kern_thread.c revision 103055
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 * $FreeBSD: head/sys/kern/kern_thread.c 103055 2002-09-07 01:48:53Z julian $ 29 */ 30 31#include <sys/param.h> 32#include <sys/systm.h> 33#include <sys/kernel.h> 34#include <sys/lock.h> 35#include <sys/malloc.h> 36#include <sys/mutex.h> 37#include <sys/proc.h> 38#include <sys/sysctl.h> 39#include <sys/filedesc.h> 40#include <sys/tty.h> 41#include <sys/signalvar.h> 42#include <sys/sx.h> 43#include <sys/user.h> 44#include <sys/jail.h> 45#include <sys/kse.h> 46#include <sys/ktr.h> 47 48#include <vm/vm.h> 49#include <vm/vm_object.h> 50#include <vm/pmap.h> 51#include <vm/uma.h> 52#include <vm/vm_map.h> 53 54#include <machine/frame.h> 55 56/* 57 * Thread related storage. 58 */ 59static uma_zone_t thread_zone; 60static int allocated_threads; 61static int active_threads; 62static int cached_threads; 63 64SYSCTL_NODE(_kern, OID_AUTO, threads, CTLFLAG_RW, 0, "thread allocation"); 65 66SYSCTL_INT(_kern_threads, OID_AUTO, active, CTLFLAG_RD, 67 &active_threads, 0, "Number of active threads in system."); 68 69SYSCTL_INT(_kern_threads, OID_AUTO, cached, CTLFLAG_RD, 70 &cached_threads, 0, "Number of threads in thread cache."); 71 72SYSCTL_INT(_kern_threads, OID_AUTO, allocated, CTLFLAG_RD, 73 &allocated_threads, 0, "Number of threads in zone."); 74 75static int oiks_debug = 1; /* 0 disable, 1 printf, 2 enter debugger */ 76SYSCTL_INT(_kern_threads, OID_AUTO, oiks, CTLFLAG_RW, 77 &oiks_debug, 0, "OIKS thread debug"); 78 79#define RANGEOF(type, start, end) (offsetof(type, end) - offsetof(type, start)) 80 81struct threadqueue zombie_threads = TAILQ_HEAD_INITIALIZER(zombie_threads); 82struct mtx zombie_thread_lock; 83MTX_SYSINIT(zombie_thread_lock, &zombie_thread_lock, 84 "zombie_thread_lock", MTX_SPIN); 85 86/* 87 * Pepare a thread for use. 88 */ 89static void 90thread_ctor(void *mem, int size, void *arg) 91{ 92 struct thread *td; 93 94 KASSERT((size == sizeof(struct thread)), 95 ("size mismatch: %d != %d\n", size, (int)sizeof(struct thread))); 96 97 td = (struct thread *)mem; 98 td->td_state = TDS_NEW; 99 td->td_flags |= TDF_UNBOUND; 100 cached_threads--; /* XXXSMP */ 101 active_threads++; /* XXXSMP */ 102} 103 104/* 105 * Reclaim a thread after use. 106 */ 107static void 108thread_dtor(void *mem, int size, void *arg) 109{ 110 struct thread *td; 111 112 KASSERT((size == sizeof(struct thread)), 113 ("size mismatch: %d != %d\n", size, (int)sizeof(struct thread))); 114 115 td = (struct thread *)mem; 116 117#ifdef INVARIANTS 118 /* Verify that this thread is in a safe state to free. */ 119 switch (td->td_state) { 120 case TDS_SLP: 121 case TDS_MTX: 122 case TDS_RUNQ: 123 /* 124 * We must never unlink a thread that is in one of 125 * these states, because it is currently active. 126 */ 127 panic("bad state for thread unlinking"); 128 /* NOTREACHED */ 129 case TDS_UNQUEUED: 130 case TDS_NEW: 131 case TDS_RUNNING: 132 case TDS_SURPLUS: 133 break; 134 default: 135 panic("bad thread state"); 136 /* NOTREACHED */ 137 } 138#endif 139 140 /* Update counters. */ 141 active_threads--; /* XXXSMP */ 142 cached_threads++; /* XXXSMP */ 143} 144 145/* 146 * Initialize type-stable parts of a thread (when newly created). 147 */ 148static void 149thread_init(void *mem, int size) 150{ 151 struct thread *td; 152 153 KASSERT((size == sizeof(struct thread)), 154 ("size mismatch: %d != %d\n", size, (int)sizeof(struct thread))); 155 156 td = (struct thread *)mem; 157 pmap_new_thread(td); 158 cpu_thread_setup(td); 159 cached_threads++; /* XXXSMP */ 160 allocated_threads++; /* XXXSMP */ 161} 162 163/* 164 * Tear down type-stable parts of a thread (just before being discarded). 165 */ 166static void 167thread_fini(void *mem, int size) 168{ 169 struct thread *td; 170 171 KASSERT((size == sizeof(struct thread)), 172 ("size mismatch: %d != %d\n", size, (int)sizeof(struct thread))); 173 174 td = (struct thread *)mem; 175 pmap_dispose_thread(td); 176 cached_threads--; /* XXXSMP */ 177 allocated_threads--; /* XXXSMP */ 178} 179 180/* 181 * Initialize global thread allocation resources. 182 */ 183void 184threadinit(void) 185{ 186 187 thread_zone = uma_zcreate("THREAD", sizeof (struct thread), 188 thread_ctor, thread_dtor, thread_init, thread_fini, 189 UMA_ALIGN_CACHE, 0); 190} 191 192/* 193 * Stash an embarasingly extra thread into the zombie thread queue. 194 */ 195void 196thread_stash(struct thread *td) 197{ 198 mtx_lock_spin(&zombie_thread_lock); 199 TAILQ_INSERT_HEAD(&zombie_threads, td, td_runq); 200 mtx_unlock_spin(&zombie_thread_lock); 201} 202 203/* 204 * reap any zombie threads. 205 */ 206void 207thread_reap(void) 208{ 209 struct thread *td_reaped; 210 211 /* 212 * don't even bother to lock if none at this instant 213 * We really don't care about the next instant.. 214 */ 215 if (!TAILQ_EMPTY(&zombie_threads)) { 216 mtx_lock_spin(&zombie_thread_lock); 217 while (!TAILQ_EMPTY(&zombie_threads)) { 218 td_reaped = TAILQ_FIRST(&zombie_threads); 219 TAILQ_REMOVE(&zombie_threads, td_reaped, td_runq); 220 mtx_unlock_spin(&zombie_thread_lock); 221 thread_free(td_reaped); 222 mtx_lock_spin(&zombie_thread_lock); 223 } 224 mtx_unlock_spin(&zombie_thread_lock); 225 } 226} 227 228/* 229 * Allocate a thread. 230 */ 231struct thread * 232thread_alloc(void) 233{ 234 thread_reap(); /* check if any zombies to get */ 235 return (uma_zalloc(thread_zone, M_WAITOK)); 236} 237 238/* 239 * Deallocate a thread. 240 */ 241void 242thread_free(struct thread *td) 243{ 244 uma_zfree(thread_zone, td); 245} 246 247/* 248 * Store the thread context in the UTS's mailbox. 249 */ 250int 251thread_export_context(struct thread *td) 252{ 253 struct kse *ke; 254 uintptr_t td2_mbx; 255 void *addr1; 256 void *addr2; 257 int error; 258 259#ifdef __ia64__ 260 td2_mbx = 0; /* pacify gcc (!) */ 261#endif 262 /* Export the register contents. */ 263 error = cpu_export_context(td); 264 265 ke = td->td_kse; 266 addr1 = (caddr_t)ke->ke_mailbox 267 + offsetof(struct kse_mailbox, kmbx_completed_threads); 268 addr2 = (caddr_t)td->td_mailbox 269 + offsetof(struct thread_mailbox , next_completed); 270 /* Then link it into it's KSE's list of completed threads. */ 271 if (!error) { 272 error = td2_mbx = fuword(addr1); 273 if (error == -1) 274 error = EFAULT; 275 else 276 error = 0; 277 } 278 if (!error) 279 error = suword(addr2, td2_mbx); 280 if (!error) 281 error = suword(addr1, (u_long)td->td_mailbox); 282 if (error == -1) 283 error = EFAULT; 284 return (error); 285} 286 287 288/* 289 * Discard the current thread and exit from its context. 290 * 291 * Because we can't free a thread while we're operating under its context, 292 * push the current thread into our KSE's ke_tdspare slot, freeing the 293 * thread that might be there currently. Because we know that only this 294 * processor will run our KSE, we needn't worry about someone else grabbing 295 * our context before we do a cpu_throw. 296 */ 297void 298thread_exit(void) 299{ 300 struct thread *td; 301 struct kse *ke; 302 struct proc *p; 303 struct ksegrp *kg; 304 305 td = curthread; 306 kg = td->td_ksegrp; 307 p = td->td_proc; 308 ke = td->td_kse; 309 310 mtx_assert(&sched_lock, MA_OWNED); 311 KASSERT(p != NULL, ("thread exiting without a process")); 312 KASSERT(ke != NULL, ("thread exiting without a kse")); 313 KASSERT(kg != NULL, ("thread exiting without a kse group")); 314 PROC_LOCK_ASSERT(p, MA_OWNED); 315 CTR1(KTR_PROC, "thread_exit: thread %p", td); 316 KASSERT(!mtx_owned(&Giant), ("dying thread owns giant")); 317 318 if (ke->ke_tdspare != NULL) { 319 thread_free(ke->ke_tdspare); 320 ke->ke_tdspare = NULL; 321 } 322 cpu_thread_exit(td); /* XXXSMP */ 323 324 /* 325 * The last thread is left attached to the process 326 * So that the whole bundle gets recycled. Skip 327 * all this stuff. 328 */ 329 if (p->p_numthreads > 1) { 330 /* Reassign this thread's KSE. */ 331 ke->ke_thread = NULL; 332 td->td_kse = NULL; 333 ke->ke_state = KES_UNQUEUED; 334 kse_reassign(ke); 335 336 /* Unlink this thread from its proc. and the kseg */ 337 TAILQ_REMOVE(&p->p_threads, td, td_plist); 338 p->p_numthreads--; 339 TAILQ_REMOVE(&kg->kg_threads, td, td_kglist); 340 kg->kg_numthreads--; 341 /* 342 * The test below is NOT true if we are the 343 * sole exiting thread. P_STOPPED_SNGL is unset 344 * in exit1() after it is the only survivor. 345 */ 346 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) { 347 if (p->p_numthreads == p->p_suspcount) { 348 TAILQ_REMOVE(&p->p_suspended, 349 p->p_singlethread, td_runq); 350 setrunqueue(p->p_singlethread); 351 p->p_suspcount--; 352 } 353 } 354 PROC_UNLOCK(p); 355 td->td_state = TDS_SURPLUS; 356 td->td_proc = NULL; 357 td->td_ksegrp = NULL; 358 td->td_last_kse = NULL; 359 ke->ke_tdspare = td; 360 } else { 361 PROC_UNLOCK(p); 362 } 363 364 cpu_throw(); 365 /* NOTREACHED */ 366} 367 368/* 369 * Link a thread to a process. 370 * set up anything that needs to be initialized for it to 371 * be used by the process. 372 * 373 * Note that we do not link to the proc's ucred here. 374 * The thread is linked as if running but no KSE assigned. 375 */ 376void 377thread_link(struct thread *td, struct ksegrp *kg) 378{ 379 struct proc *p; 380 381 p = kg->kg_proc; 382 td->td_state = TDS_NEW; 383 td->td_proc = p; 384 td->td_ksegrp = kg; 385 td->td_last_kse = NULL; 386 387 LIST_INIT(&td->td_contested); 388 callout_init(&td->td_slpcallout, 1); 389 TAILQ_INSERT_HEAD(&p->p_threads, td, td_plist); 390 TAILQ_INSERT_HEAD(&kg->kg_threads, td, td_kglist); 391 p->p_numthreads++; 392 kg->kg_numthreads++; 393 if (oiks_debug && p->p_numthreads > 4) { 394 printf("OIKS %d\n", p->p_numthreads); 395 if (oiks_debug > 1) 396 Debugger("OIKS"); 397 } 398 td->td_kse = NULL; 399} 400 401/* 402 * Set up the upcall pcb in either a given thread or a new one 403 * if none given. Use the upcall for the given KSE 404 * XXXKSE possibly fix cpu_set_upcall() to not need td->td_kse set. 405 */ 406struct thread * 407thread_schedule_upcall(struct thread *td, struct kse *ke) 408{ 409 struct thread *td2; 410 411 mtx_assert(&sched_lock, MA_OWNED); 412 if (ke->ke_tdspare != NULL) { 413 td2 = ke->ke_tdspare; 414 ke->ke_tdspare = NULL; 415 } else { 416 mtx_unlock_spin(&sched_lock); 417 td2 = thread_alloc(); 418 mtx_lock_spin(&sched_lock); 419 } 420 CTR3(KTR_PROC, "thread_schedule_upcall: thread %p (pid %d, %s)", 421 td, td->td_proc->p_pid, td->td_proc->p_comm); 422 bzero(&td->td_startzero, 423 (unsigned)RANGEOF(struct thread, td_startzero, td_endzero)); 424 bcopy(&td->td_startcopy, &td2->td_startcopy, 425 (unsigned) RANGEOF(struct thread, td_startcopy, td_endcopy)); 426 thread_link(td2, ke->ke_ksegrp); 427 cpu_set_upcall(td2, ke->ke_pcb); 428 td2->td_ucred = crhold(td->td_ucred); 429 td2->td_flags = TDF_UNBOUND|TDF_UPCALLING; 430 setrunqueue(td2); 431 return (td2); 432} 433 434/* 435 * The extra work we go through if we are a threaded process when we 436 * return to userland 437 * 438 * If we are a KSE process and returning to user mode, check for 439 * extra work to do before we return (e.g. for more syscalls 440 * to complete first). If we were in a critical section, we should 441 * just return to let it finish. Same if we were in the UTS (in 442 * which case we will have no thread mailbox registered). The only 443 * traps we suport will have set the mailbox. We will clear it here. 444 */ 445int 446thread_userret(struct proc *p, struct ksegrp *kg, struct kse *ke, 447 struct thread *td, struct trapframe *frame) 448{ 449 int error = 0; 450 451 if (ke->ke_tdspare == NULL) { 452 ke->ke_tdspare = thread_alloc(); 453 } 454 if (td->td_flags & TDF_UNBOUND) { 455 /* 456 * Are we returning from a thread that had a mailbox? 457 * 458 * XXX Maybe this should be in a separate function. 459 */ 460 if (((td->td_flags & TDF_UPCALLING) == 0) && td->td_mailbox) { 461 /* 462 * [XXXKSE Future enhancement] 463 * We could also go straight back to the syscall 464 * if we never had to do an upcall since then. 465 * If the KSE's copy is == the thread's copy.. 466 * AND there are no other completed threads. 467 */ 468 /* 469 * We will go back as an upcall or go do another thread. 470 * Either way we need to save the context back to 471 * the user thread mailbox. 472 * So the UTS can restart it later. 473 */ 474 error = thread_export_context(td); 475 td->td_mailbox = NULL; 476 if (error) { 477 /* 478 * Failing to do the KSE 479 * operation just defaults operation 480 * back to synchonous operation. 481 */ 482 goto cont; 483 } 484 485 if (TAILQ_FIRST(&kg->kg_runq)) { 486 /* 487 * Uh-oh.. don't return to the user. 488 * Instead, switch to the thread that 489 * needs to run. The question is: 490 * What do we do with the thread we have now? 491 * We have put the completion block 492 * on the kse mailbox. If we had more energy, 493 * we could lazily do so, assuming someone 494 * else might get to userland earlier 495 * and deliver it earlier than we could. 496 * To do that we could save it off the KSEG. 497 * An upcalling KSE would 'reap' all completed 498 * threads. 499 * Being in a hurry, we'll do nothing and 500 * leave it on the current KSE for now. 501 * 502 * As for the other threads to run; 503 * we COULD rush through all the threads 504 * in this KSEG at this priority, or we 505 * could throw the ball back into the court 506 * and just run the highest prio kse available. 507 * What is OUR priority? 508 * the priority of the highest sycall waiting 509 * to be returned? 510 * For now, just let another KSE run (easiest). 511 */ 512 PROC_LOCK(p); 513 mtx_lock_spin(&sched_lock); 514 thread_exit(); /* Abandon current thread. */ 515 /* NOTREACHED */ 516 } else { /* if (number of returning syscalls = 1) */ 517 /* 518 * Swap our frame for the upcall frame. 519 * 520 * XXXKSE Assumes we are going to user land 521 * and not nested in the kernel 522 */ 523 td->td_flags |= TDF_UPCALLING; 524 } 525 } 526 /* 527 * This is NOT just an 'else' clause for the above test... 528 */ 529 if (td->td_flags & TDF_UPCALLING) { 530 CTR3(KTR_PROC, "userret: upcall thread %p (pid %d, %s)", 531 td, p->p_pid, p->p_comm); 532 /* 533 * Make sure that it has the correct frame loaded. 534 * While we know that we are on the same KSEGRP 535 * as we were created on, we could very easily 536 * have come in on another KSE. We therefore need 537 * to do the copy of the frame after the last 538 * possible switch() (the one above). 539 */ 540 bcopy(ke->ke_frame, frame, sizeof(struct trapframe)); 541 542 /* 543 * Decide what we are sending to the user 544 * upcall sets one argument. The address of the mbox. 545 */ 546 cpu_set_args(td, ke); 547 548 /* 549 * There is no more work to do and we are going to ride 550 * this thead/KSE up to userland. Make sure the user's 551 * pointer to the thread mailbox is cleared before we 552 * re-enter the kernel next time for any reason.. 553 * We might as well do it here. 554 */ 555 td->td_flags &= ~TDF_UPCALLING; /* Hmmmm. */ 556 error = suword((caddr_t)td->td_kse->ke_mailbox + 557 offsetof(struct kse_mailbox, kmbx_current_thread), 558 0); 559 } 560 /* 561 * Stop any chance that we may be separated from 562 * the KSE we are currently on. This is "biting the bullet", 563 * we are committing to go to user space as as THIS KSE here. 564 */ 565cont: 566 td->td_flags &= ~TDF_UNBOUND; 567 } 568 return (error); 569} 570 571/* 572 * Enforce single-threading. 573 * 574 * Returns 1 if the caller must abort (another thread is waiting to 575 * exit the process or similar). Process is locked! 576 * Returns 0 when you are successfully the only thread running. 577 * A process has successfully single threaded in the suspend mode when 578 * There are no threads in user mode. Threads in the kernel must be 579 * allowed to continue until they get to the user boundary. They may even 580 * copy out their return values and data before suspending. They may however be 581 * accellerated in reaching the user boundary as we will wake up 582 * any sleeping threads that are interruptable. (PCATCH). 583 */ 584int 585thread_single(int force_exit) 586{ 587 struct thread *td; 588 struct thread *td2; 589 struct proc *p; 590 591 td = curthread; 592 p = td->td_proc; 593 PROC_LOCK_ASSERT(p, MA_OWNED); 594 KASSERT((td != NULL), ("curthread is NULL")); 595 596 if ((p->p_flag & P_KSES) == 0) 597 return (0); 598 599 /* Is someone already single threading? */ 600 if (p->p_singlethread) 601 return (1); 602 603 if (force_exit == SINGLE_EXIT) 604 p->p_flag |= P_SINGLE_EXIT; 605 else 606 p->p_flag &= ~P_SINGLE_EXIT; 607 p->p_flag |= P_STOPPED_SINGLE; 608 p->p_singlethread = td; 609 while ((p->p_numthreads - p->p_suspcount) != 1) { 610 FOREACH_THREAD_IN_PROC(p, td2) { 611 if (td2 == td) 612 continue; 613 switch(td2->td_state) { 614 case TDS_SUSPENDED: 615 if (force_exit == SINGLE_EXIT) { 616 mtx_lock_spin(&sched_lock); 617 TAILQ_REMOVE(&p->p_suspended, 618 td, td_runq); 619 p->p_suspcount--; 620 setrunqueue(td); /* Should suicide. */ 621 mtx_unlock_spin(&sched_lock); 622 } 623 case TDS_SLP: 624 if (td2->td_flags & TDF_CVWAITQ) 625 cv_abort(td2); 626 else 627 abortsleep(td2); 628 break; 629 /* case TDS RUNNABLE: XXXKSE maybe raise priority? */ 630 default: /* needed to avoid an error */ 631 break; 632 } 633 } 634 /* 635 * Wake us up when everyone else has suspended. 636 * In the mean time we suspend as well. 637 */ 638 mtx_lock_spin(&sched_lock); 639 TAILQ_INSERT_TAIL(&p->p_suspended, td, td_runq); 640 td->td_state = TDS_SUSPENDED; 641 p->p_suspcount++; 642 mtx_unlock(&Giant); 643 PROC_UNLOCK(p); 644 mi_switch(); 645 mtx_unlock_spin(&sched_lock); 646 mtx_lock(&Giant); 647 PROC_LOCK(p); 648 } 649 return (0); 650} 651 652/* 653 * Called in from locations that can safely check to see 654 * whether we have to suspend or at least throttle for a 655 * single-thread event (e.g. fork). 656 * 657 * Such locations include userret(). 658 * If the "return_instead" argument is non zero, the thread must be able to 659 * accept 0 (caller may continue), or 1 (caller must abort) as a result. 660 * 661 * The 'return_instead' argument tells the function if it may do a 662 * thread_exit() or suspend, or whether the caller must abort and back 663 * out instead. 664 * 665 * If the thread that set the single_threading request has set the 666 * P_SINGLE_EXIT bit in the process flags then this call will never return 667 * if 'return_instead' is false, but will exit. 668 * 669 * P_SINGLE_EXIT | return_instead == 0| return_instead != 0 670 *---------------+--------------------+--------------------- 671 * 0 | returns 0 | returns 0 or 1 672 * | when ST ends | immediatly 673 *---------------+--------------------+--------------------- 674 * 1 | thread exits | returns 1 675 * | | immediatly 676 * 0 = thread_exit() or suspension ok, 677 * other = return error instead of stopping the thread. 678 * 679 * While a full suspension is under effect, even a single threading 680 * thread would be suspended if it made this call (but it shouldn't). 681 * This call should only be made from places where 682 * thread_exit() would be safe as that may be the outcome unless 683 * return_instead is set. 684 */ 685int 686thread_suspend_check(int return_instead) 687{ 688 struct thread *td = curthread; 689 struct proc *p = td->td_proc; 690 691 td = curthread; 692 p = td->td_proc; 693 PROC_LOCK_ASSERT(p, MA_OWNED); 694 while (P_SHOULDSTOP(p)) { 695 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) { 696 KASSERT(p->p_singlethread != NULL, 697 ("singlethread not set")); 698 /* 699 * The only suspension in action is a 700 * single-threading. Single threader need not stop. 701 * XXX Should be safe to access unlocked 702 * as it can only be set to be true by us. 703 */ 704 if (p->p_singlethread == td) 705 return (0); /* Exempt from stopping. */ 706 } 707 if (return_instead) 708 return (1); 709 710 /* 711 * If the process is waiting for us to exit, 712 * this thread should just suicide. 713 * Assumes that P_SINGLE_EXIT implies P_STOPPED_SINGLE. 714 */ 715 if ((p->p_flag & P_SINGLE_EXIT) && (p->p_singlethread != td)) { 716 mtx_lock_spin(&sched_lock); 717 while (mtx_owned(&Giant)) 718 mtx_unlock(&Giant); 719 thread_exit(); 720 } 721 722 /* 723 * When a thread suspends, it just 724 * moves to the processes's suspend queue 725 * and stays there. 726 * 727 * XXXKSE if TDF_BOUND is true 728 * it will not release it's KSE which might 729 * lead to deadlock if there are not enough KSEs 730 * to complete all waiting threads. 731 * Maybe be able to 'lend' it out again. 732 * (lent kse's can not go back to userland?) 733 * and can only be lent in STOPPED state. 734 */ 735 mtx_lock_spin(&sched_lock); 736 if ((p->p_flag & P_STOPPED_SIG) && 737 (p->p_suspcount+1 == p->p_numthreads)) { 738 mtx_unlock_spin(&sched_lock); 739 PROC_LOCK(p->p_pptr); 740 if ((p->p_pptr->p_procsig->ps_flag & 741 PS_NOCLDSTOP) == 0) { 742 psignal(p->p_pptr, SIGCHLD); 743 } 744 PROC_UNLOCK(p->p_pptr); 745 mtx_lock_spin(&sched_lock); 746 } 747 mtx_assert(&Giant, MA_NOTOWNED); 748 p->p_suspcount++; 749 td->td_state = TDS_SUSPENDED; 750 TAILQ_INSERT_TAIL(&p->p_suspended, td, td_runq); 751 PROC_UNLOCK(p); 752 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) { 753 if (p->p_numthreads == p->p_suspcount) { 754 TAILQ_REMOVE(&p->p_suspended, 755 p->p_singlethread, td_runq); 756 p->p_suspcount--; 757 setrunqueue(p->p_singlethread); 758 } 759 } 760 p->p_stats->p_ru.ru_nivcsw++; 761 mi_switch(); 762 mtx_unlock_spin(&sched_lock); 763 PROC_LOCK(p); 764 } 765 return (0); 766} 767 768void 769thread_suspend_one(struct thread *td) 770{ 771 struct proc *p = td->td_proc; 772 773 mtx_assert(&sched_lock, MA_OWNED); 774 p->p_suspcount++; 775 td->td_state = TDS_SUSPENDED; 776 TAILQ_INSERT_TAIL(&p->p_suspended, td, td_runq); 777} 778 779void 780thread_unsuspend_one(struct thread *td) 781{ 782 struct proc *p = td->td_proc; 783 784 mtx_assert(&sched_lock, MA_OWNED); 785 TAILQ_REMOVE(&p->p_suspended, td, td_runq); 786 p->p_suspcount--; 787 if (td->td_wchan != NULL) { 788 td->td_state = TDS_SLP; 789 } else { 790 if (td->td_ksegrp->kg_slptime > 1) { 791 updatepri(td->td_ksegrp); 792 td->td_ksegrp->kg_slptime = 0; 793 } 794 setrunqueue(td); 795 } 796} 797 798/* 799 * Allow all threads blocked by single threading to continue running. 800 */ 801void 802thread_unsuspend(struct proc *p) 803{ 804 struct thread *td; 805 806 mtx_assert(&sched_lock, MA_OWNED); 807 PROC_LOCK_ASSERT(p, MA_OWNED); 808 if (!P_SHOULDSTOP(p)) { 809 while (( td = TAILQ_FIRST(&p->p_suspended))) { 810 thread_unsuspend_one(td); 811 } 812 } else if ((P_SHOULDSTOP(p) == P_STOPPED_SINGLE) && 813 (p->p_numthreads == p->p_suspcount)) { 814 /* 815 * Stopping everything also did the job for the single 816 * threading request. Now we've downgraded to single-threaded, 817 * let it continue. 818 */ 819 thread_unsuspend_one(p->p_singlethread); 820 } 821} 822 823void 824thread_single_end(void) 825{ 826 struct thread *td; 827 struct proc *p; 828 829 td = curthread; 830 p = td->td_proc; 831 PROC_LOCK_ASSERT(p, MA_OWNED); 832 p->p_flag &= ~P_STOPPED_SINGLE; 833 p->p_singlethread = NULL; 834 /* 835 * If there are other threads they mey now run, 836 * unless of course there is a blanket 'stop order' 837 * on the process. The single threader must be allowed 838 * to continue however as this is a bad place to stop. 839 */ 840 if ((p->p_numthreads != 1) && (!P_SHOULDSTOP(p))) { 841 mtx_lock_spin(&sched_lock); 842 while (( td = TAILQ_FIRST(&p->p_suspended))) { 843 TAILQ_REMOVE(&p->p_suspended, td, td_runq); 844 p->p_suspcount--; 845 setrunqueue(td); 846 } 847 mtx_unlock_spin(&sched_lock); 848 } 849} 850 851 852