1 /*- 2 * SPDX-License-Identifier: BSD-2-Clause 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/systm.h> 35 #include <sys/asan.h> 36 #include <sys/kernel.h> 37 #include <sys/lock.h> 38 #include <sys/msan.h> 39 #include <sys/mutex.h> 40 #include <sys/proc.h> 41 #include <sys/bitstring.h> 42 #include <sys/epoch.h> 43 #include <sys/rangelock.h> 44 #include <sys/resourcevar.h> 45 #include <sys/sdt.h> 46 #include <sys/smp.h> 47 #include <sys/sched.h> 48 #include <sys/sleepqueue.h> 49 #include <sys/selinfo.h> 50 #include <sys/syscallsubr.h> 51 #include <sys/dtrace_bsd.h> 52 #include <sys/sysent.h> 53 #include <sys/turnstile.h> 54 #include <sys/taskqueue.h> 55 #include <sys/ktr.h> 56 #include <sys/rwlock.h> 57 #include <sys/umtxvar.h> 58 #include <sys/vmmeter.h> 59 #include <sys/cpuset.h> 60 #ifdef HWPMC_HOOKS 61 #include <sys/pmckern.h> 62 #endif 63 #include <sys/priv.h> 64 65 #include <security/audit/audit.h> 66 67 #include <vm/pmap.h> 68 #include <vm/vm.h> 69 #include <vm/vm_extern.h> 70 #include <vm/uma.h> 71 #include <vm/vm_phys.h> 72 #include <sys/eventhandler.h> 73 74 /* 75 * Asserts below verify the stability of struct thread and struct proc 76 * layout, as exposed by KBI to modules. On head, the KBI is allowed 77 * to drift, change to the structures must be accompanied by the 78 * assert update. 79 * 80 * On the stable branches after KBI freeze, conditions must not be 81 * violated. Typically new fields are moved to the end of the 82 * structures. 83 */ 84 #ifdef __amd64__ 85 _Static_assert(offsetof(struct thread, td_flags) == 0x108, 86 "struct thread KBI td_flags"); 87 _Static_assert(offsetof(struct thread, td_pflags) == 0x114, 88 "struct thread KBI td_pflags"); 89 _Static_assert(offsetof(struct thread, td_frame) == 0x4b8, 90 "struct thread KBI td_frame"); 91 _Static_assert(offsetof(struct thread, td_emuldata) == 0x6c0, 92 "struct thread KBI td_emuldata"); 93 _Static_assert(offsetof(struct proc, p_flag) == 0xb8, 94 "struct proc KBI p_flag"); 95 _Static_assert(offsetof(struct proc, p_pid) == 0xc4, 96 "struct proc KBI p_pid"); 97 _Static_assert(offsetof(struct proc, p_filemon) == 0x3c8, 98 "struct proc KBI p_filemon"); 99 _Static_assert(offsetof(struct proc, p_comm) == 0x3e0, 100 "struct proc KBI p_comm"); 101 _Static_assert(offsetof(struct proc, p_emuldata) == 0x4d0, 102 "struct proc KBI p_emuldata"); 103 #endif 104 #ifdef __i386__ 105 _Static_assert(offsetof(struct thread, td_flags) == 0x9c, 106 "struct thread KBI td_flags"); 107 _Static_assert(offsetof(struct thread, td_pflags) == 0xa8, 108 "struct thread KBI td_pflags"); 109 _Static_assert(offsetof(struct thread, td_frame) == 0x318, 110 "struct thread KBI td_frame"); 111 _Static_assert(offsetof(struct thread, td_emuldata) == 0x35c, 112 "struct thread KBI td_emuldata"); 113 _Static_assert(offsetof(struct proc, p_flag) == 0x6c, 114 "struct proc KBI p_flag"); 115 _Static_assert(offsetof(struct proc, p_pid) == 0x78, 116 "struct proc KBI p_pid"); 117 _Static_assert(offsetof(struct proc, p_filemon) == 0x270, 118 "struct proc KBI p_filemon"); 119 _Static_assert(offsetof(struct proc, p_comm) == 0x284, 120 "struct proc KBI p_comm"); 121 _Static_assert(offsetof(struct proc, p_emuldata) == 0x318, 122 "struct proc KBI p_emuldata"); 123 #endif 124 125 SDT_PROVIDER_DECLARE(proc); 126 SDT_PROBE_DEFINE(proc, , , lwp__exit); 127 128 /* 129 * thread related storage. 130 */ 131 static uma_zone_t thread_zone; 132 133 struct thread_domain_data { 134 struct thread *tdd_zombies; 135 int tdd_reapticks; 136 } __aligned(CACHE_LINE_SIZE); 137 138 static struct thread_domain_data thread_domain_data[MAXMEMDOM]; 139 140 static struct task thread_reap_task; 141 static struct callout thread_reap_callout; 142 143 static void thread_zombie(struct thread *); 144 static void thread_reap(void); 145 static void thread_reap_all(void); 146 static void thread_reap_task_cb(void *, int); 147 static void thread_reap_callout_cb(void *); 148 static int thread_unsuspend_one(struct thread *td, struct proc *p, 149 bool boundary); 150 static void thread_free_batched(struct thread *td); 151 152 static __exclusive_cache_line struct mtx tid_lock; 153 static bitstr_t *tid_bitmap; 154 155 static MALLOC_DEFINE(M_TIDHASH, "tidhash", "thread hash"); 156 157 static int maxthread; 158 SYSCTL_INT(_kern, OID_AUTO, maxthread, CTLFLAG_RDTUN, 159 &maxthread, 0, "Maximum number of threads"); 160 161 static __exclusive_cache_line int nthreads; 162 163 static LIST_HEAD(tidhashhead, thread) *tidhashtbl; 164 static u_long tidhash; 165 static u_long tidhashlock; 166 static struct rwlock *tidhashtbl_lock; 167 #define TIDHASH(tid) (&tidhashtbl[(tid) & tidhash]) 168 #define TIDHASHLOCK(tid) (&tidhashtbl_lock[(tid) & tidhashlock]) 169 170 EVENTHANDLER_LIST_DEFINE(thread_ctor); 171 EVENTHANDLER_LIST_DEFINE(thread_dtor); 172 EVENTHANDLER_LIST_DEFINE(thread_init); 173 EVENTHANDLER_LIST_DEFINE(thread_fini); 174 175 static bool 176 thread_count_inc_try(void) 177 { 178 int nthreads_new; 179 180 nthreads_new = atomic_fetchadd_int(&nthreads, 1) + 1; 181 if (nthreads_new >= maxthread - 100) { 182 if (priv_check_cred(curthread->td_ucred, PRIV_MAXPROC) != 0 || 183 nthreads_new >= maxthread) { 184 atomic_subtract_int(&nthreads, 1); 185 return (false); 186 } 187 } 188 return (true); 189 } 190 191 static bool 192 thread_count_inc(void) 193 { 194 static struct timeval lastfail; 195 static int curfail; 196 197 thread_reap(); 198 if (thread_count_inc_try()) { 199 return (true); 200 } 201 202 thread_reap_all(); 203 if (thread_count_inc_try()) { 204 return (true); 205 } 206 207 if (ppsratecheck(&lastfail, &curfail, 1)) { 208 printf("maxthread limit exceeded by uid %u " 209 "(pid %d); consider increasing kern.maxthread\n", 210 curthread->td_ucred->cr_ruid, curproc->p_pid); 211 } 212 return (false); 213 } 214 215 static void 216 thread_count_sub(int n) 217 { 218 219 atomic_subtract_int(&nthreads, n); 220 } 221 222 static void 223 thread_count_dec(void) 224 { 225 226 thread_count_sub(1); 227 } 228 229 static lwpid_t 230 tid_alloc(void) 231 { 232 static lwpid_t trytid; 233 lwpid_t tid; 234 235 mtx_lock(&tid_lock); 236 /* 237 * It is an invariant that the bitmap is big enough to hold maxthread 238 * IDs. If we got to this point there has to be at least one free. 239 */ 240 if (trytid >= maxthread) 241 trytid = 0; 242 bit_ffc_at(tid_bitmap, trytid, maxthread, &tid); 243 if (tid == -1) { 244 KASSERT(trytid != 0, ("unexpectedly ran out of IDs")); 245 trytid = 0; 246 bit_ffc_at(tid_bitmap, trytid, maxthread, &tid); 247 KASSERT(tid != -1, ("unexpectedly ran out of IDs")); 248 } 249 bit_set(tid_bitmap, tid); 250 trytid = tid + 1; 251 mtx_unlock(&tid_lock); 252 return (tid + NO_PID); 253 } 254 255 static void 256 tid_free_locked(lwpid_t rtid) 257 { 258 lwpid_t tid; 259 260 mtx_assert(&tid_lock, MA_OWNED); 261 KASSERT(rtid >= NO_PID, 262 ("%s: invalid tid %d\n", __func__, rtid)); 263 tid = rtid - NO_PID; 264 KASSERT(bit_test(tid_bitmap, tid) != 0, 265 ("thread ID %d not allocated\n", rtid)); 266 bit_clear(tid_bitmap, tid); 267 } 268 269 static void 270 tid_free(lwpid_t rtid) 271 { 272 273 mtx_lock(&tid_lock); 274 tid_free_locked(rtid); 275 mtx_unlock(&tid_lock); 276 } 277 278 static void 279 tid_free_batch(lwpid_t *batch, int n) 280 { 281 int i; 282 283 mtx_lock(&tid_lock); 284 for (i = 0; i < n; i++) { 285 tid_free_locked(batch[i]); 286 } 287 mtx_unlock(&tid_lock); 288 } 289 290 /* 291 * Batching for thread reapping. 292 */ 293 struct tidbatch { 294 lwpid_t tab[16]; 295 int n; 296 }; 297 298 static void 299 tidbatch_prep(struct tidbatch *tb) 300 { 301 302 tb->n = 0; 303 } 304 305 static void 306 tidbatch_add(struct tidbatch *tb, struct thread *td) 307 { 308 309 KASSERT(tb->n < nitems(tb->tab), 310 ("%s: count too high %d", __func__, tb->n)); 311 tb->tab[tb->n] = td->td_tid; 312 tb->n++; 313 } 314 315 static void 316 tidbatch_process(struct tidbatch *tb) 317 { 318 319 KASSERT(tb->n <= nitems(tb->tab), 320 ("%s: count too high %d", __func__, tb->n)); 321 if (tb->n == nitems(tb->tab)) { 322 tid_free_batch(tb->tab, tb->n); 323 tb->n = 0; 324 } 325 } 326 327 static void 328 tidbatch_final(struct tidbatch *tb) 329 { 330 331 KASSERT(tb->n <= nitems(tb->tab), 332 ("%s: count too high %d", __func__, tb->n)); 333 if (tb->n != 0) { 334 tid_free_batch(tb->tab, tb->n); 335 } 336 } 337 338 /* 339 * Batching thread count free, for consistency 340 */ 341 struct tdcountbatch { 342 int n; 343 }; 344 345 static void 346 tdcountbatch_prep(struct tdcountbatch *tb) 347 { 348 349 tb->n = 0; 350 } 351 352 static void 353 tdcountbatch_add(struct tdcountbatch *tb, struct thread *td __unused) 354 { 355 356 tb->n++; 357 } 358 359 static void 360 tdcountbatch_process(struct tdcountbatch *tb) 361 { 362 363 if (tb->n == 32) { 364 thread_count_sub(tb->n); 365 tb->n = 0; 366 } 367 } 368 369 static void 370 tdcountbatch_final(struct tdcountbatch *tb) 371 { 372 373 if (tb->n != 0) { 374 thread_count_sub(tb->n); 375 } 376 } 377 378 /* 379 * Prepare a thread for use. 380 */ 381 static int 382 thread_ctor(void *mem, int size, void *arg, int flags) 383 { 384 struct thread *td; 385 386 td = (struct thread *)mem; 387 TD_SET_STATE(td, TDS_INACTIVE); 388 td->td_lastcpu = td->td_oncpu = NOCPU; 389 390 /* 391 * Note that td_critnest begins life as 1 because the thread is not 392 * running and is thereby implicitly waiting to be on the receiving 393 * end of a context switch. 394 */ 395 td->td_critnest = 1; 396 td->td_lend_user_pri = PRI_MAX; 397 #ifdef AUDIT 398 audit_thread_alloc(td); 399 #endif 400 #ifdef KDTRACE_HOOKS 401 kdtrace_thread_ctor(td); 402 #endif 403 umtx_thread_alloc(td); 404 MPASS(td->td_sel == NULL); 405 return (0); 406 } 407 408 /* 409 * Reclaim a thread after use. 410 */ 411 static void 412 thread_dtor(void *mem, int size, void *arg) 413 { 414 struct thread *td; 415 416 td = (struct thread *)mem; 417 418 #ifdef INVARIANTS 419 /* Verify that this thread is in a safe state to free. */ 420 switch (TD_GET_STATE(td)) { 421 case TDS_INHIBITED: 422 case TDS_RUNNING: 423 case TDS_CAN_RUN: 424 case TDS_RUNQ: 425 /* 426 * We must never unlink a thread that is in one of 427 * these states, because it is currently active. 428 */ 429 panic("bad state for thread unlinking"); 430 /* NOTREACHED */ 431 case TDS_INACTIVE: 432 break; 433 default: 434 panic("bad thread state"); 435 /* NOTREACHED */ 436 } 437 #endif 438 #ifdef AUDIT 439 audit_thread_free(td); 440 #endif 441 #ifdef KDTRACE_HOOKS 442 kdtrace_thread_dtor(td); 443 #endif 444 /* Free all OSD associated to this thread. */ 445 osd_thread_exit(td); 446 ast_kclear(td); 447 seltdfini(td); 448 } 449 450 /* 451 * Initialize type-stable parts of a thread (when newly created). 452 */ 453 static int 454 thread_init(void *mem, int size, int flags) 455 { 456 struct thread *td; 457 458 td = (struct thread *)mem; 459 460 td->td_allocdomain = vm_phys_domain(vtophys(td)); 461 td->td_sleepqueue = sleepq_alloc(); 462 td->td_turnstile = turnstile_alloc(); 463 td->td_rlqe = NULL; 464 EVENTHANDLER_DIRECT_INVOKE(thread_init, td); 465 umtx_thread_init(td); 466 td->td_kstack = 0; 467 td->td_sel = NULL; 468 return (0); 469 } 470 471 /* 472 * Tear down type-stable parts of a thread (just before being discarded). 473 */ 474 static void 475 thread_fini(void *mem, int size) 476 { 477 struct thread *td; 478 479 td = (struct thread *)mem; 480 EVENTHANDLER_DIRECT_INVOKE(thread_fini, td); 481 rlqentry_free(td->td_rlqe); 482 turnstile_free(td->td_turnstile); 483 sleepq_free(td->td_sleepqueue); 484 umtx_thread_fini(td); 485 MPASS(td->td_sel == NULL); 486 } 487 488 /* 489 * For a newly created process, 490 * link up all the structures and its initial threads etc. 491 * called from: 492 * {arch}/{arch}/machdep.c {arch}_init(), init386() etc. 493 * proc_dtor() (should go away) 494 * proc_init() 495 */ 496 void 497 proc_linkup0(struct proc *p, struct thread *td) 498 { 499 TAILQ_INIT(&p->p_threads); /* all threads in proc */ 500 proc_linkup(p, td); 501 } 502 503 void 504 proc_linkup(struct proc *p, struct thread *td) 505 { 506 507 sigqueue_init(&p->p_sigqueue, p); 508 p->p_ksi = ksiginfo_alloc(M_WAITOK); 509 if (p->p_ksi != NULL) { 510 /* XXX p_ksi may be null if ksiginfo zone is not ready */ 511 p->p_ksi->ksi_flags = KSI_EXT | KSI_INS; 512 } 513 LIST_INIT(&p->p_mqnotifier); 514 p->p_numthreads = 0; 515 thread_link(td, p); 516 } 517 518 static void 519 ast_suspend(struct thread *td, int tda __unused) 520 { 521 struct proc *p; 522 523 p = td->td_proc; 524 /* 525 * We need to check to see if we have to exit or wait due to a 526 * single threading requirement or some other STOP condition. 527 */ 528 PROC_LOCK(p); 529 thread_suspend_check(0); 530 PROC_UNLOCK(p); 531 } 532 533 extern int max_threads_per_proc; 534 535 /* 536 * Initialize global thread allocation resources. 537 */ 538 void 539 threadinit(void) 540 { 541 u_long i; 542 lwpid_t tid0; 543 544 /* 545 * Place an upper limit on threads which can be allocated. 546 * 547 * Note that other factors may make the de facto limit much lower. 548 * 549 * Platform limits are somewhat arbitrary but deemed "more than good 550 * enough" for the foreseable future. 551 */ 552 if (maxthread == 0) { 553 #ifdef _LP64 554 maxthread = MIN(maxproc * max_threads_per_proc, 1000000); 555 #else 556 maxthread = MIN(maxproc * max_threads_per_proc, 100000); 557 #endif 558 } 559 560 mtx_init(&tid_lock, "TID lock", NULL, MTX_DEF); 561 tid_bitmap = bit_alloc(maxthread, M_TIDHASH, M_WAITOK); 562 /* 563 * Handle thread0. 564 */ 565 thread_count_inc(); 566 tid0 = tid_alloc(); 567 if (tid0 != THREAD0_TID) 568 panic("tid0 %d != %d\n", tid0, THREAD0_TID); 569 570 /* 571 * Thread structures are specially aligned so that (at least) the 572 * 5 lower bits of a pointer to 'struct thead' must be 0. These bits 573 * are used by synchronization primitives to store flags in pointers to 574 * such structures. 575 */ 576 thread_zone = uma_zcreate("THREAD", sched_sizeof_thread(), 577 thread_ctor, thread_dtor, thread_init, thread_fini, 578 UMA_ALIGN_CACHE_AND_MASK(32 - 1), UMA_ZONE_NOFREE); 579 tidhashtbl = hashinit(maxproc / 2, M_TIDHASH, &tidhash); 580 tidhashlock = (tidhash + 1) / 64; 581 if (tidhashlock > 0) 582 tidhashlock--; 583 tidhashtbl_lock = malloc(sizeof(*tidhashtbl_lock) * (tidhashlock + 1), 584 M_TIDHASH, M_WAITOK | M_ZERO); 585 for (i = 0; i < tidhashlock + 1; i++) 586 rw_init(&tidhashtbl_lock[i], "tidhash"); 587 588 TASK_INIT(&thread_reap_task, 0, thread_reap_task_cb, NULL); 589 callout_init(&thread_reap_callout, 1); 590 callout_reset(&thread_reap_callout, 5 * hz, 591 thread_reap_callout_cb, NULL); 592 ast_register(TDA_SUSPEND, ASTR_ASTF_REQUIRED, 0, ast_suspend); 593 } 594 595 /* 596 * Place an unused thread on the zombie list. 597 */ 598 void 599 thread_zombie(struct thread *td) 600 { 601 struct thread_domain_data *tdd; 602 struct thread *ztd; 603 604 tdd = &thread_domain_data[td->td_allocdomain]; 605 ztd = atomic_load_ptr(&tdd->tdd_zombies); 606 for (;;) { 607 td->td_zombie = ztd; 608 if (atomic_fcmpset_rel_ptr((uintptr_t *)&tdd->tdd_zombies, 609 (uintptr_t *)&ztd, (uintptr_t)td)) 610 break; 611 continue; 612 } 613 } 614 615 /* 616 * Release a thread that has exited after cpu_throw(). 617 */ 618 void 619 thread_stash(struct thread *td) 620 { 621 atomic_subtract_rel_int(&td->td_proc->p_exitthreads, 1); 622 thread_zombie(td); 623 } 624 625 /* 626 * Reap zombies from passed domain. 627 */ 628 static void 629 thread_reap_domain(struct thread_domain_data *tdd) 630 { 631 struct thread *itd, *ntd; 632 struct tidbatch tidbatch; 633 struct credbatch credbatch; 634 struct limbatch limbatch; 635 struct tdcountbatch tdcountbatch; 636 637 /* 638 * Reading upfront is pessimal if followed by concurrent atomic_swap, 639 * but most of the time the list is empty. 640 */ 641 if (tdd->tdd_zombies == NULL) 642 return; 643 644 itd = (struct thread *)atomic_swap_ptr((uintptr_t *)&tdd->tdd_zombies, 645 (uintptr_t)NULL); 646 if (itd == NULL) 647 return; 648 649 /* 650 * Multiple CPUs can get here, the race is fine as ticks is only 651 * advisory. 652 */ 653 tdd->tdd_reapticks = ticks; 654 655 tidbatch_prep(&tidbatch); 656 credbatch_prep(&credbatch); 657 limbatch_prep(&limbatch); 658 tdcountbatch_prep(&tdcountbatch); 659 660 while (itd != NULL) { 661 ntd = itd->td_zombie; 662 EVENTHANDLER_DIRECT_INVOKE(thread_dtor, itd); 663 664 tidbatch_add(&tidbatch, itd); 665 credbatch_add(&credbatch, itd); 666 limbatch_add(&limbatch, itd); 667 tdcountbatch_add(&tdcountbatch, itd); 668 669 thread_free_batched(itd); 670 671 tidbatch_process(&tidbatch); 672 credbatch_process(&credbatch); 673 limbatch_process(&limbatch); 674 tdcountbatch_process(&tdcountbatch); 675 676 itd = ntd; 677 } 678 679 tidbatch_final(&tidbatch); 680 credbatch_final(&credbatch); 681 limbatch_final(&limbatch); 682 tdcountbatch_final(&tdcountbatch); 683 } 684 685 /* 686 * Reap zombies from all domains. 687 */ 688 static void 689 thread_reap_all(void) 690 { 691 struct thread_domain_data *tdd; 692 int i, domain; 693 694 domain = PCPU_GET(domain); 695 for (i = 0; i < vm_ndomains; i++) { 696 tdd = &thread_domain_data[(i + domain) % vm_ndomains]; 697 thread_reap_domain(tdd); 698 } 699 } 700 701 /* 702 * Reap zombies from local domain. 703 */ 704 static void 705 thread_reap(void) 706 { 707 struct thread_domain_data *tdd; 708 int domain; 709 710 domain = PCPU_GET(domain); 711 tdd = &thread_domain_data[domain]; 712 713 thread_reap_domain(tdd); 714 } 715 716 static void 717 thread_reap_task_cb(void *arg __unused, int pending __unused) 718 { 719 720 thread_reap_all(); 721 } 722 723 static void 724 thread_reap_callout_cb(void *arg __unused) 725 { 726 struct thread_domain_data *tdd; 727 int i, cticks, lticks; 728 bool wantreap; 729 730 wantreap = false; 731 cticks = atomic_load_int(&ticks); 732 for (i = 0; i < vm_ndomains; i++) { 733 tdd = &thread_domain_data[i]; 734 lticks = tdd->tdd_reapticks; 735 if (tdd->tdd_zombies != NULL && 736 (u_int)(cticks - lticks) > 5 * hz) { 737 wantreap = true; 738 break; 739 } 740 } 741 742 if (wantreap) 743 taskqueue_enqueue(taskqueue_thread, &thread_reap_task); 744 callout_reset(&thread_reap_callout, 5 * hz, 745 thread_reap_callout_cb, NULL); 746 } 747 748 /* 749 * Calling this function guarantees that any thread that exited before 750 * the call is reaped when the function returns. By 'exited' we mean 751 * a thread removed from the process linkage with thread_unlink(). 752 * Practically this means that caller must lock/unlock corresponding 753 * process lock before the call, to synchronize with thread_exit(). 754 */ 755 void 756 thread_reap_barrier(void) 757 { 758 struct task *t; 759 760 /* 761 * First do context switches to each CPU to ensure that all 762 * PCPU pc_deadthreads are moved to zombie list. 763 */ 764 quiesce_all_cpus("", PDROP); 765 766 /* 767 * Second, fire the task in the same thread as normal 768 * thread_reap() is done, to serialize reaping. 769 */ 770 t = malloc(sizeof(*t), M_TEMP, M_WAITOK); 771 TASK_INIT(t, 0, thread_reap_task_cb, t); 772 taskqueue_enqueue(taskqueue_thread, t); 773 taskqueue_drain(taskqueue_thread, t); 774 free(t, M_TEMP); 775 } 776 777 /* 778 * Allocate a thread. 779 */ 780 struct thread * 781 thread_alloc(int pages) 782 { 783 struct thread *td; 784 lwpid_t tid; 785 786 if (!thread_count_inc()) { 787 return (NULL); 788 } 789 790 tid = tid_alloc(); 791 td = uma_zalloc(thread_zone, M_WAITOK); 792 KASSERT(td->td_kstack == 0, ("thread_alloc got thread with kstack")); 793 if (!vm_thread_new(td, pages)) { 794 uma_zfree(thread_zone, td); 795 tid_free(tid); 796 thread_count_dec(); 797 return (NULL); 798 } 799 td->td_tid = tid; 800 bzero(&td->td_sa.args, sizeof(td->td_sa.args)); 801 kasan_thread_alloc(td); 802 kmsan_thread_alloc(td); 803 cpu_thread_alloc(td); 804 EVENTHANDLER_DIRECT_INVOKE(thread_ctor, td); 805 return (td); 806 } 807 808 int 809 thread_recycle(struct thread *td, int pages) 810 { 811 if (td->td_kstack == 0 || td->td_kstack_pages != pages) { 812 if (td->td_kstack != 0) 813 vm_thread_dispose(td); 814 if (!vm_thread_new(td, pages)) 815 return (ENOMEM); 816 cpu_thread_alloc(td); 817 } 818 kasan_thread_alloc(td); 819 kmsan_thread_alloc(td); 820 return (0); 821 } 822 823 /* 824 * Deallocate a thread. 825 */ 826 static void 827 thread_free_batched(struct thread *td) 828 { 829 830 lock_profile_thread_exit(td); 831 if (td->td_cpuset) 832 cpuset_rel(td->td_cpuset); 833 td->td_cpuset = NULL; 834 cpu_thread_free(td); 835 if (td->td_kstack != 0) 836 vm_thread_dispose(td); 837 callout_drain(&td->td_slpcallout); 838 /* 839 * Freeing handled by the caller. 840 */ 841 td->td_tid = -1; 842 kmsan_thread_free(td); 843 uma_zfree(thread_zone, td); 844 } 845 846 void 847 thread_free(struct thread *td) 848 { 849 lwpid_t tid; 850 851 EVENTHANDLER_DIRECT_INVOKE(thread_dtor, td); 852 tid = td->td_tid; 853 thread_free_batched(td); 854 tid_free(tid); 855 thread_count_dec(); 856 } 857 858 void 859 thread_cow_get_proc(struct thread *newtd, struct proc *p) 860 { 861 862 PROC_LOCK_ASSERT(p, MA_OWNED); 863 newtd->td_realucred = crcowget(p->p_ucred); 864 newtd->td_ucred = newtd->td_realucred; 865 newtd->td_limit = lim_hold(p->p_limit); 866 newtd->td_cowgen = p->p_cowgen; 867 } 868 869 void 870 thread_cow_get(struct thread *newtd, struct thread *td) 871 { 872 873 MPASS(td->td_realucred == td->td_ucred); 874 newtd->td_realucred = crcowget(td->td_realucred); 875 newtd->td_ucred = newtd->td_realucred; 876 newtd->td_limit = lim_hold(td->td_limit); 877 newtd->td_cowgen = td->td_cowgen; 878 } 879 880 void 881 thread_cow_free(struct thread *td) 882 { 883 884 if (td->td_realucred != NULL) 885 crcowfree(td); 886 if (td->td_limit != NULL) 887 lim_free(td->td_limit); 888 } 889 890 void 891 thread_cow_update(struct thread *td) 892 { 893 struct proc *p; 894 struct ucred *oldcred; 895 struct plimit *oldlimit; 896 897 p = td->td_proc; 898 PROC_LOCK(p); 899 oldcred = crcowsync(); 900 oldlimit = lim_cowsync(); 901 td->td_cowgen = p->p_cowgen; 902 PROC_UNLOCK(p); 903 if (oldcred != NULL) 904 crfree(oldcred); 905 if (oldlimit != NULL) 906 lim_free(oldlimit); 907 } 908 909 void 910 thread_cow_synced(struct thread *td) 911 { 912 struct proc *p; 913 914 p = td->td_proc; 915 PROC_LOCK_ASSERT(p, MA_OWNED); 916 MPASS(td->td_cowgen != p->p_cowgen); 917 MPASS(td->td_ucred == p->p_ucred); 918 MPASS(td->td_limit == p->p_limit); 919 td->td_cowgen = p->p_cowgen; 920 } 921 922 /* 923 * Discard the current thread and exit from its context. 924 * Always called with scheduler locked. 925 * 926 * Because we can't free a thread while we're operating under its context, 927 * push the current thread into our CPU's deadthread holder. This means 928 * we needn't worry about someone else grabbing our context before we 929 * do a cpu_throw(). 930 */ 931 void 932 thread_exit(void) 933 { 934 uint64_t runtime, new_switchtime; 935 struct thread *td; 936 struct thread *td2; 937 struct proc *p; 938 int wakeup_swapper; 939 940 td = curthread; 941 p = td->td_proc; 942 943 PROC_SLOCK_ASSERT(p, MA_OWNED); 944 mtx_assert(&Giant, MA_NOTOWNED); 945 946 PROC_LOCK_ASSERT(p, MA_OWNED); 947 KASSERT(p != NULL, ("thread exiting without a process")); 948 CTR3(KTR_PROC, "thread_exit: thread %p (pid %ld, %s)", td, 949 (long)p->p_pid, td->td_name); 950 SDT_PROBE0(proc, , , lwp__exit); 951 KASSERT(TAILQ_EMPTY(&td->td_sigqueue.sq_list), ("signal pending")); 952 MPASS(td->td_realucred == td->td_ucred); 953 954 /* 955 * drop FPU & debug register state storage, or any other 956 * architecture specific resources that 957 * would not be on a new untouched process. 958 */ 959 cpu_thread_exit(td); 960 961 /* 962 * The last thread is left attached to the process 963 * So that the whole bundle gets recycled. Skip 964 * all this stuff if we never had threads. 965 * EXIT clears all sign of other threads when 966 * it goes to single threading, so the last thread always 967 * takes the short path. 968 */ 969 if (p->p_flag & P_HADTHREADS) { 970 if (p->p_numthreads > 1) { 971 atomic_add_int(&td->td_proc->p_exitthreads, 1); 972 thread_unlink(td); 973 td2 = FIRST_THREAD_IN_PROC(p); 974 sched_exit_thread(td2, td); 975 976 /* 977 * The test below is NOT true if we are the 978 * sole exiting thread. P_STOPPED_SINGLE is unset 979 * in exit1() after it is the only survivor. 980 */ 981 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) { 982 if (p->p_numthreads == p->p_suspcount) { 983 thread_lock(p->p_singlethread); 984 wakeup_swapper = thread_unsuspend_one( 985 p->p_singlethread, p, false); 986 if (wakeup_swapper) 987 kick_proc0(); 988 } 989 } 990 991 PCPU_SET(deadthread, td); 992 } else { 993 /* 994 * The last thread is exiting.. but not through exit() 995 */ 996 panic ("thread_exit: Last thread exiting on its own"); 997 } 998 } 999 #ifdef HWPMC_HOOKS 1000 /* 1001 * If this thread is part of a process that is being tracked by hwpmc(4), 1002 * inform the module of the thread's impending exit. 1003 */ 1004 if (PMC_PROC_IS_USING_PMCS(td->td_proc)) { 1005 PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_OUT); 1006 PMC_CALL_HOOK_UNLOCKED(td, PMC_FN_THR_EXIT, NULL); 1007 } else if (PMC_SYSTEM_SAMPLING_ACTIVE()) 1008 PMC_CALL_HOOK_UNLOCKED(td, PMC_FN_THR_EXIT_LOG, NULL); 1009 #endif 1010 PROC_UNLOCK(p); 1011 PROC_STATLOCK(p); 1012 thread_lock(td); 1013 PROC_SUNLOCK(p); 1014 1015 /* Do the same timestamp bookkeeping that mi_switch() would do. */ 1016 new_switchtime = cpu_ticks(); 1017 runtime = new_switchtime - PCPU_GET(switchtime); 1018 td->td_runtime += runtime; 1019 td->td_incruntime += runtime; 1020 PCPU_SET(switchtime, new_switchtime); 1021 PCPU_SET(switchticks, ticks); 1022 VM_CNT_INC(v_swtch); 1023 1024 /* Save our resource usage in our process. */ 1025 td->td_ru.ru_nvcsw++; 1026 ruxagg_locked(p, td); 1027 rucollect(&p->p_ru, &td->td_ru); 1028 PROC_STATUNLOCK(p); 1029 1030 TD_SET_STATE(td, TDS_INACTIVE); 1031 #ifdef WITNESS 1032 witness_thread_exit(td); 1033 #endif 1034 CTR1(KTR_PROC, "thread_exit: cpu_throw() thread %p", td); 1035 sched_throw(td); 1036 panic("I'm a teapot!"); 1037 /* NOTREACHED */ 1038 } 1039 1040 /* 1041 * Do any thread specific cleanups that may be needed in wait() 1042 * called with Giant, proc and schedlock not held. 1043 */ 1044 void 1045 thread_wait(struct proc *p) 1046 { 1047 struct thread *td; 1048 1049 mtx_assert(&Giant, MA_NOTOWNED); 1050 KASSERT(p->p_numthreads == 1, ("multiple threads in thread_wait()")); 1051 KASSERT(p->p_exitthreads == 0, ("p_exitthreads leaking")); 1052 td = FIRST_THREAD_IN_PROC(p); 1053 /* Lock the last thread so we spin until it exits cpu_throw(). */ 1054 thread_lock(td); 1055 thread_unlock(td); 1056 lock_profile_thread_exit(td); 1057 cpuset_rel(td->td_cpuset); 1058 td->td_cpuset = NULL; 1059 cpu_thread_clean(td); 1060 thread_cow_free(td); 1061 callout_drain(&td->td_slpcallout); 1062 thread_reap(); /* check for zombie threads etc. */ 1063 } 1064 1065 /* 1066 * Link a thread to a process. 1067 * set up anything that needs to be initialized for it to 1068 * be used by the process. 1069 */ 1070 void 1071 thread_link(struct thread *td, struct proc *p) 1072 { 1073 1074 /* 1075 * XXX This can't be enabled because it's called for proc0 before 1076 * its lock has been created. 1077 * PROC_LOCK_ASSERT(p, MA_OWNED); 1078 */ 1079 TD_SET_STATE(td, TDS_INACTIVE); 1080 td->td_proc = p; 1081 td->td_flags = TDF_INMEM; 1082 1083 LIST_INIT(&td->td_contested); 1084 LIST_INIT(&td->td_lprof[0]); 1085 LIST_INIT(&td->td_lprof[1]); 1086 #ifdef EPOCH_TRACE 1087 SLIST_INIT(&td->td_epochs); 1088 #endif 1089 sigqueue_init(&td->td_sigqueue, p); 1090 callout_init(&td->td_slpcallout, 1); 1091 TAILQ_INSERT_TAIL(&p->p_threads, td, td_plist); 1092 p->p_numthreads++; 1093 } 1094 1095 /* 1096 * Called from: 1097 * thread_exit() 1098 */ 1099 void 1100 thread_unlink(struct thread *td) 1101 { 1102 struct proc *p = td->td_proc; 1103 1104 PROC_LOCK_ASSERT(p, MA_OWNED); 1105 #ifdef EPOCH_TRACE 1106 MPASS(SLIST_EMPTY(&td->td_epochs)); 1107 #endif 1108 1109 TAILQ_REMOVE(&p->p_threads, td, td_plist); 1110 p->p_numthreads--; 1111 /* could clear a few other things here */ 1112 /* Must NOT clear links to proc! */ 1113 } 1114 1115 static int 1116 calc_remaining(struct proc *p, int mode) 1117 { 1118 int remaining; 1119 1120 PROC_LOCK_ASSERT(p, MA_OWNED); 1121 PROC_SLOCK_ASSERT(p, MA_OWNED); 1122 if (mode == SINGLE_EXIT) 1123 remaining = p->p_numthreads; 1124 else if (mode == SINGLE_BOUNDARY) 1125 remaining = p->p_numthreads - p->p_boundary_count; 1126 else if (mode == SINGLE_NO_EXIT || mode == SINGLE_ALLPROC) 1127 remaining = p->p_numthreads - p->p_suspcount; 1128 else 1129 panic("calc_remaining: wrong mode %d", mode); 1130 return (remaining); 1131 } 1132 1133 static int 1134 remain_for_mode(int mode) 1135 { 1136 1137 return (mode == SINGLE_ALLPROC ? 0 : 1); 1138 } 1139 1140 static int 1141 weed_inhib(int mode, struct thread *td2, struct proc *p) 1142 { 1143 int wakeup_swapper; 1144 1145 PROC_LOCK_ASSERT(p, MA_OWNED); 1146 PROC_SLOCK_ASSERT(p, MA_OWNED); 1147 THREAD_LOCK_ASSERT(td2, MA_OWNED); 1148 1149 wakeup_swapper = 0; 1150 1151 /* 1152 * Since the thread lock is dropped by the scheduler we have 1153 * to retry to check for races. 1154 */ 1155 restart: 1156 switch (mode) { 1157 case SINGLE_EXIT: 1158 if (TD_IS_SUSPENDED(td2)) { 1159 wakeup_swapper |= thread_unsuspend_one(td2, p, true); 1160 thread_lock(td2); 1161 goto restart; 1162 } 1163 if (TD_CAN_ABORT(td2)) { 1164 wakeup_swapper |= sleepq_abort(td2, EINTR); 1165 return (wakeup_swapper); 1166 } 1167 break; 1168 case SINGLE_BOUNDARY: 1169 case SINGLE_NO_EXIT: 1170 if (TD_IS_SUSPENDED(td2) && 1171 (td2->td_flags & TDF_BOUNDARY) == 0) { 1172 wakeup_swapper |= thread_unsuspend_one(td2, p, false); 1173 thread_lock(td2); 1174 goto restart; 1175 } 1176 if (TD_CAN_ABORT(td2)) { 1177 wakeup_swapper |= sleepq_abort(td2, ERESTART); 1178 return (wakeup_swapper); 1179 } 1180 break; 1181 case SINGLE_ALLPROC: 1182 /* 1183 * ALLPROC suspend tries to avoid spurious EINTR for 1184 * threads sleeping interruptable, by suspending the 1185 * thread directly, similarly to sig_suspend_threads(). 1186 * Since such sleep is not neccessary performed at the user 1187 * boundary, TDF_ALLPROCSUSP is used to avoid immediate 1188 * un-suspend. 1189 */ 1190 if (TD_IS_SUSPENDED(td2) && 1191 (td2->td_flags & TDF_ALLPROCSUSP) == 0) { 1192 wakeup_swapper |= thread_unsuspend_one(td2, p, false); 1193 thread_lock(td2); 1194 goto restart; 1195 } 1196 if (TD_CAN_ABORT(td2)) { 1197 td2->td_flags |= TDF_ALLPROCSUSP; 1198 wakeup_swapper |= sleepq_abort(td2, ERESTART); 1199 return (wakeup_swapper); 1200 } 1201 break; 1202 default: 1203 break; 1204 } 1205 thread_unlock(td2); 1206 return (wakeup_swapper); 1207 } 1208 1209 /* 1210 * Enforce single-threading. 1211 * 1212 * Returns 1 if the caller must abort (another thread is waiting to 1213 * exit the process or similar). Process is locked! 1214 * Returns 0 when you are successfully the only thread running. 1215 * A process has successfully single threaded in the suspend mode when 1216 * There are no threads in user mode. Threads in the kernel must be 1217 * allowed to continue until they get to the user boundary. They may even 1218 * copy out their return values and data before suspending. They may however be 1219 * accelerated in reaching the user boundary as we will wake up 1220 * any sleeping threads that are interruptable. (PCATCH). 1221 */ 1222 int 1223 thread_single(struct proc *p, int mode) 1224 { 1225 struct thread *td; 1226 struct thread *td2; 1227 int remaining, wakeup_swapper; 1228 1229 td = curthread; 1230 KASSERT(mode == SINGLE_EXIT || mode == SINGLE_BOUNDARY || 1231 mode == SINGLE_ALLPROC || mode == SINGLE_NO_EXIT, 1232 ("invalid mode %d", mode)); 1233 /* 1234 * If allowing non-ALLPROC singlethreading for non-curproc 1235 * callers, calc_remaining() and remain_for_mode() should be 1236 * adjusted to also account for td->td_proc != p. For now 1237 * this is not implemented because it is not used. 1238 */ 1239 KASSERT((mode == SINGLE_ALLPROC && td->td_proc != p) || 1240 (mode != SINGLE_ALLPROC && td->td_proc == p), 1241 ("mode %d proc %p curproc %p", mode, p, td->td_proc)); 1242 mtx_assert(&Giant, MA_NOTOWNED); 1243 PROC_LOCK_ASSERT(p, MA_OWNED); 1244 1245 /* 1246 * Is someone already single threading? 1247 * Or may be singlethreading is not needed at all. 1248 */ 1249 if (mode == SINGLE_ALLPROC) { 1250 while ((p->p_flag & P_STOPPED_SINGLE) != 0) { 1251 if ((p->p_flag2 & P2_WEXIT) != 0) 1252 return (1); 1253 msleep(&p->p_flag, &p->p_mtx, PCATCH, "thrsgl", 0); 1254 } 1255 if ((p->p_flag & (P_STOPPED_SIG | P_TRACED)) != 0 || 1256 (p->p_flag2 & P2_WEXIT) != 0) 1257 return (1); 1258 } else if ((p->p_flag & P_HADTHREADS) == 0) 1259 return (0); 1260 if (p->p_singlethread != NULL && p->p_singlethread != td) 1261 return (1); 1262 1263 if (mode == SINGLE_EXIT) { 1264 p->p_flag |= P_SINGLE_EXIT; 1265 p->p_flag &= ~P_SINGLE_BOUNDARY; 1266 } else { 1267 p->p_flag &= ~P_SINGLE_EXIT; 1268 if (mode == SINGLE_BOUNDARY) 1269 p->p_flag |= P_SINGLE_BOUNDARY; 1270 else 1271 p->p_flag &= ~P_SINGLE_BOUNDARY; 1272 } 1273 if (mode == SINGLE_ALLPROC) 1274 p->p_flag |= P_TOTAL_STOP; 1275 p->p_flag |= P_STOPPED_SINGLE; 1276 PROC_SLOCK(p); 1277 p->p_singlethread = td; 1278 remaining = calc_remaining(p, mode); 1279 while (remaining != remain_for_mode(mode)) { 1280 if (P_SHOULDSTOP(p) != P_STOPPED_SINGLE) 1281 goto stopme; 1282 wakeup_swapper = 0; 1283 FOREACH_THREAD_IN_PROC(p, td2) { 1284 if (td2 == td) 1285 continue; 1286 thread_lock(td2); 1287 ast_sched_locked(td2, TDA_SUSPEND); 1288 if (TD_IS_INHIBITED(td2)) { 1289 wakeup_swapper |= weed_inhib(mode, td2, p); 1290 #ifdef SMP 1291 } else if (TD_IS_RUNNING(td2)) { 1292 forward_signal(td2); 1293 thread_unlock(td2); 1294 #endif 1295 } else 1296 thread_unlock(td2); 1297 } 1298 if (wakeup_swapper) 1299 kick_proc0(); 1300 remaining = calc_remaining(p, mode); 1301 1302 /* 1303 * Maybe we suspended some threads.. was it enough? 1304 */ 1305 if (remaining == remain_for_mode(mode)) 1306 break; 1307 1308 stopme: 1309 /* 1310 * Wake us up when everyone else has suspended. 1311 * In the mean time we suspend as well. 1312 */ 1313 thread_suspend_switch(td, p); 1314 remaining = calc_remaining(p, mode); 1315 } 1316 if (mode == SINGLE_EXIT) { 1317 /* 1318 * Convert the process to an unthreaded process. The 1319 * SINGLE_EXIT is called by exit1() or execve(), in 1320 * both cases other threads must be retired. 1321 */ 1322 KASSERT(p->p_numthreads == 1, ("Unthreading with >1 threads")); 1323 p->p_singlethread = NULL; 1324 p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT | P_HADTHREADS); 1325 1326 /* 1327 * Wait for any remaining threads to exit cpu_throw(). 1328 */ 1329 while (p->p_exitthreads != 0) { 1330 PROC_SUNLOCK(p); 1331 PROC_UNLOCK(p); 1332 sched_relinquish(td); 1333 PROC_LOCK(p); 1334 PROC_SLOCK(p); 1335 } 1336 } else if (mode == SINGLE_BOUNDARY) { 1337 /* 1338 * Wait until all suspended threads are removed from 1339 * the processors. The thread_suspend_check() 1340 * increments p_boundary_count while it is still 1341 * running, which makes it possible for the execve() 1342 * to destroy vmspace while our other threads are 1343 * still using the address space. 1344 * 1345 * We lock the thread, which is only allowed to 1346 * succeed after context switch code finished using 1347 * the address space. 1348 */ 1349 FOREACH_THREAD_IN_PROC(p, td2) { 1350 if (td2 == td) 1351 continue; 1352 thread_lock(td2); 1353 KASSERT((td2->td_flags & TDF_BOUNDARY) != 0, 1354 ("td %p not on boundary", td2)); 1355 KASSERT(TD_IS_SUSPENDED(td2), 1356 ("td %p is not suspended", td2)); 1357 thread_unlock(td2); 1358 } 1359 } 1360 PROC_SUNLOCK(p); 1361 return (0); 1362 } 1363 1364 bool 1365 thread_suspend_check_needed(void) 1366 { 1367 struct proc *p; 1368 struct thread *td; 1369 1370 td = curthread; 1371 p = td->td_proc; 1372 PROC_LOCK_ASSERT(p, MA_OWNED); 1373 return (P_SHOULDSTOP(p) || ((p->p_flag & P_TRACED) != 0 && 1374 (td->td_dbgflags & TDB_SUSPEND) != 0)); 1375 } 1376 1377 /* 1378 * Called in from locations that can safely check to see 1379 * whether we have to suspend or at least throttle for a 1380 * single-thread event (e.g. fork). 1381 * 1382 * Such locations include userret(). 1383 * If the "return_instead" argument is non zero, the thread must be able to 1384 * accept 0 (caller may continue), or 1 (caller must abort) as a result. 1385 * 1386 * The 'return_instead' argument tells the function if it may do a 1387 * thread_exit() or suspend, or whether the caller must abort and back 1388 * out instead. 1389 * 1390 * If the thread that set the single_threading request has set the 1391 * P_SINGLE_EXIT bit in the process flags then this call will never return 1392 * if 'return_instead' is false, but will exit. 1393 * 1394 * P_SINGLE_EXIT | return_instead == 0| return_instead != 0 1395 *---------------+--------------------+--------------------- 1396 * 0 | returns 0 | returns 0 or 1 1397 * | when ST ends | immediately 1398 *---------------+--------------------+--------------------- 1399 * 1 | thread exits | returns 1 1400 * | | immediately 1401 * 0 = thread_exit() or suspension ok, 1402 * other = return error instead of stopping the thread. 1403 * 1404 * While a full suspension is under effect, even a single threading 1405 * thread would be suspended if it made this call (but it shouldn't). 1406 * This call should only be made from places where 1407 * thread_exit() would be safe as that may be the outcome unless 1408 * return_instead is set. 1409 */ 1410 int 1411 thread_suspend_check(int return_instead) 1412 { 1413 struct thread *td; 1414 struct proc *p; 1415 int wakeup_swapper; 1416 1417 td = curthread; 1418 p = td->td_proc; 1419 mtx_assert(&Giant, MA_NOTOWNED); 1420 PROC_LOCK_ASSERT(p, MA_OWNED); 1421 while (thread_suspend_check_needed()) { 1422 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) { 1423 KASSERT(p->p_singlethread != NULL, 1424 ("singlethread not set")); 1425 /* 1426 * The only suspension in action is a 1427 * single-threading. Single threader need not stop. 1428 * It is safe to access p->p_singlethread unlocked 1429 * because it can only be set to our address by us. 1430 */ 1431 if (p->p_singlethread == td) 1432 return (0); /* Exempt from stopping. */ 1433 } 1434 if ((p->p_flag & P_SINGLE_EXIT) && return_instead) 1435 return (EINTR); 1436 1437 /* Should we goto user boundary if we didn't come from there? */ 1438 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE && 1439 (p->p_flag & P_SINGLE_BOUNDARY) && return_instead) 1440 return (ERESTART); 1441 1442 /* 1443 * Ignore suspend requests if they are deferred. 1444 */ 1445 if ((td->td_flags & TDF_SBDRY) != 0) { 1446 KASSERT(return_instead, 1447 ("TDF_SBDRY set for unsafe thread_suspend_check")); 1448 KASSERT((td->td_flags & (TDF_SEINTR | TDF_SERESTART)) != 1449 (TDF_SEINTR | TDF_SERESTART), 1450 ("both TDF_SEINTR and TDF_SERESTART")); 1451 return (TD_SBDRY_INTR(td) ? TD_SBDRY_ERRNO(td) : 0); 1452 } 1453 1454 /* 1455 * If the process is waiting for us to exit, 1456 * this thread should just suicide. 1457 * Assumes that P_SINGLE_EXIT implies P_STOPPED_SINGLE. 1458 */ 1459 if ((p->p_flag & P_SINGLE_EXIT) && (p->p_singlethread != td)) { 1460 PROC_UNLOCK(p); 1461 1462 /* 1463 * Allow Linux emulation layer to do some work 1464 * before thread suicide. 1465 */ 1466 if (__predict_false(p->p_sysent->sv_thread_detach != NULL)) 1467 (p->p_sysent->sv_thread_detach)(td); 1468 umtx_thread_exit(td); 1469 kern_thr_exit(td); 1470 panic("stopped thread did not exit"); 1471 } 1472 1473 PROC_SLOCK(p); 1474 thread_stopped(p); 1475 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) { 1476 if (p->p_numthreads == p->p_suspcount + 1) { 1477 thread_lock(p->p_singlethread); 1478 wakeup_swapper = thread_unsuspend_one( 1479 p->p_singlethread, p, false); 1480 if (wakeup_swapper) 1481 kick_proc0(); 1482 } 1483 } 1484 PROC_UNLOCK(p); 1485 thread_lock(td); 1486 /* 1487 * When a thread suspends, it just 1488 * gets taken off all queues. 1489 */ 1490 thread_suspend_one(td); 1491 if (return_instead == 0) { 1492 p->p_boundary_count++; 1493 td->td_flags |= TDF_BOUNDARY; 1494 } 1495 PROC_SUNLOCK(p); 1496 mi_switch(SW_INVOL | SWT_SUSPEND); 1497 PROC_LOCK(p); 1498 } 1499 return (0); 1500 } 1501 1502 /* 1503 * Check for possible stops and suspensions while executing a 1504 * casueword or similar transiently failing operation. 1505 * 1506 * The sleep argument controls whether the function can handle a stop 1507 * request itself or it should return ERESTART and the request is 1508 * proceed at the kernel/user boundary in ast. 1509 * 1510 * Typically, when retrying due to casueword(9) failure (rv == 1), we 1511 * should handle the stop requests there, with exception of cases when 1512 * the thread owns a kernel resource, for instance busied the umtx 1513 * key, or when functions return immediately if thread_check_susp() 1514 * returned non-zero. On the other hand, retrying the whole lock 1515 * operation, we better not stop there but delegate the handling to 1516 * ast. 1517 * 1518 * If the request is for thread termination P_SINGLE_EXIT, we cannot 1519 * handle it at all, and simply return EINTR. 1520 */ 1521 int 1522 thread_check_susp(struct thread *td, bool sleep) 1523 { 1524 struct proc *p; 1525 int error; 1526 1527 /* 1528 * The check for TDA_SUSPEND is racy, but it is enough to 1529 * eventually break the lockstep loop. 1530 */ 1531 if (!td_ast_pending(td, TDA_SUSPEND)) 1532 return (0); 1533 error = 0; 1534 p = td->td_proc; 1535 PROC_LOCK(p); 1536 if (p->p_flag & P_SINGLE_EXIT) 1537 error = EINTR; 1538 else if (P_SHOULDSTOP(p) || 1539 ((p->p_flag & P_TRACED) && (td->td_dbgflags & TDB_SUSPEND))) 1540 error = sleep ? thread_suspend_check(0) : ERESTART; 1541 PROC_UNLOCK(p); 1542 return (error); 1543 } 1544 1545 void 1546 thread_suspend_switch(struct thread *td, struct proc *p) 1547 { 1548 1549 KASSERT(!TD_IS_SUSPENDED(td), ("already suspended")); 1550 PROC_LOCK_ASSERT(p, MA_OWNED); 1551 PROC_SLOCK_ASSERT(p, MA_OWNED); 1552 /* 1553 * We implement thread_suspend_one in stages here to avoid 1554 * dropping the proc lock while the thread lock is owned. 1555 */ 1556 if (p == td->td_proc) { 1557 thread_stopped(p); 1558 p->p_suspcount++; 1559 } 1560 PROC_UNLOCK(p); 1561 thread_lock(td); 1562 ast_unsched_locked(td, TDA_SUSPEND); 1563 TD_SET_SUSPENDED(td); 1564 sched_sleep(td, 0); 1565 PROC_SUNLOCK(p); 1566 DROP_GIANT(); 1567 mi_switch(SW_VOL | SWT_SUSPEND); 1568 PICKUP_GIANT(); 1569 PROC_LOCK(p); 1570 PROC_SLOCK(p); 1571 } 1572 1573 void 1574 thread_suspend_one(struct thread *td) 1575 { 1576 struct proc *p; 1577 1578 p = td->td_proc; 1579 PROC_SLOCK_ASSERT(p, MA_OWNED); 1580 THREAD_LOCK_ASSERT(td, MA_OWNED); 1581 KASSERT(!TD_IS_SUSPENDED(td), ("already suspended")); 1582 p->p_suspcount++; 1583 ast_unsched_locked(td, TDA_SUSPEND); 1584 TD_SET_SUSPENDED(td); 1585 sched_sleep(td, 0); 1586 } 1587 1588 static int 1589 thread_unsuspend_one(struct thread *td, struct proc *p, bool boundary) 1590 { 1591 1592 THREAD_LOCK_ASSERT(td, MA_OWNED); 1593 KASSERT(TD_IS_SUSPENDED(td), ("Thread not suspended")); 1594 TD_CLR_SUSPENDED(td); 1595 td->td_flags &= ~TDF_ALLPROCSUSP; 1596 if (td->td_proc == p) { 1597 PROC_SLOCK_ASSERT(p, MA_OWNED); 1598 p->p_suspcount--; 1599 if (boundary && (td->td_flags & TDF_BOUNDARY) != 0) { 1600 td->td_flags &= ~TDF_BOUNDARY; 1601 p->p_boundary_count--; 1602 } 1603 } 1604 return (setrunnable(td, 0)); 1605 } 1606 1607 void 1608 thread_run_flash(struct thread *td) 1609 { 1610 struct proc *p; 1611 1612 p = td->td_proc; 1613 PROC_LOCK_ASSERT(p, MA_OWNED); 1614 1615 if (TD_ON_SLEEPQ(td)) 1616 sleepq_remove_nested(td); 1617 else 1618 thread_lock(td); 1619 1620 THREAD_LOCK_ASSERT(td, MA_OWNED); 1621 KASSERT(TD_IS_SUSPENDED(td), ("Thread not suspended")); 1622 1623 TD_CLR_SUSPENDED(td); 1624 PROC_SLOCK(p); 1625 MPASS(p->p_suspcount > 0); 1626 p->p_suspcount--; 1627 PROC_SUNLOCK(p); 1628 if (setrunnable(td, 0)) 1629 kick_proc0(); 1630 } 1631 1632 /* 1633 * Allow all threads blocked by single threading to continue running. 1634 */ 1635 void 1636 thread_unsuspend(struct proc *p) 1637 { 1638 struct thread *td; 1639 int wakeup_swapper; 1640 1641 PROC_LOCK_ASSERT(p, MA_OWNED); 1642 PROC_SLOCK_ASSERT(p, MA_OWNED); 1643 wakeup_swapper = 0; 1644 if (!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 true); 1650 else 1651 thread_unlock(td); 1652 } 1653 } else if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE && 1654 p->p_numthreads == p->p_suspcount) { 1655 /* 1656 * Stopping everything also did the job for the single 1657 * threading request. Now we've downgraded to single-threaded, 1658 * let it continue. 1659 */ 1660 if (p->p_singlethread->td_proc == p) { 1661 thread_lock(p->p_singlethread); 1662 wakeup_swapper = thread_unsuspend_one( 1663 p->p_singlethread, p, false); 1664 } 1665 } 1666 if (wakeup_swapper) 1667 kick_proc0(); 1668 } 1669 1670 /* 1671 * End the single threading mode.. 1672 */ 1673 void 1674 thread_single_end(struct proc *p, int mode) 1675 { 1676 struct thread *td; 1677 int wakeup_swapper; 1678 1679 KASSERT(mode == SINGLE_EXIT || mode == SINGLE_BOUNDARY || 1680 mode == SINGLE_ALLPROC || mode == SINGLE_NO_EXIT, 1681 ("invalid mode %d", mode)); 1682 PROC_LOCK_ASSERT(p, MA_OWNED); 1683 KASSERT((mode == SINGLE_ALLPROC && (p->p_flag & P_TOTAL_STOP) != 0) || 1684 (mode != SINGLE_ALLPROC && (p->p_flag & P_TOTAL_STOP) == 0), 1685 ("mode %d does not match P_TOTAL_STOP", mode)); 1686 KASSERT(mode == SINGLE_ALLPROC || p->p_singlethread == curthread, 1687 ("thread_single_end from other thread %p %p", 1688 curthread, p->p_singlethread)); 1689 KASSERT(mode != SINGLE_BOUNDARY || 1690 (p->p_flag & P_SINGLE_BOUNDARY) != 0, 1691 ("mis-matched SINGLE_BOUNDARY flags %x", p->p_flag)); 1692 p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT | P_SINGLE_BOUNDARY | 1693 P_TOTAL_STOP); 1694 PROC_SLOCK(p); 1695 p->p_singlethread = NULL; 1696 wakeup_swapper = 0; 1697 /* 1698 * If there are other threads they may now run, 1699 * unless of course there is a blanket 'stop order' 1700 * on the process. The single threader must be allowed 1701 * to continue however as this is a bad place to stop. 1702 */ 1703 if (p->p_numthreads != remain_for_mode(mode) && !P_SHOULDSTOP(p)) { 1704 FOREACH_THREAD_IN_PROC(p, td) { 1705 thread_lock(td); 1706 if (TD_IS_SUSPENDED(td)) { 1707 wakeup_swapper |= thread_unsuspend_one(td, p, 1708 true); 1709 } else 1710 thread_unlock(td); 1711 } 1712 } 1713 KASSERT(mode != SINGLE_BOUNDARY || p->p_boundary_count == 0, 1714 ("inconsistent boundary count %d", p->p_boundary_count)); 1715 PROC_SUNLOCK(p); 1716 if (wakeup_swapper) 1717 kick_proc0(); 1718 wakeup(&p->p_flag); 1719 } 1720 1721 /* 1722 * Locate a thread by number and return with proc lock held. 1723 * 1724 * thread exit establishes proc -> tidhash lock ordering, but lookup 1725 * takes tidhash first and needs to return locked proc. 1726 * 1727 * The problem is worked around by relying on type-safety of both 1728 * structures and doing the work in 2 steps: 1729 * - tidhash-locked lookup which saves both thread and proc pointers 1730 * - proc-locked verification that the found thread still matches 1731 */ 1732 static bool 1733 tdfind_hash(lwpid_t tid, pid_t pid, struct proc **pp, struct thread **tdp) 1734 { 1735 #define RUN_THRESH 16 1736 struct proc *p; 1737 struct thread *td; 1738 int run; 1739 bool locked; 1740 1741 run = 0; 1742 rw_rlock(TIDHASHLOCK(tid)); 1743 locked = true; 1744 LIST_FOREACH(td, TIDHASH(tid), td_hash) { 1745 if (td->td_tid != tid) { 1746 run++; 1747 continue; 1748 } 1749 p = td->td_proc; 1750 if (pid != -1 && p->p_pid != pid) { 1751 td = NULL; 1752 break; 1753 } 1754 if (run > RUN_THRESH) { 1755 if (rw_try_upgrade(TIDHASHLOCK(tid))) { 1756 LIST_REMOVE(td, td_hash); 1757 LIST_INSERT_HEAD(TIDHASH(td->td_tid), 1758 td, td_hash); 1759 rw_wunlock(TIDHASHLOCK(tid)); 1760 locked = false; 1761 break; 1762 } 1763 } 1764 break; 1765 } 1766 if (locked) 1767 rw_runlock(TIDHASHLOCK(tid)); 1768 if (td == NULL) 1769 return (false); 1770 *pp = p; 1771 *tdp = td; 1772 return (true); 1773 } 1774 1775 struct thread * 1776 tdfind(lwpid_t tid, pid_t pid) 1777 { 1778 struct proc *p; 1779 struct thread *td; 1780 1781 td = curthread; 1782 if (td->td_tid == tid) { 1783 if (pid != -1 && td->td_proc->p_pid != pid) 1784 return (NULL); 1785 PROC_LOCK(td->td_proc); 1786 return (td); 1787 } 1788 1789 for (;;) { 1790 if (!tdfind_hash(tid, pid, &p, &td)) 1791 return (NULL); 1792 PROC_LOCK(p); 1793 if (td->td_tid != tid) { 1794 PROC_UNLOCK(p); 1795 continue; 1796 } 1797 if (td->td_proc != p) { 1798 PROC_UNLOCK(p); 1799 continue; 1800 } 1801 if (p->p_state == PRS_NEW) { 1802 PROC_UNLOCK(p); 1803 return (NULL); 1804 } 1805 return (td); 1806 } 1807 } 1808 1809 void 1810 tidhash_add(struct thread *td) 1811 { 1812 rw_wlock(TIDHASHLOCK(td->td_tid)); 1813 LIST_INSERT_HEAD(TIDHASH(td->td_tid), td, td_hash); 1814 rw_wunlock(TIDHASHLOCK(td->td_tid)); 1815 } 1816 1817 void 1818 tidhash_remove(struct thread *td) 1819 { 1820 1821 rw_wlock(TIDHASHLOCK(td->td_tid)); 1822 LIST_REMOVE(td, td_hash); 1823 rw_wunlock(TIDHASHLOCK(td->td_tid)); 1824 } 1825