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_kdtrace.h" 31 #include "opt_hwpmc_hooks.h" 32 33 #include <sys/cdefs.h> 34 __FBSDID("$FreeBSD: releng/10.3/sys/kern/kern_thread.c 294614 2016-01-23 01:21:11Z jhb $"); 35 36 #include <sys/param.h> 37 #include <sys/systm.h> 38 #include <sys/kernel.h> 39 #include <sys/lock.h> 40 #include <sys/mutex.h> 41 #include <sys/proc.h> 42 #include <sys/rangelock.h> 43 #include <sys/resourcevar.h> 44 #include <sys/sdt.h> 45 #include <sys/smp.h> 46 #include <sys/sched.h> 47 #include <sys/sleepqueue.h> 48 #include <sys/selinfo.h> 49 #include <sys/syscallsubr.h> 50 #include <sys/sysent.h> 51 #include <sys/turnstile.h> 52 #include <sys/ktr.h> 53 #include <sys/rwlock.h> 54 #include <sys/umtx.h> 55 #include <sys/cpuset.h> 56 #ifdef HWPMC_HOOKS 57 #include <sys/pmckern.h> 58 #endif 59 60 #include <security/audit/audit.h> 61 62 #include <vm/vm.h> 63 #include <vm/vm_extern.h> 64 #include <vm/uma.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 td->td_sched = (struct td_sched *)&td[1]; 215 umtx_thread_init(td); 216 td->td_kstack = 0; 217 td->td_sel = NULL; 218 return (0); 219 } 220 221 /* 222 * Tear down type-stable parts of a thread (just before being discarded). 223 */ 224 static void 225 thread_fini(void *mem, int size) 226 { 227 struct thread *td; 228 229 td = (struct thread *)mem; 230 EVENTHANDLER_INVOKE(thread_fini, td); 231 rlqentry_free(td->td_rlqe); 232 turnstile_free(td->td_turnstile); 233 sleepq_free(td->td_sleepqueue); 234 umtx_thread_fini(td); 235 seltdfini(td); 236 } 237 238 /* 239 * For a newly created process, 240 * link up all the structures and its initial threads etc. 241 * called from: 242 * {arch}/{arch}/machdep.c ia64_init(), init386() etc. 243 * proc_dtor() (should go away) 244 * proc_init() 245 */ 246 void 247 proc_linkup0(struct proc *p, struct thread *td) 248 { 249 TAILQ_INIT(&p->p_threads); /* all threads in proc */ 250 proc_linkup(p, td); 251 } 252 253 void 254 proc_linkup(struct proc *p, struct thread *td) 255 { 256 257 sigqueue_init(&p->p_sigqueue, p); 258 p->p_ksi = ksiginfo_alloc(1); 259 if (p->p_ksi != NULL) { 260 /* XXX p_ksi may be null if ksiginfo zone is not ready */ 261 p->p_ksi->ksi_flags = KSI_EXT | KSI_INS; 262 } 263 LIST_INIT(&p->p_mqnotifier); 264 p->p_numthreads = 0; 265 thread_link(td, p); 266 } 267 268 /* 269 * Initialize global thread allocation resources. 270 */ 271 void 272 threadinit(void) 273 { 274 275 mtx_init(&tid_lock, "TID lock", NULL, MTX_DEF); 276 277 /* 278 * pid_max cannot be greater than PID_MAX. 279 * leave one number for thread0. 280 */ 281 tid_unrhdr = new_unrhdr(PID_MAX + 2, INT_MAX, &tid_lock); 282 283 thread_zone = uma_zcreate("THREAD", sched_sizeof_thread(), 284 thread_ctor, thread_dtor, thread_init, thread_fini, 285 16 - 1, UMA_ZONE_NOFREE); 286 tidhashtbl = hashinit(maxproc / 2, M_TIDHASH, &tidhash); 287 rw_init(&tidhash_lock, "tidhash"); 288 } 289 290 /* 291 * Place an unused thread on the zombie list. 292 * Use the slpq as that must be unused by now. 293 */ 294 void 295 thread_zombie(struct thread *td) 296 { 297 mtx_lock_spin(&zombie_lock); 298 TAILQ_INSERT_HEAD(&zombie_threads, td, td_slpq); 299 mtx_unlock_spin(&zombie_lock); 300 } 301 302 /* 303 * Release a thread that has exited after cpu_throw(). 304 */ 305 void 306 thread_stash(struct thread *td) 307 { 308 atomic_subtract_rel_int(&td->td_proc->p_exitthreads, 1); 309 thread_zombie(td); 310 } 311 312 /* 313 * Reap zombie resources. 314 */ 315 void 316 thread_reap(void) 317 { 318 struct thread *td_first, *td_next; 319 320 /* 321 * Don't even bother to lock if none at this instant, 322 * we really don't care about the next instant.. 323 */ 324 if (!TAILQ_EMPTY(&zombie_threads)) { 325 mtx_lock_spin(&zombie_lock); 326 td_first = TAILQ_FIRST(&zombie_threads); 327 if (td_first) 328 TAILQ_INIT(&zombie_threads); 329 mtx_unlock_spin(&zombie_lock); 330 while (td_first) { 331 td_next = TAILQ_NEXT(td_first, td_slpq); 332 if (td_first->td_ucred) 333 crfree(td_first->td_ucred); 334 thread_free(td_first); 335 td_first = td_next; 336 } 337 } 338 } 339 340 /* 341 * Allocate a thread. 342 */ 343 struct thread * 344 thread_alloc(int pages) 345 { 346 struct thread *td; 347 348 thread_reap(); /* check if any zombies to get */ 349 350 td = (struct thread *)uma_zalloc(thread_zone, M_WAITOK); 351 KASSERT(td->td_kstack == 0, ("thread_alloc got thread with kstack")); 352 if (!vm_thread_new(td, pages)) { 353 uma_zfree(thread_zone, td); 354 return (NULL); 355 } 356 cpu_thread_alloc(td); 357 return (td); 358 } 359 360 int 361 thread_alloc_stack(struct thread *td, int pages) 362 { 363 364 KASSERT(td->td_kstack == 0, 365 ("thread_alloc_stack called on a thread with kstack")); 366 if (!vm_thread_new(td, pages)) 367 return (0); 368 cpu_thread_alloc(td); 369 return (1); 370 } 371 372 /* 373 * Deallocate a thread. 374 */ 375 void 376 thread_free(struct thread *td) 377 { 378 379 lock_profile_thread_exit(td); 380 if (td->td_cpuset) 381 cpuset_rel(td->td_cpuset); 382 td->td_cpuset = NULL; 383 cpu_thread_free(td); 384 if (td->td_kstack != 0) 385 vm_thread_dispose(td); 386 uma_zfree(thread_zone, td); 387 } 388 389 /* 390 * Discard the current thread and exit from its context. 391 * Always called with scheduler locked. 392 * 393 * Because we can't free a thread while we're operating under its context, 394 * push the current thread into our CPU's deadthread holder. This means 395 * we needn't worry about someone else grabbing our context before we 396 * do a cpu_throw(). 397 */ 398 void 399 thread_exit(void) 400 { 401 uint64_t runtime, new_switchtime; 402 struct thread *td; 403 struct thread *td2; 404 struct proc *p; 405 int wakeup_swapper; 406 407 td = curthread; 408 p = td->td_proc; 409 410 PROC_SLOCK_ASSERT(p, MA_OWNED); 411 mtx_assert(&Giant, MA_NOTOWNED); 412 413 PROC_LOCK_ASSERT(p, MA_OWNED); 414 KASSERT(p != NULL, ("thread exiting without a process")); 415 CTR3(KTR_PROC, "thread_exit: thread %p (pid %ld, %s)", td, 416 (long)p->p_pid, td->td_name); 417 KASSERT(TAILQ_EMPTY(&td->td_sigqueue.sq_list), ("signal pending")); 418 419 #ifdef AUDIT 420 AUDIT_SYSCALL_EXIT(0, td); 421 #endif 422 /* 423 * drop FPU & debug register state storage, or any other 424 * architecture specific resources that 425 * would not be on a new untouched process. 426 */ 427 cpu_thread_exit(td); /* XXXSMP */ 428 429 /* 430 * The last thread is left attached to the process 431 * So that the whole bundle gets recycled. Skip 432 * all this stuff if we never had threads. 433 * EXIT clears all sign of other threads when 434 * it goes to single threading, so the last thread always 435 * takes the short path. 436 */ 437 if (p->p_flag & P_HADTHREADS) { 438 if (p->p_numthreads > 1) { 439 atomic_add_int(&td->td_proc->p_exitthreads, 1); 440 thread_unlink(td); 441 td2 = FIRST_THREAD_IN_PROC(p); 442 sched_exit_thread(td2, td); 443 444 /* 445 * The test below is NOT true if we are the 446 * sole exiting thread. P_STOPPED_SINGLE is unset 447 * in exit1() after it is the only survivor. 448 */ 449 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) { 450 if (p->p_numthreads == p->p_suspcount) { 451 thread_lock(p->p_singlethread); 452 wakeup_swapper = thread_unsuspend_one( 453 p->p_singlethread, p, false); 454 thread_unlock(p->p_singlethread); 455 if (wakeup_swapper) 456 kick_proc0(); 457 } 458 } 459 460 PCPU_SET(deadthread, td); 461 } else { 462 /* 463 * The last thread is exiting.. but not through exit() 464 */ 465 panic ("thread_exit: Last thread exiting on its own"); 466 } 467 } 468 #ifdef HWPMC_HOOKS 469 /* 470 * If this thread is part of a process that is being tracked by hwpmc(4), 471 * inform the module of the thread's impending exit. 472 */ 473 if (PMC_PROC_IS_USING_PMCS(td->td_proc)) 474 PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_OUT); 475 #endif 476 PROC_UNLOCK(p); 477 PROC_STATLOCK(p); 478 thread_lock(td); 479 PROC_SUNLOCK(p); 480 481 /* Do the same timestamp bookkeeping that mi_switch() would do. */ 482 new_switchtime = cpu_ticks(); 483 runtime = new_switchtime - PCPU_GET(switchtime); 484 td->td_runtime += runtime; 485 td->td_incruntime += runtime; 486 PCPU_SET(switchtime, new_switchtime); 487 PCPU_SET(switchticks, ticks); 488 PCPU_INC(cnt.v_swtch); 489 490 /* Save our resource usage in our process. */ 491 td->td_ru.ru_nvcsw++; 492 ruxagg(p, td); 493 rucollect(&p->p_ru, &td->td_ru); 494 PROC_STATUNLOCK(p); 495 496 td->td_state = TDS_INACTIVE; 497 #ifdef WITNESS 498 witness_thread_exit(td); 499 #endif 500 CTR1(KTR_PROC, "thread_exit: cpu_throw() thread %p", td); 501 sched_throw(td); 502 panic("I'm a teapot!"); 503 /* NOTREACHED */ 504 } 505 506 /* 507 * Do any thread specific cleanups that may be needed in wait() 508 * called with Giant, proc and schedlock not held. 509 */ 510 void 511 thread_wait(struct proc *p) 512 { 513 struct thread *td; 514 515 mtx_assert(&Giant, MA_NOTOWNED); 516 KASSERT(p->p_numthreads == 1, ("multiple threads in thread_wait()")); 517 KASSERT(p->p_exitthreads == 0, ("p_exitthreads leaking")); 518 td = FIRST_THREAD_IN_PROC(p); 519 /* Lock the last thread so we spin until it exits cpu_throw(). */ 520 thread_lock(td); 521 thread_unlock(td); 522 lock_profile_thread_exit(td); 523 cpuset_rel(td->td_cpuset); 524 td->td_cpuset = NULL; 525 cpu_thread_clean(td); 526 crfree(td->td_ucred); 527 thread_reap(); /* check for zombie threads etc. */ 528 } 529 530 /* 531 * Link a thread to a process. 532 * set up anything that needs to be initialized for it to 533 * be used by the process. 534 */ 535 void 536 thread_link(struct thread *td, struct proc *p) 537 { 538 539 /* 540 * XXX This can't be enabled because it's called for proc0 before 541 * its lock has been created. 542 * PROC_LOCK_ASSERT(p, MA_OWNED); 543 */ 544 td->td_state = TDS_INACTIVE; 545 td->td_proc = p; 546 td->td_flags = TDF_INMEM; 547 548 LIST_INIT(&td->td_contested); 549 LIST_INIT(&td->td_lprof[0]); 550 LIST_INIT(&td->td_lprof[1]); 551 sigqueue_init(&td->td_sigqueue, p); 552 callout_init(&td->td_slpcallout, CALLOUT_MPSAFE); 553 TAILQ_INSERT_HEAD(&p->p_threads, td, td_plist); 554 p->p_numthreads++; 555 } 556 557 /* 558 * Called from: 559 * thread_exit() 560 */ 561 void 562 thread_unlink(struct thread *td) 563 { 564 struct proc *p = td->td_proc; 565 566 PROC_LOCK_ASSERT(p, MA_OWNED); 567 TAILQ_REMOVE(&p->p_threads, td, td_plist); 568 p->p_numthreads--; 569 /* could clear a few other things here */ 570 /* Must NOT clear links to proc! */ 571 } 572 573 static int 574 calc_remaining(struct proc *p, int mode) 575 { 576 int remaining; 577 578 PROC_LOCK_ASSERT(p, MA_OWNED); 579 PROC_SLOCK_ASSERT(p, MA_OWNED); 580 if (mode == SINGLE_EXIT) 581 remaining = p->p_numthreads; 582 else if (mode == SINGLE_BOUNDARY) 583 remaining = p->p_numthreads - p->p_boundary_count; 584 else if (mode == SINGLE_NO_EXIT || mode == SINGLE_ALLPROC) 585 remaining = p->p_numthreads - p->p_suspcount; 586 else 587 panic("calc_remaining: wrong mode %d", mode); 588 return (remaining); 589 } 590 591 static int 592 remain_for_mode(int mode) 593 { 594 595 return (mode == SINGLE_ALLPROC ? 0 : 1); 596 } 597 598 static int 599 weed_inhib(int mode, struct thread *td2, struct proc *p) 600 { 601 int wakeup_swapper; 602 603 PROC_LOCK_ASSERT(p, MA_OWNED); 604 PROC_SLOCK_ASSERT(p, MA_OWNED); 605 THREAD_LOCK_ASSERT(td2, MA_OWNED); 606 607 wakeup_swapper = 0; 608 switch (mode) { 609 case SINGLE_EXIT: 610 if (TD_IS_SUSPENDED(td2)) 611 wakeup_swapper |= thread_unsuspend_one(td2, p, true); 612 if (TD_ON_SLEEPQ(td2) && (td2->td_flags & TDF_SINTR) != 0) 613 wakeup_swapper |= sleepq_abort(td2, EINTR); 614 break; 615 case SINGLE_BOUNDARY: 616 if (TD_IS_SUSPENDED(td2) && (td2->td_flags & TDF_BOUNDARY) == 0) 617 wakeup_swapper |= thread_unsuspend_one(td2, p, false); 618 if (TD_ON_SLEEPQ(td2) && (td2->td_flags & TDF_SINTR) != 0) 619 wakeup_swapper |= sleepq_abort(td2, ERESTART); 620 break; 621 case SINGLE_NO_EXIT: 622 if (TD_IS_SUSPENDED(td2) && (td2->td_flags & TDF_BOUNDARY) == 0) 623 wakeup_swapper |= thread_unsuspend_one(td2, p, false); 624 if (TD_ON_SLEEPQ(td2) && (td2->td_flags & TDF_SINTR) != 0) 625 wakeup_swapper |= sleepq_abort(td2, ERESTART); 626 break; 627 case SINGLE_ALLPROC: 628 /* 629 * ALLPROC suspend tries to avoid spurious EINTR for 630 * threads sleeping interruptable, by suspending the 631 * thread directly, similarly to sig_suspend_threads(). 632 * Since such sleep is not performed at the user 633 * boundary, TDF_BOUNDARY flag is not set, and TDF_ALLPROCSUSP 634 * is used to avoid immediate un-suspend. 635 */ 636 if (TD_IS_SUSPENDED(td2) && (td2->td_flags & (TDF_BOUNDARY | 637 TDF_ALLPROCSUSP)) == 0) 638 wakeup_swapper |= thread_unsuspend_one(td2, p, false); 639 if (TD_ON_SLEEPQ(td2) && (td2->td_flags & TDF_SINTR) != 0) { 640 if ((td2->td_flags & TDF_SBDRY) == 0) { 641 thread_suspend_one(td2); 642 td2->td_flags |= TDF_ALLPROCSUSP; 643 } else { 644 wakeup_swapper |= sleepq_abort(td2, ERESTART); 645 } 646 } 647 break; 648 } 649 return (wakeup_swapper); 650 } 651 652 /* 653 * Enforce single-threading. 654 * 655 * Returns 1 if the caller must abort (another thread is waiting to 656 * exit the process or similar). Process is locked! 657 * Returns 0 when you are successfully the only thread running. 658 * A process has successfully single threaded in the suspend mode when 659 * There are no threads in user mode. Threads in the kernel must be 660 * allowed to continue until they get to the user boundary. They may even 661 * copy out their return values and data before suspending. They may however be 662 * accelerated in reaching the user boundary as we will wake up 663 * any sleeping threads that are interruptable. (PCATCH). 664 */ 665 int 666 thread_single(struct proc *p, int mode) 667 { 668 struct thread *td; 669 struct thread *td2; 670 int remaining, wakeup_swapper; 671 672 td = curthread; 673 KASSERT(mode == SINGLE_EXIT || mode == SINGLE_BOUNDARY || 674 mode == SINGLE_ALLPROC || mode == SINGLE_NO_EXIT, 675 ("invalid mode %d", mode)); 676 /* 677 * If allowing non-ALLPROC singlethreading for non-curproc 678 * callers, calc_remaining() and remain_for_mode() should be 679 * adjusted to also account for td->td_proc != p. For now 680 * this is not implemented because it is not used. 681 */ 682 KASSERT((mode == SINGLE_ALLPROC && td->td_proc != p) || 683 (mode != SINGLE_ALLPROC && td->td_proc == p), 684 ("mode %d proc %p curproc %p", mode, p, td->td_proc)); 685 mtx_assert(&Giant, MA_NOTOWNED); 686 PROC_LOCK_ASSERT(p, MA_OWNED); 687 688 if ((p->p_flag & P_HADTHREADS) == 0 && mode != SINGLE_ALLPROC) 689 return (0); 690 691 /* Is someone already single threading? */ 692 if (p->p_singlethread != NULL && p->p_singlethread != td) 693 return (1); 694 695 if (mode == SINGLE_EXIT) { 696 p->p_flag |= P_SINGLE_EXIT; 697 p->p_flag &= ~P_SINGLE_BOUNDARY; 698 } else { 699 p->p_flag &= ~P_SINGLE_EXIT; 700 if (mode == SINGLE_BOUNDARY) 701 p->p_flag |= P_SINGLE_BOUNDARY; 702 else 703 p->p_flag &= ~P_SINGLE_BOUNDARY; 704 } 705 if (mode == SINGLE_ALLPROC) 706 p->p_flag |= P_TOTAL_STOP; 707 p->p_flag |= P_STOPPED_SINGLE; 708 PROC_SLOCK(p); 709 p->p_singlethread = td; 710 remaining = calc_remaining(p, mode); 711 while (remaining != remain_for_mode(mode)) { 712 if (P_SHOULDSTOP(p) != P_STOPPED_SINGLE) 713 goto stopme; 714 wakeup_swapper = 0; 715 FOREACH_THREAD_IN_PROC(p, td2) { 716 if (td2 == td) 717 continue; 718 thread_lock(td2); 719 td2->td_flags |= TDF_ASTPENDING | TDF_NEEDSUSPCHK; 720 if (TD_IS_INHIBITED(td2)) { 721 wakeup_swapper |= weed_inhib(mode, td2, p); 722 #ifdef SMP 723 } else if (TD_IS_RUNNING(td2) && td != td2) { 724 forward_signal(td2); 725 #endif 726 } 727 thread_unlock(td2); 728 } 729 if (wakeup_swapper) 730 kick_proc0(); 731 remaining = calc_remaining(p, mode); 732 733 /* 734 * Maybe we suspended some threads.. was it enough? 735 */ 736 if (remaining == remain_for_mode(mode)) 737 break; 738 739 stopme: 740 /* 741 * Wake us up when everyone else has suspended. 742 * In the mean time we suspend as well. 743 */ 744 thread_suspend_switch(td, p); 745 remaining = calc_remaining(p, mode); 746 } 747 if (mode == SINGLE_EXIT) { 748 /* 749 * Convert the process to an unthreaded process. The 750 * SINGLE_EXIT is called by exit1() or execve(), in 751 * both cases other threads must be retired. 752 */ 753 KASSERT(p->p_numthreads == 1, ("Unthreading with >1 threads")); 754 p->p_singlethread = NULL; 755 p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT | P_HADTHREADS); 756 757 /* 758 * Wait for any remaining threads to exit cpu_throw(). 759 */ 760 while (p->p_exitthreads != 0) { 761 PROC_SUNLOCK(p); 762 PROC_UNLOCK(p); 763 sched_relinquish(td); 764 PROC_LOCK(p); 765 PROC_SLOCK(p); 766 } 767 } else if (mode == SINGLE_BOUNDARY) { 768 /* 769 * Wait until all suspended threads are removed from 770 * the processors. The thread_suspend_check() 771 * increments p_boundary_count while it is still 772 * running, which makes it possible for the execve() 773 * to destroy vmspace while our other threads are 774 * still using the address space. 775 * 776 * We lock the thread, which is only allowed to 777 * succeed after context switch code finished using 778 * the address space. 779 */ 780 FOREACH_THREAD_IN_PROC(p, td2) { 781 if (td2 == td) 782 continue; 783 thread_lock(td2); 784 KASSERT((td2->td_flags & TDF_BOUNDARY) != 0, 785 ("td %p not on boundary", td2)); 786 KASSERT(TD_IS_SUSPENDED(td2), 787 ("td %p is not suspended", td2)); 788 thread_unlock(td2); 789 } 790 } 791 PROC_SUNLOCK(p); 792 return (0); 793 } 794 795 bool 796 thread_suspend_check_needed(void) 797 { 798 struct proc *p; 799 struct thread *td; 800 801 td = curthread; 802 p = td->td_proc; 803 PROC_LOCK_ASSERT(p, MA_OWNED); 804 return (P_SHOULDSTOP(p) || ((p->p_flag & P_TRACED) != 0 && 805 (td->td_dbgflags & TDB_SUSPEND) != 0)); 806 } 807 808 /* 809 * Called in from locations that can safely check to see 810 * whether we have to suspend or at least throttle for a 811 * single-thread event (e.g. fork). 812 * 813 * Such locations include userret(). 814 * If the "return_instead" argument is non zero, the thread must be able to 815 * accept 0 (caller may continue), or 1 (caller must abort) as a result. 816 * 817 * The 'return_instead' argument tells the function if it may do a 818 * thread_exit() or suspend, or whether the caller must abort and back 819 * out instead. 820 * 821 * If the thread that set the single_threading request has set the 822 * P_SINGLE_EXIT bit in the process flags then this call will never return 823 * if 'return_instead' is false, but will exit. 824 * 825 * P_SINGLE_EXIT | return_instead == 0| return_instead != 0 826 *---------------+--------------------+--------------------- 827 * 0 | returns 0 | returns 0 or 1 828 * | when ST ends | immediately 829 *---------------+--------------------+--------------------- 830 * 1 | thread exits | returns 1 831 * | | immediately 832 * 0 = thread_exit() or suspension ok, 833 * other = return error instead of stopping the thread. 834 * 835 * While a full suspension is under effect, even a single threading 836 * thread would be suspended if it made this call (but it shouldn't). 837 * This call should only be made from places where 838 * thread_exit() would be safe as that may be the outcome unless 839 * return_instead is set. 840 */ 841 int 842 thread_suspend_check(int return_instead) 843 { 844 struct thread *td; 845 struct proc *p; 846 int wakeup_swapper; 847 848 td = curthread; 849 p = td->td_proc; 850 mtx_assert(&Giant, MA_NOTOWNED); 851 PROC_LOCK_ASSERT(p, MA_OWNED); 852 while (thread_suspend_check_needed()) { 853 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) { 854 KASSERT(p->p_singlethread != NULL, 855 ("singlethread not set")); 856 /* 857 * The only suspension in action is a 858 * single-threading. Single threader need not stop. 859 * XXX Should be safe to access unlocked 860 * as it can only be set to be true by us. 861 */ 862 if (p->p_singlethread == td) 863 return (0); /* Exempt from stopping. */ 864 } 865 if ((p->p_flag & P_SINGLE_EXIT) && return_instead) 866 return (EINTR); 867 868 /* Should we goto user boundary if we didn't come from there? */ 869 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE && 870 (p->p_flag & P_SINGLE_BOUNDARY) && return_instead) 871 return (ERESTART); 872 873 /* 874 * Ignore suspend requests if they are deferred. 875 */ 876 if ((td->td_flags & TDF_SBDRY) != 0) { 877 KASSERT(return_instead, 878 ("TDF_SBDRY set for unsafe thread_suspend_check")); 879 return (0); 880 } 881 882 /* 883 * If the process is waiting for us to exit, 884 * this thread should just suicide. 885 * Assumes that P_SINGLE_EXIT implies P_STOPPED_SINGLE. 886 */ 887 if ((p->p_flag & P_SINGLE_EXIT) && (p->p_singlethread != td)) { 888 PROC_UNLOCK(p); 889 890 /* 891 * Allow Linux emulation layer to do some work 892 * before thread suicide. 893 */ 894 if (__predict_false(p->p_sysent->sv_thread_detach != NULL)) 895 (p->p_sysent->sv_thread_detach)(td); 896 kern_thr_exit(td); 897 panic("stopped thread did not exit"); 898 } 899 900 PROC_SLOCK(p); 901 thread_stopped(p); 902 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) { 903 if (p->p_numthreads == p->p_suspcount + 1) { 904 thread_lock(p->p_singlethread); 905 wakeup_swapper = thread_unsuspend_one( 906 p->p_singlethread, p, false); 907 thread_unlock(p->p_singlethread); 908 if (wakeup_swapper) 909 kick_proc0(); 910 } 911 } 912 PROC_UNLOCK(p); 913 thread_lock(td); 914 /* 915 * When a thread suspends, it just 916 * gets taken off all queues. 917 */ 918 thread_suspend_one(td); 919 if (return_instead == 0) { 920 p->p_boundary_count++; 921 td->td_flags |= TDF_BOUNDARY; 922 } 923 PROC_SUNLOCK(p); 924 mi_switch(SW_INVOL | SWT_SUSPEND, NULL); 925 thread_unlock(td); 926 PROC_LOCK(p); 927 } 928 return (0); 929 } 930 931 void 932 thread_suspend_switch(struct thread *td, struct proc *p) 933 { 934 935 KASSERT(!TD_IS_SUSPENDED(td), ("already suspended")); 936 PROC_LOCK_ASSERT(p, MA_OWNED); 937 PROC_SLOCK_ASSERT(p, MA_OWNED); 938 /* 939 * We implement thread_suspend_one in stages here to avoid 940 * dropping the proc lock while the thread lock is owned. 941 */ 942 if (p == td->td_proc) { 943 thread_stopped(p); 944 p->p_suspcount++; 945 } 946 PROC_UNLOCK(p); 947 thread_lock(td); 948 td->td_flags &= ~TDF_NEEDSUSPCHK; 949 TD_SET_SUSPENDED(td); 950 sched_sleep(td, 0); 951 PROC_SUNLOCK(p); 952 DROP_GIANT(); 953 mi_switch(SW_VOL | SWT_SUSPEND, NULL); 954 thread_unlock(td); 955 PICKUP_GIANT(); 956 PROC_LOCK(p); 957 PROC_SLOCK(p); 958 } 959 960 void 961 thread_suspend_one(struct thread *td) 962 { 963 struct proc *p; 964 965 p = td->td_proc; 966 PROC_SLOCK_ASSERT(p, MA_OWNED); 967 THREAD_LOCK_ASSERT(td, MA_OWNED); 968 KASSERT(!TD_IS_SUSPENDED(td), ("already suspended")); 969 p->p_suspcount++; 970 td->td_flags &= ~TDF_NEEDSUSPCHK; 971 TD_SET_SUSPENDED(td); 972 sched_sleep(td, 0); 973 } 974 975 static int 976 thread_unsuspend_one(struct thread *td, struct proc *p, bool boundary) 977 { 978 979 THREAD_LOCK_ASSERT(td, MA_OWNED); 980 KASSERT(TD_IS_SUSPENDED(td), ("Thread not suspended")); 981 TD_CLR_SUSPENDED(td); 982 td->td_flags &= ~TDF_ALLPROCSUSP; 983 if (td->td_proc == p) { 984 PROC_SLOCK_ASSERT(p, MA_OWNED); 985 p->p_suspcount--; 986 if (boundary && (td->td_flags & TDF_BOUNDARY) != 0) { 987 td->td_flags &= ~TDF_BOUNDARY; 988 p->p_boundary_count--; 989 } 990 } 991 return (setrunnable(td)); 992 } 993 994 /* 995 * Allow all threads blocked by single threading to continue running. 996 */ 997 void 998 thread_unsuspend(struct proc *p) 999 { 1000 struct thread *td; 1001 int wakeup_swapper; 1002 1003 PROC_LOCK_ASSERT(p, MA_OWNED); 1004 PROC_SLOCK_ASSERT(p, MA_OWNED); 1005 wakeup_swapper = 0; 1006 if (!P_SHOULDSTOP(p)) { 1007 FOREACH_THREAD_IN_PROC(p, td) { 1008 thread_lock(td); 1009 if (TD_IS_SUSPENDED(td)) { 1010 wakeup_swapper |= thread_unsuspend_one(td, p, 1011 true); 1012 } 1013 thread_unlock(td); 1014 } 1015 } else if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE && 1016 p->p_numthreads == p->p_suspcount) { 1017 /* 1018 * Stopping everything also did the job for the single 1019 * threading request. Now we've downgraded to single-threaded, 1020 * let it continue. 1021 */ 1022 if (p->p_singlethread->td_proc == p) { 1023 thread_lock(p->p_singlethread); 1024 wakeup_swapper = thread_unsuspend_one( 1025 p->p_singlethread, p, false); 1026 thread_unlock(p->p_singlethread); 1027 } 1028 } 1029 if (wakeup_swapper) 1030 kick_proc0(); 1031 } 1032 1033 /* 1034 * End the single threading mode.. 1035 */ 1036 void 1037 thread_single_end(struct proc *p, int mode) 1038 { 1039 struct thread *td; 1040 int wakeup_swapper; 1041 1042 KASSERT(mode == SINGLE_EXIT || mode == SINGLE_BOUNDARY || 1043 mode == SINGLE_ALLPROC || mode == SINGLE_NO_EXIT, 1044 ("invalid mode %d", mode)); 1045 PROC_LOCK_ASSERT(p, MA_OWNED); 1046 KASSERT((mode == SINGLE_ALLPROC && (p->p_flag & P_TOTAL_STOP) != 0) || 1047 (mode != SINGLE_ALLPROC && (p->p_flag & P_TOTAL_STOP) == 0), 1048 ("mode %d does not match P_TOTAL_STOP", mode)); 1049 KASSERT(mode == SINGLE_ALLPROC || p->p_singlethread == curthread, 1050 ("thread_single_end from other thread %p %p", 1051 curthread, p->p_singlethread)); 1052 KASSERT(mode != SINGLE_BOUNDARY || 1053 (p->p_flag & P_SINGLE_BOUNDARY) != 0, 1054 ("mis-matched SINGLE_BOUNDARY flags %x", p->p_flag)); 1055 p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT | P_SINGLE_BOUNDARY | 1056 P_TOTAL_STOP); 1057 PROC_SLOCK(p); 1058 p->p_singlethread = NULL; 1059 wakeup_swapper = 0; 1060 /* 1061 * If there are other threads they may now run, 1062 * unless of course there is a blanket 'stop order' 1063 * on the process. The single threader must be allowed 1064 * to continue however as this is a bad place to stop. 1065 */ 1066 if (p->p_numthreads != remain_for_mode(mode) && !P_SHOULDSTOP(p)) { 1067 FOREACH_THREAD_IN_PROC(p, td) { 1068 thread_lock(td); 1069 if (TD_IS_SUSPENDED(td)) { 1070 wakeup_swapper |= thread_unsuspend_one(td, p, 1071 mode == SINGLE_BOUNDARY); 1072 } 1073 thread_unlock(td); 1074 } 1075 } 1076 KASSERT(mode != SINGLE_BOUNDARY || p->p_boundary_count == 0, 1077 ("inconsistent boundary count %d", p->p_boundary_count)); 1078 PROC_SUNLOCK(p); 1079 if (wakeup_swapper) 1080 kick_proc0(); 1081 } 1082 1083 struct thread * 1084 thread_find(struct proc *p, lwpid_t tid) 1085 { 1086 struct thread *td; 1087 1088 PROC_LOCK_ASSERT(p, MA_OWNED); 1089 FOREACH_THREAD_IN_PROC(p, td) { 1090 if (td->td_tid == tid) 1091 break; 1092 } 1093 return (td); 1094 } 1095 1096 /* Locate a thread by number; return with proc lock held. */ 1097 struct thread * 1098 tdfind(lwpid_t tid, pid_t pid) 1099 { 1100 #define RUN_THRESH 16 1101 struct thread *td; 1102 int run = 0; 1103 1104 rw_rlock(&tidhash_lock); 1105 LIST_FOREACH(td, TIDHASH(tid), td_hash) { 1106 if (td->td_tid == tid) { 1107 if (pid != -1 && td->td_proc->p_pid != pid) { 1108 td = NULL; 1109 break; 1110 } 1111 PROC_LOCK(td->td_proc); 1112 if (td->td_proc->p_state == PRS_NEW) { 1113 PROC_UNLOCK(td->td_proc); 1114 td = NULL; 1115 break; 1116 } 1117 if (run > RUN_THRESH) { 1118 if (rw_try_upgrade(&tidhash_lock)) { 1119 LIST_REMOVE(td, td_hash); 1120 LIST_INSERT_HEAD(TIDHASH(td->td_tid), 1121 td, td_hash); 1122 rw_wunlock(&tidhash_lock); 1123 return (td); 1124 } 1125 } 1126 break; 1127 } 1128 run++; 1129 } 1130 rw_runlock(&tidhash_lock); 1131 return (td); 1132 } 1133 1134 void 1135 tidhash_add(struct thread *td) 1136 { 1137 rw_wlock(&tidhash_lock); 1138 LIST_INSERT_HEAD(TIDHASH(td->td_tid), td, td_hash); 1139 rw_wunlock(&tidhash_lock); 1140 } 1141 1142 void 1143 tidhash_remove(struct thread *td) 1144 { 1145 rw_wlock(&tidhash_lock); 1146 LIST_REMOVE(td, td_hash); 1147 rw_wunlock(&tidhash_lock); 1148 }
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