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/resourcevar.h> 42 #include <sys/smp.h> 43 #include <sys/sysctl.h> 44 #include <sys/sched.h> 45 #include <sys/sleepqueue.h> 46 #include <sys/selinfo.h> 47 #include <sys/turnstile.h> 48 #include <sys/ktr.h> 49 #include <sys/rwlock.h> 50 #include <sys/umtx.h> 51 #include <sys/cpuset.h> 52 #ifdef HWPMC_HOOKS 53 #include <sys/pmckern.h> 54 #endif 55 56 #include <security/audit/audit.h> 57 58 #include <vm/vm.h> 59 #include <vm/vm_extern.h> 60 #include <vm/uma.h> 61 #include <sys/eventhandler.h> 62 63 /* 64 * thread related storage. 65 */ 66 static uma_zone_t thread_zone; 67 68 SYSCTL_NODE(_kern, OID_AUTO, threads, CTLFLAG_RW, 0, "thread allocation"); 69 70 int max_threads_per_proc = 1500; 71 SYSCTL_INT(_kern_threads, OID_AUTO, max_threads_per_proc, CTLFLAG_RW, 72 &max_threads_per_proc, 0, "Limit on threads per proc"); 73 74 int max_threads_hits; 75 SYSCTL_INT(_kern_threads, OID_AUTO, max_threads_hits, CTLFLAG_RD, 76 &max_threads_hits, 0, ""); 77 78 TAILQ_HEAD(, thread) zombie_threads = TAILQ_HEAD_INITIALIZER(zombie_threads); 79 static struct mtx zombie_lock; 80 MTX_SYSINIT(zombie_lock, &zombie_lock, "zombie lock", MTX_SPIN); 81 82 static void thread_zombie(struct thread *); 83 84 #define TID_BUFFER_SIZE 1024 85 86 struct mtx tid_lock; 87 static struct unrhdr *tid_unrhdr; 88 static lwpid_t tid_buffer[TID_BUFFER_SIZE]; 89 static int tid_head, tid_tail; 90 static MALLOC_DEFINE(M_TIDHASH, "tidhash", "thread hash"); 91 92 struct tidhashhead *tidhashtbl; 93 u_long tidhash; 94 struct rwlock tidhash_lock; 95 96 static lwpid_t 97 tid_alloc(void) 98 { 99 lwpid_t tid; 100 101 tid = alloc_unr(tid_unrhdr); 102 if (tid != -1) 103 return (tid); 104 mtx_lock(&tid_lock); 105 if (tid_head == tid_tail) { 106 mtx_unlock(&tid_lock); 107 return (-1); 108 } 109 tid = tid_buffer[tid_head++]; 110 tid_head %= TID_BUFFER_SIZE; 111 mtx_unlock(&tid_lock); 112 return (tid); 113 } 114 115 static void 116 tid_free(lwpid_t tid) 117 { 118 lwpid_t tmp_tid = -1; 119 120 mtx_lock(&tid_lock); 121 if ((tid_tail + 1) % TID_BUFFER_SIZE == tid_head) { 122 tmp_tid = tid_buffer[tid_head++]; 123 tid_head = (tid_head + 1) % TID_BUFFER_SIZE; 124 } 125 tid_buffer[tid_tail++] = tid; 126 tid_tail %= TID_BUFFER_SIZE; 127 mtx_unlock(&tid_lock); 128 if (tmp_tid != -1) 129 free_unr(tid_unrhdr, tmp_tid); 130 } 131 132 /* 133 * Prepare a thread for use. 134 */ 135 static int 136 thread_ctor(void *mem, int size, void *arg, int flags) 137 { 138 struct thread *td; 139 140 td = (struct thread *)mem; 141 td->td_state = TDS_INACTIVE; 142 td->td_oncpu = NOCPU; 143 144 td->td_tid = tid_alloc(); 145 146 /* 147 * Note that td_critnest begins life as 1 because the thread is not 148 * running and is thereby implicitly waiting to be on the receiving 149 * end of a context switch. 150 */ 151 td->td_critnest = 1; 152 td->td_lend_user_pri = PRI_MAX; 153 EVENTHANDLER_INVOKE(thread_ctor, td); 154 #ifdef AUDIT 155 audit_thread_alloc(td); 156 #endif 157 umtx_thread_alloc(td); 158 return (0); 159 } 160 161 /* 162 * Reclaim a thread after use. 163 */ 164 static void 165 thread_dtor(void *mem, int size, void *arg) 166 { 167 struct thread *td; 168 169 td = (struct thread *)mem; 170 171 #ifdef INVARIANTS 172 /* Verify that this thread is in a safe state to free. */ 173 switch (td->td_state) { 174 case TDS_INHIBITED: 175 case TDS_RUNNING: 176 case TDS_CAN_RUN: 177 case TDS_RUNQ: 178 /* 179 * We must never unlink a thread that is in one of 180 * these states, because it is currently active. 181 */ 182 panic("bad state for thread unlinking"); 183 /* NOTREACHED */ 184 case TDS_INACTIVE: 185 break; 186 default: 187 panic("bad thread state"); 188 /* NOTREACHED */ 189 } 190 #endif 191 #ifdef AUDIT 192 audit_thread_free(td); 193 #endif 194 /* Free all OSD associated to this thread. */ 195 osd_thread_exit(td); 196 197 EVENTHANDLER_INVOKE(thread_dtor, td); 198 tid_free(td->td_tid); 199 } 200 201 /* 202 * Initialize type-stable parts of a thread (when newly created). 203 */ 204 static int 205 thread_init(void *mem, int size, int flags) 206 { 207 struct thread *td; 208 209 td = (struct thread *)mem; 210 211 td->td_sleepqueue = sleepq_alloc(); 212 td->td_turnstile = turnstile_alloc(); 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 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 turnstile_free(td->td_turnstile); 231 sleepq_free(td->td_sleepqueue); 232 umtx_thread_fini(td); 233 seltdfini(td); 234 } 235 236 /* 237 * For a newly created process, 238 * link up all the structures and its initial threads etc. 239 * called from: 240 * {arch}/{arch}/machdep.c ia64_init(), init386() etc. 241 * proc_dtor() (should go away) 242 * proc_init() 243 */ 244 void 245 proc_linkup0(struct proc *p, struct thread *td) 246 { 247 TAILQ_INIT(&p->p_threads); /* all threads in proc */ 248 proc_linkup(p, td); 249 } 250 251 void 252 proc_linkup(struct proc *p, struct thread *td) 253 { 254 255 sigqueue_init(&p->p_sigqueue, p); 256 p->p_ksi = ksiginfo_alloc(1); 257 if (p->p_ksi != NULL) { 258 /* XXX p_ksi may be null if ksiginfo zone is not ready */ 259 p->p_ksi->ksi_flags = KSI_EXT | KSI_INS; 260 } 261 LIST_INIT(&p->p_mqnotifier); 262 p->p_numthreads = 0; 263 thread_link(td, p); 264 } 265 266 /* 267 * Initialize global thread allocation resources. 268 */ 269 void 270 threadinit(void) 271 { 272 273 mtx_init(&tid_lock, "TID lock", NULL, MTX_DEF); 274 /* leave one number for thread0 */ 275 tid_unrhdr = new_unrhdr(PID_MAX + 2, INT_MAX, &tid_lock); 276 277 thread_zone = uma_zcreate("THREAD", sched_sizeof_thread(), 278 thread_ctor, thread_dtor, thread_init, thread_fini, 279 16 - 1, 0); 280 tidhashtbl = hashinit(maxproc / 2, M_TIDHASH, &tidhash); 281 rw_init(&tidhash_lock, "tidhash"); 282 } 283 284 /* 285 * Place an unused thread on the zombie list. 286 * Use the slpq as that must be unused by now. 287 */ 288 void 289 thread_zombie(struct thread *td) 290 { 291 mtx_lock_spin(&zombie_lock); 292 TAILQ_INSERT_HEAD(&zombie_threads, td, td_slpq); 293 mtx_unlock_spin(&zombie_lock); 294 } 295 296 /* 297 * Release a thread that has exited after cpu_throw(). 298 */ 299 void 300 thread_stash(struct thread *td) 301 { 302 atomic_subtract_rel_int(&td->td_proc->p_exitthreads, 1); 303 thread_zombie(td); 304 } 305 306 /* 307 * Reap zombie resources. 308 */ 309 void 310 thread_reap(void) 311 { 312 struct thread *td_first, *td_next; 313 314 /* 315 * Don't even bother to lock if none at this instant, 316 * we really don't care about the next instant.. 317 */ 318 if (!TAILQ_EMPTY(&zombie_threads)) { 319 mtx_lock_spin(&zombie_lock); 320 td_first = TAILQ_FIRST(&zombie_threads); 321 if (td_first) 322 TAILQ_INIT(&zombie_threads); 323 mtx_unlock_spin(&zombie_lock); 324 while (td_first) { 325 td_next = TAILQ_NEXT(td_first, td_slpq); 326 if (td_first->td_ucred) 327 crfree(td_first->td_ucred); 328 thread_free(td_first); 329 td_first = td_next; 330 } 331 } 332 } 333 334 /* 335 * Allocate a thread. 336 */ 337 struct thread * 338 thread_alloc(int pages) 339 { 340 struct thread *td; 341 342 thread_reap(); /* check if any zombies to get */ 343 344 td = (struct thread *)uma_zalloc(thread_zone, M_WAITOK); 345 KASSERT(td->td_kstack == 0, ("thread_alloc got thread with kstack")); 346 if (!vm_thread_new(td, pages)) { 347 uma_zfree(thread_zone, td); 348 return (NULL); 349 } 350 cpu_thread_alloc(td); 351 return (td); 352 } 353 354 int 355 thread_alloc_stack(struct thread *td, int pages) 356 { 357 358 KASSERT(td->td_kstack == 0, 359 ("thread_alloc_stack called on a thread with kstack")); 360 if (!vm_thread_new(td, pages)) 361 return (0); 362 cpu_thread_alloc(td); 363 return (1); 364 } 365 366 /* 367 * Deallocate a thread. 368 */ 369 void 370 thread_free(struct thread *td) 371 { 372 373 lock_profile_thread_exit(td); 374 if (td->td_cpuset) 375 cpuset_rel(td->td_cpuset); 376 td->td_cpuset = NULL; 377 cpu_thread_free(td); 378 if (td->td_kstack != 0) 379 vm_thread_dispose(td); 380 uma_zfree(thread_zone, td); 381 } 382 383 /* 384 * Discard the current thread and exit from its context. 385 * Always called with scheduler locked. 386 * 387 * Because we can't free a thread while we're operating under its context, 388 * push the current thread into our CPU's deadthread holder. This means 389 * we needn't worry about someone else grabbing our context before we 390 * do a cpu_throw(). 391 */ 392 void 393 thread_exit(void) 394 { 395 uint64_t new_switchtime; 396 struct thread *td; 397 struct thread *td2; 398 struct proc *p; 399 int wakeup_swapper; 400 401 td = curthread; 402 p = td->td_proc; 403 404 PROC_SLOCK_ASSERT(p, MA_OWNED); 405 mtx_assert(&Giant, MA_NOTOWNED); 406 407 PROC_LOCK_ASSERT(p, MA_OWNED); 408 KASSERT(p != NULL, ("thread exiting without a process")); 409 CTR3(KTR_PROC, "thread_exit: thread %p (pid %ld, %s)", td, 410 (long)p->p_pid, td->td_name); 411 KASSERT(TAILQ_EMPTY(&td->td_sigqueue.sq_list), ("signal pending")); 412 413 #ifdef AUDIT 414 AUDIT_SYSCALL_EXIT(0, td); 415 #endif 416 umtx_thread_exit(td); 417 /* 418 * drop FPU & debug register state storage, or any other 419 * architecture specific resources that 420 * would not be on a new untouched process. 421 */ 422 cpu_thread_exit(td); /* XXXSMP */ 423 424 /* Do the same timestamp bookkeeping that mi_switch() would do. */ 425 new_switchtime = cpu_ticks(); 426 p->p_rux.rux_runtime += (new_switchtime - PCPU_GET(switchtime)); 427 PCPU_SET(switchtime, new_switchtime); 428 PCPU_SET(switchticks, ticks); 429 PCPU_INC(cnt.v_swtch); 430 /* Save our resource usage in our process. */ 431 td->td_ru.ru_nvcsw++; 432 rucollect(&p->p_ru, &td->td_ru); 433 /* 434 * The last thread is left attached to the process 435 * So that the whole bundle gets recycled. Skip 436 * all this stuff if we never had threads. 437 * EXIT clears all sign of other threads when 438 * it goes to single threading, so the last thread always 439 * takes the short path. 440 */ 441 if (p->p_flag & P_HADTHREADS) { 442 if (p->p_numthreads > 1) { 443 thread_unlink(td); 444 td2 = FIRST_THREAD_IN_PROC(p); 445 sched_exit_thread(td2, td); 446 447 /* 448 * The test below is NOT true if we are the 449 * sole exiting thread. P_STOPPED_SINGLE is unset 450 * in exit1() after it is the only survivor. 451 */ 452 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) { 453 if (p->p_numthreads == p->p_suspcount) { 454 thread_lock(p->p_singlethread); 455 wakeup_swapper = thread_unsuspend_one( 456 p->p_singlethread); 457 thread_unlock(p->p_singlethread); 458 if (wakeup_swapper) 459 kick_proc0(); 460 } 461 } 462 463 atomic_add_int(&td->td_proc->p_exitthreads, 1); 464 PCPU_SET(deadthread, td); 465 } else { 466 /* 467 * The last thread is exiting.. but not through exit() 468 */ 469 panic ("thread_exit: Last thread exiting on its own"); 470 } 471 } 472 #ifdef HWPMC_HOOKS 473 /* 474 * If this thread is part of a process that is being tracked by hwpmc(4), 475 * inform the module of the thread's impending exit. 476 */ 477 if (PMC_PROC_IS_USING_PMCS(td->td_proc)) 478 PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_OUT); 479 #endif 480 PROC_UNLOCK(p); 481 ruxagg(p, td); 482 thread_lock(td); 483 PROC_SUNLOCK(p); 484 td->td_state = TDS_INACTIVE; 485 #ifdef WITNESS 486 witness_thread_exit(td); 487 #endif 488 CTR1(KTR_PROC, "thread_exit: cpu_throw() thread %p", td); 489 sched_throw(td); 490 panic("I'm a teapot!"); 491 /* NOTREACHED */ 492 } 493 494 /* 495 * Do any thread specific cleanups that may be needed in wait() 496 * called with Giant, proc and schedlock not held. 497 */ 498 void 499 thread_wait(struct proc *p) 500 { 501 struct thread *td; 502 503 mtx_assert(&Giant, MA_NOTOWNED); 504 KASSERT((p->p_numthreads == 1), ("Multiple threads in wait1()")); 505 td = FIRST_THREAD_IN_PROC(p); 506 /* Lock the last thread so we spin until it exits cpu_throw(). */ 507 thread_lock(td); 508 thread_unlock(td); 509 /* Wait for any remaining threads to exit cpu_throw(). */ 510 while (p->p_exitthreads) 511 sched_relinquish(curthread); 512 lock_profile_thread_exit(td); 513 cpuset_rel(td->td_cpuset); 514 td->td_cpuset = NULL; 515 cpu_thread_clean(td); 516 crfree(td->td_ucred); 517 thread_reap(); /* check for zombie threads etc. */ 518 } 519 520 /* 521 * Link a thread to a process. 522 * set up anything that needs to be initialized for it to 523 * be used by the process. 524 */ 525 void 526 thread_link(struct thread *td, struct proc *p) 527 { 528 529 /* 530 * XXX This can't be enabled because it's called for proc0 before 531 * its lock has been created. 532 * PROC_LOCK_ASSERT(p, MA_OWNED); 533 */ 534 td->td_state = TDS_INACTIVE; 535 td->td_proc = p; 536 td->td_flags = TDF_INMEM; 537 538 LIST_INIT(&td->td_contested); 539 LIST_INIT(&td->td_lprof[0]); 540 LIST_INIT(&td->td_lprof[1]); 541 sigqueue_init(&td->td_sigqueue, p); 542 callout_init(&td->td_slpcallout, CALLOUT_MPSAFE); 543 TAILQ_INSERT_HEAD(&p->p_threads, td, td_plist); 544 p->p_numthreads++; 545 } 546 547 /* 548 * Convert a process with one thread to an unthreaded process. 549 */ 550 void 551 thread_unthread(struct thread *td) 552 { 553 struct proc *p = td->td_proc; 554 555 KASSERT((p->p_numthreads == 1), ("Unthreading with >1 threads")); 556 p->p_flag &= ~P_HADTHREADS; 557 } 558 559 /* 560 * Called from: 561 * thread_exit() 562 */ 563 void 564 thread_unlink(struct thread *td) 565 { 566 struct proc *p = td->td_proc; 567 568 PROC_LOCK_ASSERT(p, MA_OWNED); 569 TAILQ_REMOVE(&p->p_threads, td, td_plist); 570 p->p_numthreads--; 571 /* could clear a few other things here */ 572 /* Must NOT clear links to proc! */ 573 } 574 575 static int 576 calc_remaining(struct proc *p, int mode) 577 { 578 int remaining; 579 580 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) 585 remaining = p->p_numthreads - p->p_suspcount; 586 else 587 panic("calc_remaining: wrong mode %d", mode); 588 return (remaining); 589 } 590 591 /* 592 * Enforce single-threading. 593 * 594 * Returns 1 if the caller must abort (another thread is waiting to 595 * exit the process or similar). Process is locked! 596 * Returns 0 when you are successfully the only thread running. 597 * A process has successfully single threaded in the suspend mode when 598 * There are no threads in user mode. Threads in the kernel must be 599 * allowed to continue until they get to the user boundary. They may even 600 * copy out their return values and data before suspending. They may however be 601 * accelerated in reaching the user boundary as we will wake up 602 * any sleeping threads that are interruptable. (PCATCH). 603 */ 604 int 605 thread_single(int mode) 606 { 607 struct thread *td; 608 struct thread *td2; 609 struct proc *p; 610 int remaining, wakeup_swapper; 611 612 td = curthread; 613 p = td->td_proc; 614 mtx_assert(&Giant, MA_NOTOWNED); 615 PROC_LOCK_ASSERT(p, MA_OWNED); 616 KASSERT((td != NULL), ("curthread is NULL")); 617 618 if ((p->p_flag & P_HADTHREADS) == 0) 619 return (0); 620 621 /* Is someone already single threading? */ 622 if (p->p_singlethread != NULL && p->p_singlethread != td) 623 return (1); 624 625 if (mode == SINGLE_EXIT) { 626 p->p_flag |= P_SINGLE_EXIT; 627 p->p_flag &= ~P_SINGLE_BOUNDARY; 628 } else { 629 p->p_flag &= ~P_SINGLE_EXIT; 630 if (mode == SINGLE_BOUNDARY) 631 p->p_flag |= P_SINGLE_BOUNDARY; 632 else 633 p->p_flag &= ~P_SINGLE_BOUNDARY; 634 } 635 p->p_flag |= P_STOPPED_SINGLE; 636 PROC_SLOCK(p); 637 p->p_singlethread = td; 638 remaining = calc_remaining(p, mode); 639 while (remaining != 1) { 640 if (P_SHOULDSTOP(p) != P_STOPPED_SINGLE) 641 goto stopme; 642 wakeup_swapper = 0; 643 FOREACH_THREAD_IN_PROC(p, td2) { 644 if (td2 == td) 645 continue; 646 thread_lock(td2); 647 td2->td_flags |= TDF_ASTPENDING | TDF_NEEDSUSPCHK; 648 if (TD_IS_INHIBITED(td2)) { 649 switch (mode) { 650 case SINGLE_EXIT: 651 if (TD_IS_SUSPENDED(td2)) 652 wakeup_swapper |= 653 thread_unsuspend_one(td2); 654 if (TD_ON_SLEEPQ(td2) && 655 (td2->td_flags & TDF_SINTR)) 656 wakeup_swapper |= 657 sleepq_abort(td2, EINTR); 658 break; 659 case SINGLE_BOUNDARY: 660 if (TD_IS_SUSPENDED(td2) && 661 !(td2->td_flags & TDF_BOUNDARY)) 662 wakeup_swapper |= 663 thread_unsuspend_one(td2); 664 if (TD_ON_SLEEPQ(td2) && 665 (td2->td_flags & TDF_SINTR)) 666 wakeup_swapper |= 667 sleepq_abort(td2, ERESTART); 668 break; 669 case SINGLE_NO_EXIT: 670 if (TD_IS_SUSPENDED(td2) && 671 !(td2->td_flags & TDF_BOUNDARY)) 672 wakeup_swapper |= 673 thread_unsuspend_one(td2); 674 if (TD_ON_SLEEPQ(td2) && 675 (td2->td_flags & TDF_SINTR)) 676 wakeup_swapper |= 677 sleepq_abort(td2, ERESTART); 678 break; 679 default: 680 break; 681 } 682 } 683 #ifdef SMP 684 else if (TD_IS_RUNNING(td2) && td != td2) { 685 forward_signal(td2); 686 } 687 #endif 688 thread_unlock(td2); 689 } 690 if (wakeup_swapper) 691 kick_proc0(); 692 remaining = calc_remaining(p, mode); 693 694 /* 695 * Maybe we suspended some threads.. was it enough? 696 */ 697 if (remaining == 1) 698 break; 699 700 stopme: 701 /* 702 * Wake us up when everyone else has suspended. 703 * In the mean time we suspend as well. 704 */ 705 thread_suspend_switch(td); 706 remaining = calc_remaining(p, mode); 707 } 708 if (mode == SINGLE_EXIT) { 709 /* 710 * We have gotten rid of all the other threads and we 711 * are about to either exit or exec. In either case, 712 * we try our utmost to revert to being a non-threaded 713 * process. 714 */ 715 p->p_singlethread = NULL; 716 p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT); 717 thread_unthread(td); 718 } 719 PROC_SUNLOCK(p); 720 return (0); 721 } 722 723 /* 724 * Called in from locations that can safely check to see 725 * whether we have to suspend or at least throttle for a 726 * single-thread event (e.g. fork). 727 * 728 * Such locations include userret(). 729 * If the "return_instead" argument is non zero, the thread must be able to 730 * accept 0 (caller may continue), or 1 (caller must abort) as a result. 731 * 732 * The 'return_instead' argument tells the function if it may do a 733 * thread_exit() or suspend, or whether the caller must abort and back 734 * out instead. 735 * 736 * If the thread that set the single_threading request has set the 737 * P_SINGLE_EXIT bit in the process flags then this call will never return 738 * if 'return_instead' is false, but will exit. 739 * 740 * P_SINGLE_EXIT | return_instead == 0| return_instead != 0 741 *---------------+--------------------+--------------------- 742 * 0 | returns 0 | returns 0 or 1 743 * | when ST ends | immediatly 744 *---------------+--------------------+--------------------- 745 * 1 | thread exits | returns 1 746 * | | immediatly 747 * 0 = thread_exit() or suspension ok, 748 * other = return error instead of stopping the thread. 749 * 750 * While a full suspension is under effect, even a single threading 751 * thread would be suspended if it made this call (but it shouldn't). 752 * This call should only be made from places where 753 * thread_exit() would be safe as that may be the outcome unless 754 * return_instead is set. 755 */ 756 int 757 thread_suspend_check(int return_instead) 758 { 759 struct thread *td; 760 struct proc *p; 761 int wakeup_swapper; 762 763 td = curthread; 764 p = td->td_proc; 765 mtx_assert(&Giant, MA_NOTOWNED); 766 PROC_LOCK_ASSERT(p, MA_OWNED); 767 while (P_SHOULDSTOP(p) || 768 ((p->p_flag & P_TRACED) && (td->td_dbgflags & TDB_SUSPEND))) { 769 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) { 770 KASSERT(p->p_singlethread != NULL, 771 ("singlethread not set")); 772 /* 773 * The only suspension in action is a 774 * single-threading. Single threader need not stop. 775 * XXX Should be safe to access unlocked 776 * as it can only be set to be true by us. 777 */ 778 if (p->p_singlethread == td) 779 return (0); /* Exempt from stopping. */ 780 } 781 if ((p->p_flag & P_SINGLE_EXIT) && return_instead) 782 return (EINTR); 783 784 /* Should we goto user boundary if we didn't come from there? */ 785 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE && 786 (p->p_flag & P_SINGLE_BOUNDARY) && return_instead) 787 return (ERESTART); 788 789 /* 790 * If the process is waiting for us to exit, 791 * this thread should just suicide. 792 * Assumes that P_SINGLE_EXIT implies P_STOPPED_SINGLE. 793 */ 794 if ((p->p_flag & P_SINGLE_EXIT) && (p->p_singlethread != td)) { 795 PROC_UNLOCK(p); 796 tidhash_remove(td); 797 PROC_LOCK(p); 798 tdsigcleanup(td); 799 PROC_SLOCK(p); 800 thread_stopped(p); 801 thread_exit(); 802 } 803 804 PROC_SLOCK(p); 805 thread_stopped(p); 806 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) { 807 if (p->p_numthreads == p->p_suspcount + 1) { 808 thread_lock(p->p_singlethread); 809 wakeup_swapper = 810 thread_unsuspend_one(p->p_singlethread); 811 thread_unlock(p->p_singlethread); 812 if (wakeup_swapper) 813 kick_proc0(); 814 } 815 } 816 PROC_UNLOCK(p); 817 thread_lock(td); 818 /* 819 * When a thread suspends, it just 820 * gets taken off all queues. 821 */ 822 thread_suspend_one(td); 823 if (return_instead == 0) { 824 p->p_boundary_count++; 825 td->td_flags |= TDF_BOUNDARY; 826 } 827 PROC_SUNLOCK(p); 828 mi_switch(SW_INVOL | SWT_SUSPEND, NULL); 829 if (return_instead == 0) 830 td->td_flags &= ~TDF_BOUNDARY; 831 thread_unlock(td); 832 PROC_LOCK(p); 833 if (return_instead == 0) 834 p->p_boundary_count--; 835 } 836 return (0); 837 } 838 839 void 840 thread_suspend_switch(struct thread *td) 841 { 842 struct proc *p; 843 844 p = td->td_proc; 845 KASSERT(!TD_IS_SUSPENDED(td), ("already suspended")); 846 PROC_LOCK_ASSERT(p, MA_OWNED); 847 PROC_SLOCK_ASSERT(p, MA_OWNED); 848 /* 849 * We implement thread_suspend_one in stages here to avoid 850 * dropping the proc lock while the thread lock is owned. 851 */ 852 thread_stopped(p); 853 p->p_suspcount++; 854 PROC_UNLOCK(p); 855 thread_lock(td); 856 td->td_flags &= ~TDF_NEEDSUSPCHK; 857 TD_SET_SUSPENDED(td); 858 sched_sleep(td, 0); 859 PROC_SUNLOCK(p); 860 DROP_GIANT(); 861 mi_switch(SW_VOL | SWT_SUSPEND, NULL); 862 thread_unlock(td); 863 PICKUP_GIANT(); 864 PROC_LOCK(p); 865 PROC_SLOCK(p); 866 } 867 868 void 869 thread_suspend_one(struct thread *td) 870 { 871 struct proc *p = td->td_proc; 872 873 PROC_SLOCK_ASSERT(p, MA_OWNED); 874 THREAD_LOCK_ASSERT(td, MA_OWNED); 875 KASSERT(!TD_IS_SUSPENDED(td), ("already suspended")); 876 p->p_suspcount++; 877 td->td_flags &= ~TDF_NEEDSUSPCHK; 878 TD_SET_SUSPENDED(td); 879 sched_sleep(td, 0); 880 } 881 882 int 883 thread_unsuspend_one(struct thread *td) 884 { 885 struct proc *p = td->td_proc; 886 887 PROC_SLOCK_ASSERT(p, MA_OWNED); 888 THREAD_LOCK_ASSERT(td, MA_OWNED); 889 KASSERT(TD_IS_SUSPENDED(td), ("Thread not suspended")); 890 TD_CLR_SUSPENDED(td); 891 p->p_suspcount--; 892 return (setrunnable(td)); 893 } 894 895 /* 896 * Allow all threads blocked by single threading to continue running. 897 */ 898 void 899 thread_unsuspend(struct proc *p) 900 { 901 struct thread *td; 902 int wakeup_swapper; 903 904 PROC_LOCK_ASSERT(p, MA_OWNED); 905 PROC_SLOCK_ASSERT(p, MA_OWNED); 906 wakeup_swapper = 0; 907 if (!P_SHOULDSTOP(p)) { 908 FOREACH_THREAD_IN_PROC(p, td) { 909 thread_lock(td); 910 if (TD_IS_SUSPENDED(td)) { 911 wakeup_swapper |= thread_unsuspend_one(td); 912 } 913 thread_unlock(td); 914 } 915 } else if ((P_SHOULDSTOP(p) == P_STOPPED_SINGLE) && 916 (p->p_numthreads == p->p_suspcount)) { 917 /* 918 * Stopping everything also did the job for the single 919 * threading request. Now we've downgraded to single-threaded, 920 * let it continue. 921 */ 922 thread_lock(p->p_singlethread); 923 wakeup_swapper = thread_unsuspend_one(p->p_singlethread); 924 thread_unlock(p->p_singlethread); 925 } 926 if (wakeup_swapper) 927 kick_proc0(); 928 } 929 930 /* 931 * End the single threading mode.. 932 */ 933 void 934 thread_single_end(void) 935 { 936 struct thread *td; 937 struct proc *p; 938 int wakeup_swapper; 939 940 td = curthread; 941 p = td->td_proc; 942 PROC_LOCK_ASSERT(p, MA_OWNED); 943 p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT | P_SINGLE_BOUNDARY); 944 PROC_SLOCK(p); 945 p->p_singlethread = NULL; 946 wakeup_swapper = 0; 947 /* 948 * If there are other threads they may now run, 949 * unless of course there is a blanket 'stop order' 950 * on the process. The single threader must be allowed 951 * to continue however as this is a bad place to stop. 952 */ 953 if ((p->p_numthreads != 1) && (!P_SHOULDSTOP(p))) { 954 FOREACH_THREAD_IN_PROC(p, td) { 955 thread_lock(td); 956 if (TD_IS_SUSPENDED(td)) { 957 wakeup_swapper |= thread_unsuspend_one(td); 958 } 959 thread_unlock(td); 960 } 961 } 962 PROC_SUNLOCK(p); 963 if (wakeup_swapper) 964 kick_proc0(); 965 } 966 967 struct thread * 968 thread_find(struct proc *p, lwpid_t tid) 969 { 970 struct thread *td; 971 972 PROC_LOCK_ASSERT(p, MA_OWNED); 973 FOREACH_THREAD_IN_PROC(p, td) { 974 if (td->td_tid == tid) 975 break; 976 } 977 return (td); 978 } 979 980 /* Locate a thread by number; return with proc lock held. */ 981 struct thread * 982 tdfind(lwpid_t tid, pid_t pid) 983 { 984 #define RUN_THRESH 16 985 struct thread *td; 986 int run = 0; 987 988 rw_rlock(&tidhash_lock); 989 LIST_FOREACH(td, TIDHASH(tid), td_hash) { 990 if (td->td_tid == tid) { 991 if (pid != -1 && td->td_proc->p_pid != pid) { 992 td = NULL; 993 break; 994 } 995 if (td->td_proc->p_state == PRS_NEW) { 996 td = NULL; 997 break; 998 } 999 if (run > RUN_THRESH) { 1000 if (rw_try_upgrade(&tidhash_lock)) { 1001 LIST_REMOVE(td, td_hash); 1002 LIST_INSERT_HEAD(TIDHASH(td->td_tid), 1003 td, td_hash); 1004 PROC_LOCK(td->td_proc); 1005 rw_wunlock(&tidhash_lock); 1006 return (td); 1007 } 1008 } 1009 PROC_LOCK(td->td_proc); 1010 break; 1011 } 1012 run++; 1013 } 1014 rw_runlock(&tidhash_lock); 1015 return (td); 1016 } 1017 1018 void 1019 tidhash_add(struct thread *td) 1020 { 1021 rw_wlock(&tidhash_lock); 1022 LIST_INSERT_HEAD(TIDHASH(td->td_tid), td, td_hash); 1023 rw_wunlock(&tidhash_lock); 1024 } 1025 1026 void 1027 tidhash_remove(struct thread *td) 1028 { 1029 rw_wlock(&tidhash_lock); 1030 LIST_REMOVE(td, td_hash); 1031 rw_wunlock(&tidhash_lock); 1032 } 1033