error; 1472 1473 /* 1474 * The check for TDF_NEEDSUSPCHK is racy, but it is enough to 1475 * eventually break the lockstep loop. 1476 */ 1477 if ((td->td_flags & TDF_NEEDSUSPCHK) == 0) 1478 return (0); 1479 error = 0; 1480 p = td->td_proc; 1481 PROC_LOCK(p); 1482 if (p->p_flag & P_SINGLE_EXIT) 1483 error = EINTR; 1484 else if (P_SHOULDSTOP(p) || 1485 ((p->p_flag & P_TRACED) && (td->td_dbgflags & TDB_SUSPEND))) 1486 error = sleep ? thread_suspend_check(0) : ERESTART; 1487 PROC_UNLOCK(p); 1488 return (error); 1489 } 1490 1491 void 1492 thread_suspend_switch(struct thread *td, struct proc *p) 1493 { 1494 1495 KASSERT(!TD_IS_SUSPENDED(td), ("already suspended")); 1496 PROC_LOCK_ASSERT(p, MA_OWNED); 1497 PROC_SLOCK_ASSERT(p, MA_OWNED); 1498 /* 1499 * We implement thread_suspend_one in stages here to avoid 1500 * dropping the proc lock while the thread lock is owned. 1501 */ 1502 if (p == td->td_proc) { 1503 thread_stopped(p); 1504 p->p_suspcount++; 1505 } 1506 PROC_UNLOCK(p); 1507 thread_lock(td); 1508 td->td_flags &= ~TDF_NEEDSUSPCHK; 1509 TD_SET_SUSPENDED(td); 1510 sched_sleep(td, 0); 1511 PROC_SUNLOCK(p); 1512 DROP_GIANT(); 1513 mi_switch(SW_VOL | SWT_SUSPEND); 1514 PICKUP_GIANT(); 1515 PROC_LOCK(p); 1516 PROC_SLOCK(p); 1517 } 1518 1519 void 1520 thread_suspend_one(struct thread *td) 1521 { 1522 struct proc *p; 1523 1524 p = td->td_proc; 1525 PROC_SLOCK_ASSERT(p, MA_OWNED); 1526 THREAD_LOCK_ASSERT(td, MA_OWNED); 1527 KASSERT(!TD_IS_SUSPENDED(td), ("already suspended")); 1528 p->p_suspcount++; 1529 td->td_flags &= ~TDF_NEEDSUSPCHK; 1530 TD_SET_SUSPENDED(td); 1531 sched_sleep(td, 0); 1532 } 1533 1534 static int 1535 thread_unsuspend_one(struct thread *td, struct proc *p, bool boundary) 1536 { 1537 1538 THREAD_LOCK_ASSERT(td, MA_OWNED); 1539 KASSERT(TD_IS_SUSPENDED(td), ("Thread not suspended")); 1540 TD_CLR_SUSPENDED(td); 1541 td->td_flags &= ~TDF_ALLPROCSUSP; 1542 if (td->td_proc == p) { 1543 PROC_SLOCK_ASSERT(p, MA_OWNED); 1544 p->p_suspcount--; 1545 if (boundary && (td->td_flags & TDF_BOUNDARY) != 0) { 1546 td->td_flags &= ~TDF_BOUNDARY; 1547 p->p_boundary_count--; 1548 } 1549 } 1550 return (setrunnable(td, 0)); 1551 } 1552 1553 void 1554 thread_run_flash(struct thread *td) 1555 { 1556 struct proc *p; 1557 1558 p = td->td_proc; 1559 PROC_LOCK_ASSERT(p, MA_OWNED); 1560 1561 if (TD_ON_SLEEPQ(td)) 1562 sleepq_remove_nested(td); 1563 else 1564 thread_lock(td); 1565 1566 THREAD_LOCK_ASSERT(td, MA_OWNED); 1567 KASSERT(TD_IS_SUSPENDED(td), ("Thread not suspended")); 1568 1569 TD_CLR_SUSPENDED(td); 1570 PROC_SLOCK(p); 1571 MPASS(p->p_suspcount > 0); 1572 p->p_suspcount--; 1573 PROC_SUNLOCK(p); 1574 if (setrunnable(td, 0)) 1575 kick_proc0(); 1576 } 1577 1578 /* 1579 * Allow all threads blocked by single threading to continue running. 1580 */ 1581 void 1582 thread_unsuspend(struct proc *p) 1583 { 1584 struct thread *td; 1585 int wakeup_swapper; 1586 1587 PROC_LOCK_ASSERT(p, MA_OWNED); 1588 PROC_SLOCK_ASSERT(p, MA_OWNED); 1589 wakeup_swapper = 0; 1590 if (!P_SHOULDSTOP(p)) { 1591 FOREACH_THREAD_IN_PROC(p, td) { 1592 thread_lock(td); 1593 if (TD_IS_SUSPENDED(td)) 1594 wakeup_swapper |= thread_unsuspend_one(td, p, 1595 true); 1596 else 1597 thread_unlock(td); 1598 } 1599 } else if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE && 1600 p->p_numthreads == p->p_suspcount) { 1601 /* 1602 * Stopping everything also did the job for the single 1603 * threading request. Now we've downgraded to single-threaded, 1604 * let it continue. 1605 */ 1606 if (p->p_singlethread->td_proc == p) { 1607 thread_lock(p->p_singlethread); 1608 wakeup_swapper = thread_unsuspend_one( 1609 p->p_singlethread, p, false); 1610 } 1611 } 1612 if (wakeup_swapper) 1613 kick_proc0(); 1614 } 1615 1616 /* 1617 * End the single threading mode.. 1618 */ 1619 void 1620 thread_single_end(struct proc *p, int mode) 1621 { 1622 struct thread *td; 1623 int wakeup_swapper; 1624 1625 KASSERT(mode == SINGLE_EXIT || mode == SINGLE_BOUNDARY || 1626 mode == SINGLE_ALLPROC || mode == SINGLE_NO_EXIT, 1627 ("invalid mode %d", mode)); 1628 PROC_LOCK_ASSERT(p, MA_OWNED); 1629 KASSERT((mode == SINGLE_ALLPROC && (p->p_flag & P_TOTAL_STOP) != 0) || 1630 (mode != SINGLE_ALLPROC && (p->p_flag & P_TOTAL_STOP) == 0), 1631 ("mode %d does not match P_TOTAL_STOP", mode)); 1632 KASSERT(mode == SINGLE_ALLPROC || p->p_singlethread == curthread, 1633 ("thread_single_end from other thread %p %p", 1634 curthread, p->p_singlethread)); 1635 KASSERT(mode != SINGLE_BOUNDARY || 1636 (p->p_flag & P_SINGLE_BOUNDARY) != 0, 1637 ("mis-matched SINGLE_BOUNDARY flags %x", p->p_flag)); 1638 p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT | P_SINGLE_BOUNDARY | 1639 P_TOTAL_STOP); 1640 PROC_SLOCK(p); 1641 p->p_singlethread = NULL; 1642 wakeup_swapper = 0; 1643 /* 1644 * If there are other threads they may now run, 1645 * unless of course there is a blanket 'stop order' 1646 * on the process. The single threader must be allowed 1647 * to continue however as this is a bad place to stop. 1648 */ 1649 if (p->p_numthreads != remain_for_mode(mode) && !P_SHOULDSTOP(p)) { 1650 FOREACH_THREAD_IN_PROC(p, td) { 1651 thread_lock(td); 1652 if (TD_IS_SUSPENDED(td)) { 1653 wakeup_swapper |= thread_unsuspend_one(td, p, 1654 true); 1655 } else 1656 thread_unlock(td); 1657 } 1658 } 1659 KASSERT(mode != SINGLE_BOUNDARY || p->p_boundary_count == 0, 1660 ("inconsistent boundary count %d", p->p_boundary_count)); 1661 PROC_SUNLOCK(p); 1662 if (wakeup_swapper) 1663 kick_proc0(); 1664 wakeup(&p->p_flag); 1665 } 1666 1667 /* 1668 * Locate a thread by number and return with proc lock held. 1669 * 1670 * thread exit establishes proc -> tidhash lock ordering, but lookup 1671 * takes tidhash first and needs to return locked proc. 1672 * 1673 * The problem is worked around by relying on type-safety of both 1674 * structures and doing the work in 2 steps: 1675 * - tidhash-locked lookup which saves both thread and proc pointers 1676 * - proc-locked verification that the found thread still matches 1677 */ 1678 static bool 1679 tdfind_hash(lwpid_t tid, pid_t pid, struct proc **pp, struct thread **tdp) 1680 { 1681 #define RUN_THRESH 16 1682 struct proc *p; 1683 struct thread *td; 1684 int run; 1685 bool locked; 1686 1687 run = 0; 1688 rw_rlock(TIDHASHLOCK(tid)); 1689 locked = true; 1690 LIST_FOREACH(td, TIDHASH(tid), td_hash) { 1691 if (td->td_tid != tid) { 1692 run++; 1693 continue; 1694 } 1695 p = td->td_proc; 1696 if (pid != -1 && p->p_pid != pid) { 1697 td = NULL; 1698 break; 1699 } 1700 if (run > RUN_THRESH) { 1701 if (rw_try_upgrade(TIDHASHLOCK(tid))) { 1702 LIST_REMOVE(td, td_hash); 1703 LIST_INSERT_HEAD(TIDHASH(td->td_tid), 1704 td, td_hash); 1705 rw_wunlock(TIDHASHLOCK(tid)); 1706 locked = false; 1707 break; 1708 } 1709 } 1710 break; 1711 } 1712 if (locked) 1713 rw_runlock(TIDHASHLOCK(tid)); 1714 if (td == NULL) 1715 return (false); 1716 *pp = p; 1717 *tdp = td; 1718 return (true); 1719 } 1720 1721 struct thread * 1722 tdfind(lwpid_t tid, pid_t pid) 1723 { 1724 struct proc *p; 1725 struct thread *td; 1726 1727 td = curthread; 1728 if (td->td_tid == tid) { 1729 if (pid != -1 && td->td_proc->p_pid != pid) 1730 return (NULL); 1731 PROC_LOCK(td->td_proc); 1732 return (td); 1733 } 1734 1735 for (;;) { 1736 if (!tdfind_hash(tid, pid, &p, &td)) 1737 return (NULL); 1738 PROC_LOCK(p); 1739 if (td->td_tid != tid) { 1740 PROC_UNLOCK(p); 1741 continue; 1742 } 1743 if (td->td_proc != p) { 1744 PROC_UNLOCK(p); 1745 continue; 1746 } 1747 if (p->p_state == PRS_NEW) { 1748 PROC_UNLOCK(p); 1749 return (NULL); 1750 } 1751 return (td); 1752 } 1753 } 1754 1755 void 1756 tidhash_add(struct thread *td) 1757 { 1758 rw_wlock(TIDHASHLOCK(td->td_tid)); 1759 LIST_INSERT_HEAD(TIDHASH(td->td_tid), td, td_hash); 1760 rw_wunlock(TIDHASHLOCK(td->td_tid)); 1761 } 1762 1763 void 1764 tidhash_remove(struct thread *td) 1765 { 1766 1767 rw_wlock(TIDHASHLOCK(td->td_tid)); 1768 LIST_REMOVE(td, td_hash); 1769 rw_wunlock(TIDHASHLOCK(td->td_tid)); 1770 }
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