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/9.1/sys/kern/kern_thread.c 236344 2012-05-30 23:22:52Z rstone $");
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/resourcevar.h>
43 #include <sys/sdt.h>
44 #include <sys/smp.h>
45 #include <sys/sched.h>
46 #include <sys/sleepqueue.h>
47 #include <sys/selinfo.h>
48 #include <sys/turnstile.h>
49 #include <sys/ktr.h>
50 #include <sys/rwlock.h>
51 #include <sys/umtx.h>
52 #include <sys/cpuset.h>
53 #ifdef HWPMC_HOOKS
54 #include <sys/pmckern.h>
55 #endif
56
57 #include <security/audit/audit.h>
58
59 #include <vm/vm.h>
60 #include <vm/vm_extern.h>
61 #include <vm/uma.h>
62 #include <sys/eventhandler.h>
63
64 SDT_PROVIDER_DECLARE(proc);
65 SDT_PROBE_DEFINE(proc, , , lwp_exit, lwp-exit);
66
67
68 /*
69 * thread related storage.
70 */
71 static uma_zone_t thread_zone;
72
73 TAILQ_HEAD(, thread) zombie_threads = TAILQ_HEAD_INITIALIZER(zombie_threads);
74 static struct mtx zombie_lock;
75 MTX_SYSINIT(zombie_lock, &zombie_lock, "zombie lock", MTX_SPIN);
76
77 static void thread_zombie(struct thread *);
78
79 #define TID_BUFFER_SIZE 1024
80
81 struct mtx tid_lock;
82 static struct unrhdr *tid_unrhdr;
83 static lwpid_t tid_buffer[TID_BUFFER_SIZE];
84 static int tid_head, tid_tail;
85 static MALLOC_DEFINE(M_TIDHASH, "tidhash", "thread hash");
86
87 struct tidhashhead *tidhashtbl;
88 u_long tidhash;
89 struct rwlock tidhash_lock;
90
91 static lwpid_t
92 tid_alloc(void)
93 {
94 lwpid_t tid;
95
96 tid = alloc_unr(tid_unrhdr);
97 if (tid != -1)
98 return (tid);
99 mtx_lock(&tid_lock);
100 if (tid_head == tid_tail) {
101 mtx_unlock(&tid_lock);
102 return (-1);
103 }
104 tid = tid_buffer[tid_head++];
105 tid_head %= TID_BUFFER_SIZE;
106 mtx_unlock(&tid_lock);
107 return (tid);
108 }
109
110 static void
111 tid_free(lwpid_t tid)
112 {
113 lwpid_t tmp_tid = -1;
114
115 mtx_lock(&tid_lock);
116 if ((tid_tail + 1) % TID_BUFFER_SIZE == tid_head) {
117 tmp_tid = tid_buffer[tid_head++];
118 tid_head = (tid_head + 1) % TID_BUFFER_SIZE;
119 }
120 tid_buffer[tid_tail++] = tid;
121 tid_tail %= TID_BUFFER_SIZE;
122 mtx_unlock(&tid_lock);
123 if (tmp_tid != -1)
124 free_unr(tid_unrhdr, tmp_tid);
125 }
126
127 /*
128 * Prepare a thread for use.
129 */
130 static int
131 thread_ctor(void *mem, int size, void *arg, int flags)
132 {
133 struct thread *td;
134
135 td = (struct thread *)mem;
136 td->td_state = TDS_INACTIVE;
137 td->td_oncpu = NOCPU;
138
139 td->td_tid = tid_alloc();
140
141 /*
142 * Note that td_critnest begins life as 1 because the thread is not
143 * running and is thereby implicitly waiting to be on the receiving
144 * end of a context switch.
145 */
146 td->td_critnest = 1;
147 td->td_lend_user_pri = PRI_MAX;
148 EVENTHANDLER_INVOKE(thread_ctor, td);
149 #ifdef AUDIT
150 audit_thread_alloc(td);
151 #endif
152 umtx_thread_alloc(td);
153 return (0);
154 }
155
156 /*
157 * Reclaim a thread after use.
158 */
159 static void
160 thread_dtor(void *mem, int size, void *arg)
161 {
162 struct thread *td;
163
164 td = (struct thread *)mem;
165
166 #ifdef INVARIANTS
167 /* Verify that this thread is in a safe state to free. */
168 switch (td->td_state) {
169 case TDS_INHIBITED:
170 case TDS_RUNNING:
171 case TDS_CAN_RUN:
172 case TDS_RUNQ:
173 /*
174 * We must never unlink a thread that is in one of
175 * these states, because it is currently active.
176 */
177 panic("bad state for thread unlinking");
178 /* NOTREACHED */
179 case TDS_INACTIVE:
180 break;
181 default:
182 panic("bad thread state");
183 /* NOTREACHED */
184 }
185 #endif
186 #ifdef AUDIT
187 audit_thread_free(td);
188 #endif
189 /* Free all OSD associated to this thread. */
190 osd_thread_exit(td);
191
192 EVENTHANDLER_INVOKE(thread_dtor, td);
193 tid_free(td->td_tid);
194 }
195
196 /*
197 * Initialize type-stable parts of a thread (when newly created).
198 */
199 static int
200 thread_init(void *mem, int size, int flags)
201 {
202 struct thread *td;
203
204 td = (struct thread *)mem;
205
206 td->td_sleepqueue = sleepq_alloc();
207 td->td_turnstile = turnstile_alloc();
208 EVENTHANDLER_INVOKE(thread_init, td);
209 td->td_sched = (struct td_sched *)&td[1];
210 umtx_thread_init(td);
211 td->td_kstack = 0;
212 return (0);
213 }
214
215 /*
216 * Tear down type-stable parts of a thread (just before being discarded).
217 */
218 static void
219 thread_fini(void *mem, int size)
220 {
221 struct thread *td;
222
223 td = (struct thread *)mem;
224 EVENTHANDLER_INVOKE(thread_fini, td);
225 turnstile_free(td->td_turnstile);
226 sleepq_free(td->td_sleepqueue);
227 umtx_thread_fini(td);
228 seltdfini(td);
229 }
230
231 /*
232 * For a newly created process,
233 * link up all the structures and its initial threads etc.
234 * called from:
235 * {arch}/{arch}/machdep.c ia64_init(), init386() etc.
236 * proc_dtor() (should go away)
237 * proc_init()
238 */
239 void
240 proc_linkup0(struct proc *p, struct thread *td)
241 {
242 TAILQ_INIT(&p->p_threads); /* all threads in proc */
243 proc_linkup(p, td);
244 }
245
246 void
247 proc_linkup(struct proc *p, struct thread *td)
248 {
249
250 sigqueue_init(&p->p_sigqueue, p);
251 p->p_ksi = ksiginfo_alloc(1);
252 if (p->p_ksi != NULL) {
253 /* XXX p_ksi may be null if ksiginfo zone is not ready */
254 p->p_ksi->ksi_flags = KSI_EXT | KSI_INS;
255 }
256 LIST_INIT(&p->p_mqnotifier);
257 p->p_numthreads = 0;
258 thread_link(td, p);
259 }
260
261 /*
262 * Initialize global thread allocation resources.
263 */
264 void
265 threadinit(void)
266 {
267
268 mtx_init(&tid_lock, "TID lock", NULL, MTX_DEF);
269 /* leave one number for thread0 */
270 tid_unrhdr = new_unrhdr(PID_MAX + 2, INT_MAX, &tid_lock);
271
272 thread_zone = uma_zcreate("THREAD", sched_sizeof_thread(),
273 thread_ctor, thread_dtor, thread_init, thread_fini,
274 16 - 1, 0);
275 tidhashtbl = hashinit(maxproc / 2, M_TIDHASH, &tidhash);
276 rw_init(&tidhash_lock, "tidhash");
277 }
278
279 /*
280 * Place an unused thread on the zombie list.
281 * Use the slpq as that must be unused by now.
282 */
283 void
284 thread_zombie(struct thread *td)
285 {
286 mtx_lock_spin(&zombie_lock);
287 TAILQ_INSERT_HEAD(&zombie_threads, td, td_slpq);
288 mtx_unlock_spin(&zombie_lock);
289 }
290
291 /*
292 * Release a thread that has exited after cpu_throw().
293 */
294 void
295 thread_stash(struct thread *td)
296 {
297 atomic_subtract_rel_int(&td->td_proc->p_exitthreads, 1);
298 thread_zombie(td);
299 }
300
301 /*
302 * Reap zombie resources.
303 */
304 void
305 thread_reap(void)
306 {
307 struct thread *td_first, *td_next;
308
309 /*
310 * Don't even bother to lock if none at this instant,
311 * we really don't care about the next instant..
312 */
313 if (!TAILQ_EMPTY(&zombie_threads)) {
314 mtx_lock_spin(&zombie_lock);
315 td_first = TAILQ_FIRST(&zombie_threads);
316 if (td_first)
317 TAILQ_INIT(&zombie_threads);
318 mtx_unlock_spin(&zombie_lock);
319 while (td_first) {
320 td_next = TAILQ_NEXT(td_first, td_slpq);
321 if (td_first->td_ucred)
322 crfree(td_first->td_ucred);
323 thread_free(td_first);
324 td_first = td_next;
325 }
326 }
327 }
328
329 /*
330 * Allocate a thread.
331 */
332 struct thread *
333 thread_alloc(int pages)
334 {
335 struct thread *td;
336
337 thread_reap(); /* check if any zombies to get */
338
339 td = (struct thread *)uma_zalloc(thread_zone, M_WAITOK);
340 KASSERT(td->td_kstack == 0, ("thread_alloc got thread with kstack"));
341 if (!vm_thread_new(td, pages)) {
342 uma_zfree(thread_zone, td);
343 return (NULL);
344 }
345 cpu_thread_alloc(td);
346 return (td);
347 }
348
349 int
350 thread_alloc_stack(struct thread *td, int pages)
351 {
352
353 KASSERT(td->td_kstack == 0,
354 ("thread_alloc_stack called on a thread with kstack"));
355 if (!vm_thread_new(td, pages))
356 return (0);
357 cpu_thread_alloc(td);
358 return (1);
359 }
360
361 /*
362 * Deallocate a thread.
363 */
364 void
365 thread_free(struct thread *td)
366 {
367
368 lock_profile_thread_exit(td);
369 if (td->td_cpuset)
370 cpuset_rel(td->td_cpuset);
371 td->td_cpuset = NULL;
372 cpu_thread_free(td);
373 if (td->td_kstack != 0)
374 vm_thread_dispose(td);
375 uma_zfree(thread_zone, td);
376 }
377
378 /*
379 * Discard the current thread and exit from its context.
380 * Always called with scheduler locked.
381 *
382 * Because we can't free a thread while we're operating under its context,
383 * push the current thread into our CPU's deadthread holder. This means
384 * we needn't worry about someone else grabbing our context before we
385 * do a cpu_throw().
386 */
387 void
388 thread_exit(void)
389 {
390 uint64_t runtime, new_switchtime;
391 struct thread *td;
392 struct thread *td2;
393 struct proc *p;
394 int wakeup_swapper;
395
396 td = curthread;
397 p = td->td_proc;
398
399 PROC_SLOCK_ASSERT(p, MA_OWNED);
400 mtx_assert(&Giant, MA_NOTOWNED);
401
402 PROC_LOCK_ASSERT(p, MA_OWNED);
403 KASSERT(p != NULL, ("thread exiting without a process"));
404 CTR3(KTR_PROC, "thread_exit: thread %p (pid %ld, %s)", td,
405 (long)p->p_pid, td->td_name);
406 KASSERT(TAILQ_EMPTY(&td->td_sigqueue.sq_list), ("signal pending"));
407
408 #ifdef AUDIT
409 AUDIT_SYSCALL_EXIT(0, td);
410 #endif
411 umtx_thread_exit(td);
412 /*
413 * drop FPU & debug register state storage, or any other
414 * architecture specific resources that
415 * would not be on a new untouched process.
416 */
417 cpu_thread_exit(td); /* XXXSMP */
418
419 /*
420 * The last thread is left attached to the process
421 * So that the whole bundle gets recycled. Skip
422 * all this stuff if we never had threads.
423 * EXIT clears all sign of other threads when
424 * it goes to single threading, so the last thread always
425 * takes the short path.
426 */
427 if (p->p_flag & P_HADTHREADS) {
428 if (p->p_numthreads > 1) {
429 thread_unlink(td);
430 td2 = FIRST_THREAD_IN_PROC(p);
431 sched_exit_thread(td2, td);
432
433 /*
434 * The test below is NOT true if we are the
435 * sole exiting thread. P_STOPPED_SINGLE is unset
436 * in exit1() after it is the only survivor.
437 */
438 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
439 if (p->p_numthreads == p->p_suspcount) {
440 thread_lock(p->p_singlethread);
441 wakeup_swapper = thread_unsuspend_one(
442 p->p_singlethread);
443 thread_unlock(p->p_singlethread);
444 if (wakeup_swapper)
445 kick_proc0();
446 }
447 }
448
449 atomic_add_int(&td->td_proc->p_exitthreads, 1);
450 PCPU_SET(deadthread, td);
451 } else {
452 /*
453 * The last thread is exiting.. but not through exit()
454 */
455 panic ("thread_exit: Last thread exiting on its own");
456 }
457 }
458 #ifdef HWPMC_HOOKS
459 /*
460 * If this thread is part of a process that is being tracked by hwpmc(4),
461 * inform the module of the thread's impending exit.
462 */
463 if (PMC_PROC_IS_USING_PMCS(td->td_proc))
464 PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_OUT);
465 #endif
466 PROC_UNLOCK(p);
467
468 /* Do the same timestamp bookkeeping that mi_switch() would do. */
469 new_switchtime = cpu_ticks();
470 runtime = new_switchtime - PCPU_GET(switchtime);
471 td->td_runtime += runtime;
472 td->td_incruntime += runtime;
473 PCPU_SET(switchtime, new_switchtime);
474 PCPU_SET(switchticks, ticks);
475 PCPU_INC(cnt.v_swtch);
476
477 /* Save our resource usage in our process. */
478 td->td_ru.ru_nvcsw++;
479 ruxagg(p, td);
480 rucollect(&p->p_ru, &td->td_ru);
481
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 PROC_LOCK_ASSERT(p, MA_OWNED);
581 PROC_SLOCK_ASSERT(p, MA_OWNED);
582 if (mode == SINGLE_EXIT)
583 remaining = p->p_numthreads;
584 else if (mode == SINGLE_BOUNDARY)
585 remaining = p->p_numthreads - p->p_boundary_count;
586 else if (mode == SINGLE_NO_EXIT)
587 remaining = p->p_numthreads - p->p_suspcount;
588 else
589 panic("calc_remaining: wrong mode %d", mode);
590 return (remaining);
591 }
592
593 /*
594 * Enforce single-threading.
595 *
596 * Returns 1 if the caller must abort (another thread is waiting to
597 * exit the process or similar). Process is locked!
598 * Returns 0 when you are successfully the only thread running.
599 * A process has successfully single threaded in the suspend mode when
600 * There are no threads in user mode. Threads in the kernel must be
601 * allowed to continue until they get to the user boundary. They may even
602 * copy out their return values and data before suspending. They may however be
603 * accelerated in reaching the user boundary as we will wake up
604 * any sleeping threads that are interruptable. (PCATCH).
605 */
606 int
607 thread_single(int mode)
608 {
609 struct thread *td;
610 struct thread *td2;
611 struct proc *p;
612 int remaining, wakeup_swapper;
613
614 td = curthread;
615 p = td->td_proc;
616 mtx_assert(&Giant, MA_NOTOWNED);
617 PROC_LOCK_ASSERT(p, MA_OWNED);
618 KASSERT((td != NULL), ("curthread is NULL"));
619
620 if ((p->p_flag & P_HADTHREADS) == 0)
621 return (0);
622
623 /* Is someone already single threading? */
624 if (p->p_singlethread != NULL && p->p_singlethread != td)
625 return (1);
626
627 if (mode == SINGLE_EXIT) {
628 p->p_flag |= P_SINGLE_EXIT;
629 p->p_flag &= ~P_SINGLE_BOUNDARY;
630 } else {
631 p->p_flag &= ~P_SINGLE_EXIT;
632 if (mode == SINGLE_BOUNDARY)
633 p->p_flag |= P_SINGLE_BOUNDARY;
634 else
635 p->p_flag &= ~P_SINGLE_BOUNDARY;
636 }
637 p->p_flag |= P_STOPPED_SINGLE;
638 PROC_SLOCK(p);
639 p->p_singlethread = td;
640 remaining = calc_remaining(p, mode);
641 while (remaining != 1) {
642 if (P_SHOULDSTOP(p) != P_STOPPED_SINGLE)
643 goto stopme;
644 wakeup_swapper = 0;
645 FOREACH_THREAD_IN_PROC(p, td2) {
646 if (td2 == td)
647 continue;
648 thread_lock(td2);
649 td2->td_flags |= TDF_ASTPENDING | TDF_NEEDSUSPCHK;
650 if (TD_IS_INHIBITED(td2)) {
651 switch (mode) {
652 case SINGLE_EXIT:
653 if (TD_IS_SUSPENDED(td2))
654 wakeup_swapper |=
655 thread_unsuspend_one(td2);
656 if (TD_ON_SLEEPQ(td2) &&
657 (td2->td_flags & TDF_SINTR))
658 wakeup_swapper |=
659 sleepq_abort(td2, EINTR);
660 break;
661 case SINGLE_BOUNDARY:
662 if (TD_IS_SUSPENDED(td2) &&
663 !(td2->td_flags & TDF_BOUNDARY))
664 wakeup_swapper |=
665 thread_unsuspend_one(td2);
666 if (TD_ON_SLEEPQ(td2) &&
667 (td2->td_flags & TDF_SINTR))
668 wakeup_swapper |=
669 sleepq_abort(td2, ERESTART);
670 break;
671 case SINGLE_NO_EXIT:
672 if (TD_IS_SUSPENDED(td2) &&
673 !(td2->td_flags & TDF_BOUNDARY))
674 wakeup_swapper |=
675 thread_unsuspend_one(td2);
676 if (TD_ON_SLEEPQ(td2) &&
677 (td2->td_flags & TDF_SINTR))
678 wakeup_swapper |=
679 sleepq_abort(td2, ERESTART);
680 break;
681 default:
682 break;
683 }
684 }
685 #ifdef SMP
686 else if (TD_IS_RUNNING(td2) && td != td2) {
687 forward_signal(td2);
688 }
689 #endif
690 thread_unlock(td2);
691 }
692 if (wakeup_swapper)
693 kick_proc0();
694 remaining = calc_remaining(p, mode);
695
696 /*
697 * Maybe we suspended some threads.. was it enough?
698 */
699 if (remaining == 1)
700 break;
701
702 stopme:
703 /*
704 * Wake us up when everyone else has suspended.
705 * In the mean time we suspend as well.
706 */
707 thread_suspend_switch(td);
708 remaining = calc_remaining(p, mode);
709 }
710 if (mode == SINGLE_EXIT) {
711 /*
712 * We have gotten rid of all the other threads and we
713 * are about to either exit or exec. In either case,
714 * we try our utmost to revert to being a non-threaded
715 * process.
716 */
717 p->p_singlethread = NULL;
718 p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT);
719 thread_unthread(td);
720 }
721 PROC_SUNLOCK(p);
722 return (0);
723 }
724
725 /*
726 * Called in from locations that can safely check to see
727 * whether we have to suspend or at least throttle for a
728 * single-thread event (e.g. fork).
729 *
730 * Such locations include userret().
731 * If the "return_instead" argument is non zero, the thread must be able to
732 * accept 0 (caller may continue), or 1 (caller must abort) as a result.
733 *
734 * The 'return_instead' argument tells the function if it may do a
735 * thread_exit() or suspend, or whether the caller must abort and back
736 * out instead.
737 *
738 * If the thread that set the single_threading request has set the
739 * P_SINGLE_EXIT bit in the process flags then this call will never return
740 * if 'return_instead' is false, but will exit.
741 *
742 * P_SINGLE_EXIT | return_instead == 0| return_instead != 0
743 *---------------+--------------------+---------------------
744 * 0 | returns 0 | returns 0 or 1
745 * | when ST ends | immediatly
746 *---------------+--------------------+---------------------
747 * 1 | thread exits | returns 1
748 * | | immediatly
749 * 0 = thread_exit() or suspension ok,
750 * other = return error instead of stopping the thread.
751 *
752 * While a full suspension is under effect, even a single threading
753 * thread would be suspended if it made this call (but it shouldn't).
754 * This call should only be made from places where
755 * thread_exit() would be safe as that may be the outcome unless
756 * return_instead is set.
757 */
758 int
759 thread_suspend_check(int return_instead)
760 {
761 struct thread *td;
762 struct proc *p;
763 int wakeup_swapper;
764
765 td = curthread;
766 p = td->td_proc;
767 mtx_assert(&Giant, MA_NOTOWNED);
768 PROC_LOCK_ASSERT(p, MA_OWNED);
769 while (P_SHOULDSTOP(p) ||
770 ((p->p_flag & P_TRACED) && (td->td_dbgflags & TDB_SUSPEND))) {
771 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
772 KASSERT(p->p_singlethread != NULL,
773 ("singlethread not set"));
774 /*
775 * The only suspension in action is a
776 * single-threading. Single threader need not stop.
777 * XXX Should be safe to access unlocked
778 * as it can only be set to be true by us.
779 */
780 if (p->p_singlethread == td)
781 return (0); /* Exempt from stopping. */
782 }
783 if ((p->p_flag & P_SINGLE_EXIT) && return_instead)
784 return (EINTR);
785
786 /* Should we goto user boundary if we didn't come from there? */
787 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE &&
788 (p->p_flag & P_SINGLE_BOUNDARY) && return_instead)
789 return (ERESTART);
790
791 /*
792 * If the process is waiting for us to exit,
793 * this thread should just suicide.
794 * Assumes that P_SINGLE_EXIT implies P_STOPPED_SINGLE.
795 */
796 if ((p->p_flag & P_SINGLE_EXIT) && (p->p_singlethread != td)) {
797 PROC_UNLOCK(p);
798 tidhash_remove(td);
799 PROC_LOCK(p);
800 tdsigcleanup(td);
801 PROC_SLOCK(p);
802 thread_stopped(p);
803 thread_exit();
804 }
805
806 PROC_SLOCK(p);
807 thread_stopped(p);
808 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
809 if (p->p_numthreads == p->p_suspcount + 1) {
810 thread_lock(p->p_singlethread);
811 wakeup_swapper =
812 thread_unsuspend_one(p->p_singlethread);
813 thread_unlock(p->p_singlethread);
814 if (wakeup_swapper)
815 kick_proc0();
816 }
817 }
818 PROC_UNLOCK(p);
819 thread_lock(td);
820 /*
821 * When a thread suspends, it just
822 * gets taken off all queues.
823 */
824 thread_suspend_one(td);
825 if (return_instead == 0) {
826 p->p_boundary_count++;
827 td->td_flags |= TDF_BOUNDARY;
828 }
829 PROC_SUNLOCK(p);
830 mi_switch(SW_INVOL | SWT_SUSPEND, NULL);
831 if (return_instead == 0)
832 td->td_flags &= ~TDF_BOUNDARY;
833 thread_unlock(td);
834 PROC_LOCK(p);
835 if (return_instead == 0) {
836 PROC_SLOCK(p);
837 p->p_boundary_count--;
838 PROC_SUNLOCK(p);
839 }
840 }
841 return (0);
842 }
843
844 void
845 thread_suspend_switch(struct thread *td)
846 {
847 struct proc *p;
848
849 p = td->td_proc;
850 KASSERT(!TD_IS_SUSPENDED(td), ("already suspended"));
851 PROC_LOCK_ASSERT(p, MA_OWNED);
852 PROC_SLOCK_ASSERT(p, MA_OWNED);
853 /*
854 * We implement thread_suspend_one in stages here to avoid
855 * dropping the proc lock while the thread lock is owned.
856 */
857 thread_stopped(p);
858 p->p_suspcount++;
859 PROC_UNLOCK(p);
860 thread_lock(td);
861 td->td_flags &= ~TDF_NEEDSUSPCHK;
862 TD_SET_SUSPENDED(td);
863 sched_sleep(td, 0);
864 PROC_SUNLOCK(p);
865 DROP_GIANT();
866 mi_switch(SW_VOL | SWT_SUSPEND, NULL);
867 thread_unlock(td);
868 PICKUP_GIANT();
869 PROC_LOCK(p);
870 PROC_SLOCK(p);
871 }
872
873 void
874 thread_suspend_one(struct thread *td)
875 {
876 struct proc *p = td->td_proc;
877
878 PROC_SLOCK_ASSERT(p, MA_OWNED);
879 THREAD_LOCK_ASSERT(td, MA_OWNED);
880 KASSERT(!TD_IS_SUSPENDED(td), ("already suspended"));
881 p->p_suspcount++;
882 td->td_flags &= ~TDF_NEEDSUSPCHK;
883 TD_SET_SUSPENDED(td);
884 sched_sleep(td, 0);
885 }
886
887 int
888 thread_unsuspend_one(struct thread *td)
889 {
890 struct proc *p = td->td_proc;
891
892 PROC_SLOCK_ASSERT(p, MA_OWNED);
893 THREAD_LOCK_ASSERT(td, MA_OWNED);
894 KASSERT(TD_IS_SUSPENDED(td), ("Thread not suspended"));
895 TD_CLR_SUSPENDED(td);
896 p->p_suspcount--;
897 return (setrunnable(td));
898 }
899
900 /*
901 * Allow all threads blocked by single threading to continue running.
902 */
903 void
904 thread_unsuspend(struct proc *p)
905 {
906 struct thread *td;
907 int wakeup_swapper;
908
909 PROC_LOCK_ASSERT(p, MA_OWNED);
910 PROC_SLOCK_ASSERT(p, MA_OWNED);
911 wakeup_swapper = 0;
912 if (!P_SHOULDSTOP(p)) {
913 FOREACH_THREAD_IN_PROC(p, td) {
914 thread_lock(td);
915 if (TD_IS_SUSPENDED(td)) {
916 wakeup_swapper |= thread_unsuspend_one(td);
917 }
918 thread_unlock(td);
919 }
920 } else if ((P_SHOULDSTOP(p) == P_STOPPED_SINGLE) &&
921 (p->p_numthreads == p->p_suspcount)) {
922 /*
923 * Stopping everything also did the job for the single
924 * threading request. Now we've downgraded to single-threaded,
925 * let it continue.
926 */
927 thread_lock(p->p_singlethread);
928 wakeup_swapper = thread_unsuspend_one(p->p_singlethread);
929 thread_unlock(p->p_singlethread);
930 }
931 if (wakeup_swapper)
932 kick_proc0();
933 }
934
935 /*
936 * End the single threading mode..
937 */
938 void
939 thread_single_end(void)
940 {
941 struct thread *td;
942 struct proc *p;
943 int wakeup_swapper;
944
945 td = curthread;
946 p = td->td_proc;
947 PROC_LOCK_ASSERT(p, MA_OWNED);
948 p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT | P_SINGLE_BOUNDARY);
949 PROC_SLOCK(p);
950 p->p_singlethread = NULL;
951 wakeup_swapper = 0;
952 /*
953 * If there are other threads they may now run,
954 * unless of course there is a blanket 'stop order'
955 * on the process. The single threader must be allowed
956 * to continue however as this is a bad place to stop.
957 */
958 if ((p->p_numthreads != 1) && (!P_SHOULDSTOP(p))) {
959 FOREACH_THREAD_IN_PROC(p, td) {
960 thread_lock(td);
961 if (TD_IS_SUSPENDED(td)) {
962 wakeup_swapper |= thread_unsuspend_one(td);
963 }
964 thread_unlock(td);
965 }
966 }
967 PROC_SUNLOCK(p);
968 if (wakeup_swapper)
969 kick_proc0();
970 }
971
972 struct thread *
973 thread_find(struct proc *p, lwpid_t tid)
974 {
975 struct thread *td;
976
977 PROC_LOCK_ASSERT(p, MA_OWNED);
978 FOREACH_THREAD_IN_PROC(p, td) {
979 if (td->td_tid == tid)
980 break;
981 }
982 return (td);
983 }
984
985 /* Locate a thread by number; return with proc lock held. */
986 struct thread *
987 tdfind(lwpid_t tid, pid_t pid)
988 {
989 #define RUN_THRESH 16
990 struct thread *td;
991 int run = 0;
992
993 rw_rlock(&tidhash_lock);
994 LIST_FOREACH(td, TIDHASH(tid), td_hash) {
995 if (td->td_tid == tid) {
996 if (pid != -1 && td->td_proc->p_pid != pid) {
997 td = NULL;
998 break;
999 }
1000 PROC_LOCK(td->td_proc);
1001 if (td->td_proc->p_state == PRS_NEW) {
1002 PROC_UNLOCK(td->td_proc);
1003 td = NULL;
1004 break;
1005 }
1006 if (run > RUN_THRESH) {
1007 if (rw_try_upgrade(&tidhash_lock)) {
1008 LIST_REMOVE(td, td_hash);
1009 LIST_INSERT_HEAD(TIDHASH(td->td_tid),
1010 td, td_hash);
1011 rw_wunlock(&tidhash_lock);
1012 return (td);
1013 }
1014 }
1015 break;
1016 }
1017 run++;
1018 }
1019 rw_runlock(&tidhash_lock);
1020 return (td);
1021 }
1022
1023 void
1024 tidhash_add(struct thread *td)
1025 {
1026 rw_wlock(&tidhash_lock);
1027 LIST_INSERT_HEAD(TIDHASH(td->td_tid), td, td_hash);
1028 rw_wunlock(&tidhash_lock);
1029 }
1030
1031 void
1032 tidhash_remove(struct thread *td)
1033 {
1034 rw_wlock(&tidhash_lock);
1035 LIST_REMOVE(td, td_hash);
1036 rw_wunlock(&tidhash_lock);
1037 }
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