Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
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sys/kern/kern_thread.c
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1 /*- 2 * Copyright (C) 2001 Julian Elischer <julian@freebsd.org>. 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice(s), this list of conditions and the following disclaimer as 10 * the first lines of this file unmodified other than the possible 11 * addition of one or more copyright notices. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice(s), this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 16 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY 17 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 18 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 19 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE LIABLE FOR ANY 20 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES 21 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR 22 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER 23 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH 26 * DAMAGE. 27 */ 28 29 #include "opt_witness.h" 30 #include "opt_hwpmc_hooks.h" 31 32 #include <sys/cdefs.h> 33 __FBSDID("$FreeBSD: releng/11.0/sys/kern/kern_thread.c 302328 2016-07-03 18:19:48Z kib $"); 34 35 #include <sys/param.h> 36 #include <sys/systm.h> 37 #include <sys/kernel.h> 38 #include <sys/lock.h> 39 #include <sys/mutex.h> 40 #include <sys/proc.h> 41 #include <sys/rangelock.h> 42 #include <sys/resourcevar.h> 43 #include <sys/sdt.h> 44 #include <sys/smp.h> 45 #include <sys/sched.h> 46 #include <sys/sleepqueue.h> 47 #include <sys/selinfo.h> 48 #include <sys/syscallsubr.h> 49 #include <sys/sysent.h> 50 #include <sys/turnstile.h> 51 #include <sys/ktr.h> 52 #include <sys/rwlock.h> 53 #include <sys/umtx.h> 54 #include <sys/cpuset.h> 55 #ifdef HWPMC_HOOKS 56 #include <sys/pmckern.h> 57 #endif 58 59 #include <security/audit/audit.h> 60 61 #include <vm/vm.h> 62 #include <vm/vm_extern.h> 63 #include <vm/uma.h> 64 #include <vm/vm_domain.h> 65 #include <sys/eventhandler.h> 66 67 SDT_PROVIDER_DECLARE(proc); 68 SDT_PROBE_DEFINE(proc, , , lwp__exit); 69 70 /* 71 * thread related storage. 72 */ 73 static uma_zone_t thread_zone; 74 75 TAILQ_HEAD(, thread) zombie_threads = TAILQ_HEAD_INITIALIZER(zombie_threads); 76 static struct mtx zombie_lock; 77 MTX_SYSINIT(zombie_lock, &zombie_lock, "zombie lock", MTX_SPIN); 78 79 static void thread_zombie(struct thread *); 80 static int thread_unsuspend_one(struct thread *td, struct proc *p, 81 bool boundary); 82 83 #define TID_BUFFER_SIZE 1024 84 85 struct mtx tid_lock; 86 static struct unrhdr *tid_unrhdr; 87 static lwpid_t tid_buffer[TID_BUFFER_SIZE]; 88 static int tid_head, tid_tail; 89 static MALLOC_DEFINE(M_TIDHASH, "tidhash", "thread hash"); 90 91 struct tidhashhead *tidhashtbl; 92 u_long tidhash; 93 struct rwlock tidhash_lock; 94 95 static lwpid_t 96 tid_alloc(void) 97 { 98 lwpid_t tid; 99 100 tid = alloc_unr(tid_unrhdr); 101 if (tid != -1) 102 return (tid); 103 mtx_lock(&tid_lock); 104 if (tid_head == tid_tail) { 105 mtx_unlock(&tid_lock); 106 return (-1); 107 } 108 tid = tid_buffer[tid_head]; 109 tid_head = (tid_head + 1) % TID_BUFFER_SIZE; 110 mtx_unlock(&tid_lock); 111 return (tid); 112 } 113 114 static void 115 tid_free(lwpid_t tid) 116 { 117 lwpid_t tmp_tid = -1; 118 119 mtx_lock(&tid_lock); 120 if ((tid_tail + 1) % TID_BUFFER_SIZE == tid_head) { 121 tmp_tid = tid_buffer[tid_head]; 122 tid_head = (tid_head + 1) % TID_BUFFER_SIZE; 123 } 124 tid_buffer[tid_tail] = tid; 125 tid_tail = (tid_tail + 1) % TID_BUFFER_SIZE; 126 mtx_unlock(&tid_lock); 127 if (tmp_tid != -1) 128 free_unr(tid_unrhdr, tmp_tid); 129 } 130 131 /* 132 * Prepare a thread for use. 133 */ 134 static int 135 thread_ctor(void *mem, int size, void *arg, int flags) 136 { 137 struct thread *td; 138 139 td = (struct thread *)mem; 140 td->td_state = TDS_INACTIVE; 141 td->td_oncpu = NOCPU; 142 143 td->td_tid = tid_alloc(); 144 145 /* 146 * Note that td_critnest begins life as 1 because the thread is not 147 * running and is thereby implicitly waiting to be on the receiving 148 * end of a context switch. 149 */ 150 td->td_critnest = 1; 151 td->td_lend_user_pri = PRI_MAX; 152 EVENTHANDLER_INVOKE(thread_ctor, td); 153 #ifdef AUDIT 154 audit_thread_alloc(td); 155 #endif 156 umtx_thread_alloc(td); 157 return (0); 158 } 159 160 /* 161 * Reclaim a thread after use. 162 */ 163 static void 164 thread_dtor(void *mem, int size, void *arg) 165 { 166 struct thread *td; 167 168 td = (struct thread *)mem; 169 170 #ifdef INVARIANTS 171 /* Verify that this thread is in a safe state to free. */ 172 switch (td->td_state) { 173 case TDS_INHIBITED: 174 case TDS_RUNNING: 175 case TDS_CAN_RUN: 176 case TDS_RUNQ: 177 /* 178 * We must never unlink a thread that is in one of 179 * these states, because it is currently active. 180 */ 181 panic("bad state for thread unlinking"); 182 /* NOTREACHED */ 183 case TDS_INACTIVE: 184 break; 185 default: 186 panic("bad thread state"); 187 /* NOTREACHED */ 188 } 189 #endif 190 #ifdef AUDIT 191 audit_thread_free(td); 192 #endif 193 /* Free all OSD associated to this thread. */ 194 osd_thread_exit(td); 195 196 EVENTHANDLER_INVOKE(thread_dtor, td); 197 tid_free(td->td_tid); 198 } 199 200 /* 201 * Initialize type-stable parts of a thread (when newly created). 202 */ 203 static int 204 thread_init(void *mem, int size, int flags) 205 { 206 struct thread *td; 207 208 td = (struct thread *)mem; 209 210 td->td_sleepqueue = sleepq_alloc(); 211 td->td_turnstile = turnstile_alloc(); 212 td->td_rlqe = NULL; 213 EVENTHANDLER_INVOKE(thread_init, td); 214 umtx_thread_init(td); 215 td->td_kstack = 0; 216 td->td_sel = NULL; 217 return (0); 218 } 219 220 /* 221 * Tear down type-stable parts of a thread (just before being discarded). 222 */ 223 static void 224 thread_fini(void *mem, int size) 225 { 226 struct thread *td; 227 228 td = (struct thread *)mem; 229 EVENTHANDLER_INVOKE(thread_fini, td); 230 rlqentry_free(td->td_rlqe); 231 turnstile_free(td->td_turnstile); 232 sleepq_free(td->td_sleepqueue); 233 umtx_thread_fini(td); 234 seltdfini(td); 235 } 236 237 /* 238 * For a newly created process, 239 * link up all the structures and its initial threads etc. 240 * called from: 241 * {arch}/{arch}/machdep.c {arch}_init(), init386() etc. 242 * proc_dtor() (should go away) 243 * proc_init() 244 */ 245 void 246 proc_linkup0(struct proc *p, struct thread *td) 247 { 248 TAILQ_INIT(&p->p_threads); /* all threads in proc */ 249 proc_linkup(p, td); 250 } 251 252 void 253 proc_linkup(struct proc *p, struct thread *td) 254 { 255 256 sigqueue_init(&p->p_sigqueue, p); 257 p->p_ksi = ksiginfo_alloc(1); 258 if (p->p_ksi != NULL) { 259 /* XXX p_ksi may be null if ksiginfo zone is not ready */ 260 p->p_ksi->ksi_flags = KSI_EXT | KSI_INS; 261 } 262 LIST_INIT(&p->p_mqnotifier); 263 p->p_numthreads = 0; 264 thread_link(td, p); 265 } 266 267 /* 268 * Initialize global thread allocation resources. 269 */ 270 void 271 threadinit(void) 272 { 273 274 mtx_init(&tid_lock, "TID lock", NULL, MTX_DEF); 275 276 /* 277 * pid_max cannot be greater than PID_MAX. 278 * leave one number for thread0. 279 */ 280 tid_unrhdr = new_unrhdr(PID_MAX + 2, INT_MAX, &tid_lock); 281 282 thread_zone = uma_zcreate("THREAD", sched_sizeof_thread(), 283 thread_ctor, thread_dtor, thread_init, thread_fini, 284 16 - 1, UMA_ZONE_NOFREE); 285 tidhashtbl = hashinit(maxproc / 2, M_TIDHASH, &tidhash); 286 rw_init(&tidhash_lock, "tidhash"); 287 } 288 289 /* 290 * Place an unused thread on the zombie list. 291 * Use the slpq as that must be unused by now. 292 */ 293 void 294 thread_zombie(struct thread *td) 295 { 296 mtx_lock_spin(&zombie_lock); 297 TAILQ_INSERT_HEAD(&zombie_threads, td, td_slpq); 298 mtx_unlock_spin(&zombie_lock); 299 } 300 301 /* 302 * Release a thread that has exited after cpu_throw(). 303 */ 304 void 305 thread_stash(struct thread *td) 306 { 307 atomic_subtract_rel_int(&td->td_proc->p_exitthreads, 1); 308 thread_zombie(td); 309 } 310 311 /* 312 * Reap zombie resources. 313 */ 314 void 315 thread_reap(void) 316 { 317 struct thread *td_first, *td_next; 318 319 /* 320 * Don't even bother to lock if none at this instant, 321 * we really don't care about the next instant.. 322 */ 323 if (!TAILQ_EMPTY(&zombie_threads)) { 324 mtx_lock_spin(&zombie_lock); 325 td_first = TAILQ_FIRST(&zombie_threads); 326 if (td_first) 327 TAILQ_INIT(&zombie_threads); 328 mtx_unlock_spin(&zombie_lock); 329 while (td_first) { 330 td_next = TAILQ_NEXT(td_first, td_slpq); 331 thread_cow_free(td_first); 332 thread_free(td_first); 333 td_first = td_next; 334 } 335 } 336 } 337 338 /* 339 * Allocate a thread. 340 */ 341 struct thread * 342 thread_alloc(int pages) 343 { 344 struct thread *td; 345 346 thread_reap(); /* check if any zombies to get */ 347 348 td = (struct thread *)uma_zalloc(thread_zone, M_WAITOK); 349 KASSERT(td->td_kstack == 0, ("thread_alloc got thread with kstack")); 350 if (!vm_thread_new(td, pages)) { 351 uma_zfree(thread_zone, td); 352 return (NULL); 353 } 354 cpu_thread_alloc(td); 355 vm_domain_policy_init(&td->td_vm_dom_policy); 356 return (td); 357 } 358 359 int 360 thread_alloc_stack(struct thread *td, int pages) 361 { 362 363 KASSERT(td->td_kstack == 0, 364 ("thread_alloc_stack called on a thread with kstack")); 365 if (!vm_thread_new(td, pages)) 366 return (0); 367 cpu_thread_alloc(td); 368 return (1); 369 } 370 371 /* 372 * Deallocate a thread. 373 */ 374 void 375 thread_free(struct thread *td) 376 { 377 378 lock_profile_thread_exit(td); 379 if (td->td_cpuset) 380 cpuset_rel(td->td_cpuset); 381 td->td_cpuset = NULL; 382 cpu_thread_free(td); 383 if (td->td_kstack != 0) 384 vm_thread_dispose(td); 385 vm_domain_policy_cleanup(&td->td_vm_dom_policy); 386 uma_zfree(thread_zone, td); 387 } 388 389 void 390 thread_cow_get_proc(struct thread *newtd, struct proc *p) 391 { 392 393 PROC_LOCK_ASSERT(p, MA_OWNED); 394 newtd->td_ucred = crhold(p->p_ucred); 395 newtd->td_limit = lim_hold(p->p_limit); 396 newtd->td_cowgen = p->p_cowgen; 397 } 398 399 void 400 thread_cow_get(struct thread *newtd, struct thread *td) 401 { 402 403 newtd->td_ucred = crhold(td->td_ucred); 404 newtd->td_limit = lim_hold(td->td_limit); 405 newtd->td_cowgen = td->td_cowgen; 406 } 407 408 void 409 thread_cow_free(struct thread *td) 410 { 411 412 if (td->td_ucred != NULL) 413 crfree(td->td_ucred); 414 if (td->td_limit != NULL) 415 lim_free(td->td_limit); 416 } 417 418 void 419 thread_cow_update(struct thread *td) 420 { 421 struct proc *p; 422 struct ucred *oldcred; 423 struct plimit *oldlimit; 424 425 p = td->td_proc; 426 oldcred = NULL; 427 oldlimit = NULL; 428 PROC_LOCK(p); 429 if (td->td_ucred != p->p_ucred) { 430 oldcred = td->td_ucred; 431 td->td_ucred = crhold(p->p_ucred); 432 } 433 if (td->td_limit != p->p_limit) { 434 oldlimit = td->td_limit; 435 td->td_limit = lim_hold(p->p_limit); 436 } 437 td->td_cowgen = p->p_cowgen; 438 PROC_UNLOCK(p); 439 if (oldcred != NULL) 440 crfree(oldcred); 441 if (oldlimit != NULL) 442 lim_free(oldlimit); 443 } 444 445 /* 446 * Discard the current thread and exit from its context. 447 * Always called with scheduler locked. 448 * 449 * Because we can't free a thread while we're operating under its context, 450 * push the current thread into our CPU's deadthread holder. This means 451 * we needn't worry about someone else grabbing our context before we 452 * do a cpu_throw(). 453 */ 454 void 455 thread_exit(void) 456 { 457 uint64_t runtime, new_switchtime; 458 struct thread *td; 459 struct thread *td2; 460 struct proc *p; 461 int wakeup_swapper; 462 463 td = curthread; 464 p = td->td_proc; 465 466 PROC_SLOCK_ASSERT(p, MA_OWNED); 467 mtx_assert(&Giant, MA_NOTOWNED); 468 469 PROC_LOCK_ASSERT(p, MA_OWNED); 470 KASSERT(p != NULL, ("thread exiting without a process")); 471 CTR3(KTR_PROC, "thread_exit: thread %p (pid %ld, %s)", td, 472 (long)p->p_pid, td->td_name); 473 KASSERT(TAILQ_EMPTY(&td->td_sigqueue.sq_list), ("signal pending")); 474 475 #ifdef AUDIT 476 AUDIT_SYSCALL_EXIT(0, td); 477 #endif 478 /* 479 * drop FPU & debug register state storage, or any other 480 * architecture specific resources that 481 * would not be on a new untouched process. 482 */ 483 cpu_thread_exit(td); 484 485 /* 486 * The last thread is left attached to the process 487 * So that the whole bundle gets recycled. Skip 488 * all this stuff if we never had threads. 489 * EXIT clears all sign of other threads when 490 * it goes to single threading, so the last thread always 491 * takes the short path. 492 */ 493 if (p->p_flag & P_HADTHREADS) { 494 if (p->p_numthreads > 1) { 495 atomic_add_int(&td->td_proc->p_exitthreads, 1); 496 thread_unlink(td); 497 td2 = FIRST_THREAD_IN_PROC(p); 498 sched_exit_thread(td2, td); 499 500 /* 501 * The test below is NOT true if we are the 502 * sole exiting thread. P_STOPPED_SINGLE is unset 503 * in exit1() after it is the only survivor. 504 */ 505 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) { 506 if (p->p_numthreads == p->p_suspcount) { 507 thread_lock(p->p_singlethread); 508 wakeup_swapper = thread_unsuspend_one( 509 p->p_singlethread, p, false); 510 thread_unlock(p->p_singlethread); 511 if (wakeup_swapper) 512 kick_proc0(); 513 } 514 } 515 516 PCPU_SET(deadthread, td); 517 } else { 518 /* 519 * The last thread is exiting.. but not through exit() 520 */ 521 panic ("thread_exit: Last thread exiting on its own"); 522 } 523 } 524 #ifdef HWPMC_HOOKS 525 /* 526 * If this thread is part of a process that is being tracked by hwpmc(4), 527 * inform the module of the thread's impending exit. 528 */ 529 if (PMC_PROC_IS_USING_PMCS(td->td_proc)) 530 PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_OUT); 531 #endif 532 PROC_UNLOCK(p); 533 PROC_STATLOCK(p); 534 thread_lock(td); 535 PROC_SUNLOCK(p); 536 537 /* Do the same timestamp bookkeeping that mi_switch() would do. */ 538 new_switchtime = cpu_ticks(); 539 runtime = new_switchtime - PCPU_GET(switchtime); 540 td->td_runtime += runtime; 541 td->td_incruntime += runtime; 542 PCPU_SET(switchtime, new_switchtime); 543 PCPU_SET(switchticks, ticks); 544 PCPU_INC(cnt.v_swtch); 545 546 /* Save our resource usage in our process. */ 547 td->td_ru.ru_nvcsw++; 548 ruxagg(p, td); 549 rucollect(&p->p_ru, &td->td_ru); 550 PROC_STATUNLOCK(p); 551 552 td->td_state = TDS_INACTIVE; 553 #ifdef WITNESS 554 witness_thread_exit(td); 555 #endif 556 CTR1(KTR_PROC, "thread_exit: cpu_throw() thread %p", td); 557 sched_throw(td); 558 panic("I'm a teapot!"); 559 /* NOTREACHED */ 560 } 561 562 /* 563 * Do any thread specific cleanups that may be needed in wait() 564 * called with Giant, proc and schedlock not held. 565 */ 566 void 567 thread_wait(struct proc *p) 568 { 569 struct thread *td; 570 571 mtx_assert(&Giant, MA_NOTOWNED); 572 KASSERT(p->p_numthreads == 1, ("multiple threads in thread_wait()")); 573 KASSERT(p->p_exitthreads == 0, ("p_exitthreads leaking")); 574 td = FIRST_THREAD_IN_PROC(p); 575 /* Lock the last thread so we spin until it exits cpu_throw(). */ 576 thread_lock(td); 577 thread_unlock(td); 578 lock_profile_thread_exit(td); 579 cpuset_rel(td->td_cpuset); 580 td->td_cpuset = NULL; 581 cpu_thread_clean(td); 582 thread_cow_free(td); 583 thread_reap(); /* check for zombie threads etc. */ 584 } 585 586 /* 587 * Link a thread to a process. 588 * set up anything that needs to be initialized for it to 589 * be used by the process. 590 */ 591 void 592 thread_link(struct thread *td, struct proc *p) 593 { 594 595 /* 596 * XXX This can't be enabled because it's called for proc0 before 597 * its lock has been created. 598 * PROC_LOCK_ASSERT(p, MA_OWNED); 599 */ 600 td->td_state = TDS_INACTIVE; 601 td->td_proc = p; 602 td->td_flags = TDF_INMEM; 603 604 LIST_INIT(&td->td_contested); 605 LIST_INIT(&td->td_lprof[0]); 606 LIST_INIT(&td->td_lprof[1]); 607 sigqueue_init(&td->td_sigqueue, p); 608 callout_init(&td->td_slpcallout, 1); 609 TAILQ_INSERT_TAIL(&p->p_threads, td, td_plist); 610 p->p_numthreads++; 611 } 612 613 /* 614 * Called from: 615 * thread_exit() 616 */ 617 void 618 thread_unlink(struct thread *td) 619 { 620 struct proc *p = td->td_proc; 621 622 PROC_LOCK_ASSERT(p, MA_OWNED); 623 TAILQ_REMOVE(&p->p_threads, td, td_plist); 624 p->p_numthreads--; 625 /* could clear a few other things here */ 626 /* Must NOT clear links to proc! */ 627 } 628 629 static int 630 calc_remaining(struct proc *p, int mode) 631 { 632 int remaining; 633 634 PROC_LOCK_ASSERT(p, MA_OWNED); 635 PROC_SLOCK_ASSERT(p, MA_OWNED); 636 if (mode == SINGLE_EXIT) 637 remaining = p->p_numthreads; 638 else if (mode == SINGLE_BOUNDARY) 639 remaining = p->p_numthreads - p->p_boundary_count; 640 else if (mode == SINGLE_NO_EXIT || mode == SINGLE_ALLPROC) 641 remaining = p->p_numthreads - p->p_suspcount; 642 else 643 panic("calc_remaining: wrong mode %d", mode); 644 return (remaining); 645 } 646 647 static int 648 remain_for_mode(int mode) 649 { 650 651 return (mode == SINGLE_ALLPROC ? 0 : 1); 652 } 653 654 static int 655 weed_inhib(int mode, struct thread *td2, struct proc *p) 656 { 657 int wakeup_swapper; 658 659 PROC_LOCK_ASSERT(p, MA_OWNED); 660 PROC_SLOCK_ASSERT(p, MA_OWNED); 661 THREAD_LOCK_ASSERT(td2, MA_OWNED); 662 663 wakeup_swapper = 0; 664 switch (mode) { 665 case SINGLE_EXIT: 666 if (TD_IS_SUSPENDED(td2)) 667 wakeup_swapper |= thread_unsuspend_one(td2, p, true); 668 if (TD_ON_SLEEPQ(td2) && (td2->td_flags & TDF_SINTR) != 0) 669 wakeup_swapper |= sleepq_abort(td2, EINTR); 670 break; 671 case SINGLE_BOUNDARY: 672 case SINGLE_NO_EXIT: 673 if (TD_IS_SUSPENDED(td2) && (td2->td_flags & TDF_BOUNDARY) == 0) 674 wakeup_swapper |= thread_unsuspend_one(td2, p, false); 675 if (TD_ON_SLEEPQ(td2) && (td2->td_flags & TDF_SINTR) != 0) 676 wakeup_swapper |= sleepq_abort(td2, ERESTART); 677 break; 678 case SINGLE_ALLPROC: 679 /* 680 * ALLPROC suspend tries to avoid spurious EINTR for 681 * threads sleeping interruptable, by suspending the 682 * thread directly, similarly to sig_suspend_threads(). 683 * Since such sleep is not performed at the user 684 * boundary, TDF_BOUNDARY flag is not set, and TDF_ALLPROCSUSP 685 * is used to avoid immediate un-suspend. 686 */ 687 if (TD_IS_SUSPENDED(td2) && (td2->td_flags & (TDF_BOUNDARY | 688 TDF_ALLPROCSUSP)) == 0) 689 wakeup_swapper |= thread_unsuspend_one(td2, p, false); 690 if (TD_ON_SLEEPQ(td2) && (td2->td_flags & TDF_SINTR) != 0) { 691 if ((td2->td_flags & TDF_SBDRY) == 0) { 692 thread_suspend_one(td2); 693 td2->td_flags |= TDF_ALLPROCSUSP; 694 } else { 695 wakeup_swapper |= sleepq_abort(td2, ERESTART); 696 } 697 } 698 break; 699 } 700 return (wakeup_swapper); 701 } 702 703 /* 704 * Enforce single-threading. 705 * 706 * Returns 1 if the caller must abort (another thread is waiting to 707 * exit the process or similar). Process is locked! 708 * Returns 0 when you are successfully the only thread running. 709 * A process has successfully single threaded in the suspend mode when 710 * There are no threads in user mode. Threads in the kernel must be 711 * allowed to continue until they get to the user boundary. They may even 712 * copy out their return values and data before suspending. They may however be 713 * accelerated in reaching the user boundary as we will wake up 714 * any sleeping threads that are interruptable. (PCATCH). 715 */ 716 int 717 thread_single(struct proc *p, int mode) 718 { 719 struct thread *td; 720 struct thread *td2; 721 int remaining, wakeup_swapper; 722 723 td = curthread; 724 KASSERT(mode == SINGLE_EXIT || mode == SINGLE_BOUNDARY || 725 mode == SINGLE_ALLPROC || mode == SINGLE_NO_EXIT, 726 ("invalid mode %d", mode)); 727 /* 728 * If allowing non-ALLPROC singlethreading for non-curproc 729 * callers, calc_remaining() and remain_for_mode() should be 730 * adjusted to also account for td->td_proc != p. For now 731 * this is not implemented because it is not used. 732 */ 733 KASSERT((mode == SINGLE_ALLPROC && td->td_proc != p) || 734 (mode != SINGLE_ALLPROC && td->td_proc == p), 735 ("mode %d proc %p curproc %p", mode, p, td->td_proc)); 736 mtx_assert(&Giant, MA_NOTOWNED); 737 PROC_LOCK_ASSERT(p, MA_OWNED); 738 739 if ((p->p_flag & P_HADTHREADS) == 0 && mode != SINGLE_ALLPROC) 740 return (0); 741 742 /* Is someone already single threading? */ 743 if (p->p_singlethread != NULL && p->p_singlethread != td) 744 return (1); 745 746 if (mode == SINGLE_EXIT) { 747 p->p_flag |= P_SINGLE_EXIT; 748 p->p_flag &= ~P_SINGLE_BOUNDARY; 749 } else { 750 p->p_flag &= ~P_SINGLE_EXIT; 751 if (mode == SINGLE_BOUNDARY) 752 p->p_flag |= P_SINGLE_BOUNDARY; 753 else 754 p->p_flag &= ~P_SINGLE_BOUNDARY; 755 } 756 if (mode == SINGLE_ALLPROC) 757 p->p_flag |= P_TOTAL_STOP; 758 p->p_flag |= P_STOPPED_SINGLE; 759 PROC_SLOCK(p); 760 p->p_singlethread = td; 761 remaining = calc_remaining(p, mode); 762 while (remaining != remain_for_mode(mode)) { 763 if (P_SHOULDSTOP(p) != P_STOPPED_SINGLE) 764 goto stopme; 765 wakeup_swapper = 0; 766 FOREACH_THREAD_IN_PROC(p, td2) { 767 if (td2 == td) 768 continue; 769 thread_lock(td2); 770 td2->td_flags |= TDF_ASTPENDING | TDF_NEEDSUSPCHK; 771 if (TD_IS_INHIBITED(td2)) { 772 wakeup_swapper |= weed_inhib(mode, td2, p); 773 #ifdef SMP 774 } else if (TD_IS_RUNNING(td2) && td != td2) { 775 forward_signal(td2); 776 #endif 777 } 778 thread_unlock(td2); 779 } 780 if (wakeup_swapper) 781 kick_proc0(); 782 remaining = calc_remaining(p, mode); 783 784 /* 785 * Maybe we suspended some threads.. was it enough? 786 */ 787 if (remaining == remain_for_mode(mode)) 788 break; 789 790 stopme: 791 /* 792 * Wake us up when everyone else has suspended. 793 * In the mean time we suspend as well. 794 */ 795 thread_suspend_switch(td, p); 796 remaining = calc_remaining(p, mode); 797 } 798 if (mode == SINGLE_EXIT) { 799 /* 800 * Convert the process to an unthreaded process. The 801 * SINGLE_EXIT is called by exit1() or execve(), in 802 * both cases other threads must be retired. 803 */ 804 KASSERT(p->p_numthreads == 1, ("Unthreading with >1 threads")); 805 p->p_singlethread = NULL; 806 p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT | P_HADTHREADS); 807 808 /* 809 * Wait for any remaining threads to exit cpu_throw(). 810 */ 811 while (p->p_exitthreads != 0) { 812 PROC_SUNLOCK(p); 813 PROC_UNLOCK(p); 814 sched_relinquish(td); 815 PROC_LOCK(p); 816 PROC_SLOCK(p); 817 } 818 } else if (mode == SINGLE_BOUNDARY) { 819 /* 820 * Wait until all suspended threads are removed from 821 * the processors. The thread_suspend_check() 822 * increments p_boundary_count while it is still 823 * running, which makes it possible for the execve() 824 * to destroy vmspace while our other threads are 825 * still using the address space. 826 * 827 * We lock the thread, which is only allowed to 828 * succeed after context switch code finished using 829 * the address space. 830 */ 831 FOREACH_THREAD_IN_PROC(p, td2) { 832 if (td2 == td) 833 continue; 834 thread_lock(td2); 835 KASSERT((td2->td_flags & TDF_BOUNDARY) != 0, 836 ("td %p not on boundary", td2)); 837 KASSERT(TD_IS_SUSPENDED(td2), 838 ("td %p is not suspended", td2)); 839 thread_unlock(td2); 840 } 841 } 842 PROC_SUNLOCK(p); 843 return (0); 844 } 845 846 bool 847 thread_suspend_check_needed(void) 848 { 849 struct proc *p; 850 struct thread *td; 851 852 td = curthread; 853 p = td->td_proc; 854 PROC_LOCK_ASSERT(p, MA_OWNED); 855 return (P_SHOULDSTOP(p) || ((p->p_flag & P_TRACED) != 0 && 856 (td->td_dbgflags & TDB_SUSPEND) != 0)); 857 } 858 859 /* 860 * Called in from locations that can safely check to see 861 * whether we have to suspend or at least throttle for a 862 * single-thread event (e.g. fork). 863 * 864 * Such locations include userret(). 865 * If the "return_instead" argument is non zero, the thread must be able to 866 * accept 0 (caller may continue), or 1 (caller must abort) as a result. 867 * 868 * The 'return_instead' argument tells the function if it may do a 869 * thread_exit() or suspend, or whether the caller must abort and back 870 * out instead. 871 * 872 * If the thread that set the single_threading request has set the 873 * P_SINGLE_EXIT bit in the process flags then this call will never return 874 * if 'return_instead' is false, but will exit. 875 * 876 * P_SINGLE_EXIT | return_instead == 0| return_instead != 0 877 *---------------+--------------------+--------------------- 878 * 0 | returns 0 | returns 0 or 1 879 * | when ST ends | immediately 880 *---------------+--------------------+--------------------- 881 * 1 | thread exits | returns 1 882 * | | immediately 883 * 0 = thread_exit() or suspension ok, 884 * other = return error instead of stopping the thread. 885 * 886 * While a full suspension is under effect, even a single threading 887 * thread would be suspended if it made this call (but it shouldn't). 888 * This call should only be made from places where 889 * thread_exit() would be safe as that may be the outcome unless 890 * return_instead is set. 891 */ 892 int 893 thread_suspend_check(int return_instead) 894 { 895 struct thread *td; 896 struct proc *p; 897 int wakeup_swapper; 898 899 td = curthread; 900 p = td->td_proc; 901 mtx_assert(&Giant, MA_NOTOWNED); 902 PROC_LOCK_ASSERT(p, MA_OWNED); 903 while (thread_suspend_check_needed()) { 904 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) { 905 KASSERT(p->p_singlethread != NULL, 906 ("singlethread not set")); 907 /* 908 * The only suspension in action is a 909 * single-threading. Single threader need not stop. 910 * It is safe to access p->p_singlethread unlocked 911 * because it can only be set to our address by us. 912 */ 913 if (p->p_singlethread == td) 914 return (0); /* Exempt from stopping. */ 915 } 916 if ((p->p_flag & P_SINGLE_EXIT) && return_instead) 917 return (EINTR); 918 919 /* Should we goto user boundary if we didn't come from there? */ 920 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE && 921 (p->p_flag & P_SINGLE_BOUNDARY) && return_instead) 922 return (ERESTART); 923 924 /* 925 * Ignore suspend requests if they are deferred. 926 */ 927 if ((td->td_flags & TDF_SBDRY) != 0) { 928 KASSERT(return_instead, 929 ("TDF_SBDRY set for unsafe thread_suspend_check")); 930 KASSERT((td->td_flags & (TDF_SEINTR | TDF_SERESTART)) != 931 (TDF_SEINTR | TDF_SERESTART), 932 ("both TDF_SEINTR and TDF_SERESTART")); 933 return (TD_SBDRY_INTR(td) ? TD_SBDRY_ERRNO(td) : 0); 934 } 935 936 /* 937 * If the process is waiting for us to exit, 938 * this thread should just suicide. 939 * Assumes that P_SINGLE_EXIT implies P_STOPPED_SINGLE. 940 */ 941 if ((p->p_flag & P_SINGLE_EXIT) && (p->p_singlethread != td)) { 942 PROC_UNLOCK(p); 943 944 /* 945 * Allow Linux emulation layer to do some work 946 * before thread suicide. 947 */ 948 if (__predict_false(p->p_sysent->sv_thread_detach != NULL)) 949 (p->p_sysent->sv_thread_detach)(td); 950 umtx_thread_exit(td); 951 kern_thr_exit(td); 952 panic("stopped thread did not exit"); 953 } 954 955 PROC_SLOCK(p); 956 thread_stopped(p); 957 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) { 958 if (p->p_numthreads == p->p_suspcount + 1) { 959 thread_lock(p->p_singlethread); 960 wakeup_swapper = thread_unsuspend_one( 961 p->p_singlethread, p, false); 962 thread_unlock(p->p_singlethread); 963 if (wakeup_swapper) 964 kick_proc0(); 965 } 966 } 967 PROC_UNLOCK(p); 968 thread_lock(td); 969 /* 970 * When a thread suspends, it just 971 * gets taken off all queues. 972 */ 973 thread_suspend_one(td); 974 if (return_instead == 0) { 975 p->p_boundary_count++; 976 td->td_flags |= TDF_BOUNDARY; 977 } 978 PROC_SUNLOCK(p); 979 mi_switch(SW_INVOL | SWT_SUSPEND, NULL); 980 thread_unlock(td); 981 PROC_LOCK(p); 982 } 983 return (0); 984 } 985 986 void 987 thread_suspend_switch(struct thread *td, struct proc *p) 988 { 989 990 KASSERT(!TD_IS_SUSPENDED(td), ("already suspended")); 991 PROC_LOCK_ASSERT(p, MA_OWNED); 992 PROC_SLOCK_ASSERT(p, MA_OWNED); 993 /* 994 * We implement thread_suspend_one in stages here to avoid 995 * dropping the proc lock while the thread lock is owned. 996 */ 997 if (p == td->td_proc) { 998 thread_stopped(p); 999 p->p_suspcount++; 1000 } 1001 PROC_UNLOCK(p); 1002 thread_lock(td); 1003 td->td_flags &= ~TDF_NEEDSUSPCHK; 1004 TD_SET_SUSPENDED(td); 1005 sched_sleep(td, 0); 1006 PROC_SUNLOCK(p); 1007 DROP_GIANT(); 1008 mi_switch(SW_VOL | SWT_SUSPEND, NULL); 1009 thread_unlock(td); 1010 PICKUP_GIANT(); 1011 PROC_LOCK(p); 1012 PROC_SLOCK(p); 1013 } 1014 1015 void 1016 thread_suspend_one(struct thread *td) 1017 { 1018 struct proc *p; 1019 1020 p = td->td_proc; 1021 PROC_SLOCK_ASSERT(p, MA_OWNED); 1022 THREAD_LOCK_ASSERT(td, MA_OWNED); 1023 KASSERT(!TD_IS_SUSPENDED(td), ("already suspended")); 1024 p->p_suspcount++; 1025 td->td_flags &= ~TDF_NEEDSUSPCHK; 1026 TD_SET_SUSPENDED(td); 1027 sched_sleep(td, 0); 1028 } 1029 1030 static int 1031 thread_unsuspend_one(struct thread *td, struct proc *p, bool boundary) 1032 { 1033 1034 THREAD_LOCK_ASSERT(td, MA_OWNED); 1035 KASSERT(TD_IS_SUSPENDED(td), ("Thread not suspended")); 1036 TD_CLR_SUSPENDED(td); 1037 td->td_flags &= ~TDF_ALLPROCSUSP; 1038 if (td->td_proc == p) { 1039 PROC_SLOCK_ASSERT(p, MA_OWNED); 1040 p->p_suspcount--; 1041 if (boundary && (td->td_flags & TDF_BOUNDARY) != 0) { 1042 td->td_flags &= ~TDF_BOUNDARY; 1043 p->p_boundary_count--; 1044 } 1045 } 1046 return (setrunnable(td)); 1047 } 1048 1049 /* 1050 * Allow all threads blocked by single threading to continue running. 1051 */ 1052 void 1053 thread_unsuspend(struct proc *p) 1054 { 1055 struct thread *td; 1056 int wakeup_swapper; 1057 1058 PROC_LOCK_ASSERT(p, MA_OWNED); 1059 PROC_SLOCK_ASSERT(p, MA_OWNED); 1060 wakeup_swapper = 0; 1061 if (!P_SHOULDSTOP(p)) { 1062 FOREACH_THREAD_IN_PROC(p, td) { 1063 thread_lock(td); 1064 if (TD_IS_SUSPENDED(td)) { 1065 wakeup_swapper |= thread_unsuspend_one(td, p, 1066 true); 1067 } 1068 thread_unlock(td); 1069 } 1070 } else if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE && 1071 p->p_numthreads == p->p_suspcount) { 1072 /* 1073 * Stopping everything also did the job for the single 1074 * threading request. Now we've downgraded to single-threaded, 1075 * let it continue. 1076 */ 1077 if (p->p_singlethread->td_proc == p) { 1078 thread_lock(p->p_singlethread); 1079 wakeup_swapper = thread_unsuspend_one( 1080 p->p_singlethread, p, false); 1081 thread_unlock(p->p_singlethread); 1082 } 1083 } 1084 if (wakeup_swapper) 1085 kick_proc0(); 1086 } 1087 1088 /* 1089 * End the single threading mode.. 1090 */ 1091 void 1092 thread_single_end(struct proc *p, int mode) 1093 { 1094 struct thread *td; 1095 int wakeup_swapper; 1096 1097 KASSERT(mode == SINGLE_EXIT || mode == SINGLE_BOUNDARY || 1098 mode == SINGLE_ALLPROC || mode == SINGLE_NO_EXIT, 1099 ("invalid mode %d", mode)); 1100 PROC_LOCK_ASSERT(p, MA_OWNED); 1101 KASSERT((mode == SINGLE_ALLPROC && (p->p_flag & P_TOTAL_STOP) != 0) || 1102 (mode != SINGLE_ALLPROC && (p->p_flag & P_TOTAL_STOP) == 0), 1103 ("mode %d does not match P_TOTAL_STOP", mode)); 1104 KASSERT(mode == SINGLE_ALLPROC || p->p_singlethread == curthread, 1105 ("thread_single_end from other thread %p %p", 1106 curthread, p->p_singlethread)); 1107 KASSERT(mode != SINGLE_BOUNDARY || 1108 (p->p_flag & P_SINGLE_BOUNDARY) != 0, 1109 ("mis-matched SINGLE_BOUNDARY flags %x", p->p_flag)); 1110 p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT | P_SINGLE_BOUNDARY | 1111 P_TOTAL_STOP); 1112 PROC_SLOCK(p); 1113 p->p_singlethread = NULL; 1114 wakeup_swapper = 0; 1115 /* 1116 * If there are other threads they may now run, 1117 * unless of course there is a blanket 'stop order' 1118 * on the process. The single threader must be allowed 1119 * to continue however as this is a bad place to stop. 1120 */ 1121 if (p->p_numthreads != remain_for_mode(mode) && !P_SHOULDSTOP(p)) { 1122 FOREACH_THREAD_IN_PROC(p, td) { 1123 thread_lock(td); 1124 if (TD_IS_SUSPENDED(td)) { 1125 wakeup_swapper |= thread_unsuspend_one(td, p, 1126 mode == SINGLE_BOUNDARY); 1127 } 1128 thread_unlock(td); 1129 } 1130 } 1131 KASSERT(mode != SINGLE_BOUNDARY || p->p_boundary_count == 0, 1132 ("inconsistent boundary count %d", p->p_boundary_count)); 1133 PROC_SUNLOCK(p); 1134 if (wakeup_swapper) 1135 kick_proc0(); 1136 } 1137 1138 struct thread * 1139 thread_find(struct proc *p, lwpid_t tid) 1140 { 1141 struct thread *td; 1142 1143 PROC_LOCK_ASSERT(p, MA_OWNED); 1144 FOREACH_THREAD_IN_PROC(p, td) { 1145 if (td->td_tid == tid) 1146 break; 1147 } 1148 return (td); 1149 } 1150 1151 /* Locate a thread by number; return with proc lock held. */ 1152 struct thread * 1153 tdfind(lwpid_t tid, pid_t pid) 1154 { 1155 #define RUN_THRESH 16 1156 struct thread *td; 1157 int run = 0; 1158 1159 rw_rlock(&tidhash_lock); 1160 LIST_FOREACH(td, TIDHASH(tid), td_hash) { 1161 if (td->td_tid == tid) { 1162 if (pid != -1 && td->td_proc->p_pid != pid) { 1163 td = NULL; 1164 break; 1165 } 1166 PROC_LOCK(td->td_proc); 1167 if (td->td_proc->p_state == PRS_NEW) { 1168 PROC_UNLOCK(td->td_proc); 1169 td = NULL; 1170 break; 1171 } 1172 if (run > RUN_THRESH) { 1173 if (rw_try_upgrade(&tidhash_lock)) { 1174 LIST_REMOVE(td, td_hash); 1175 LIST_INSERT_HEAD(TIDHASH(td->td_tid), 1176 td, td_hash); 1177 rw_wunlock(&tidhash_lock); 1178 return (td); 1179 } 1180 } 1181 break; 1182 } 1183 run++; 1184 } 1185 rw_runlock(&tidhash_lock); 1186 return (td); 1187 } 1188 1189 void 1190 tidhash_add(struct thread *td) 1191 { 1192 rw_wlock(&tidhash_lock); 1193 LIST_INSERT_HEAD(TIDHASH(td->td_tid), td, td_hash); 1194 rw_wunlock(&tidhash_lock); 1195 } 1196 1197 void 1198 tidhash_remove(struct thread *td) 1199 { 1200 rw_wlock(&tidhash_lock); 1201 LIST_REMOVE(td, td_hash); 1202 rw_wunlock(&tidhash_lock); 1203 }
Cache object: f999de9e216526fdd76bc3bb9453ced0
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