1 /*-
2 * Copyright (C) 2001 Julian Elischer <julian@freebsd.org>.
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice(s), this list of conditions and the following disclaimer as
10 * the first lines of this file unmodified other than the possible
11 * addition of one or more copyright notices.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice(s), this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY
17 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
18 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
19 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE LIABLE FOR ANY
20 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
21 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
22 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
23 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
26 * DAMAGE.
27 */
28
29 #include "opt_witness.h"
30 #include "opt_kdtrace.h"
31 #include "opt_hwpmc_hooks.h"
32
33 #include <sys/cdefs.h>
34 __FBSDID("$FreeBSD: releng/9.2/sys/kern/kern_thread.c 251147 2013-05-30 19:14:34Z jhb $");
35
36 #include <sys/param.h>
37 #include <sys/systm.h>
38 #include <sys/kernel.h>
39 #include <sys/lock.h>
40 #include <sys/mutex.h>
41 #include <sys/proc.h>
42 #include <sys/rangelock.h>
43 #include <sys/resourcevar.h>
44 #include <sys/sdt.h>
45 #include <sys/smp.h>
46 #include <sys/sched.h>
47 #include <sys/sleepqueue.h>
48 #include <sys/selinfo.h>
49 #include <sys/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 td->td_vp_reserv = 0;
211 EVENTHANDLER_INVOKE(thread_init, td);
212 td->td_sched = (struct td_sched *)&td[1];
213 umtx_thread_init(td);
214 td->td_kstack = 0;
215 return (0);
216 }
217
218 /*
219 * Tear down type-stable parts of a thread (just before being discarded).
220 */
221 static void
222 thread_fini(void *mem, int size)
223 {
224 struct thread *td;
225
226 td = (struct thread *)mem;
227 EVENTHANDLER_INVOKE(thread_fini, td);
228 rlqentry_free(td->td_rlqe);
229 turnstile_free(td->td_turnstile);
230 sleepq_free(td->td_sleepqueue);
231 umtx_thread_fini(td);
232 seltdfini(td);
233 }
234
235 /*
236 * For a newly created process,
237 * link up all the structures and its initial threads etc.
238 * called from:
239 * {arch}/{arch}/machdep.c ia64_init(), init386() etc.
240 * proc_dtor() (should go away)
241 * proc_init()
242 */
243 void
244 proc_linkup0(struct proc *p, struct thread *td)
245 {
246 TAILQ_INIT(&p->p_threads); /* all threads in proc */
247 proc_linkup(p, td);
248 }
249
250 void
251 proc_linkup(struct proc *p, struct thread *td)
252 {
253
254 sigqueue_init(&p->p_sigqueue, p);
255 p->p_ksi = ksiginfo_alloc(1);
256 if (p->p_ksi != NULL) {
257 /* XXX p_ksi may be null if ksiginfo zone is not ready */
258 p->p_ksi->ksi_flags = KSI_EXT | KSI_INS;
259 }
260 LIST_INIT(&p->p_mqnotifier);
261 p->p_numthreads = 0;
262 thread_link(td, p);
263 }
264
265 /*
266 * Initialize global thread allocation resources.
267 */
268 void
269 threadinit(void)
270 {
271
272 mtx_init(&tid_lock, "TID lock", NULL, MTX_DEF);
273
274 /*
275 * pid_max cannot be greater than PID_MAX.
276 * leave one number for thread0.
277 */
278 tid_unrhdr = new_unrhdr(PID_MAX + 2, INT_MAX, &tid_lock);
279
280 thread_zone = uma_zcreate("THREAD", sched_sizeof_thread(),
281 thread_ctor, thread_dtor, thread_init, thread_fini,
282 16 - 1, 0);
283 tidhashtbl = hashinit(maxproc / 2, M_TIDHASH, &tidhash);
284 rw_init(&tidhash_lock, "tidhash");
285 }
286
287 /*
288 * Place an unused thread on the zombie list.
289 * Use the slpq as that must be unused by now.
290 */
291 void
292 thread_zombie(struct thread *td)
293 {
294 mtx_lock_spin(&zombie_lock);
295 TAILQ_INSERT_HEAD(&zombie_threads, td, td_slpq);
296 mtx_unlock_spin(&zombie_lock);
297 }
298
299 /*
300 * Release a thread that has exited after cpu_throw().
301 */
302 void
303 thread_stash(struct thread *td)
304 {
305 atomic_subtract_rel_int(&td->td_proc->p_exitthreads, 1);
306 thread_zombie(td);
307 }
308
309 /*
310 * Reap zombie resources.
311 */
312 void
313 thread_reap(void)
314 {
315 struct thread *td_first, *td_next;
316
317 /*
318 * Don't even bother to lock if none at this instant,
319 * we really don't care about the next instant..
320 */
321 if (!TAILQ_EMPTY(&zombie_threads)) {
322 mtx_lock_spin(&zombie_lock);
323 td_first = TAILQ_FIRST(&zombie_threads);
324 if (td_first)
325 TAILQ_INIT(&zombie_threads);
326 mtx_unlock_spin(&zombie_lock);
327 while (td_first) {
328 td_next = TAILQ_NEXT(td_first, td_slpq);
329 if (td_first->td_ucred)
330 crfree(td_first->td_ucred);
331 thread_free(td_first);
332 td_first = td_next;
333 }
334 }
335 }
336
337 /*
338 * Allocate a thread.
339 */
340 struct thread *
341 thread_alloc(int pages)
342 {
343 struct thread *td;
344
345 thread_reap(); /* check if any zombies to get */
346
347 td = (struct thread *)uma_zalloc(thread_zone, M_WAITOK);
348 KASSERT(td->td_kstack == 0, ("thread_alloc got thread with kstack"));
349 if (!vm_thread_new(td, pages)) {
350 uma_zfree(thread_zone, td);
351 return (NULL);
352 }
353 cpu_thread_alloc(td);
354 return (td);
355 }
356
357 int
358 thread_alloc_stack(struct thread *td, int pages)
359 {
360
361 KASSERT(td->td_kstack == 0,
362 ("thread_alloc_stack called on a thread with kstack"));
363 if (!vm_thread_new(td, pages))
364 return (0);
365 cpu_thread_alloc(td);
366 return (1);
367 }
368
369 /*
370 * Deallocate a thread.
371 */
372 void
373 thread_free(struct thread *td)
374 {
375
376 lock_profile_thread_exit(td);
377 if (td->td_cpuset)
378 cpuset_rel(td->td_cpuset);
379 td->td_cpuset = NULL;
380 cpu_thread_free(td);
381 if (td->td_kstack != 0)
382 vm_thread_dispose(td);
383 uma_zfree(thread_zone, td);
384 }
385
386 /*
387 * Discard the current thread and exit from its context.
388 * Always called with scheduler locked.
389 *
390 * Because we can't free a thread while we're operating under its context,
391 * push the current thread into our CPU's deadthread holder. This means
392 * we needn't worry about someone else grabbing our context before we
393 * do a cpu_throw().
394 */
395 void
396 thread_exit(void)
397 {
398 uint64_t runtime, new_switchtime;
399 struct thread *td;
400 struct thread *td2;
401 struct proc *p;
402 int wakeup_swapper;
403
404 td = curthread;
405 p = td->td_proc;
406
407 PROC_SLOCK_ASSERT(p, MA_OWNED);
408 mtx_assert(&Giant, MA_NOTOWNED);
409
410 PROC_LOCK_ASSERT(p, MA_OWNED);
411 KASSERT(p != NULL, ("thread exiting without a process"));
412 CTR3(KTR_PROC, "thread_exit: thread %p (pid %ld, %s)", td,
413 (long)p->p_pid, td->td_name);
414 KASSERT(TAILQ_EMPTY(&td->td_sigqueue.sq_list), ("signal pending"));
415
416 #ifdef AUDIT
417 AUDIT_SYSCALL_EXIT(0, td);
418 #endif
419 umtx_thread_exit(td);
420 /*
421 * drop FPU & debug register state storage, or any other
422 * architecture specific resources that
423 * would not be on a new untouched process.
424 */
425 cpu_thread_exit(td); /* XXXSMP */
426
427 /*
428 * The last thread is left attached to the process
429 * So that the whole bundle gets recycled. Skip
430 * all this stuff if we never had threads.
431 * EXIT clears all sign of other threads when
432 * it goes to single threading, so the last thread always
433 * takes the short path.
434 */
435 if (p->p_flag & P_HADTHREADS) {
436 if (p->p_numthreads > 1) {
437 thread_unlink(td);
438 td2 = FIRST_THREAD_IN_PROC(p);
439 sched_exit_thread(td2, td);
440
441 /*
442 * The test below is NOT true if we are the
443 * sole exiting thread. P_STOPPED_SINGLE is unset
444 * in exit1() after it is the only survivor.
445 */
446 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
447 if (p->p_numthreads == p->p_suspcount) {
448 thread_lock(p->p_singlethread);
449 wakeup_swapper = thread_unsuspend_one(
450 p->p_singlethread);
451 thread_unlock(p->p_singlethread);
452 if (wakeup_swapper)
453 kick_proc0();
454 }
455 }
456
457 atomic_add_int(&td->td_proc->p_exitthreads, 1);
458 PCPU_SET(deadthread, td);
459 } else {
460 /*
461 * The last thread is exiting.. but not through exit()
462 */
463 panic ("thread_exit: Last thread exiting on its own");
464 }
465 }
466 #ifdef HWPMC_HOOKS
467 /*
468 * If this thread is part of a process that is being tracked by hwpmc(4),
469 * inform the module of the thread's impending exit.
470 */
471 if (PMC_PROC_IS_USING_PMCS(td->td_proc))
472 PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_OUT);
473 #endif
474 PROC_UNLOCK(p);
475
476 /* Do the same timestamp bookkeeping that mi_switch() would do. */
477 new_switchtime = cpu_ticks();
478 runtime = new_switchtime - PCPU_GET(switchtime);
479 td->td_runtime += runtime;
480 td->td_incruntime += runtime;
481 PCPU_SET(switchtime, new_switchtime);
482 PCPU_SET(switchticks, ticks);
483 PCPU_INC(cnt.v_swtch);
484
485 /* Save our resource usage in our process. */
486 td->td_ru.ru_nvcsw++;
487 ruxagg(p, td);
488 rucollect(&p->p_ru, &td->td_ru);
489
490 thread_lock(td);
491 PROC_SUNLOCK(p);
492 td->td_state = TDS_INACTIVE;
493 #ifdef WITNESS
494 witness_thread_exit(td);
495 #endif
496 CTR1(KTR_PROC, "thread_exit: cpu_throw() thread %p", td);
497 sched_throw(td);
498 panic("I'm a teapot!");
499 /* NOTREACHED */
500 }
501
502 /*
503 * Do any thread specific cleanups that may be needed in wait()
504 * called with Giant, proc and schedlock not held.
505 */
506 void
507 thread_wait(struct proc *p)
508 {
509 struct thread *td;
510
511 mtx_assert(&Giant, MA_NOTOWNED);
512 KASSERT((p->p_numthreads == 1), ("Multiple threads in wait1()"));
513 td = FIRST_THREAD_IN_PROC(p);
514 /* Lock the last thread so we spin until it exits cpu_throw(). */
515 thread_lock(td);
516 thread_unlock(td);
517 /* Wait for any remaining threads to exit cpu_throw(). */
518 while (p->p_exitthreads)
519 sched_relinquish(curthread);
520 lock_profile_thread_exit(td);
521 cpuset_rel(td->td_cpuset);
522 td->td_cpuset = NULL;
523 cpu_thread_clean(td);
524 crfree(td->td_ucred);
525 thread_reap(); /* check for zombie threads etc. */
526 }
527
528 /*
529 * Link a thread to a process.
530 * set up anything that needs to be initialized for it to
531 * be used by the process.
532 */
533 void
534 thread_link(struct thread *td, struct proc *p)
535 {
536
537 /*
538 * XXX This can't be enabled because it's called for proc0 before
539 * its lock has been created.
540 * PROC_LOCK_ASSERT(p, MA_OWNED);
541 */
542 td->td_state = TDS_INACTIVE;
543 td->td_proc = p;
544 td->td_flags = TDF_INMEM;
545
546 LIST_INIT(&td->td_contested);
547 LIST_INIT(&td->td_lprof[0]);
548 LIST_INIT(&td->td_lprof[1]);
549 sigqueue_init(&td->td_sigqueue, p);
550 callout_init(&td->td_slpcallout, CALLOUT_MPSAFE);
551 TAILQ_INSERT_HEAD(&p->p_threads, td, td_plist);
552 p->p_numthreads++;
553 }
554
555 /*
556 * Convert a process with one thread to an unthreaded process.
557 */
558 void
559 thread_unthread(struct thread *td)
560 {
561 struct proc *p = td->td_proc;
562
563 KASSERT((p->p_numthreads == 1), ("Unthreading with >1 threads"));
564 p->p_flag &= ~P_HADTHREADS;
565 }
566
567 /*
568 * Called from:
569 * thread_exit()
570 */
571 void
572 thread_unlink(struct thread *td)
573 {
574 struct proc *p = td->td_proc;
575
576 PROC_LOCK_ASSERT(p, MA_OWNED);
577 TAILQ_REMOVE(&p->p_threads, td, td_plist);
578 p->p_numthreads--;
579 /* could clear a few other things here */
580 /* Must NOT clear links to proc! */
581 }
582
583 static int
584 calc_remaining(struct proc *p, int mode)
585 {
586 int remaining;
587
588 PROC_LOCK_ASSERT(p, MA_OWNED);
589 PROC_SLOCK_ASSERT(p, MA_OWNED);
590 if (mode == SINGLE_EXIT)
591 remaining = p->p_numthreads;
592 else if (mode == SINGLE_BOUNDARY)
593 remaining = p->p_numthreads - p->p_boundary_count;
594 else if (mode == SINGLE_NO_EXIT)
595 remaining = p->p_numthreads - p->p_suspcount;
596 else
597 panic("calc_remaining: wrong mode %d", mode);
598 return (remaining);
599 }
600
601 /*
602 * Enforce single-threading.
603 *
604 * Returns 1 if the caller must abort (another thread is waiting to
605 * exit the process or similar). Process is locked!
606 * Returns 0 when you are successfully the only thread running.
607 * A process has successfully single threaded in the suspend mode when
608 * There are no threads in user mode. Threads in the kernel must be
609 * allowed to continue until they get to the user boundary. They may even
610 * copy out their return values and data before suspending. They may however be
611 * accelerated in reaching the user boundary as we will wake up
612 * any sleeping threads that are interruptable. (PCATCH).
613 */
614 int
615 thread_single(int mode)
616 {
617 struct thread *td;
618 struct thread *td2;
619 struct proc *p;
620 int remaining, wakeup_swapper;
621
622 td = curthread;
623 p = td->td_proc;
624 mtx_assert(&Giant, MA_NOTOWNED);
625 PROC_LOCK_ASSERT(p, MA_OWNED);
626
627 if ((p->p_flag & P_HADTHREADS) == 0)
628 return (0);
629
630 /* Is someone already single threading? */
631 if (p->p_singlethread != NULL && p->p_singlethread != td)
632 return (1);
633
634 if (mode == SINGLE_EXIT) {
635 p->p_flag |= P_SINGLE_EXIT;
636 p->p_flag &= ~P_SINGLE_BOUNDARY;
637 } else {
638 p->p_flag &= ~P_SINGLE_EXIT;
639 if (mode == SINGLE_BOUNDARY)
640 p->p_flag |= P_SINGLE_BOUNDARY;
641 else
642 p->p_flag &= ~P_SINGLE_BOUNDARY;
643 }
644 p->p_flag |= P_STOPPED_SINGLE;
645 PROC_SLOCK(p);
646 p->p_singlethread = td;
647 remaining = calc_remaining(p, mode);
648 while (remaining != 1) {
649 if (P_SHOULDSTOP(p) != P_STOPPED_SINGLE)
650 goto stopme;
651 wakeup_swapper = 0;
652 FOREACH_THREAD_IN_PROC(p, td2) {
653 if (td2 == td)
654 continue;
655 thread_lock(td2);
656 td2->td_flags |= TDF_ASTPENDING | TDF_NEEDSUSPCHK;
657 if (TD_IS_INHIBITED(td2)) {
658 switch (mode) {
659 case SINGLE_EXIT:
660 if (TD_IS_SUSPENDED(td2))
661 wakeup_swapper |=
662 thread_unsuspend_one(td2);
663 if (TD_ON_SLEEPQ(td2) &&
664 (td2->td_flags & TDF_SINTR))
665 wakeup_swapper |=
666 sleepq_abort(td2, EINTR);
667 break;
668 case SINGLE_BOUNDARY:
669 if (TD_IS_SUSPENDED(td2) &&
670 !(td2->td_flags & TDF_BOUNDARY))
671 wakeup_swapper |=
672 thread_unsuspend_one(td2);
673 if (TD_ON_SLEEPQ(td2) &&
674 (td2->td_flags & TDF_SINTR))
675 wakeup_swapper |=
676 sleepq_abort(td2, ERESTART);
677 break;
678 case SINGLE_NO_EXIT:
679 if (TD_IS_SUSPENDED(td2) &&
680 !(td2->td_flags & TDF_BOUNDARY))
681 wakeup_swapper |=
682 thread_unsuspend_one(td2);
683 if (TD_ON_SLEEPQ(td2) &&
684 (td2->td_flags & TDF_SINTR))
685 wakeup_swapper |=
686 sleepq_abort(td2, ERESTART);
687 break;
688 default:
689 break;
690 }
691 }
692 #ifdef SMP
693 else if (TD_IS_RUNNING(td2) && td != td2) {
694 forward_signal(td2);
695 }
696 #endif
697 thread_unlock(td2);
698 }
699 if (wakeup_swapper)
700 kick_proc0();
701 remaining = calc_remaining(p, mode);
702
703 /*
704 * Maybe we suspended some threads.. was it enough?
705 */
706 if (remaining == 1)
707 break;
708
709 stopme:
710 /*
711 * Wake us up when everyone else has suspended.
712 * In the mean time we suspend as well.
713 */
714 thread_suspend_switch(td);
715 remaining = calc_remaining(p, mode);
716 }
717 if (mode == SINGLE_EXIT) {
718 /*
719 * We have gotten rid of all the other threads and we
720 * are about to either exit or exec. In either case,
721 * we try our utmost to revert to being a non-threaded
722 * process.
723 */
724 p->p_singlethread = NULL;
725 p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT);
726 thread_unthread(td);
727 }
728 PROC_SUNLOCK(p);
729 return (0);
730 }
731
732 /*
733 * Called in from locations that can safely check to see
734 * whether we have to suspend or at least throttle for a
735 * single-thread event (e.g. fork).
736 *
737 * Such locations include userret().
738 * If the "return_instead" argument is non zero, the thread must be able to
739 * accept 0 (caller may continue), or 1 (caller must abort) as a result.
740 *
741 * The 'return_instead' argument tells the function if it may do a
742 * thread_exit() or suspend, or whether the caller must abort and back
743 * out instead.
744 *
745 * If the thread that set the single_threading request has set the
746 * P_SINGLE_EXIT bit in the process flags then this call will never return
747 * if 'return_instead' is false, but will exit.
748 *
749 * P_SINGLE_EXIT | return_instead == 0| return_instead != 0
750 *---------------+--------------------+---------------------
751 * 0 | returns 0 | returns 0 or 1
752 * | when ST ends | immediatly
753 *---------------+--------------------+---------------------
754 * 1 | thread exits | returns 1
755 * | | immediatly
756 * 0 = thread_exit() or suspension ok,
757 * other = return error instead of stopping the thread.
758 *
759 * While a full suspension is under effect, even a single threading
760 * thread would be suspended if it made this call (but it shouldn't).
761 * This call should only be made from places where
762 * thread_exit() would be safe as that may be the outcome unless
763 * return_instead is set.
764 */
765 int
766 thread_suspend_check(int return_instead)
767 {
768 struct thread *td;
769 struct proc *p;
770 int wakeup_swapper;
771
772 td = curthread;
773 p = td->td_proc;
774 mtx_assert(&Giant, MA_NOTOWNED);
775 PROC_LOCK_ASSERT(p, MA_OWNED);
776 while (P_SHOULDSTOP(p) ||
777 ((p->p_flag & P_TRACED) && (td->td_dbgflags & TDB_SUSPEND))) {
778 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
779 KASSERT(p->p_singlethread != NULL,
780 ("singlethread not set"));
781 /*
782 * The only suspension in action is a
783 * single-threading. Single threader need not stop.
784 * XXX Should be safe to access unlocked
785 * as it can only be set to be true by us.
786 */
787 if (p->p_singlethread == td)
788 return (0); /* Exempt from stopping. */
789 }
790 if ((p->p_flag & P_SINGLE_EXIT) && return_instead)
791 return (EINTR);
792
793 /* Should we goto user boundary if we didn't come from there? */
794 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE &&
795 (p->p_flag & P_SINGLE_BOUNDARY) && return_instead)
796 return (ERESTART);
797
798 /*
799 * Ignore suspend requests for stop signals if they
800 * are deferred.
801 */
802 if (P_SHOULDSTOP(p) == P_STOPPED_SIG &&
803 td->td_flags & TDF_SBDRY) {
804 KASSERT(return_instead,
805 ("TDF_SBDRY set for unsafe thread_suspend_check"));
806 return (0);
807 }
808
809 /*
810 * If the process is waiting for us to exit,
811 * this thread should just suicide.
812 * Assumes that P_SINGLE_EXIT implies P_STOPPED_SINGLE.
813 */
814 if ((p->p_flag & P_SINGLE_EXIT) && (p->p_singlethread != td)) {
815 PROC_UNLOCK(p);
816 tidhash_remove(td);
817 PROC_LOCK(p);
818 tdsigcleanup(td);
819 PROC_SLOCK(p);
820 thread_stopped(p);
821 thread_exit();
822 }
823
824 PROC_SLOCK(p);
825 thread_stopped(p);
826 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
827 if (p->p_numthreads == p->p_suspcount + 1) {
828 thread_lock(p->p_singlethread);
829 wakeup_swapper =
830 thread_unsuspend_one(p->p_singlethread);
831 thread_unlock(p->p_singlethread);
832 if (wakeup_swapper)
833 kick_proc0();
834 }
835 }
836 PROC_UNLOCK(p);
837 thread_lock(td);
838 /*
839 * When a thread suspends, it just
840 * gets taken off all queues.
841 */
842 thread_suspend_one(td);
843 if (return_instead == 0) {
844 p->p_boundary_count++;
845 td->td_flags |= TDF_BOUNDARY;
846 }
847 PROC_SUNLOCK(p);
848 mi_switch(SW_INVOL | SWT_SUSPEND, NULL);
849 if (return_instead == 0)
850 td->td_flags &= ~TDF_BOUNDARY;
851 thread_unlock(td);
852 PROC_LOCK(p);
853 if (return_instead == 0) {
854 PROC_SLOCK(p);
855 p->p_boundary_count--;
856 PROC_SUNLOCK(p);
857 }
858 }
859 return (0);
860 }
861
862 void
863 thread_suspend_switch(struct thread *td)
864 {
865 struct proc *p;
866
867 p = td->td_proc;
868 KASSERT(!TD_IS_SUSPENDED(td), ("already suspended"));
869 PROC_LOCK_ASSERT(p, MA_OWNED);
870 PROC_SLOCK_ASSERT(p, MA_OWNED);
871 /*
872 * We implement thread_suspend_one in stages here to avoid
873 * dropping the proc lock while the thread lock is owned.
874 */
875 thread_stopped(p);
876 p->p_suspcount++;
877 PROC_UNLOCK(p);
878 thread_lock(td);
879 td->td_flags &= ~TDF_NEEDSUSPCHK;
880 TD_SET_SUSPENDED(td);
881 sched_sleep(td, 0);
882 PROC_SUNLOCK(p);
883 DROP_GIANT();
884 mi_switch(SW_VOL | SWT_SUSPEND, NULL);
885 thread_unlock(td);
886 PICKUP_GIANT();
887 PROC_LOCK(p);
888 PROC_SLOCK(p);
889 }
890
891 void
892 thread_suspend_one(struct thread *td)
893 {
894 struct proc *p = td->td_proc;
895
896 PROC_SLOCK_ASSERT(p, MA_OWNED);
897 THREAD_LOCK_ASSERT(td, MA_OWNED);
898 KASSERT(!TD_IS_SUSPENDED(td), ("already suspended"));
899 p->p_suspcount++;
900 td->td_flags &= ~TDF_NEEDSUSPCHK;
901 TD_SET_SUSPENDED(td);
902 sched_sleep(td, 0);
903 }
904
905 int
906 thread_unsuspend_one(struct thread *td)
907 {
908 struct proc *p = td->td_proc;
909
910 PROC_SLOCK_ASSERT(p, MA_OWNED);
911 THREAD_LOCK_ASSERT(td, MA_OWNED);
912 KASSERT(TD_IS_SUSPENDED(td), ("Thread not suspended"));
913 TD_CLR_SUSPENDED(td);
914 p->p_suspcount--;
915 return (setrunnable(td));
916 }
917
918 /*
919 * Allow all threads blocked by single threading to continue running.
920 */
921 void
922 thread_unsuspend(struct proc *p)
923 {
924 struct thread *td;
925 int wakeup_swapper;
926
927 PROC_LOCK_ASSERT(p, MA_OWNED);
928 PROC_SLOCK_ASSERT(p, MA_OWNED);
929 wakeup_swapper = 0;
930 if (!P_SHOULDSTOP(p)) {
931 FOREACH_THREAD_IN_PROC(p, td) {
932 thread_lock(td);
933 if (TD_IS_SUSPENDED(td)) {
934 wakeup_swapper |= thread_unsuspend_one(td);
935 }
936 thread_unlock(td);
937 }
938 } else if ((P_SHOULDSTOP(p) == P_STOPPED_SINGLE) &&
939 (p->p_numthreads == p->p_suspcount)) {
940 /*
941 * Stopping everything also did the job for the single
942 * threading request. Now we've downgraded to single-threaded,
943 * let it continue.
944 */
945 thread_lock(p->p_singlethread);
946 wakeup_swapper = thread_unsuspend_one(p->p_singlethread);
947 thread_unlock(p->p_singlethread);
948 }
949 if (wakeup_swapper)
950 kick_proc0();
951 }
952
953 /*
954 * End the single threading mode..
955 */
956 void
957 thread_single_end(void)
958 {
959 struct thread *td;
960 struct proc *p;
961 int wakeup_swapper;
962
963 td = curthread;
964 p = td->td_proc;
965 PROC_LOCK_ASSERT(p, MA_OWNED);
966 p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT | P_SINGLE_BOUNDARY);
967 PROC_SLOCK(p);
968 p->p_singlethread = NULL;
969 wakeup_swapper = 0;
970 /*
971 * If there are other threads they may now run,
972 * unless of course there is a blanket 'stop order'
973 * on the process. The single threader must be allowed
974 * to continue however as this is a bad place to stop.
975 */
976 if ((p->p_numthreads != 1) && (!P_SHOULDSTOP(p))) {
977 FOREACH_THREAD_IN_PROC(p, td) {
978 thread_lock(td);
979 if (TD_IS_SUSPENDED(td)) {
980 wakeup_swapper |= thread_unsuspend_one(td);
981 }
982 thread_unlock(td);
983 }
984 }
985 PROC_SUNLOCK(p);
986 if (wakeup_swapper)
987 kick_proc0();
988 }
989
990 struct thread *
991 thread_find(struct proc *p, lwpid_t tid)
992 {
993 struct thread *td;
994
995 PROC_LOCK_ASSERT(p, MA_OWNED);
996 FOREACH_THREAD_IN_PROC(p, td) {
997 if (td->td_tid == tid)
998 break;
999 }
1000 return (td);
1001 }
1002
1003 /* Locate a thread by number; return with proc lock held. */
1004 struct thread *
1005 tdfind(lwpid_t tid, pid_t pid)
1006 {
1007 #define RUN_THRESH 16
1008 struct thread *td;
1009 int run = 0;
1010
1011 rw_rlock(&tidhash_lock);
1012 LIST_FOREACH(td, TIDHASH(tid), td_hash) {
1013 if (td->td_tid == tid) {
1014 if (pid != -1 && td->td_proc->p_pid != pid) {
1015 td = NULL;
1016 break;
1017 }
1018 PROC_LOCK(td->td_proc);
1019 if (td->td_proc->p_state == PRS_NEW) {
1020 PROC_UNLOCK(td->td_proc);
1021 td = NULL;
1022 break;
1023 }
1024 if (run > RUN_THRESH) {
1025 if (rw_try_upgrade(&tidhash_lock)) {
1026 LIST_REMOVE(td, td_hash);
1027 LIST_INSERT_HEAD(TIDHASH(td->td_tid),
1028 td, td_hash);
1029 rw_wunlock(&tidhash_lock);
1030 return (td);
1031 }
1032 }
1033 break;
1034 }
1035 run++;
1036 }
1037 rw_runlock(&tidhash_lock);
1038 return (td);
1039 }
1040
1041 void
1042 tidhash_add(struct thread *td)
1043 {
1044 rw_wlock(&tidhash_lock);
1045 LIST_INSERT_HEAD(TIDHASH(td->td_tid), td, td_hash);
1046 rw_wunlock(&tidhash_lock);
1047 }
1048
1049 void
1050 tidhash_remove(struct thread *td)
1051 {
1052 rw_wlock(&tidhash_lock);
1053 LIST_REMOVE(td, td_hash);
1054 rw_wunlock(&tidhash_lock);
1055 }
Cache object: 43d9ac1765d4741036ca111abdd67782
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