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("$FreeBSD$"); 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/turnstile.h> 49 #include <sys/ktr.h> 50 #include <sys/rwlock.h> 51 #include <sys/umtx.h> 52 #include <sys/cpuset.h> 53 #ifdef HWPMC_HOOKS 54 #include <sys/pmckern.h> 55 #endif 56 57 #include <security/audit/audit.h> 58 59 #include <vm/vm.h> 60 #include <vm/vm_extern.h> 61 #include <vm/uma.h> 62 #include <sys/eventhandler.h> 63 64 SDT_PROVIDER_DECLARE(proc); 65 SDT_PROBE_DEFINE(proc, , , lwp__exit); 66 67 68 /* 69 * thread related storage. 70 */ 71 static uma_zone_t thread_zone; 72 73 TAILQ_HEAD(, thread) zombie_threads = TAILQ_HEAD_INITIALIZER(zombie_threads); 74 static struct mtx zombie_lock; 75 MTX_SYSINIT(zombie_lock, &zombie_lock, "zombie lock", MTX_SPIN); 76 77 static void thread_zombie(struct thread *); 78 79 #define TID_BUFFER_SIZE 1024 80 81 struct mtx tid_lock; 82 static struct unrhdr *tid_unrhdr; 83 static lwpid_t tid_buffer[TID_BUFFER_SIZE]; 84 static int tid_head, tid_tail; 85 static MALLOC_DEFINE(M_TIDHASH, "tidhash", "thread hash"); 86 87 struct tidhashhead *tidhashtbl; 88 u_long tidhash; 89 struct rwlock tidhash_lock; 90 91 static lwpid_t 92 tid_alloc(void) 93 { 94 lwpid_t tid; 95 96 tid = alloc_unr(tid_unrhdr); 97 if (tid != -1) 98 return (tid); 99 mtx_lock(&tid_lock); 100 if (tid_head == tid_tail) { 101 mtx_unlock(&tid_lock); 102 return (-1); 103 } 104 tid = tid_buffer[tid_head]; 105 tid_head = (tid_head + 1) % TID_BUFFER_SIZE; 106 mtx_unlock(&tid_lock); 107 return (tid); 108 } 109 110 static void 111 tid_free(lwpid_t tid) 112 { 113 lwpid_t tmp_tid = -1; 114 115 mtx_lock(&tid_lock); 116 if ((tid_tail + 1) % TID_BUFFER_SIZE == tid_head) { 117 tmp_tid = tid_buffer[tid_head]; 118 tid_head = (tid_head + 1) % TID_BUFFER_SIZE; 119 } 120 tid_buffer[tid_tail] = tid; 121 tid_tail = (tid_tail + 1) % TID_BUFFER_SIZE; 122 mtx_unlock(&tid_lock); 123 if (tmp_tid != -1) 124 free_unr(tid_unrhdr, tmp_tid); 125 } 126 127 /* 128 * Prepare a thread for use. 129 */ 130 static int 131 thread_ctor(void *mem, int size, void *arg, int flags) 132 { 133 struct thread *td; 134 135 td = (struct thread *)mem; 136 td->td_state = TDS_INACTIVE; 137 td->td_oncpu = NOCPU; 138 139 td->td_tid = tid_alloc(); 140 141 /* 142 * Note that td_critnest begins life as 1 because the thread is not 143 * running and is thereby implicitly waiting to be on the receiving 144 * end of a context switch. 145 */ 146 td->td_critnest = 1; 147 td->td_lend_user_pri = PRI_MAX; 148 EVENTHANDLER_INVOKE(thread_ctor, td); 149 #ifdef AUDIT 150 audit_thread_alloc(td); 151 #endif 152 umtx_thread_alloc(td); 153 return (0); 154 } 155 156 /* 157 * Reclaim a thread after use. 158 */ 159 static void 160 thread_dtor(void *mem, int size, void *arg) 161 { 162 struct thread *td; 163 164 td = (struct thread *)mem; 165 166 #ifdef INVARIANTS 167 /* Verify that this thread is in a safe state to free. */ 168 switch (td->td_state) { 169 case TDS_INHIBITED: 170 case TDS_RUNNING: 171 case TDS_CAN_RUN: 172 case TDS_RUNQ: 173 /* 174 * We must never unlink a thread that is in one of 175 * these states, because it is currently active. 176 */ 177 panic("bad state for thread unlinking"); 178 /* NOTREACHED */ 179 case TDS_INACTIVE: 180 break; 181 default: 182 panic("bad thread state"); 183 /* NOTREACHED */ 184 } 185 #endif 186 #ifdef AUDIT 187 audit_thread_free(td); 188 #endif 189 /* Free all OSD associated to this thread. */ 190 osd_thread_exit(td); 191 192 EVENTHANDLER_INVOKE(thread_dtor, td); 193 tid_free(td->td_tid); 194 } 195 196 /* 197 * Initialize type-stable parts of a thread (when newly created). 198 */ 199 static int 200 thread_init(void *mem, int size, int flags) 201 { 202 struct thread *td; 203 204 td = (struct thread *)mem; 205 206 td->td_sleepqueue = sleepq_alloc(); 207 td->td_turnstile = turnstile_alloc(); 208 td->td_rlqe = NULL; 209 EVENTHANDLER_INVOKE(thread_init, td); 210 td->td_sched = (struct td_sched *)&td[1]; 211 umtx_thread_init(td); 212 td->td_kstack = 0; 213 return (0); 214 } 215 216 /* 217 * Tear down type-stable parts of a thread (just before being discarded). 218 */ 219 static void 220 thread_fini(void *mem, int size) 221 { 222 struct thread *td; 223 224 td = (struct thread *)mem; 225 EVENTHANDLER_INVOKE(thread_fini, td); 226 rlqentry_free(td->td_rlqe); 227 turnstile_free(td->td_turnstile); 228 sleepq_free(td->td_sleepqueue); 229 umtx_thread_fini(td); 230 seltdfini(td); 231 } 232 233 /* 234 * For a newly created process, 235 * link up all the structures and its initial threads etc. 236 * called from: 237 * {arch}/{arch}/machdep.c {arch}_init(), init386() etc. 238 * proc_dtor() (should go away) 239 * proc_init() 240 */ 241 void 242 proc_linkup0(struct proc *p, struct thread *td) 243 { 244 TAILQ_INIT(&p->p_threads); /* all threads in proc */ 245 proc_linkup(p, td); 246 } 247 248 void 249 proc_linkup(struct proc *p, struct thread *td) 250 { 251 252 sigqueue_init(&p->p_sigqueue, p); 253 p->p_ksi = ksiginfo_alloc(1); 254 if (p->p_ksi != NULL) { 255 /* XXX p_ksi may be null if ksiginfo zone is not ready */ 256 p->p_ksi->ksi_flags = KSI_EXT | KSI_INS; 257 } 258 LIST_INIT(&p->p_mqnotifier); 259 p->p_numthreads = 0; 260 thread_link(td, p); 261 } 262 263 /* 264 * Initialize global thread allocation resources. 265 */ 266 void 267 threadinit(void) 268 { 269 270 mtx_init(&tid_lock, "TID lock", NULL, MTX_DEF); 271 272 /* 273 * pid_max cannot be greater than PID_MAX. 274 * leave one number for thread0. 275 */ 276 tid_unrhdr = new_unrhdr(PID_MAX + 2, INT_MAX, &tid_lock); 277 278 thread_zone = uma_zcreate("THREAD", sched_sizeof_thread(), 279 thread_ctor, thread_dtor, thread_init, thread_fini, 280 16 - 1, 0); 281 tidhashtbl = hashinit(maxproc / 2, M_TIDHASH, &tidhash); 282 rw_init(&tidhash_lock, "tidhash"); 283 } 284 285 /* 286 * Place an unused thread on the zombie list. 287 * Use the slpq as that must be unused by now. 288 */ 289 void 290 thread_zombie(struct thread *td) 291 { 292 mtx_lock_spin(&zombie_lock); 293 TAILQ_INSERT_HEAD(&zombie_threads, td, td_slpq); 294 mtx_unlock_spin(&zombie_lock); 295 } 296 297 /* 298 * Release a thread that has exited after cpu_throw(). 299 */ 300 void 301 thread_stash(struct thread *td) 302 { 303 atomic_subtract_rel_int(&td->td_proc->p_exitthreads, 1); 304 thread_zombie(td); 305 } 306 307 /* 308 * Reap zombie resources. 309 */ 310 void 311 thread_reap(void) 312 { 313 struct thread *td_first, *td_next; 314 315 /* 316 * Don't even bother to lock if none at this instant, 317 * we really don't care about the next instant.. 318 */ 319 if (!TAILQ_EMPTY(&zombie_threads)) { 320 mtx_lock_spin(&zombie_lock); 321 td_first = TAILQ_FIRST(&zombie_threads); 322 if (td_first) 323 TAILQ_INIT(&zombie_threads); 324 mtx_unlock_spin(&zombie_lock); 325 while (td_first) { 326 td_next = TAILQ_NEXT(td_first, td_slpq); 327 if (td_first->td_ucred) 328 crfree(td_first->td_ucred); 329 thread_free(td_first); 330 td_first = td_next; 331 } 332 } 333 } 334 335 /* 336 * Allocate a thread. 337 */ 338 struct thread * 339 thread_alloc(int pages) 340 { 341 struct thread *td; 342 343 thread_reap(); /* check if any zombies to get */ 344 345 td = (struct thread *)uma_zalloc(thread_zone, M_WAITOK); 346 KASSERT(td->td_kstack == 0, ("thread_alloc got thread with kstack")); 347 if (!vm_thread_new(td, pages)) { 348 uma_zfree(thread_zone, td); 349 return (NULL); 350 } 351 cpu_thread_alloc(td); 352 return (td); 353 } 354 355 int 356 thread_alloc_stack(struct thread *td, int pages) 357 { 358 359 KASSERT(td->td_kstack == 0, 360 ("thread_alloc_stack called on a thread with kstack")); 361 if (!vm_thread_new(td, pages)) 362 return (0); 363 cpu_thread_alloc(td); 364 return (1); 365 } 366 367 /* 368 * Deallocate a thread. 369 */ 370 void 371 thread_free(struct thread *td) 372 { 373 374 lock_profile_thread_exit(td); 375 if (td->td_cpuset) 376 cpuset_rel(td->td_cpuset); 377 td->td_cpuset = NULL; 378 cpu_thread_free(td); 379 if (td->td_kstack != 0) 380 vm_thread_dispose(td); 381 uma_zfree(thread_zone, td); 382 } 383 384 /* 385 * Discard the current thread and exit from its context. 386 * Always called with scheduler locked. 387 * 388 * Because we can't free a thread while we're operating under its context, 389 * push the current thread into our CPU's deadthread holder. This means 390 * we needn't worry about someone else grabbing our context before we 391 * do a cpu_throw(). 392 */ 393 void 394 thread_exit(void) 395 { 396 uint64_t runtime, new_switchtime; 397 struct thread *td; 398 struct thread *td2; 399 struct proc *p; 400 int wakeup_swapper; 401 402 td = curthread; 403 p = td->td_proc; 404 405 PROC_SLOCK_ASSERT(p, MA_OWNED); 406 mtx_assert(&Giant, MA_NOTOWNED); 407 408 PROC_LOCK_ASSERT(p, MA_OWNED); 409 KASSERT(p != NULL, ("thread exiting without a process")); 410 CTR3(KTR_PROC, "thread_exit: thread %p (pid %ld, %s)", td, 411 (long)p->p_pid, td->td_name); 412 KASSERT(TAILQ_EMPTY(&td->td_sigqueue.sq_list), ("signal pending")); 413 414 #ifdef AUDIT 415 AUDIT_SYSCALL_EXIT(0, td); 416 #endif 417 umtx_thread_exit(td); 418 /* 419 * drop FPU & debug register state storage, or any other 420 * architecture specific resources that 421 * would not be on a new untouched process. 422 */ 423 cpu_thread_exit(td); /* XXXSMP */ 424 425 /* 426 * The last thread is left attached to the process 427 * So that the whole bundle gets recycled. Skip 428 * all this stuff if we never had threads. 429 * EXIT clears all sign of other threads when 430 * it goes to single threading, so the last thread always 431 * takes the short path. 432 */ 433 if (p->p_flag & P_HADTHREADS) { 434 if (p->p_numthreads > 1) { 435 thread_unlink(td); 436 td2 = FIRST_THREAD_IN_PROC(p); 437 sched_exit_thread(td2, td); 438 439 /* 440 * The test below is NOT true if we are the 441 * sole exiting thread. P_STOPPED_SINGLE is unset 442 * in exit1() after it is the only survivor. 443 */ 444 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) { 445 if (p->p_numthreads == p->p_suspcount) { 446 thread_lock(p->p_singlethread); 447 wakeup_swapper = thread_unsuspend_one( 448 p->p_singlethread); 449 thread_unlock(p->p_singlethread); 450 if (wakeup_swapper) 451 kick_proc0(); 452 } 453 } 454 455 atomic_add_int(&td->td_proc->p_exitthreads, 1); 456 PCPU_SET(deadthread, td); 457 } else { 458 /* 459 * The last thread is exiting.. but not through exit() 460 */ 461 panic ("thread_exit: Last thread exiting on its own"); 462 } 463 } 464 #ifdef HWPMC_HOOKS 465 /* 466 * If this thread is part of a process that is being tracked by hwpmc(4), 467 * inform the module of the thread's impending exit. 468 */ 469 if (PMC_PROC_IS_USING_PMCS(td->td_proc)) 470 PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_OUT); 471 #endif 472 PROC_UNLOCK(p); 473 474 /* Do the same timestamp bookkeeping that mi_switch() would do. */ 475 new_switchtime = cpu_ticks(); 476 runtime = new_switchtime - PCPU_GET(switchtime); 477 td->td_runtime += runtime; 478 td->td_incruntime += runtime; 479 PCPU_SET(switchtime, new_switchtime); 480 PCPU_SET(switchticks, ticks); 481 PCPU_INC(cnt.v_swtch); 482 483 /* Save our resource usage in our process. */ 484 td->td_ru.ru_nvcsw++; 485 ruxagg(p, td); 486 rucollect(&p->p_ru, &td->td_ru); 487 488 thread_lock(td); 489 PROC_SUNLOCK(p); 490 td->td_state = TDS_INACTIVE; 491 #ifdef WITNESS 492 witness_thread_exit(td); 493 #endif 494 CTR1(KTR_PROC, "thread_exit: cpu_throw() thread %p", td); 495 sched_throw(td); 496 panic("I'm a teapot!"); 497 /* NOTREACHED */ 498 } 499 500 /* 501 * Do any thread specific cleanups that may be needed in wait() 502 * called with Giant, proc and schedlock not held. 503 */ 504 void 505 thread_wait(struct proc *p) 506 { 507 struct thread *td; 508 509 mtx_assert(&Giant, MA_NOTOWNED); 510 KASSERT((p->p_numthreads == 1), ("Multiple threads in wait1()")); 511 td = FIRST_THREAD_IN_PROC(p); 512 /* Lock the last thread so we spin until it exits cpu_throw(). */ 513 thread_lock(td); 514 thread_unlock(td); 515 /* Wait for any remaining threads to exit cpu_throw(). */ 516 while (p->p_exitthreads) 517 sched_relinquish(curthread); 518 lock_profile_thread_exit(td); 519 cpuset_rel(td->td_cpuset); 520 td->td_cpuset = NULL; 521 cpu_thread_clean(td); 522 crfree(td->td_ucred); 523 thread_reap(); /* check for zombie threads etc. */ 524 } 525 526 /* 527 * Link a thread to a process. 528 * set up anything that needs to be initialized for it to 529 * be used by the process. 530 */ 531 void 532 thread_link(struct thread *td, struct proc *p) 533 { 534 535 /* 536 * XXX This can't be enabled because it's called for proc0 before 537 * its lock has been created. 538 * PROC_LOCK_ASSERT(p, MA_OWNED); 539 */ 540 td->td_state = TDS_INACTIVE; 541 td->td_proc = p; 542 td->td_flags = TDF_INMEM; 543 544 LIST_INIT(&td->td_contested); 545 LIST_INIT(&td->td_lprof[0]); 546 LIST_INIT(&td->td_lprof[1]); 547 sigqueue_init(&td->td_sigqueue, p); 548 callout_init(&td->td_slpcallout, CALLOUT_MPSAFE); 549 TAILQ_INSERT_TAIL(&p->p_threads, td, td_plist); 550 p->p_numthreads++; 551 } 552 553 /* 554 * Convert a process with one thread to an unthreaded process. 555 */ 556 void 557 thread_unthread(struct thread *td) 558 { 559 struct proc *p = td->td_proc; 560 561 KASSERT((p->p_numthreads == 1), ("Unthreading with >1 threads")); 562 p->p_flag &= ~P_HADTHREADS; 563 } 564 565 /* 566 * Called from: 567 * thread_exit() 568 */ 569 void 570 thread_unlink(struct thread *td) 571 { 572 struct proc *p = td->td_proc; 573 574 PROC_LOCK_ASSERT(p, MA_OWNED); 575 TAILQ_REMOVE(&p->p_threads, td, td_plist); 576 p->p_numthreads--; 577 /* could clear a few other things here */ 578 /* Must NOT clear links to proc! */ 579 } 580 581 static int 582 calc_remaining(struct proc *p, int mode) 583 { 584 int remaining; 585 586 PROC_LOCK_ASSERT(p, MA_OWNED); 587 PROC_SLOCK_ASSERT(p, MA_OWNED); 588 if (mode == SINGLE_EXIT) 589 remaining = p->p_numthreads; 590 else if (mode == SINGLE_BOUNDARY) 591 remaining = p->p_numthreads - p->p_boundary_count; 592 else if (mode == SINGLE_NO_EXIT) 593 remaining = p->p_numthreads - p->p_suspcount; 594 else 595 panic("calc_remaining: wrong mode %d", mode); 596 return (remaining); 597 } 598 599 /* 600 * Enforce single-threading. 601 * 602 * Returns 1 if the caller must abort (another thread is waiting to 603 * exit the process or similar). Process is locked! 604 * Returns 0 when you are successfully the only thread running. 605 * A process has successfully single threaded in the suspend mode when 606 * There are no threads in user mode. Threads in the kernel must be 607 * allowed to continue until they get to the user boundary. They may even 608 * copy out their return values and data before suspending. They may however be 609 * accelerated in reaching the user boundary as we will wake up 610 * any sleeping threads that are interruptable. (PCATCH). 611 */ 612 int 613 thread_single(int mode) 614 { 615 struct thread *td; 616 struct thread *td2; 617 struct proc *p; 618 int remaining, wakeup_swapper; 619 620 td = curthread; 621 p = td->td_proc; 622 mtx_assert(&Giant, MA_NOTOWNED); 623 PROC_LOCK_ASSERT(p, MA_OWNED); 624 625 if ((p->p_flag & P_HADTHREADS) == 0) 626 return (0); 627 628 /* Is someone already single threading? */ 629 if (p->p_singlethread != NULL && p->p_singlethread != td) 630 return (1); 631 632 if (mode == SINGLE_EXIT) { 633 p->p_flag |= P_SINGLE_EXIT; 634 p->p_flag &= ~P_SINGLE_BOUNDARY; 635 } else { 636 p->p_flag &= ~P_SINGLE_EXIT; 637 if (mode == SINGLE_BOUNDARY) 638 p->p_flag |= P_SINGLE_BOUNDARY; 639 else 640 p->p_flag &= ~P_SINGLE_BOUNDARY; 641 } 642 p->p_flag |= P_STOPPED_SINGLE; 643 PROC_SLOCK(p); 644 p->p_singlethread = td; 645 remaining = calc_remaining(p, mode); 646 while (remaining != 1) { 647 if (P_SHOULDSTOP(p) != P_STOPPED_SINGLE) 648 goto stopme; 649 wakeup_swapper = 0; 650 FOREACH_THREAD_IN_PROC(p, td2) { 651 if (td2 == td) 652 continue; 653 thread_lock(td2); 654 td2->td_flags |= TDF_ASTPENDING | TDF_NEEDSUSPCHK; 655 if (TD_IS_INHIBITED(td2)) { 656 switch (mode) { 657 case SINGLE_EXIT: 658 if (TD_IS_SUSPENDED(td2)) 659 wakeup_swapper |= 660 thread_unsuspend_one(td2); 661 if (TD_ON_SLEEPQ(td2) && 662 (td2->td_flags & TDF_SINTR)) 663 wakeup_swapper |= 664 sleepq_abort(td2, EINTR); 665 break; 666 case SINGLE_BOUNDARY: 667 if (TD_IS_SUSPENDED(td2) && 668 !(td2->td_flags & TDF_BOUNDARY)) 669 wakeup_swapper |= 670 thread_unsuspend_one(td2); 671 if (TD_ON_SLEEPQ(td2) && 672 (td2->td_flags & TDF_SINTR)) 673 wakeup_swapper |= 674 sleepq_abort(td2, ERESTART); 675 break; 676 case SINGLE_NO_EXIT: 677 if (TD_IS_SUSPENDED(td2) && 678 !(td2->td_flags & TDF_BOUNDARY)) 679 wakeup_swapper |= 680 thread_unsuspend_one(td2); 681 if (TD_ON_SLEEPQ(td2) && 682 (td2->td_flags & TDF_SINTR)) 683 wakeup_swapper |= 684 sleepq_abort(td2, ERESTART); 685 break; 686 default: 687 break; 688 } 689 } 690 #ifdef SMP 691 else if (TD_IS_RUNNING(td2) && td != td2) { 692 forward_signal(td2); 693 } 694 #endif 695 thread_unlock(td2); 696 } 697 if (wakeup_swapper) 698 kick_proc0(); 699 remaining = calc_remaining(p, mode); 700 701 /* 702 * Maybe we suspended some threads.. was it enough? 703 */ 704 if (remaining == 1) 705 break; 706 707 stopme: 708 /* 709 * Wake us up when everyone else has suspended. 710 * In the mean time we suspend as well. 711 */ 712 thread_suspend_switch(td); 713 remaining = calc_remaining(p, mode); 714 } 715 if (mode == SINGLE_EXIT) { 716 /* 717 * We have gotten rid of all the other threads and we 718 * are about to either exit or exec. In either case, 719 * we try our utmost to revert to being a non-threaded 720 * process. 721 */ 722 p->p_singlethread = NULL; 723 p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT); 724 thread_unthread(td); 725 } 726 PROC_SUNLOCK(p); 727 return (0); 728 } 729 730 /* 731 * Called in from locations that can safely check to see 732 * whether we have to suspend or at least throttle for a 733 * single-thread event (e.g. fork). 734 * 735 * Such locations include userret(). 736 * If the "return_instead" argument is non zero, the thread must be able to 737 * accept 0 (caller may continue), or 1 (caller must abort) as a result. 738 * 739 * The 'return_instead' argument tells the function if it may do a 740 * thread_exit() or suspend, or whether the caller must abort and back 741 * out instead. 742 * 743 * If the thread that set the single_threading request has set the 744 * P_SINGLE_EXIT bit in the process flags then this call will never return 745 * if 'return_instead' is false, but will exit. 746 * 747 * P_SINGLE_EXIT | return_instead == 0| return_instead != 0 748 *---------------+--------------------+--------------------- 749 * 0 | returns 0 | returns 0 or 1 750 * | when ST ends | immediately 751 *---------------+--------------------+--------------------- 752 * 1 | thread exits | returns 1 753 * | | immediately 754 * 0 = thread_exit() or suspension ok, 755 * other = return error instead of stopping the thread. 756 * 757 * While a full suspension is under effect, even a single threading 758 * thread would be suspended if it made this call (but it shouldn't). 759 * This call should only be made from places where 760 * thread_exit() would be safe as that may be the outcome unless 761 * return_instead is set. 762 */ 763 int 764 thread_suspend_check(int return_instead) 765 { 766 struct thread *td; 767 struct proc *p; 768 int wakeup_swapper; 769 770 td = curthread; 771 p = td->td_proc; 772 mtx_assert(&Giant, MA_NOTOWNED); 773 PROC_LOCK_ASSERT(p, MA_OWNED); 774 while (P_SHOULDSTOP(p) || 775 ((p->p_flag & P_TRACED) && (td->td_dbgflags & TDB_SUSPEND))) { 776 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) { 777 KASSERT(p->p_singlethread != NULL, 778 ("singlethread not set")); 779 /* 780 * The only suspension in action is a 781 * single-threading. Single threader need not stop. 782 * XXX Should be safe to access unlocked 783 * as it can only be set to be true by us. 784 */ 785 if (p->p_singlethread == td) 786 return (0); /* Exempt from stopping. */ 787 } 788 if ((p->p_flag & P_SINGLE_EXIT) && return_instead) 789 return (EINTR); 790 791 /* Should we goto user boundary if we didn't come from there? */ 792 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE && 793 (p->p_flag & P_SINGLE_BOUNDARY) && return_instead) 794 return (ERESTART); 795 796 /* 797 * Ignore suspend requests for stop signals if they 798 * are deferred. 799 */ 800 if (P_SHOULDSTOP(p) == P_STOPPED_SIG && 801 td->td_flags & TDF_SBDRY) { 802 KASSERT(return_instead, 803 ("TDF_SBDRY set for unsafe thread_suspend_check")); 804 return (0); 805 } 806 807 /* 808 * If the process is waiting for us to exit, 809 * this thread should just suicide. 810 * Assumes that P_SINGLE_EXIT implies P_STOPPED_SINGLE. 811 */ 812 if ((p->p_flag & P_SINGLE_EXIT) && (p->p_singlethread != td)) { 813 PROC_UNLOCK(p); 814 tidhash_remove(td); 815 PROC_LOCK(p); 816 tdsigcleanup(td); 817 PROC_SLOCK(p); 818 thread_stopped(p); 819 thread_exit(); 820 } 821 822 PROC_SLOCK(p); 823 thread_stopped(p); 824 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) { 825 if (p->p_numthreads == p->p_suspcount + 1) { 826 thread_lock(p->p_singlethread); 827 wakeup_swapper = 828 thread_unsuspend_one(p->p_singlethread); 829 thread_unlock(p->p_singlethread); 830 if (wakeup_swapper) 831 kick_proc0(); 832 } 833 } 834 PROC_UNLOCK(p); 835 thread_lock(td); 836 /* 837 * When a thread suspends, it just 838 * gets taken off all queues. 839 */ 840 thread_suspend_one(td); 841 if (return_instead == 0) { 842 p->p_boundary_count++; 843 td->td_flags |= TDF_BOUNDARY; 844 } 845 PROC_SUNLOCK(p); 846 mi_switch(SW_INVOL | SWT_SUSPEND, NULL); 847 if (return_instead == 0) 848 td->td_flags &= ~TDF_BOUNDARY; 849 thread_unlock(td); 850 PROC_LOCK(p); 851 if (return_instead == 0) { 852 PROC_SLOCK(p); 853 p->p_boundary_count--; 854 PROC_SUNLOCK(p); 855 } 856 } 857 return (0); 858 } 859 860 void 861 thread_suspend_switch(struct thread *td) 862 { 863 struct proc *p; 864 865 p = td->td_proc; 866 KASSERT(!TD_IS_SUSPENDED(td), ("already suspended")); 867 PROC_LOCK_ASSERT(p, MA_OWNED); 868 PROC_SLOCK_ASSERT(p, MA_OWNED); 869 /* 870 * We implement thread_suspend_one in stages here to avoid 871 * dropping the proc lock while the thread lock is owned. 872 */ 873 thread_stopped(p); 874 p->p_suspcount++; 875 PROC_UNLOCK(p); 876 thread_lock(td); 877 td->td_flags &= ~TDF_NEEDSUSPCHK; 878 TD_SET_SUSPENDED(td); 879 sched_sleep(td, 0); 880 PROC_SUNLOCK(p); 881 DROP_GIANT(); 882 mi_switch(SW_VOL | SWT_SUSPEND, NULL); 883 thread_unlock(td); 884 PICKUP_GIANT(); 885 PROC_LOCK(p); 886 PROC_SLOCK(p); 887 } 888 889 void 890 thread_suspend_one(struct thread *td) 891 { 892 struct proc *p = td->td_proc; 893 894 PROC_SLOCK_ASSERT(p, MA_OWNED); 895 THREAD_LOCK_ASSERT(td, MA_OWNED); 896 KASSERT(!TD_IS_SUSPENDED(td), ("already suspended")); 897 p->p_suspcount++; 898 td->td_flags &= ~TDF_NEEDSUSPCHK; 899 TD_SET_SUSPENDED(td); 900 sched_sleep(td, 0); 901 } 902 903 int 904 thread_unsuspend_one(struct thread *td) 905 { 906 struct proc *p = td->td_proc; 907 908 PROC_SLOCK_ASSERT(p, MA_OWNED); 909 THREAD_LOCK_ASSERT(td, MA_OWNED); 910 KASSERT(TD_IS_SUSPENDED(td), ("Thread not suspended")); 911 TD_CLR_SUSPENDED(td); 912 p->p_suspcount--; 913 return (setrunnable(td)); 914 } 915 916 /* 917 * Allow all threads blocked by single threading to continue running. 918 */ 919 void 920 thread_unsuspend(struct proc *p) 921 { 922 struct thread *td; 923 int wakeup_swapper; 924 925 PROC_LOCK_ASSERT(p, MA_OWNED); 926 PROC_SLOCK_ASSERT(p, MA_OWNED); 927 wakeup_swapper = 0; 928 if (!P_SHOULDSTOP(p)) { 929 FOREACH_THREAD_IN_PROC(p, td) { 930 thread_lock(td); 931 if (TD_IS_SUSPENDED(td)) { 932 wakeup_swapper |= thread_unsuspend_one(td); 933 } 934 thread_unlock(td); 935 } 936 } else if ((P_SHOULDSTOP(p) == P_STOPPED_SINGLE) && 937 (p->p_numthreads == p->p_suspcount)) { 938 /* 939 * Stopping everything also did the job for the single 940 * threading request. Now we've downgraded to single-threaded, 941 * let it continue. 942 */ 943 thread_lock(p->p_singlethread); 944 wakeup_swapper = thread_unsuspend_one(p->p_singlethread); 945 thread_unlock(p->p_singlethread); 946 } 947 if (wakeup_swapper) 948 kick_proc0(); 949 } 950 951 /* 952 * End the single threading mode.. 953 */ 954 void 955 thread_single_end(void) 956 { 957 struct thread *td; 958 struct proc *p; 959 int wakeup_swapper; 960 961 td = curthread; 962 p = td->td_proc; 963 PROC_LOCK_ASSERT(p, MA_OWNED); 964 p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT | P_SINGLE_BOUNDARY); 965 PROC_SLOCK(p); 966 p->p_singlethread = NULL; 967 wakeup_swapper = 0; 968 /* 969 * If there are other threads they may now run, 970 * unless of course there is a blanket 'stop order' 971 * on the process. The single threader must be allowed 972 * to continue however as this is a bad place to stop. 973 */ 974 if ((p->p_numthreads != 1) && (!P_SHOULDSTOP(p))) { 975 FOREACH_THREAD_IN_PROC(p, td) { 976 thread_lock(td); 977 if (TD_IS_SUSPENDED(td)) { 978 wakeup_swapper |= thread_unsuspend_one(td); 979 } 980 thread_unlock(td); 981 } 982 } 983 PROC_SUNLOCK(p); 984 if (wakeup_swapper) 985 kick_proc0(); 986 } 987 988 struct thread * 989 thread_find(struct proc *p, lwpid_t tid) 990 { 991 struct thread *td; 992 993 PROC_LOCK_ASSERT(p, MA_OWNED); 994 FOREACH_THREAD_IN_PROC(p, td) { 995 if (td->td_tid == tid) 996 break; 997 } 998 return (td); 999 } 1000 1001 /* Locate a thread by number; return with proc lock held. */ 1002 struct thread * 1003 tdfind(lwpid_t tid, pid_t pid) 1004 { 1005 #define RUN_THRESH 16 1006 struct thread *td; 1007 int run = 0; 1008 1009 rw_rlock(&tidhash_lock); 1010 LIST_FOREACH(td, TIDHASH(tid), td_hash) { 1011 if (td->td_tid == tid) { 1012 if (pid != -1 && td->td_proc->p_pid != pid) { 1013 td = NULL; 1014 break; 1015 } 1016 PROC_LOCK(td->td_proc); 1017 if (td->td_proc->p_state == PRS_NEW) { 1018 PROC_UNLOCK(td->td_proc); 1019 td = NULL; 1020 break; 1021 } 1022 if (run > RUN_THRESH) { 1023 if (rw_try_upgrade(&tidhash_lock)) { 1024 LIST_REMOVE(td, td_hash); 1025 LIST_INSERT_HEAD(TIDHASH(td->td_tid), 1026 td, td_hash); 1027 rw_wunlock(&tidhash_lock); 1028 return (td); 1029 } 1030 } 1031 break; 1032 } 1033 run++; 1034 } 1035 rw_runlock(&tidhash_lock); 1036 return (td); 1037 } 1038 1039 void 1040 tidhash_add(struct thread *td) 1041 { 1042 rw_wlock(&tidhash_lock); 1043 LIST_INSERT_HEAD(TIDHASH(td->td_tid), td, td_hash); 1044 rw_wunlock(&tidhash_lock); 1045 } 1046 1047 void 1048 tidhash_remove(struct thread *td) 1049 { 1050 rw_wlock(&tidhash_lock); 1051 LIST_REMOVE(td, td_hash); 1052 rw_wunlock(&tidhash_lock); 1053 } 1054