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/10.0/sys/kern/kern_thread.c 248584 2013-03-21 14:06:27Z 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 EVENTHANDLER_INVOKE(thread_init, td);
211 td->td_sched = (struct td_sched *)&td[1];
212 umtx_thread_init(td);
213 td->td_kstack = 0;
214 return (0);
215 }
216
217 /*
218 * Tear down type-stable parts of a thread (just before being discarded).
219 */
220 static void
221 thread_fini(void *mem, int size)
222 {
223 struct thread *td;
224
225 td = (struct thread *)mem;
226 EVENTHANDLER_INVOKE(thread_fini, td);
227 rlqentry_free(td->td_rlqe);
228 turnstile_free(td->td_turnstile);
229 sleepq_free(td->td_sleepqueue);
230 umtx_thread_fini(td);
231 seltdfini(td);
232 }
233
234 /*
235 * For a newly created process,
236 * link up all the structures and its initial threads etc.
237 * called from:
238 * {arch}/{arch}/machdep.c ia64_init(), init386() etc.
239 * proc_dtor() (should go away)
240 * proc_init()
241 */
242 void
243 proc_linkup0(struct proc *p, struct thread *td)
244 {
245 TAILQ_INIT(&p->p_threads); /* all threads in proc */
246 proc_linkup(p, td);
247 }
248
249 void
250 proc_linkup(struct proc *p, struct thread *td)
251 {
252
253 sigqueue_init(&p->p_sigqueue, p);
254 p->p_ksi = ksiginfo_alloc(1);
255 if (p->p_ksi != NULL) {
256 /* XXX p_ksi may be null if ksiginfo zone is not ready */
257 p->p_ksi->ksi_flags = KSI_EXT | KSI_INS;
258 }
259 LIST_INIT(&p->p_mqnotifier);
260 p->p_numthreads = 0;
261 thread_link(td, p);
262 }
263
264 /*
265 * Initialize global thread allocation resources.
266 */
267 void
268 threadinit(void)
269 {
270
271 mtx_init(&tid_lock, "TID lock", NULL, MTX_DEF);
272
273 /*
274 * pid_max cannot be greater than PID_MAX.
275 * leave one number for thread0.
276 */
277 tid_unrhdr = new_unrhdr(PID_MAX + 2, INT_MAX, &tid_lock);
278
279 thread_zone = uma_zcreate("THREAD", sched_sizeof_thread(),
280 thread_ctor, thread_dtor, thread_init, thread_fini,
281 16 - 1, 0);
282 tidhashtbl = hashinit(maxproc / 2, M_TIDHASH, &tidhash);
283 rw_init(&tidhash_lock, "tidhash");
284 }
285
286 /*
287 * Place an unused thread on the zombie list.
288 * Use the slpq as that must be unused by now.
289 */
290 void
291 thread_zombie(struct thread *td)
292 {
293 mtx_lock_spin(&zombie_lock);
294 TAILQ_INSERT_HEAD(&zombie_threads, td, td_slpq);
295 mtx_unlock_spin(&zombie_lock);
296 }
297
298 /*
299 * Release a thread that has exited after cpu_throw().
300 */
301 void
302 thread_stash(struct thread *td)
303 {
304 atomic_subtract_rel_int(&td->td_proc->p_exitthreads, 1);
305 thread_zombie(td);
306 }
307
308 /*
309 * Reap zombie resources.
310 */
311 void
312 thread_reap(void)
313 {
314 struct thread *td_first, *td_next;
315
316 /*
317 * Don't even bother to lock if none at this instant,
318 * we really don't care about the next instant..
319 */
320 if (!TAILQ_EMPTY(&zombie_threads)) {
321 mtx_lock_spin(&zombie_lock);
322 td_first = TAILQ_FIRST(&zombie_threads);
323 if (td_first)
324 TAILQ_INIT(&zombie_threads);
325 mtx_unlock_spin(&zombie_lock);
326 while (td_first) {
327 td_next = TAILQ_NEXT(td_first, td_slpq);
328 if (td_first->td_ucred)
329 crfree(td_first->td_ucred);
330 thread_free(td_first);
331 td_first = td_next;
332 }
333 }
334 }
335
336 /*
337 * Allocate a thread.
338 */
339 struct thread *
340 thread_alloc(int pages)
341 {
342 struct thread *td;
343
344 thread_reap(); /* check if any zombies to get */
345
346 td = (struct thread *)uma_zalloc(thread_zone, M_WAITOK);
347 KASSERT(td->td_kstack == 0, ("thread_alloc got thread with kstack"));
348 if (!vm_thread_new(td, pages)) {
349 uma_zfree(thread_zone, td);
350 return (NULL);
351 }
352 cpu_thread_alloc(td);
353 return (td);
354 }
355
356 int
357 thread_alloc_stack(struct thread *td, int pages)
358 {
359
360 KASSERT(td->td_kstack == 0,
361 ("thread_alloc_stack called on a thread with kstack"));
362 if (!vm_thread_new(td, pages))
363 return (0);
364 cpu_thread_alloc(td);
365 return (1);
366 }
367
368 /*
369 * Deallocate a thread.
370 */
371 void
372 thread_free(struct thread *td)
373 {
374
375 lock_profile_thread_exit(td);
376 if (td->td_cpuset)
377 cpuset_rel(td->td_cpuset);
378 td->td_cpuset = NULL;
379 cpu_thread_free(td);
380 if (td->td_kstack != 0)
381 vm_thread_dispose(td);
382 uma_zfree(thread_zone, td);
383 }
384
385 /*
386 * Discard the current thread and exit from its context.
387 * Always called with scheduler locked.
388 *
389 * Because we can't free a thread while we're operating under its context,
390 * push the current thread into our CPU's deadthread holder. This means
391 * we needn't worry about someone else grabbing our context before we
392 * do a cpu_throw().
393 */
394 void
395 thread_exit(void)
396 {
397 uint64_t runtime, new_switchtime;
398 struct thread *td;
399 struct thread *td2;
400 struct proc *p;
401 int wakeup_swapper;
402
403 td = curthread;
404 p = td->td_proc;
405
406 PROC_SLOCK_ASSERT(p, MA_OWNED);
407 mtx_assert(&Giant, MA_NOTOWNED);
408
409 PROC_LOCK_ASSERT(p, MA_OWNED);
410 KASSERT(p != NULL, ("thread exiting without a process"));
411 CTR3(KTR_PROC, "thread_exit: thread %p (pid %ld, %s)", td,
412 (long)p->p_pid, td->td_name);
413 KASSERT(TAILQ_EMPTY(&td->td_sigqueue.sq_list), ("signal pending"));
414
415 #ifdef AUDIT
416 AUDIT_SYSCALL_EXIT(0, td);
417 #endif
418 umtx_thread_exit(td);
419 /*
420 * drop FPU & debug register state storage, or any other
421 * architecture specific resources that
422 * would not be on a new untouched process.
423 */
424 cpu_thread_exit(td); /* XXXSMP */
425
426 /*
427 * The last thread is left attached to the process
428 * So that the whole bundle gets recycled. Skip
429 * all this stuff if we never had threads.
430 * EXIT clears all sign of other threads when
431 * it goes to single threading, so the last thread always
432 * takes the short path.
433 */
434 if (p->p_flag & P_HADTHREADS) {
435 if (p->p_numthreads > 1) {
436 thread_unlink(td);
437 td2 = FIRST_THREAD_IN_PROC(p);
438 sched_exit_thread(td2, td);
439
440 /*
441 * The test below is NOT true if we are the
442 * sole exiting thread. P_STOPPED_SINGLE is unset
443 * in exit1() after it is the only survivor.
444 */
445 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
446 if (p->p_numthreads == p->p_suspcount) {
447 thread_lock(p->p_singlethread);
448 wakeup_swapper = thread_unsuspend_one(
449 p->p_singlethread);
450 thread_unlock(p->p_singlethread);
451 if (wakeup_swapper)
452 kick_proc0();
453 }
454 }
455
456 atomic_add_int(&td->td_proc->p_exitthreads, 1);
457 PCPU_SET(deadthread, td);
458 } else {
459 /*
460 * The last thread is exiting.. but not through exit()
461 */
462 panic ("thread_exit: Last thread exiting on its own");
463 }
464 }
465 #ifdef HWPMC_HOOKS
466 /*
467 * If this thread is part of a process that is being tracked by hwpmc(4),
468 * inform the module of the thread's impending exit.
469 */
470 if (PMC_PROC_IS_USING_PMCS(td->td_proc))
471 PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_OUT);
472 #endif
473 PROC_UNLOCK(p);
474
475 /* Do the same timestamp bookkeeping that mi_switch() would do. */
476 new_switchtime = cpu_ticks();
477 runtime = new_switchtime - PCPU_GET(switchtime);
478 td->td_runtime += runtime;
479 td->td_incruntime += runtime;
480 PCPU_SET(switchtime, new_switchtime);
481 PCPU_SET(switchticks, ticks);
482 PCPU_INC(cnt.v_swtch);
483
484 /* Save our resource usage in our process. */
485 td->td_ru.ru_nvcsw++;
486 ruxagg(p, td);
487 rucollect(&p->p_ru, &td->td_ru);
488
489 thread_lock(td);
490 PROC_SUNLOCK(p);
491 td->td_state = TDS_INACTIVE;
492 #ifdef WITNESS
493 witness_thread_exit(td);
494 #endif
495 CTR1(KTR_PROC, "thread_exit: cpu_throw() thread %p", td);
496 sched_throw(td);
497 panic("I'm a teapot!");
498 /* NOTREACHED */
499 }
500
501 /*
502 * Do any thread specific cleanups that may be needed in wait()
503 * called with Giant, proc and schedlock not held.
504 */
505 void
506 thread_wait(struct proc *p)
507 {
508 struct thread *td;
509
510 mtx_assert(&Giant, MA_NOTOWNED);
511 KASSERT((p->p_numthreads == 1), ("Multiple threads in wait1()"));
512 td = FIRST_THREAD_IN_PROC(p);
513 /* Lock the last thread so we spin until it exits cpu_throw(). */
514 thread_lock(td);
515 thread_unlock(td);
516 /* Wait for any remaining threads to exit cpu_throw(). */
517 while (p->p_exitthreads)
518 sched_relinquish(curthread);
519 lock_profile_thread_exit(td);
520 cpuset_rel(td->td_cpuset);
521 td->td_cpuset = NULL;
522 cpu_thread_clean(td);
523 crfree(td->td_ucred);
524 thread_reap(); /* check for zombie threads etc. */
525 }
526
527 /*
528 * Link a thread to a process.
529 * set up anything that needs to be initialized for it to
530 * be used by the process.
531 */
532 void
533 thread_link(struct thread *td, struct proc *p)
534 {
535
536 /*
537 * XXX This can't be enabled because it's called for proc0 before
538 * its lock has been created.
539 * PROC_LOCK_ASSERT(p, MA_OWNED);
540 */
541 td->td_state = TDS_INACTIVE;
542 td->td_proc = p;
543 td->td_flags = TDF_INMEM;
544
545 LIST_INIT(&td->td_contested);
546 LIST_INIT(&td->td_lprof[0]);
547 LIST_INIT(&td->td_lprof[1]);
548 sigqueue_init(&td->td_sigqueue, p);
549 callout_init(&td->td_slpcallout, CALLOUT_MPSAFE);
550 TAILQ_INSERT_HEAD(&p->p_threads, td, td_plist);
551 p->p_numthreads++;
552 }
553
554 /*
555 * Convert a process with one thread to an unthreaded process.
556 */
557 void
558 thread_unthread(struct thread *td)
559 {
560 struct proc *p = td->td_proc;
561
562 KASSERT((p->p_numthreads == 1), ("Unthreading with >1 threads"));
563 p->p_flag &= ~P_HADTHREADS;
564 }
565
566 /*
567 * Called from:
568 * thread_exit()
569 */
570 void
571 thread_unlink(struct thread *td)
572 {
573 struct proc *p = td->td_proc;
574
575 PROC_LOCK_ASSERT(p, MA_OWNED);
576 TAILQ_REMOVE(&p->p_threads, td, td_plist);
577 p->p_numthreads--;
578 /* could clear a few other things here */
579 /* Must NOT clear links to proc! */
580 }
581
582 static int
583 calc_remaining(struct proc *p, int mode)
584 {
585 int remaining;
586
587 PROC_LOCK_ASSERT(p, MA_OWNED);
588 PROC_SLOCK_ASSERT(p, MA_OWNED);
589 if (mode == SINGLE_EXIT)
590 remaining = p->p_numthreads;
591 else if (mode == SINGLE_BOUNDARY)
592 remaining = p->p_numthreads - p->p_boundary_count;
593 else if (mode == SINGLE_NO_EXIT)
594 remaining = p->p_numthreads - p->p_suspcount;
595 else
596 panic("calc_remaining: wrong mode %d", mode);
597 return (remaining);
598 }
599
600 /*
601 * Enforce single-threading.
602 *
603 * Returns 1 if the caller must abort (another thread is waiting to
604 * exit the process or similar). Process is locked!
605 * Returns 0 when you are successfully the only thread running.
606 * A process has successfully single threaded in the suspend mode when
607 * There are no threads in user mode. Threads in the kernel must be
608 * allowed to continue until they get to the user boundary. They may even
609 * copy out their return values and data before suspending. They may however be
610 * accelerated in reaching the user boundary as we will wake up
611 * any sleeping threads that are interruptable. (PCATCH).
612 */
613 int
614 thread_single(int mode)
615 {
616 struct thread *td;
617 struct thread *td2;
618 struct proc *p;
619 int remaining, wakeup_swapper;
620
621 td = curthread;
622 p = td->td_proc;
623 mtx_assert(&Giant, MA_NOTOWNED);
624 PROC_LOCK_ASSERT(p, MA_OWNED);
625
626 if ((p->p_flag & P_HADTHREADS) == 0)
627 return (0);
628
629 /* Is someone already single threading? */
630 if (p->p_singlethread != NULL && p->p_singlethread != td)
631 return (1);
632
633 if (mode == SINGLE_EXIT) {
634 p->p_flag |= P_SINGLE_EXIT;
635 p->p_flag &= ~P_SINGLE_BOUNDARY;
636 } else {
637 p->p_flag &= ~P_SINGLE_EXIT;
638 if (mode == SINGLE_BOUNDARY)
639 p->p_flag |= P_SINGLE_BOUNDARY;
640 else
641 p->p_flag &= ~P_SINGLE_BOUNDARY;
642 }
643 p->p_flag |= P_STOPPED_SINGLE;
644 PROC_SLOCK(p);
645 p->p_singlethread = td;
646 remaining = calc_remaining(p, mode);
647 while (remaining != 1) {
648 if (P_SHOULDSTOP(p) != P_STOPPED_SINGLE)
649 goto stopme;
650 wakeup_swapper = 0;
651 FOREACH_THREAD_IN_PROC(p, td2) {
652 if (td2 == td)
653 continue;
654 thread_lock(td2);
655 td2->td_flags |= TDF_ASTPENDING | TDF_NEEDSUSPCHK;
656 if (TD_IS_INHIBITED(td2)) {
657 switch (mode) {
658 case SINGLE_EXIT:
659 if (TD_IS_SUSPENDED(td2))
660 wakeup_swapper |=
661 thread_unsuspend_one(td2);
662 if (TD_ON_SLEEPQ(td2) &&
663 (td2->td_flags & TDF_SINTR))
664 wakeup_swapper |=
665 sleepq_abort(td2, EINTR);
666 break;
667 case SINGLE_BOUNDARY:
668 if (TD_IS_SUSPENDED(td2) &&
669 !(td2->td_flags & TDF_BOUNDARY))
670 wakeup_swapper |=
671 thread_unsuspend_one(td2);
672 if (TD_ON_SLEEPQ(td2) &&
673 (td2->td_flags & TDF_SINTR))
674 wakeup_swapper |=
675 sleepq_abort(td2, ERESTART);
676 break;
677 case SINGLE_NO_EXIT:
678 if (TD_IS_SUSPENDED(td2) &&
679 !(td2->td_flags & TDF_BOUNDARY))
680 wakeup_swapper |=
681 thread_unsuspend_one(td2);
682 if (TD_ON_SLEEPQ(td2) &&
683 (td2->td_flags & TDF_SINTR))
684 wakeup_swapper |=
685 sleepq_abort(td2, ERESTART);
686 break;
687 default:
688 break;
689 }
690 }
691 #ifdef SMP
692 else if (TD_IS_RUNNING(td2) && td != td2) {
693 forward_signal(td2);
694 }
695 #endif
696 thread_unlock(td2);
697 }
698 if (wakeup_swapper)
699 kick_proc0();
700 remaining = calc_remaining(p, mode);
701
702 /*
703 * Maybe we suspended some threads.. was it enough?
704 */
705 if (remaining == 1)
706 break;
707
708 stopme:
709 /*
710 * Wake us up when everyone else has suspended.
711 * In the mean time we suspend as well.
712 */
713 thread_suspend_switch(td);
714 remaining = calc_remaining(p, mode);
715 }
716 if (mode == SINGLE_EXIT) {
717 /*
718 * We have gotten rid of all the other threads and we
719 * are about to either exit or exec. In either case,
720 * we try our utmost to revert to being a non-threaded
721 * process.
722 */
723 p->p_singlethread = NULL;
724 p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT);
725 thread_unthread(td);
726 }
727 PROC_SUNLOCK(p);
728 return (0);
729 }
730
731 /*
732 * Called in from locations that can safely check to see
733 * whether we have to suspend or at least throttle for a
734 * single-thread event (e.g. fork).
735 *
736 * Such locations include userret().
737 * If the "return_instead" argument is non zero, the thread must be able to
738 * accept 0 (caller may continue), or 1 (caller must abort) as a result.
739 *
740 * The 'return_instead' argument tells the function if it may do a
741 * thread_exit() or suspend, or whether the caller must abort and back
742 * out instead.
743 *
744 * If the thread that set the single_threading request has set the
745 * P_SINGLE_EXIT bit in the process flags then this call will never return
746 * if 'return_instead' is false, but will exit.
747 *
748 * P_SINGLE_EXIT | return_instead == 0| return_instead != 0
749 *---------------+--------------------+---------------------
750 * 0 | returns 0 | returns 0 or 1
751 * | when ST ends | immediately
752 *---------------+--------------------+---------------------
753 * 1 | thread exits | returns 1
754 * | | immediately
755 * 0 = thread_exit() or suspension ok,
756 * other = return error instead of stopping the thread.
757 *
758 * While a full suspension is under effect, even a single threading
759 * thread would be suspended if it made this call (but it shouldn't).
760 * This call should only be made from places where
761 * thread_exit() would be safe as that may be the outcome unless
762 * return_instead is set.
763 */
764 int
765 thread_suspend_check(int return_instead)
766 {
767 struct thread *td;
768 struct proc *p;
769 int wakeup_swapper;
770
771 td = curthread;
772 p = td->td_proc;
773 mtx_assert(&Giant, MA_NOTOWNED);
774 PROC_LOCK_ASSERT(p, MA_OWNED);
775 while (P_SHOULDSTOP(p) ||
776 ((p->p_flag & P_TRACED) && (td->td_dbgflags & TDB_SUSPEND))) {
777 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
778 KASSERT(p->p_singlethread != NULL,
779 ("singlethread not set"));
780 /*
781 * The only suspension in action is a
782 * single-threading. Single threader need not stop.
783 * XXX Should be safe to access unlocked
784 * as it can only be set to be true by us.
785 */
786 if (p->p_singlethread == td)
787 return (0); /* Exempt from stopping. */
788 }
789 if ((p->p_flag & P_SINGLE_EXIT) && return_instead)
790 return (EINTR);
791
792 /* Should we goto user boundary if we didn't come from there? */
793 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE &&
794 (p->p_flag & P_SINGLE_BOUNDARY) && return_instead)
795 return (ERESTART);
796
797 /*
798 * Ignore suspend requests for stop signals if they
799 * are deferred.
800 */
801 if (P_SHOULDSTOP(p) == P_STOPPED_SIG &&
802 td->td_flags & TDF_SBDRY) {
803 KASSERT(return_instead,
804 ("TDF_SBDRY set for unsafe thread_suspend_check"));
805 return (0);
806 }
807
808 /*
809 * If the process is waiting for us to exit,
810 * this thread should just suicide.
811 * Assumes that P_SINGLE_EXIT implies P_STOPPED_SINGLE.
812 */
813 if ((p->p_flag & P_SINGLE_EXIT) && (p->p_singlethread != td)) {
814 PROC_UNLOCK(p);
815 tidhash_remove(td);
816 PROC_LOCK(p);
817 tdsigcleanup(td);
818 PROC_SLOCK(p);
819 thread_stopped(p);
820 thread_exit();
821 }
822
823 PROC_SLOCK(p);
824 thread_stopped(p);
825 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
826 if (p->p_numthreads == p->p_suspcount + 1) {
827 thread_lock(p->p_singlethread);
828 wakeup_swapper =
829 thread_unsuspend_one(p->p_singlethread);
830 thread_unlock(p->p_singlethread);
831 if (wakeup_swapper)
832 kick_proc0();
833 }
834 }
835 PROC_UNLOCK(p);
836 thread_lock(td);
837 /*
838 * When a thread suspends, it just
839 * gets taken off all queues.
840 */
841 thread_suspend_one(td);
842 if (return_instead == 0) {
843 p->p_boundary_count++;
844 td->td_flags |= TDF_BOUNDARY;
845 }
846 PROC_SUNLOCK(p);
847 mi_switch(SW_INVOL | SWT_SUSPEND, NULL);
848 if (return_instead == 0)
849 td->td_flags &= ~TDF_BOUNDARY;
850 thread_unlock(td);
851 PROC_LOCK(p);
852 if (return_instead == 0) {
853 PROC_SLOCK(p);
854 p->p_boundary_count--;
855 PROC_SUNLOCK(p);
856 }
857 }
858 return (0);
859 }
860
861 void
862 thread_suspend_switch(struct thread *td)
863 {
864 struct proc *p;
865
866 p = td->td_proc;
867 KASSERT(!TD_IS_SUSPENDED(td), ("already suspended"));
868 PROC_LOCK_ASSERT(p, MA_OWNED);
869 PROC_SLOCK_ASSERT(p, MA_OWNED);
870 /*
871 * We implement thread_suspend_one in stages here to avoid
872 * dropping the proc lock while the thread lock is owned.
873 */
874 thread_stopped(p);
875 p->p_suspcount++;
876 PROC_UNLOCK(p);
877 thread_lock(td);
878 td->td_flags &= ~TDF_NEEDSUSPCHK;
879 TD_SET_SUSPENDED(td);
880 sched_sleep(td, 0);
881 PROC_SUNLOCK(p);
882 DROP_GIANT();
883 mi_switch(SW_VOL | SWT_SUSPEND, NULL);
884 thread_unlock(td);
885 PICKUP_GIANT();
886 PROC_LOCK(p);
887 PROC_SLOCK(p);
888 }
889
890 void
891 thread_suspend_one(struct thread *td)
892 {
893 struct proc *p = td->td_proc;
894
895 PROC_SLOCK_ASSERT(p, MA_OWNED);
896 THREAD_LOCK_ASSERT(td, MA_OWNED);
897 KASSERT(!TD_IS_SUSPENDED(td), ("already suspended"));
898 p->p_suspcount++;
899 td->td_flags &= ~TDF_NEEDSUSPCHK;
900 TD_SET_SUSPENDED(td);
901 sched_sleep(td, 0);
902 }
903
904 int
905 thread_unsuspend_one(struct thread *td)
906 {
907 struct proc *p = td->td_proc;
908
909 PROC_SLOCK_ASSERT(p, MA_OWNED);
910 THREAD_LOCK_ASSERT(td, MA_OWNED);
911 KASSERT(TD_IS_SUSPENDED(td), ("Thread not suspended"));
912 TD_CLR_SUSPENDED(td);
913 p->p_suspcount--;
914 return (setrunnable(td));
915 }
916
917 /*
918 * Allow all threads blocked by single threading to continue running.
919 */
920 void
921 thread_unsuspend(struct proc *p)
922 {
923 struct thread *td;
924 int wakeup_swapper;
925
926 PROC_LOCK_ASSERT(p, MA_OWNED);
927 PROC_SLOCK_ASSERT(p, MA_OWNED);
928 wakeup_swapper = 0;
929 if (!P_SHOULDSTOP(p)) {
930 FOREACH_THREAD_IN_PROC(p, td) {
931 thread_lock(td);
932 if (TD_IS_SUSPENDED(td)) {
933 wakeup_swapper |= thread_unsuspend_one(td);
934 }
935 thread_unlock(td);
936 }
937 } else if ((P_SHOULDSTOP(p) == P_STOPPED_SINGLE) &&
938 (p->p_numthreads == p->p_suspcount)) {
939 /*
940 * Stopping everything also did the job for the single
941 * threading request. Now we've downgraded to single-threaded,
942 * let it continue.
943 */
944 thread_lock(p->p_singlethread);
945 wakeup_swapper = thread_unsuspend_one(p->p_singlethread);
946 thread_unlock(p->p_singlethread);
947 }
948 if (wakeup_swapper)
949 kick_proc0();
950 }
951
952 /*
953 * End the single threading mode..
954 */
955 void
956 thread_single_end(void)
957 {
958 struct thread *td;
959 struct proc *p;
960 int wakeup_swapper;
961
962 td = curthread;
963 p = td->td_proc;
964 PROC_LOCK_ASSERT(p, MA_OWNED);
965 p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT | P_SINGLE_BOUNDARY);
966 PROC_SLOCK(p);
967 p->p_singlethread = NULL;
968 wakeup_swapper = 0;
969 /*
970 * If there are other threads they may now run,
971 * unless of course there is a blanket 'stop order'
972 * on the process. The single threader must be allowed
973 * to continue however as this is a bad place to stop.
974 */
975 if ((p->p_numthreads != 1) && (!P_SHOULDSTOP(p))) {
976 FOREACH_THREAD_IN_PROC(p, td) {
977 thread_lock(td);
978 if (TD_IS_SUSPENDED(td)) {
979 wakeup_swapper |= thread_unsuspend_one(td);
980 }
981 thread_unlock(td);
982 }
983 }
984 PROC_SUNLOCK(p);
985 if (wakeup_swapper)
986 kick_proc0();
987 }
988
989 struct thread *
990 thread_find(struct proc *p, lwpid_t tid)
991 {
992 struct thread *td;
993
994 PROC_LOCK_ASSERT(p, MA_OWNED);
995 FOREACH_THREAD_IN_PROC(p, td) {
996 if (td->td_tid == tid)
997 break;
998 }
999 return (td);
1000 }
1001
1002 /* Locate a thread by number; return with proc lock held. */
1003 struct thread *
1004 tdfind(lwpid_t tid, pid_t pid)
1005 {
1006 #define RUN_THRESH 16
1007 struct thread *td;
1008 int run = 0;
1009
1010 rw_rlock(&tidhash_lock);
1011 LIST_FOREACH(td, TIDHASH(tid), td_hash) {
1012 if (td->td_tid == tid) {
1013 if (pid != -1 && td->td_proc->p_pid != pid) {
1014 td = NULL;
1015 break;
1016 }
1017 PROC_LOCK(td->td_proc);
1018 if (td->td_proc->p_state == PRS_NEW) {
1019 PROC_UNLOCK(td->td_proc);
1020 td = NULL;
1021 break;
1022 }
1023 if (run > RUN_THRESH) {
1024 if (rw_try_upgrade(&tidhash_lock)) {
1025 LIST_REMOVE(td, td_hash);
1026 LIST_INSERT_HEAD(TIDHASH(td->td_tid),
1027 td, td_hash);
1028 rw_wunlock(&tidhash_lock);
1029 return (td);
1030 }
1031 }
1032 break;
1033 }
1034 run++;
1035 }
1036 rw_runlock(&tidhash_lock);
1037 return (td);
1038 }
1039
1040 void
1041 tidhash_add(struct thread *td)
1042 {
1043 rw_wlock(&tidhash_lock);
1044 LIST_INSERT_HEAD(TIDHASH(td->td_tid), td, td_hash);
1045 rw_wunlock(&tidhash_lock);
1046 }
1047
1048 void
1049 tidhash_remove(struct thread *td)
1050 {
1051 rw_wlock(&tidhash_lock);
1052 LIST_REMOVE(td, td_hash);
1053 rw_wunlock(&tidhash_lock);
1054 }
Cache object: b209b06e562c5d50b941d8e56564b5cc
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