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("$FreeBSD$"); 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/turnstile.h> 50 #include <sys/ktr.h> 51 #include <sys/rwlock.h> 52 #include <sys/umtx.h> 53 #include <sys/cpuset.h> 54 #ifdef HWPMC_HOOKS 55 #include <sys/pmckern.h> 56 #endif 57 58 #include <security/audit/audit.h> 59 60 #include <vm/vm.h> 61 #include <vm/vm_extern.h> 62 #include <vm/uma.h> 63 #include <sys/eventhandler.h> 64 65 SDT_PROVIDER_DECLARE(proc); 66 SDT_PROBE_DEFINE(proc, , , lwp_exit, lwp-exit); 67 68 69 /* 70 * thread related storage. 71 */ 72 static uma_zone_t thread_zone; 73 74 TAILQ_HEAD(, thread) zombie_threads = TAILQ_HEAD_INITIALIZER(zombie_threads); 75 static struct mtx zombie_lock; 76 MTX_SYSINIT(zombie_lock, &zombie_lock, "zombie lock", MTX_SPIN); 77 78 static void thread_zombie(struct thread *); 79 80 #define TID_BUFFER_SIZE 1024 81 82 struct mtx tid_lock; 83 static struct unrhdr *tid_unrhdr; 84 static lwpid_t tid_buffer[TID_BUFFER_SIZE]; 85 static int tid_head, tid_tail; 86 static MALLOC_DEFINE(M_TIDHASH, "tidhash", "thread hash"); 87 88 struct tidhashhead *tidhashtbl; 89 u_long tidhash; 90 struct rwlock tidhash_lock; 91 92 static lwpid_t 93 tid_alloc(void) 94 { 95 lwpid_t tid; 96 97 tid = alloc_unr(tid_unrhdr); 98 if (tid != -1) 99 return (tid); 100 mtx_lock(&tid_lock); 101 if (tid_head == tid_tail) { 102 mtx_unlock(&tid_lock); 103 return (-1); 104 } 105 tid = tid_buffer[tid_head]; 106 tid_head = (tid_head + 1) % TID_BUFFER_SIZE; 107 mtx_unlock(&tid_lock); 108 return (tid); 109 } 110 111 static void 112 tid_free(lwpid_t tid) 113 { 114 lwpid_t tmp_tid = -1; 115 116 mtx_lock(&tid_lock); 117 if ((tid_tail + 1) % TID_BUFFER_SIZE == tid_head) { 118 tmp_tid = tid_buffer[tid_head]; 119 tid_head = (tid_head + 1) % TID_BUFFER_SIZE; 120 } 121 tid_buffer[tid_tail] = tid; 122 tid_tail = (tid_tail + 1) % TID_BUFFER_SIZE; 123 mtx_unlock(&tid_lock); 124 if (tmp_tid != -1) 125 free_unr(tid_unrhdr, tmp_tid); 126 } 127 128 /* 129 * Prepare a thread for use. 130 */ 131 static int 132 thread_ctor(void *mem, int size, void *arg, int flags) 133 { 134 struct thread *td; 135 136 td = (struct thread *)mem; 137 td->td_state = TDS_INACTIVE; 138 td->td_oncpu = NOCPU; 139 140 td->td_tid = tid_alloc(); 141 142 /* 143 * Note that td_critnest begins life as 1 because the thread is not 144 * running and is thereby implicitly waiting to be on the receiving 145 * end of a context switch. 146 */ 147 td->td_critnest = 1; 148 td->td_lend_user_pri = PRI_MAX; 149 EVENTHANDLER_INVOKE(thread_ctor, td); 150 #ifdef AUDIT 151 audit_thread_alloc(td); 152 #endif 153 umtx_thread_alloc(td); 154 return (0); 155 } 156 157 /* 158 * Reclaim a thread after use. 159 */ 160 static void 161 thread_dtor(void *mem, int size, void *arg) 162 { 163 struct thread *td; 164 165 td = (struct thread *)mem; 166 167 #ifdef INVARIANTS 168 /* Verify that this thread is in a safe state to free. */ 169 switch (td->td_state) { 170 case TDS_INHIBITED: 171 case TDS_RUNNING: 172 case TDS_CAN_RUN: 173 case TDS_RUNQ: 174 /* 175 * We must never unlink a thread that is in one of 176 * these states, because it is currently active. 177 */ 178 panic("bad state for thread unlinking"); 179 /* NOTREACHED */ 180 case TDS_INACTIVE: 181 break; 182 default: 183 panic("bad thread state"); 184 /* NOTREACHED */ 185 } 186 #endif 187 #ifdef AUDIT 188 audit_thread_free(td); 189 #endif 190 /* Free all OSD associated to this thread. */ 191 osd_thread_exit(td); 192 193 EVENTHANDLER_INVOKE(thread_dtor, td); 194 tid_free(td->td_tid); 195 } 196 197 /* 198 * Initialize type-stable parts of a thread (when newly created). 199 */ 200 static int 201 thread_init(void *mem, int size, int flags) 202 { 203 struct thread *td; 204 205 td = (struct thread *)mem; 206 207 td->td_sleepqueue = sleepq_alloc(); 208 td->td_turnstile = turnstile_alloc(); 209 td->td_rlqe = NULL; 210 EVENTHANDLER_INVOKE(thread_init, td); 211 td->td_sched = (struct td_sched *)&td[1]; 212 umtx_thread_init(td); 213 td->td_kstack = 0; 214 return (0); 215 } 216 217 /* 218 * Tear down type-stable parts of a thread (just before being discarded). 219 */ 220 static void 221 thread_fini(void *mem, int size) 222 { 223 struct thread *td; 224 225 td = (struct thread *)mem; 226 EVENTHANDLER_INVOKE(thread_fini, td); 227 rlqentry_free(td->td_rlqe); 228 turnstile_free(td->td_turnstile); 229 sleepq_free(td->td_sleepqueue); 230 umtx_thread_fini(td); 231 seltdfini(td); 232 } 233 234 /* 235 * For a newly created process, 236 * link up all the structures and its initial threads etc. 237 * called from: 238 * {arch}/{arch}/machdep.c ia64_init(), init386() etc. 239 * proc_dtor() (should go away) 240 * proc_init() 241 */ 242 void 243 proc_linkup0(struct proc *p, struct thread *td) 244 { 245 TAILQ_INIT(&p->p_threads); /* all threads in proc */ 246 proc_linkup(p, td); 247 } 248 249 void 250 proc_linkup(struct proc *p, struct thread *td) 251 { 252 253 sigqueue_init(&p->p_sigqueue, p); 254 p->p_ksi = ksiginfo_alloc(1); 255 if (p->p_ksi != NULL) { 256 /* XXX p_ksi may be null if ksiginfo zone is not ready */ 257 p->p_ksi->ksi_flags = KSI_EXT | KSI_INS; 258 } 259 LIST_INIT(&p->p_mqnotifier); 260 p->p_numthreads = 0; 261 thread_link(td, p); 262 } 263 264 /* 265 * Initialize global thread allocation resources. 266 */ 267 void 268 threadinit(void) 269 { 270 271 mtx_init(&tid_lock, "TID lock", NULL, MTX_DEF); 272 273 /* 274 * pid_max cannot be greater than PID_MAX. 275 * leave one number for thread0. 276 */ 277 tid_unrhdr = new_unrhdr(PID_MAX + 2, INT_MAX, &tid_lock); 278 279 thread_zone = uma_zcreate("THREAD", sched_sizeof_thread(), 280 thread_ctor, thread_dtor, thread_init, thread_fini, 281 16 - 1, 0); 282 tidhashtbl = hashinit(maxproc / 2, M_TIDHASH, &tidhash); 283 rw_init(&tidhash_lock, "tidhash"); 284 } 285 286 /* 287 * Place an unused thread on the zombie list. 288 * Use the slpq as that must be unused by now. 289 */ 290 void 291 thread_zombie(struct thread *td) 292 { 293 mtx_lock_spin(&zombie_lock); 294 TAILQ_INSERT_HEAD(&zombie_threads, td, td_slpq); 295 mtx_unlock_spin(&zombie_lock); 296 } 297 298 /* 299 * Release a thread that has exited after cpu_throw(). 300 */ 301 void 302 thread_stash(struct thread *td) 303 { 304 atomic_subtract_rel_int(&td->td_proc->p_exitthreads, 1); 305 thread_zombie(td); 306 } 307 308 /* 309 * Reap zombie resources. 310 */ 311 void 312 thread_reap(void) 313 { 314 struct thread *td_first, *td_next; 315 316 /* 317 * Don't even bother to lock if none at this instant, 318 * we really don't care about the next instant.. 319 */ 320 if (!TAILQ_EMPTY(&zombie_threads)) { 321 mtx_lock_spin(&zombie_lock); 322 td_first = TAILQ_FIRST(&zombie_threads); 323 if (td_first) 324 TAILQ_INIT(&zombie_threads); 325 mtx_unlock_spin(&zombie_lock); 326 while (td_first) { 327 td_next = TAILQ_NEXT(td_first, td_slpq); 328 if (td_first->td_ucred) 329 crfree(td_first->td_ucred); 330 thread_free(td_first); 331 td_first = td_next; 332 } 333 } 334 } 335 336 /* 337 * Allocate a thread. 338 */ 339 struct thread * 340 thread_alloc(int pages) 341 { 342 struct thread *td; 343 344 thread_reap(); /* check if any zombies to get */ 345 346 td = (struct thread *)uma_zalloc(thread_zone, M_WAITOK); 347 KASSERT(td->td_kstack == 0, ("thread_alloc got thread with kstack")); 348 if (!vm_thread_new(td, pages)) { 349 uma_zfree(thread_zone, td); 350 return (NULL); 351 } 352 cpu_thread_alloc(td); 353 return (td); 354 } 355 356 int 357 thread_alloc_stack(struct thread *td, int pages) 358 { 359 360 KASSERT(td->td_kstack == 0, 361 ("thread_alloc_stack called on a thread with kstack")); 362 if (!vm_thread_new(td, pages)) 363 return (0); 364 cpu_thread_alloc(td); 365 return (1); 366 } 367 368 /* 369 * Deallocate a thread. 370 */ 371 void 372 thread_free(struct thread *td) 373 { 374 375 lock_profile_thread_exit(td); 376 if (td->td_cpuset) 377 cpuset_rel(td->td_cpuset); 378 td->td_cpuset = NULL; 379 cpu_thread_free(td); 380 if (td->td_kstack != 0) 381 vm_thread_dispose(td); 382 uma_zfree(thread_zone, td); 383 } 384 385 /* 386 * Discard the current thread and exit from its context. 387 * Always called with scheduler locked. 388 * 389 * Because we can't free a thread while we're operating under its context, 390 * push the current thread into our CPU's deadthread holder. This means 391 * we needn't worry about someone else grabbing our context before we 392 * do a cpu_throw(). 393 */ 394 void 395 thread_exit(void) 396 { 397 uint64_t runtime, new_switchtime; 398 struct thread *td; 399 struct thread *td2; 400 struct proc *p; 401 int wakeup_swapper; 402 403 td = curthread; 404 p = td->td_proc; 405 406 PROC_SLOCK_ASSERT(p, MA_OWNED); 407 mtx_assert(&Giant, MA_NOTOWNED); 408 409 PROC_LOCK_ASSERT(p, MA_OWNED); 410 KASSERT(p != NULL, ("thread exiting without a process")); 411 CTR3(KTR_PROC, "thread_exit: thread %p (pid %ld, %s)", td, 412 (long)p->p_pid, td->td_name); 413 KASSERT(TAILQ_EMPTY(&td->td_sigqueue.sq_list), ("signal pending")); 414 415 #ifdef AUDIT 416 AUDIT_SYSCALL_EXIT(0, td); 417 #endif 418 umtx_thread_exit(td); 419 /* 420 * drop FPU & debug register state storage, or any other 421 * architecture specific resources that 422 * would not be on a new untouched process. 423 */ 424 cpu_thread_exit(td); /* XXXSMP */ 425 426 /* 427 * The last thread is left attached to the process 428 * So that the whole bundle gets recycled. Skip 429 * all this stuff if we never had threads. 430 * EXIT clears all sign of other threads when 431 * it goes to single threading, so the last thread always 432 * takes the short path. 433 */ 434 if (p->p_flag & P_HADTHREADS) { 435 if (p->p_numthreads > 1) { 436 thread_unlink(td); 437 td2 = FIRST_THREAD_IN_PROC(p); 438 sched_exit_thread(td2, td); 439 440 /* 441 * The test below is NOT true if we are the 442 * sole exiting thread. P_STOPPED_SINGLE is unset 443 * in exit1() after it is the only survivor. 444 */ 445 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) { 446 if (p->p_numthreads == p->p_suspcount) { 447 thread_lock(p->p_singlethread); 448 wakeup_swapper = thread_unsuspend_one( 449 p->p_singlethread); 450 thread_unlock(p->p_singlethread); 451 if (wakeup_swapper) 452 kick_proc0(); 453 } 454 } 455 456 atomic_add_int(&td->td_proc->p_exitthreads, 1); 457 PCPU_SET(deadthread, td); 458 } else { 459 /* 460 * The last thread is exiting.. but not through exit() 461 */ 462 panic ("thread_exit: Last thread exiting on its own"); 463 } 464 } 465 #ifdef HWPMC_HOOKS 466 /* 467 * If this thread is part of a process that is being tracked by hwpmc(4), 468 * inform the module of the thread's impending exit. 469 */ 470 if (PMC_PROC_IS_USING_PMCS(td->td_proc)) 471 PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_OUT); 472 #endif 473 PROC_UNLOCK(p); 474 475 /* Do the same timestamp bookkeeping that mi_switch() would do. */ 476 new_switchtime = cpu_ticks(); 477 runtime = new_switchtime - PCPU_GET(switchtime); 478 td->td_runtime += runtime; 479 td->td_incruntime += runtime; 480 PCPU_SET(switchtime, new_switchtime); 481 PCPU_SET(switchticks, ticks); 482 PCPU_INC(cnt.v_swtch); 483 484 /* Save our resource usage in our process. */ 485 td->td_ru.ru_nvcsw++; 486 ruxagg(p, td); 487 rucollect(&p->p_ru, &td->td_ru); 488 489 thread_lock(td); 490 PROC_SUNLOCK(p); 491 td->td_state = TDS_INACTIVE; 492 #ifdef WITNESS 493 witness_thread_exit(td); 494 #endif 495 CTR1(KTR_PROC, "thread_exit: cpu_throw() thread %p", td); 496 sched_throw(td); 497 panic("I'm a teapot!"); 498 /* NOTREACHED */ 499 } 500 501 /* 502 * Do any thread specific cleanups that may be needed in wait() 503 * called with Giant, proc and schedlock not held. 504 */ 505 void 506 thread_wait(struct proc *p) 507 { 508 struct thread *td; 509 510 mtx_assert(&Giant, MA_NOTOWNED); 511 KASSERT((p->p_numthreads == 1), ("Multiple threads in wait1()")); 512 td = FIRST_THREAD_IN_PROC(p); 513 /* Lock the last thread so we spin until it exits cpu_throw(). */ 514 thread_lock(td); 515 thread_unlock(td); 516 /* Wait for any remaining threads to exit cpu_throw(). */ 517 while (p->p_exitthreads) 518 sched_relinquish(curthread); 519 lock_profile_thread_exit(td); 520 cpuset_rel(td->td_cpuset); 521 td->td_cpuset = NULL; 522 cpu_thread_clean(td); 523 crfree(td->td_ucred); 524 thread_reap(); /* check for zombie threads etc. */ 525 } 526 527 /* 528 * Link a thread to a process. 529 * set up anything that needs to be initialized for it to 530 * be used by the process. 531 */ 532 void 533 thread_link(struct thread *td, struct proc *p) 534 { 535 536 /* 537 * XXX This can't be enabled because it's called for proc0 before 538 * its lock has been created. 539 * PROC_LOCK_ASSERT(p, MA_OWNED); 540 */ 541 td->td_state = TDS_INACTIVE; 542 td->td_proc = p; 543 td->td_flags = TDF_INMEM; 544 545 LIST_INIT(&td->td_contested); 546 LIST_INIT(&td->td_lprof[0]); 547 LIST_INIT(&td->td_lprof[1]); 548 sigqueue_init(&td->td_sigqueue, p); 549 callout_init(&td->td_slpcallout, CALLOUT_MPSAFE); 550 TAILQ_INSERT_HEAD(&p->p_threads, td, td_plist); 551 p->p_numthreads++; 552 } 553 554 /* 555 * Convert a process with one thread to an unthreaded process. 556 */ 557 void 558 thread_unthread(struct thread *td) 559 { 560 struct proc *p = td->td_proc; 561 562 KASSERT((p->p_numthreads == 1), ("Unthreading with >1 threads")); 563 p->p_flag &= ~P_HADTHREADS; 564 } 565 566 /* 567 * Called from: 568 * thread_exit() 569 */ 570 void 571 thread_unlink(struct thread *td) 572 { 573 struct proc *p = td->td_proc; 574 575 PROC_LOCK_ASSERT(p, MA_OWNED); 576 TAILQ_REMOVE(&p->p_threads, td, td_plist); 577 p->p_numthreads--; 578 /* could clear a few other things here */ 579 /* Must NOT clear links to proc! */ 580 } 581 582 static int 583 calc_remaining(struct proc *p, int mode) 584 { 585 int remaining; 586 587 PROC_LOCK_ASSERT(p, MA_OWNED); 588 PROC_SLOCK_ASSERT(p, MA_OWNED); 589 if (mode == SINGLE_EXIT) 590 remaining = p->p_numthreads; 591 else if (mode == SINGLE_BOUNDARY) 592 remaining = p->p_numthreads - p->p_boundary_count; 593 else if (mode == SINGLE_NO_EXIT) 594 remaining = p->p_numthreads - p->p_suspcount; 595 else 596 panic("calc_remaining: wrong mode %d", mode); 597 return (remaining); 598 } 599 600 /* 601 * Enforce single-threading. 602 * 603 * Returns 1 if the caller must abort (another thread is waiting to 604 * exit the process or similar). Process is locked! 605 * Returns 0 when you are successfully the only thread running. 606 * A process has successfully single threaded in the suspend mode when 607 * There are no threads in user mode. Threads in the kernel must be 608 * allowed to continue until they get to the user boundary. They may even 609 * copy out their return values and data before suspending. They may however be 610 * accelerated in reaching the user boundary as we will wake up 611 * any sleeping threads that are interruptable. (PCATCH). 612 */ 613 int 614 thread_single(int mode) 615 { 616 struct thread *td; 617 struct thread *td2; 618 struct proc *p; 619 int remaining, wakeup_swapper; 620 621 td = curthread; 622 p = td->td_proc; 623 mtx_assert(&Giant, MA_NOTOWNED); 624 PROC_LOCK_ASSERT(p, MA_OWNED); 625 626 if ((p->p_flag & P_HADTHREADS) == 0) 627 return (0); 628 629 /* Is someone already single threading? */ 630 if (p->p_singlethread != NULL && p->p_singlethread != td) 631 return (1); 632 633 if (mode == SINGLE_EXIT) { 634 p->p_flag |= P_SINGLE_EXIT; 635 p->p_flag &= ~P_SINGLE_BOUNDARY; 636 } else { 637 p->p_flag &= ~P_SINGLE_EXIT; 638 if (mode == SINGLE_BOUNDARY) 639 p->p_flag |= P_SINGLE_BOUNDARY; 640 else 641 p->p_flag &= ~P_SINGLE_BOUNDARY; 642 } 643 p->p_flag |= P_STOPPED_SINGLE; 644 PROC_SLOCK(p); 645 p->p_singlethread = td; 646 remaining = calc_remaining(p, mode); 647 while (remaining != 1) { 648 if (P_SHOULDSTOP(p) != P_STOPPED_SINGLE) 649 goto stopme; 650 wakeup_swapper = 0; 651 FOREACH_THREAD_IN_PROC(p, td2) { 652 if (td2 == td) 653 continue; 654 thread_lock(td2); 655 td2->td_flags |= TDF_ASTPENDING | TDF_NEEDSUSPCHK; 656 if (TD_IS_INHIBITED(td2)) { 657 switch (mode) { 658 case SINGLE_EXIT: 659 if (TD_IS_SUSPENDED(td2)) 660 wakeup_swapper |= 661 thread_unsuspend_one(td2); 662 if (TD_ON_SLEEPQ(td2) && 663 (td2->td_flags & TDF_SINTR)) 664 wakeup_swapper |= 665 sleepq_abort(td2, EINTR); 666 break; 667 case SINGLE_BOUNDARY: 668 if (TD_IS_SUSPENDED(td2) && 669 !(td2->td_flags & TDF_BOUNDARY)) 670 wakeup_swapper |= 671 thread_unsuspend_one(td2); 672 if (TD_ON_SLEEPQ(td2) && 673 (td2->td_flags & TDF_SINTR)) 674 wakeup_swapper |= 675 sleepq_abort(td2, ERESTART); 676 break; 677 case SINGLE_NO_EXIT: 678 if (TD_IS_SUSPENDED(td2) && 679 !(td2->td_flags & TDF_BOUNDARY)) 680 wakeup_swapper |= 681 thread_unsuspend_one(td2); 682 if (TD_ON_SLEEPQ(td2) && 683 (td2->td_flags & TDF_SINTR)) 684 wakeup_swapper |= 685 sleepq_abort(td2, ERESTART); 686 break; 687 default: 688 break; 689 } 690 } 691 #ifdef SMP 692 else if (TD_IS_RUNNING(td2) && td != td2) { 693 forward_signal(td2); 694 } 695 #endif 696 thread_unlock(td2); 697 } 698 if (wakeup_swapper) 699 kick_proc0(); 700 remaining = calc_remaining(p, mode); 701 702 /* 703 * Maybe we suspended some threads.. was it enough? 704 */ 705 if (remaining == 1) 706 break; 707 708 stopme: 709 /* 710 * Wake us up when everyone else has suspended. 711 * In the mean time we suspend as well. 712 */ 713 thread_suspend_switch(td); 714 remaining = calc_remaining(p, mode); 715 } 716 if (mode == SINGLE_EXIT) { 717 /* 718 * We have gotten rid of all the other threads and we 719 * are about to either exit or exec. In either case, 720 * we try our utmost to revert to being a non-threaded 721 * process. 722 */ 723 p->p_singlethread = NULL; 724 p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT); 725 thread_unthread(td); 726 } 727 PROC_SUNLOCK(p); 728 return (0); 729 } 730 731 /* 732 * Called in from locations that can safely check to see 733 * whether we have to suspend or at least throttle for a 734 * single-thread event (e.g. fork). 735 * 736 * Such locations include userret(). 737 * If the "return_instead" argument is non zero, the thread must be able to 738 * accept 0 (caller may continue), or 1 (caller must abort) as a result. 739 * 740 * The 'return_instead' argument tells the function if it may do a 741 * thread_exit() or suspend, or whether the caller must abort and back 742 * out instead. 743 * 744 * If the thread that set the single_threading request has set the 745 * P_SINGLE_EXIT bit in the process flags then this call will never return 746 * if 'return_instead' is false, but will exit. 747 * 748 * P_SINGLE_EXIT | return_instead == 0| return_instead != 0 749 *---------------+--------------------+--------------------- 750 * 0 | returns 0 | returns 0 or 1 751 * | when ST ends | immediately 752 *---------------+--------------------+--------------------- 753 * 1 | thread exits | returns 1 754 * | | immediately 755 * 0 = thread_exit() or suspension ok, 756 * other = return error instead of stopping the thread. 757 * 758 * While a full suspension is under effect, even a single threading 759 * thread would be suspended if it made this call (but it shouldn't). 760 * This call should only be made from places where 761 * thread_exit() would be safe as that may be the outcome unless 762 * return_instead is set. 763 */ 764 int 765 thread_suspend_check(int return_instead) 766 { 767 struct thread *td; 768 struct proc *p; 769 int wakeup_swapper; 770 771 td = curthread; 772 p = td->td_proc; 773 mtx_assert(&Giant, MA_NOTOWNED); 774 PROC_LOCK_ASSERT(p, MA_OWNED); 775 while (P_SHOULDSTOP(p) || 776 ((p->p_flag & P_TRACED) && (td->td_dbgflags & TDB_SUSPEND))) { 777 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) { 778 KASSERT(p->p_singlethread != NULL, 779 ("singlethread not set")); 780 /* 781 * The only suspension in action is a 782 * single-threading. Single threader need not stop. 783 * XXX Should be safe to access unlocked 784 * as it can only be set to be true by us. 785 */ 786 if (p->p_singlethread == td) 787 return (0); /* Exempt from stopping. */ 788 } 789 if ((p->p_flag & P_SINGLE_EXIT) && return_instead) 790 return (EINTR); 791 792 /* Should we goto user boundary if we didn't come from there? */ 793 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE && 794 (p->p_flag & P_SINGLE_BOUNDARY) && return_instead) 795 return (ERESTART); 796 797 /* 798 * Ignore suspend requests for stop signals if they 799 * are deferred. 800 */ 801 if (P_SHOULDSTOP(p) == P_STOPPED_SIG && 802 td->td_flags & TDF_SBDRY) { 803 KASSERT(return_instead, 804 ("TDF_SBDRY set for unsafe thread_suspend_check")); 805 return (0); 806 } 807 808 /* 809 * If the process is waiting for us to exit, 810 * this thread should just suicide. 811 * Assumes that P_SINGLE_EXIT implies P_STOPPED_SINGLE. 812 */ 813 if ((p->p_flag & P_SINGLE_EXIT) && (p->p_singlethread != td)) { 814 PROC_UNLOCK(p); 815 tidhash_remove(td); 816 PROC_LOCK(p); 817 tdsigcleanup(td); 818 PROC_SLOCK(p); 819 thread_stopped(p); 820 thread_exit(); 821 } 822 823 PROC_SLOCK(p); 824 thread_stopped(p); 825 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) { 826 if (p->p_numthreads == p->p_suspcount + 1) { 827 thread_lock(p->p_singlethread); 828 wakeup_swapper = 829 thread_unsuspend_one(p->p_singlethread); 830 thread_unlock(p->p_singlethread); 831 if (wakeup_swapper) 832 kick_proc0(); 833 } 834 } 835 PROC_UNLOCK(p); 836 thread_lock(td); 837 /* 838 * When a thread suspends, it just 839 * gets taken off all queues. 840 */ 841 thread_suspend_one(td); 842 if (return_instead == 0) { 843 p->p_boundary_count++; 844 td->td_flags |= TDF_BOUNDARY; 845 } 846 PROC_SUNLOCK(p); 847 mi_switch(SW_INVOL | SWT_SUSPEND, NULL); 848 if (return_instead == 0) 849 td->td_flags &= ~TDF_BOUNDARY; 850 thread_unlock(td); 851 PROC_LOCK(p); 852 if (return_instead == 0) { 853 PROC_SLOCK(p); 854 p->p_boundary_count--; 855 PROC_SUNLOCK(p); 856 } 857 } 858 return (0); 859 } 860 861 void 862 thread_suspend_switch(struct thread *td) 863 { 864 struct proc *p; 865 866 p = td->td_proc; 867 KASSERT(!TD_IS_SUSPENDED(td), ("already suspended")); 868 PROC_LOCK_ASSERT(p, MA_OWNED); 869 PROC_SLOCK_ASSERT(p, MA_OWNED); 870 /* 871 * We implement thread_suspend_one in stages here to avoid 872 * dropping the proc lock while the thread lock is owned. 873 */ 874 thread_stopped(p); 875 p->p_suspcount++; 876 PROC_UNLOCK(p); 877 thread_lock(td); 878 td->td_flags &= ~TDF_NEEDSUSPCHK; 879 TD_SET_SUSPENDED(td); 880 sched_sleep(td, 0); 881 PROC_SUNLOCK(p); 882 DROP_GIANT(); 883 mi_switch(SW_VOL | SWT_SUSPEND, NULL); 884 thread_unlock(td); 885 PICKUP_GIANT(); 886 PROC_LOCK(p); 887 PROC_SLOCK(p); 888 } 889 890 void 891 thread_suspend_one(struct thread *td) 892 { 893 struct proc *p = td->td_proc; 894 895 PROC_SLOCK_ASSERT(p, MA_OWNED); 896 THREAD_LOCK_ASSERT(td, MA_OWNED); 897 KASSERT(!TD_IS_SUSPENDED(td), ("already suspended")); 898 p->p_suspcount++; 899 td->td_flags &= ~TDF_NEEDSUSPCHK; 900 TD_SET_SUSPENDED(td); 901 sched_sleep(td, 0); 902 } 903 904 int 905 thread_unsuspend_one(struct thread *td) 906 { 907 struct proc *p = td->td_proc; 908 909 PROC_SLOCK_ASSERT(p, MA_OWNED); 910 THREAD_LOCK_ASSERT(td, MA_OWNED); 911 KASSERT(TD_IS_SUSPENDED(td), ("Thread not suspended")); 912 TD_CLR_SUSPENDED(td); 913 p->p_suspcount--; 914 return (setrunnable(td)); 915 } 916 917 /* 918 * Allow all threads blocked by single threading to continue running. 919 */ 920 void 921 thread_unsuspend(struct proc *p) 922 { 923 struct thread *td; 924 int wakeup_swapper; 925 926 PROC_LOCK_ASSERT(p, MA_OWNED); 927 PROC_SLOCK_ASSERT(p, MA_OWNED); 928 wakeup_swapper = 0; 929 if (!P_SHOULDSTOP(p)) { 930 FOREACH_THREAD_IN_PROC(p, td) { 931 thread_lock(td); 932 if (TD_IS_SUSPENDED(td)) { 933 wakeup_swapper |= thread_unsuspend_one(td); 934 } 935 thread_unlock(td); 936 } 937 } else if ((P_SHOULDSTOP(p) == P_STOPPED_SINGLE) && 938 (p->p_numthreads == p->p_suspcount)) { 939 /* 940 * Stopping everything also did the job for the single 941 * threading request. Now we've downgraded to single-threaded, 942 * let it continue. 943 */ 944 thread_lock(p->p_singlethread); 945 wakeup_swapper = thread_unsuspend_one(p->p_singlethread); 946 thread_unlock(p->p_singlethread); 947 } 948 if (wakeup_swapper) 949 kick_proc0(); 950 } 951 952 /* 953 * End the single threading mode.. 954 */ 955 void 956 thread_single_end(void) 957 { 958 struct thread *td; 959 struct proc *p; 960 int wakeup_swapper; 961 962 td = curthread; 963 p = td->td_proc; 964 PROC_LOCK_ASSERT(p, MA_OWNED); 965 p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT | P_SINGLE_BOUNDARY); 966 PROC_SLOCK(p); 967 p->p_singlethread = NULL; 968 wakeup_swapper = 0; 969 /* 970 * If there are other threads they may now run, 971 * unless of course there is a blanket 'stop order' 972 * on the process. The single threader must be allowed 973 * to continue however as this is a bad place to stop. 974 */ 975 if ((p->p_numthreads != 1) && (!P_SHOULDSTOP(p))) { 976 FOREACH_THREAD_IN_PROC(p, td) { 977 thread_lock(td); 978 if (TD_IS_SUSPENDED(td)) { 979 wakeup_swapper |= thread_unsuspend_one(td); 980 } 981 thread_unlock(td); 982 } 983 } 984 PROC_SUNLOCK(p); 985 if (wakeup_swapper) 986 kick_proc0(); 987 } 988 989 struct thread * 990 thread_find(struct proc *p, lwpid_t tid) 991 { 992 struct thread *td; 993 994 PROC_LOCK_ASSERT(p, MA_OWNED); 995 FOREACH_THREAD_IN_PROC(p, td) { 996 if (td->td_tid == tid) 997 break; 998 } 999 return (td); 1000 } 1001 1002 /* Locate a thread by number; return with proc lock held. */ 1003 struct thread * 1004 tdfind(lwpid_t tid, pid_t pid) 1005 { 1006 #define RUN_THRESH 16 1007 struct thread *td; 1008 int run = 0; 1009 1010 rw_rlock(&tidhash_lock); 1011 LIST_FOREACH(td, TIDHASH(tid), td_hash) { 1012 if (td->td_tid == tid) { 1013 if (pid != -1 && td->td_proc->p_pid != pid) { 1014 td = NULL; 1015 break; 1016 } 1017 PROC_LOCK(td->td_proc); 1018 if (td->td_proc->p_state == PRS_NEW) { 1019 PROC_UNLOCK(td->td_proc); 1020 td = NULL; 1021 break; 1022 } 1023 if (run > RUN_THRESH) { 1024 if (rw_try_upgrade(&tidhash_lock)) { 1025 LIST_REMOVE(td, td_hash); 1026 LIST_INSERT_HEAD(TIDHASH(td->td_tid), 1027 td, td_hash); 1028 rw_wunlock(&tidhash_lock); 1029 return (td); 1030 } 1031 } 1032 break; 1033 } 1034 run++; 1035 } 1036 rw_runlock(&tidhash_lock); 1037 return (td); 1038 } 1039 1040 void 1041 tidhash_add(struct thread *td) 1042 { 1043 rw_wlock(&tidhash_lock); 1044 LIST_INSERT_HEAD(TIDHASH(td->td_tid), td, td_hash); 1045 rw_wunlock(&tidhash_lock); 1046 } 1047 1048 void 1049 tidhash_remove(struct thread *td) 1050 { 1051 rw_wlock(&tidhash_lock); 1052 LIST_REMOVE(td, td_hash); 1053 rw_wunlock(&tidhash_lock); 1054 } 1055