1 /*-
2 * Copyright (C) 2001 Julian Elischer <julian@freebsd.org>.
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice(s), this list of conditions and the following disclaimer as
10 * the first lines of this file unmodified other than the possible
11 * addition of one or more copyright notices.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice(s), this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY
17 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
18 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
19 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE LIABLE FOR ANY
20 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
21 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
22 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
23 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
26 * DAMAGE.
27 */
28
29 #include "opt_witness.h"
30 #include "opt_hwpmc_hooks.h"
31
32 #include <sys/cdefs.h>
33 __FBSDID("$FreeBSD: releng/9.0/sys/kern/kern_thread.c 227886 2011-11-23 15:16:05Z kib $");
34
35 #include <sys/param.h>
36 #include <sys/systm.h>
37 #include <sys/kernel.h>
38 #include <sys/lock.h>
39 #include <sys/mutex.h>
40 #include <sys/proc.h>
41 #include <sys/resourcevar.h>
42 #include <sys/smp.h>
43 #include <sys/sched.h>
44 #include <sys/sleepqueue.h>
45 #include <sys/selinfo.h>
46 #include <sys/turnstile.h>
47 #include <sys/ktr.h>
48 #include <sys/rwlock.h>
49 #include <sys/umtx.h>
50 #include <sys/cpuset.h>
51 #ifdef HWPMC_HOOKS
52 #include <sys/pmckern.h>
53 #endif
54
55 #include <security/audit/audit.h>
56
57 #include <vm/vm.h>
58 #include <vm/vm_extern.h>
59 #include <vm/uma.h>
60 #include <sys/eventhandler.h>
61
62 /*
63 * thread related storage.
64 */
65 static uma_zone_t thread_zone;
66
67 TAILQ_HEAD(, thread) zombie_threads = TAILQ_HEAD_INITIALIZER(zombie_threads);
68 static struct mtx zombie_lock;
69 MTX_SYSINIT(zombie_lock, &zombie_lock, "zombie lock", MTX_SPIN);
70
71 static void thread_zombie(struct thread *);
72
73 #define TID_BUFFER_SIZE 1024
74
75 struct mtx tid_lock;
76 static struct unrhdr *tid_unrhdr;
77 static lwpid_t tid_buffer[TID_BUFFER_SIZE];
78 static int tid_head, tid_tail;
79 static MALLOC_DEFINE(M_TIDHASH, "tidhash", "thread hash");
80
81 struct tidhashhead *tidhashtbl;
82 u_long tidhash;
83 struct rwlock tidhash_lock;
84
85 static lwpid_t
86 tid_alloc(void)
87 {
88 lwpid_t tid;
89
90 tid = alloc_unr(tid_unrhdr);
91 if (tid != -1)
92 return (tid);
93 mtx_lock(&tid_lock);
94 if (tid_head == tid_tail) {
95 mtx_unlock(&tid_lock);
96 return (-1);
97 }
98 tid = tid_buffer[tid_head++];
99 tid_head %= TID_BUFFER_SIZE;
100 mtx_unlock(&tid_lock);
101 return (tid);
102 }
103
104 static void
105 tid_free(lwpid_t tid)
106 {
107 lwpid_t tmp_tid = -1;
108
109 mtx_lock(&tid_lock);
110 if ((tid_tail + 1) % TID_BUFFER_SIZE == tid_head) {
111 tmp_tid = tid_buffer[tid_head++];
112 tid_head = (tid_head + 1) % TID_BUFFER_SIZE;
113 }
114 tid_buffer[tid_tail++] = tid;
115 tid_tail %= TID_BUFFER_SIZE;
116 mtx_unlock(&tid_lock);
117 if (tmp_tid != -1)
118 free_unr(tid_unrhdr, tmp_tid);
119 }
120
121 /*
122 * Prepare a thread for use.
123 */
124 static int
125 thread_ctor(void *mem, int size, void *arg, int flags)
126 {
127 struct thread *td;
128
129 td = (struct thread *)mem;
130 td->td_state = TDS_INACTIVE;
131 td->td_oncpu = NOCPU;
132
133 td->td_tid = tid_alloc();
134
135 /*
136 * Note that td_critnest begins life as 1 because the thread is not
137 * running and is thereby implicitly waiting to be on the receiving
138 * end of a context switch.
139 */
140 td->td_critnest = 1;
141 td->td_lend_user_pri = PRI_MAX;
142 EVENTHANDLER_INVOKE(thread_ctor, td);
143 #ifdef AUDIT
144 audit_thread_alloc(td);
145 #endif
146 umtx_thread_alloc(td);
147 return (0);
148 }
149
150 /*
151 * Reclaim a thread after use.
152 */
153 static void
154 thread_dtor(void *mem, int size, void *arg)
155 {
156 struct thread *td;
157
158 td = (struct thread *)mem;
159
160 #ifdef INVARIANTS
161 /* Verify that this thread is in a safe state to free. */
162 switch (td->td_state) {
163 case TDS_INHIBITED:
164 case TDS_RUNNING:
165 case TDS_CAN_RUN:
166 case TDS_RUNQ:
167 /*
168 * We must never unlink a thread that is in one of
169 * these states, because it is currently active.
170 */
171 panic("bad state for thread unlinking");
172 /* NOTREACHED */
173 case TDS_INACTIVE:
174 break;
175 default:
176 panic("bad thread state");
177 /* NOTREACHED */
178 }
179 #endif
180 #ifdef AUDIT
181 audit_thread_free(td);
182 #endif
183 /* Free all OSD associated to this thread. */
184 osd_thread_exit(td);
185
186 EVENTHANDLER_INVOKE(thread_dtor, td);
187 tid_free(td->td_tid);
188 }
189
190 /*
191 * Initialize type-stable parts of a thread (when newly created).
192 */
193 static int
194 thread_init(void *mem, int size, int flags)
195 {
196 struct thread *td;
197
198 td = (struct thread *)mem;
199
200 td->td_sleepqueue = sleepq_alloc();
201 td->td_turnstile = turnstile_alloc();
202 EVENTHANDLER_INVOKE(thread_init, td);
203 td->td_sched = (struct td_sched *)&td[1];
204 umtx_thread_init(td);
205 td->td_kstack = 0;
206 return (0);
207 }
208
209 /*
210 * Tear down type-stable parts of a thread (just before being discarded).
211 */
212 static void
213 thread_fini(void *mem, int size)
214 {
215 struct thread *td;
216
217 td = (struct thread *)mem;
218 EVENTHANDLER_INVOKE(thread_fini, td);
219 turnstile_free(td->td_turnstile);
220 sleepq_free(td->td_sleepqueue);
221 umtx_thread_fini(td);
222 seltdfini(td);
223 }
224
225 /*
226 * For a newly created process,
227 * link up all the structures and its initial threads etc.
228 * called from:
229 * {arch}/{arch}/machdep.c ia64_init(), init386() etc.
230 * proc_dtor() (should go away)
231 * proc_init()
232 */
233 void
234 proc_linkup0(struct proc *p, struct thread *td)
235 {
236 TAILQ_INIT(&p->p_threads); /* all threads in proc */
237 proc_linkup(p, td);
238 }
239
240 void
241 proc_linkup(struct proc *p, struct thread *td)
242 {
243
244 sigqueue_init(&p->p_sigqueue, p);
245 p->p_ksi = ksiginfo_alloc(1);
246 if (p->p_ksi != NULL) {
247 /* XXX p_ksi may be null if ksiginfo zone is not ready */
248 p->p_ksi->ksi_flags = KSI_EXT | KSI_INS;
249 }
250 LIST_INIT(&p->p_mqnotifier);
251 p->p_numthreads = 0;
252 thread_link(td, p);
253 }
254
255 /*
256 * Initialize global thread allocation resources.
257 */
258 void
259 threadinit(void)
260 {
261
262 mtx_init(&tid_lock, "TID lock", NULL, MTX_DEF);
263 /* leave one number for thread0 */
264 tid_unrhdr = new_unrhdr(PID_MAX + 2, INT_MAX, &tid_lock);
265
266 thread_zone = uma_zcreate("THREAD", sched_sizeof_thread(),
267 thread_ctor, thread_dtor, thread_init, thread_fini,
268 16 - 1, 0);
269 tidhashtbl = hashinit(maxproc / 2, M_TIDHASH, &tidhash);
270 rw_init(&tidhash_lock, "tidhash");
271 }
272
273 /*
274 * Place an unused thread on the zombie list.
275 * Use the slpq as that must be unused by now.
276 */
277 void
278 thread_zombie(struct thread *td)
279 {
280 mtx_lock_spin(&zombie_lock);
281 TAILQ_INSERT_HEAD(&zombie_threads, td, td_slpq);
282 mtx_unlock_spin(&zombie_lock);
283 }
284
285 /*
286 * Release a thread that has exited after cpu_throw().
287 */
288 void
289 thread_stash(struct thread *td)
290 {
291 atomic_subtract_rel_int(&td->td_proc->p_exitthreads, 1);
292 thread_zombie(td);
293 }
294
295 /*
296 * Reap zombie resources.
297 */
298 void
299 thread_reap(void)
300 {
301 struct thread *td_first, *td_next;
302
303 /*
304 * Don't even bother to lock if none at this instant,
305 * we really don't care about the next instant..
306 */
307 if (!TAILQ_EMPTY(&zombie_threads)) {
308 mtx_lock_spin(&zombie_lock);
309 td_first = TAILQ_FIRST(&zombie_threads);
310 if (td_first)
311 TAILQ_INIT(&zombie_threads);
312 mtx_unlock_spin(&zombie_lock);
313 while (td_first) {
314 td_next = TAILQ_NEXT(td_first, td_slpq);
315 if (td_first->td_ucred)
316 crfree(td_first->td_ucred);
317 thread_free(td_first);
318 td_first = td_next;
319 }
320 }
321 }
322
323 /*
324 * Allocate a thread.
325 */
326 struct thread *
327 thread_alloc(int pages)
328 {
329 struct thread *td;
330
331 thread_reap(); /* check if any zombies to get */
332
333 td = (struct thread *)uma_zalloc(thread_zone, M_WAITOK);
334 KASSERT(td->td_kstack == 0, ("thread_alloc got thread with kstack"));
335 if (!vm_thread_new(td, pages)) {
336 uma_zfree(thread_zone, td);
337 return (NULL);
338 }
339 cpu_thread_alloc(td);
340 return (td);
341 }
342
343 int
344 thread_alloc_stack(struct thread *td, int pages)
345 {
346
347 KASSERT(td->td_kstack == 0,
348 ("thread_alloc_stack called on a thread with kstack"));
349 if (!vm_thread_new(td, pages))
350 return (0);
351 cpu_thread_alloc(td);
352 return (1);
353 }
354
355 /*
356 * Deallocate a thread.
357 */
358 void
359 thread_free(struct thread *td)
360 {
361
362 lock_profile_thread_exit(td);
363 if (td->td_cpuset)
364 cpuset_rel(td->td_cpuset);
365 td->td_cpuset = NULL;
366 cpu_thread_free(td);
367 if (td->td_kstack != 0)
368 vm_thread_dispose(td);
369 uma_zfree(thread_zone, td);
370 }
371
372 /*
373 * Discard the current thread and exit from its context.
374 * Always called with scheduler locked.
375 *
376 * Because we can't free a thread while we're operating under its context,
377 * push the current thread into our CPU's deadthread holder. This means
378 * we needn't worry about someone else grabbing our context before we
379 * do a cpu_throw().
380 */
381 void
382 thread_exit(void)
383 {
384 uint64_t new_switchtime;
385 struct thread *td;
386 struct thread *td2;
387 struct proc *p;
388 int wakeup_swapper;
389
390 td = curthread;
391 p = td->td_proc;
392
393 PROC_SLOCK_ASSERT(p, MA_OWNED);
394 mtx_assert(&Giant, MA_NOTOWNED);
395
396 PROC_LOCK_ASSERT(p, MA_OWNED);
397 KASSERT(p != NULL, ("thread exiting without a process"));
398 CTR3(KTR_PROC, "thread_exit: thread %p (pid %ld, %s)", td,
399 (long)p->p_pid, td->td_name);
400 KASSERT(TAILQ_EMPTY(&td->td_sigqueue.sq_list), ("signal pending"));
401
402 #ifdef AUDIT
403 AUDIT_SYSCALL_EXIT(0, td);
404 #endif
405 umtx_thread_exit(td);
406 /*
407 * drop FPU & debug register state storage, or any other
408 * architecture specific resources that
409 * would not be on a new untouched process.
410 */
411 cpu_thread_exit(td); /* XXXSMP */
412
413 /* Do the same timestamp bookkeeping that mi_switch() would do. */
414 new_switchtime = cpu_ticks();
415 p->p_rux.rux_runtime += (new_switchtime - PCPU_GET(switchtime));
416 PCPU_SET(switchtime, new_switchtime);
417 PCPU_SET(switchticks, ticks);
418 PCPU_INC(cnt.v_swtch);
419 /* Save our resource usage in our process. */
420 td->td_ru.ru_nvcsw++;
421 rucollect(&p->p_ru, &td->td_ru);
422 /*
423 * The last thread is left attached to the process
424 * So that the whole bundle gets recycled. Skip
425 * all this stuff if we never had threads.
426 * EXIT clears all sign of other threads when
427 * it goes to single threading, so the last thread always
428 * takes the short path.
429 */
430 if (p->p_flag & P_HADTHREADS) {
431 if (p->p_numthreads > 1) {
432 thread_unlink(td);
433 td2 = FIRST_THREAD_IN_PROC(p);
434 sched_exit_thread(td2, td);
435
436 /*
437 * The test below is NOT true if we are the
438 * sole exiting thread. P_STOPPED_SINGLE is unset
439 * in exit1() after it is the only survivor.
440 */
441 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
442 if (p->p_numthreads == p->p_suspcount) {
443 thread_lock(p->p_singlethread);
444 wakeup_swapper = thread_unsuspend_one(
445 p->p_singlethread);
446 thread_unlock(p->p_singlethread);
447 if (wakeup_swapper)
448 kick_proc0();
449 }
450 }
451
452 atomic_add_int(&td->td_proc->p_exitthreads, 1);
453 PCPU_SET(deadthread, td);
454 } else {
455 /*
456 * The last thread is exiting.. but not through exit()
457 */
458 panic ("thread_exit: Last thread exiting on its own");
459 }
460 }
461 #ifdef HWPMC_HOOKS
462 /*
463 * If this thread is part of a process that is being tracked by hwpmc(4),
464 * inform the module of the thread's impending exit.
465 */
466 if (PMC_PROC_IS_USING_PMCS(td->td_proc))
467 PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_OUT);
468 #endif
469 PROC_UNLOCK(p);
470 ruxagg(p, td);
471 thread_lock(td);
472 PROC_SUNLOCK(p);
473 td->td_state = TDS_INACTIVE;
474 #ifdef WITNESS
475 witness_thread_exit(td);
476 #endif
477 CTR1(KTR_PROC, "thread_exit: cpu_throw() thread %p", td);
478 sched_throw(td);
479 panic("I'm a teapot!");
480 /* NOTREACHED */
481 }
482
483 /*
484 * Do any thread specific cleanups that may be needed in wait()
485 * called with Giant, proc and schedlock not held.
486 */
487 void
488 thread_wait(struct proc *p)
489 {
490 struct thread *td;
491
492 mtx_assert(&Giant, MA_NOTOWNED);
493 KASSERT((p->p_numthreads == 1), ("Multiple threads in wait1()"));
494 td = FIRST_THREAD_IN_PROC(p);
495 /* Lock the last thread so we spin until it exits cpu_throw(). */
496 thread_lock(td);
497 thread_unlock(td);
498 /* Wait for any remaining threads to exit cpu_throw(). */
499 while (p->p_exitthreads)
500 sched_relinquish(curthread);
501 lock_profile_thread_exit(td);
502 cpuset_rel(td->td_cpuset);
503 td->td_cpuset = NULL;
504 cpu_thread_clean(td);
505 crfree(td->td_ucred);
506 thread_reap(); /* check for zombie threads etc. */
507 }
508
509 /*
510 * Link a thread to a process.
511 * set up anything that needs to be initialized for it to
512 * be used by the process.
513 */
514 void
515 thread_link(struct thread *td, struct proc *p)
516 {
517
518 /*
519 * XXX This can't be enabled because it's called for proc0 before
520 * its lock has been created.
521 * PROC_LOCK_ASSERT(p, MA_OWNED);
522 */
523 td->td_state = TDS_INACTIVE;
524 td->td_proc = p;
525 td->td_flags = TDF_INMEM;
526
527 LIST_INIT(&td->td_contested);
528 LIST_INIT(&td->td_lprof[0]);
529 LIST_INIT(&td->td_lprof[1]);
530 sigqueue_init(&td->td_sigqueue, p);
531 callout_init(&td->td_slpcallout, CALLOUT_MPSAFE);
532 TAILQ_INSERT_HEAD(&p->p_threads, td, td_plist);
533 p->p_numthreads++;
534 }
535
536 /*
537 * Convert a process with one thread to an unthreaded process.
538 */
539 void
540 thread_unthread(struct thread *td)
541 {
542 struct proc *p = td->td_proc;
543
544 KASSERT((p->p_numthreads == 1), ("Unthreading with >1 threads"));
545 p->p_flag &= ~P_HADTHREADS;
546 }
547
548 /*
549 * Called from:
550 * thread_exit()
551 */
552 void
553 thread_unlink(struct thread *td)
554 {
555 struct proc *p = td->td_proc;
556
557 PROC_LOCK_ASSERT(p, MA_OWNED);
558 TAILQ_REMOVE(&p->p_threads, td, td_plist);
559 p->p_numthreads--;
560 /* could clear a few other things here */
561 /* Must NOT clear links to proc! */
562 }
563
564 static int
565 calc_remaining(struct proc *p, int mode)
566 {
567 int remaining;
568
569 PROC_LOCK_ASSERT(p, MA_OWNED);
570 PROC_SLOCK_ASSERT(p, MA_OWNED);
571 if (mode == SINGLE_EXIT)
572 remaining = p->p_numthreads;
573 else if (mode == SINGLE_BOUNDARY)
574 remaining = p->p_numthreads - p->p_boundary_count;
575 else if (mode == SINGLE_NO_EXIT)
576 remaining = p->p_numthreads - p->p_suspcount;
577 else
578 panic("calc_remaining: wrong mode %d", mode);
579 return (remaining);
580 }
581
582 /*
583 * Enforce single-threading.
584 *
585 * Returns 1 if the caller must abort (another thread is waiting to
586 * exit the process or similar). Process is locked!
587 * Returns 0 when you are successfully the only thread running.
588 * A process has successfully single threaded in the suspend mode when
589 * There are no threads in user mode. Threads in the kernel must be
590 * allowed to continue until they get to the user boundary. They may even
591 * copy out their return values and data before suspending. They may however be
592 * accelerated in reaching the user boundary as we will wake up
593 * any sleeping threads that are interruptable. (PCATCH).
594 */
595 int
596 thread_single(int mode)
597 {
598 struct thread *td;
599 struct thread *td2;
600 struct proc *p;
601 int remaining, wakeup_swapper;
602
603 td = curthread;
604 p = td->td_proc;
605 mtx_assert(&Giant, MA_NOTOWNED);
606 PROC_LOCK_ASSERT(p, MA_OWNED);
607 KASSERT((td != NULL), ("curthread is NULL"));
608
609 if ((p->p_flag & P_HADTHREADS) == 0)
610 return (0);
611
612 /* Is someone already single threading? */
613 if (p->p_singlethread != NULL && p->p_singlethread != td)
614 return (1);
615
616 if (mode == SINGLE_EXIT) {
617 p->p_flag |= P_SINGLE_EXIT;
618 p->p_flag &= ~P_SINGLE_BOUNDARY;
619 } else {
620 p->p_flag &= ~P_SINGLE_EXIT;
621 if (mode == SINGLE_BOUNDARY)
622 p->p_flag |= P_SINGLE_BOUNDARY;
623 else
624 p->p_flag &= ~P_SINGLE_BOUNDARY;
625 }
626 p->p_flag |= P_STOPPED_SINGLE;
627 PROC_SLOCK(p);
628 p->p_singlethread = td;
629 remaining = calc_remaining(p, mode);
630 while (remaining != 1) {
631 if (P_SHOULDSTOP(p) != P_STOPPED_SINGLE)
632 goto stopme;
633 wakeup_swapper = 0;
634 FOREACH_THREAD_IN_PROC(p, td2) {
635 if (td2 == td)
636 continue;
637 thread_lock(td2);
638 td2->td_flags |= TDF_ASTPENDING | TDF_NEEDSUSPCHK;
639 if (TD_IS_INHIBITED(td2)) {
640 switch (mode) {
641 case SINGLE_EXIT:
642 if (TD_IS_SUSPENDED(td2))
643 wakeup_swapper |=
644 thread_unsuspend_one(td2);
645 if (TD_ON_SLEEPQ(td2) &&
646 (td2->td_flags & TDF_SINTR))
647 wakeup_swapper |=
648 sleepq_abort(td2, EINTR);
649 break;
650 case SINGLE_BOUNDARY:
651 if (TD_IS_SUSPENDED(td2) &&
652 !(td2->td_flags & TDF_BOUNDARY))
653 wakeup_swapper |=
654 thread_unsuspend_one(td2);
655 if (TD_ON_SLEEPQ(td2) &&
656 (td2->td_flags & TDF_SINTR))
657 wakeup_swapper |=
658 sleepq_abort(td2, ERESTART);
659 break;
660 case SINGLE_NO_EXIT:
661 if (TD_IS_SUSPENDED(td2) &&
662 !(td2->td_flags & TDF_BOUNDARY))
663 wakeup_swapper |=
664 thread_unsuspend_one(td2);
665 if (TD_ON_SLEEPQ(td2) &&
666 (td2->td_flags & TDF_SINTR))
667 wakeup_swapper |=
668 sleepq_abort(td2, ERESTART);
669 break;
670 default:
671 break;
672 }
673 }
674 #ifdef SMP
675 else if (TD_IS_RUNNING(td2) && td != td2) {
676 forward_signal(td2);
677 }
678 #endif
679 thread_unlock(td2);
680 }
681 if (wakeup_swapper)
682 kick_proc0();
683 remaining = calc_remaining(p, mode);
684
685 /*
686 * Maybe we suspended some threads.. was it enough?
687 */
688 if (remaining == 1)
689 break;
690
691 stopme:
692 /*
693 * Wake us up when everyone else has suspended.
694 * In the mean time we suspend as well.
695 */
696 thread_suspend_switch(td);
697 remaining = calc_remaining(p, mode);
698 }
699 if (mode == SINGLE_EXIT) {
700 /*
701 * We have gotten rid of all the other threads and we
702 * are about to either exit or exec. In either case,
703 * we try our utmost to revert to being a non-threaded
704 * process.
705 */
706 p->p_singlethread = NULL;
707 p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT);
708 thread_unthread(td);
709 }
710 PROC_SUNLOCK(p);
711 return (0);
712 }
713
714 /*
715 * Called in from locations that can safely check to see
716 * whether we have to suspend or at least throttle for a
717 * single-thread event (e.g. fork).
718 *
719 * Such locations include userret().
720 * If the "return_instead" argument is non zero, the thread must be able to
721 * accept 0 (caller may continue), or 1 (caller must abort) as a result.
722 *
723 * The 'return_instead' argument tells the function if it may do a
724 * thread_exit() or suspend, or whether the caller must abort and back
725 * out instead.
726 *
727 * If the thread that set the single_threading request has set the
728 * P_SINGLE_EXIT bit in the process flags then this call will never return
729 * if 'return_instead' is false, but will exit.
730 *
731 * P_SINGLE_EXIT | return_instead == 0| return_instead != 0
732 *---------------+--------------------+---------------------
733 * 0 | returns 0 | returns 0 or 1
734 * | when ST ends | immediatly
735 *---------------+--------------------+---------------------
736 * 1 | thread exits | returns 1
737 * | | immediatly
738 * 0 = thread_exit() or suspension ok,
739 * other = return error instead of stopping the thread.
740 *
741 * While a full suspension is under effect, even a single threading
742 * thread would be suspended if it made this call (but it shouldn't).
743 * This call should only be made from places where
744 * thread_exit() would be safe as that may be the outcome unless
745 * return_instead is set.
746 */
747 int
748 thread_suspend_check(int return_instead)
749 {
750 struct thread *td;
751 struct proc *p;
752 int wakeup_swapper;
753
754 td = curthread;
755 p = td->td_proc;
756 mtx_assert(&Giant, MA_NOTOWNED);
757 PROC_LOCK_ASSERT(p, MA_OWNED);
758 while (P_SHOULDSTOP(p) ||
759 ((p->p_flag & P_TRACED) && (td->td_dbgflags & TDB_SUSPEND))) {
760 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
761 KASSERT(p->p_singlethread != NULL,
762 ("singlethread not set"));
763 /*
764 * The only suspension in action is a
765 * single-threading. Single threader need not stop.
766 * XXX Should be safe to access unlocked
767 * as it can only be set to be true by us.
768 */
769 if (p->p_singlethread == td)
770 return (0); /* Exempt from stopping. */
771 }
772 if ((p->p_flag & P_SINGLE_EXIT) && return_instead)
773 return (EINTR);
774
775 /* Should we goto user boundary if we didn't come from there? */
776 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE &&
777 (p->p_flag & P_SINGLE_BOUNDARY) && return_instead)
778 return (ERESTART);
779
780 /*
781 * If the process is waiting for us to exit,
782 * this thread should just suicide.
783 * Assumes that P_SINGLE_EXIT implies P_STOPPED_SINGLE.
784 */
785 if ((p->p_flag & P_SINGLE_EXIT) && (p->p_singlethread != td)) {
786 PROC_UNLOCK(p);
787 tidhash_remove(td);
788 PROC_LOCK(p);
789 tdsigcleanup(td);
790 PROC_SLOCK(p);
791 thread_stopped(p);
792 thread_exit();
793 }
794
795 PROC_SLOCK(p);
796 thread_stopped(p);
797 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
798 if (p->p_numthreads == p->p_suspcount + 1) {
799 thread_lock(p->p_singlethread);
800 wakeup_swapper =
801 thread_unsuspend_one(p->p_singlethread);
802 thread_unlock(p->p_singlethread);
803 if (wakeup_swapper)
804 kick_proc0();
805 }
806 }
807 PROC_UNLOCK(p);
808 thread_lock(td);
809 /*
810 * When a thread suspends, it just
811 * gets taken off all queues.
812 */
813 thread_suspend_one(td);
814 if (return_instead == 0) {
815 p->p_boundary_count++;
816 td->td_flags |= TDF_BOUNDARY;
817 }
818 PROC_SUNLOCK(p);
819 mi_switch(SW_INVOL | SWT_SUSPEND, NULL);
820 if (return_instead == 0)
821 td->td_flags &= ~TDF_BOUNDARY;
822 thread_unlock(td);
823 PROC_LOCK(p);
824 if (return_instead == 0) {
825 PROC_SLOCK(p);
826 p->p_boundary_count--;
827 PROC_SUNLOCK(p);
828 }
829 }
830 return (0);
831 }
832
833 void
834 thread_suspend_switch(struct thread *td)
835 {
836 struct proc *p;
837
838 p = td->td_proc;
839 KASSERT(!TD_IS_SUSPENDED(td), ("already suspended"));
840 PROC_LOCK_ASSERT(p, MA_OWNED);
841 PROC_SLOCK_ASSERT(p, MA_OWNED);
842 /*
843 * We implement thread_suspend_one in stages here to avoid
844 * dropping the proc lock while the thread lock is owned.
845 */
846 thread_stopped(p);
847 p->p_suspcount++;
848 PROC_UNLOCK(p);
849 thread_lock(td);
850 td->td_flags &= ~TDF_NEEDSUSPCHK;
851 TD_SET_SUSPENDED(td);
852 sched_sleep(td, 0);
853 PROC_SUNLOCK(p);
854 DROP_GIANT();
855 mi_switch(SW_VOL | SWT_SUSPEND, NULL);
856 thread_unlock(td);
857 PICKUP_GIANT();
858 PROC_LOCK(p);
859 PROC_SLOCK(p);
860 }
861
862 void
863 thread_suspend_one(struct thread *td)
864 {
865 struct proc *p = td->td_proc;
866
867 PROC_SLOCK_ASSERT(p, MA_OWNED);
868 THREAD_LOCK_ASSERT(td, MA_OWNED);
869 KASSERT(!TD_IS_SUSPENDED(td), ("already suspended"));
870 p->p_suspcount++;
871 td->td_flags &= ~TDF_NEEDSUSPCHK;
872 TD_SET_SUSPENDED(td);
873 sched_sleep(td, 0);
874 }
875
876 int
877 thread_unsuspend_one(struct thread *td)
878 {
879 struct proc *p = td->td_proc;
880
881 PROC_SLOCK_ASSERT(p, MA_OWNED);
882 THREAD_LOCK_ASSERT(td, MA_OWNED);
883 KASSERT(TD_IS_SUSPENDED(td), ("Thread not suspended"));
884 TD_CLR_SUSPENDED(td);
885 p->p_suspcount--;
886 return (setrunnable(td));
887 }
888
889 /*
890 * Allow all threads blocked by single threading to continue running.
891 */
892 void
893 thread_unsuspend(struct proc *p)
894 {
895 struct thread *td;
896 int wakeup_swapper;
897
898 PROC_LOCK_ASSERT(p, MA_OWNED);
899 PROC_SLOCK_ASSERT(p, MA_OWNED);
900 wakeup_swapper = 0;
901 if (!P_SHOULDSTOP(p)) {
902 FOREACH_THREAD_IN_PROC(p, td) {
903 thread_lock(td);
904 if (TD_IS_SUSPENDED(td)) {
905 wakeup_swapper |= thread_unsuspend_one(td);
906 }
907 thread_unlock(td);
908 }
909 } else if ((P_SHOULDSTOP(p) == P_STOPPED_SINGLE) &&
910 (p->p_numthreads == p->p_suspcount)) {
911 /*
912 * Stopping everything also did the job for the single
913 * threading request. Now we've downgraded to single-threaded,
914 * let it continue.
915 */
916 thread_lock(p->p_singlethread);
917 wakeup_swapper = thread_unsuspend_one(p->p_singlethread);
918 thread_unlock(p->p_singlethread);
919 }
920 if (wakeup_swapper)
921 kick_proc0();
922 }
923
924 /*
925 * End the single threading mode..
926 */
927 void
928 thread_single_end(void)
929 {
930 struct thread *td;
931 struct proc *p;
932 int wakeup_swapper;
933
934 td = curthread;
935 p = td->td_proc;
936 PROC_LOCK_ASSERT(p, MA_OWNED);
937 p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT | P_SINGLE_BOUNDARY);
938 PROC_SLOCK(p);
939 p->p_singlethread = NULL;
940 wakeup_swapper = 0;
941 /*
942 * If there are other threads they may now run,
943 * unless of course there is a blanket 'stop order'
944 * on the process. The single threader must be allowed
945 * to continue however as this is a bad place to stop.
946 */
947 if ((p->p_numthreads != 1) && (!P_SHOULDSTOP(p))) {
948 FOREACH_THREAD_IN_PROC(p, td) {
949 thread_lock(td);
950 if (TD_IS_SUSPENDED(td)) {
951 wakeup_swapper |= thread_unsuspend_one(td);
952 }
953 thread_unlock(td);
954 }
955 }
956 PROC_SUNLOCK(p);
957 if (wakeup_swapper)
958 kick_proc0();
959 }
960
961 struct thread *
962 thread_find(struct proc *p, lwpid_t tid)
963 {
964 struct thread *td;
965
966 PROC_LOCK_ASSERT(p, MA_OWNED);
967 FOREACH_THREAD_IN_PROC(p, td) {
968 if (td->td_tid == tid)
969 break;
970 }
971 return (td);
972 }
973
974 /* Locate a thread by number; return with proc lock held. */
975 struct thread *
976 tdfind(lwpid_t tid, pid_t pid)
977 {
978 #define RUN_THRESH 16
979 struct thread *td;
980 int run = 0;
981
982 rw_rlock(&tidhash_lock);
983 LIST_FOREACH(td, TIDHASH(tid), td_hash) {
984 if (td->td_tid == tid) {
985 if (pid != -1 && td->td_proc->p_pid != pid) {
986 td = NULL;
987 break;
988 }
989 PROC_LOCK(td->td_proc);
990 if (td->td_proc->p_state == PRS_NEW) {
991 PROC_UNLOCK(td->td_proc);
992 td = NULL;
993 break;
994 }
995 if (run > RUN_THRESH) {
996 if (rw_try_upgrade(&tidhash_lock)) {
997 LIST_REMOVE(td, td_hash);
998 LIST_INSERT_HEAD(TIDHASH(td->td_tid),
999 td, td_hash);
1000 rw_wunlock(&tidhash_lock);
1001 return (td);
1002 }
1003 }
1004 break;
1005 }
1006 run++;
1007 }
1008 rw_runlock(&tidhash_lock);
1009 return (td);
1010 }
1011
1012 void
1013 tidhash_add(struct thread *td)
1014 {
1015 rw_wlock(&tidhash_lock);
1016 LIST_INSERT_HEAD(TIDHASH(td->td_tid), td, td_hash);
1017 rw_wunlock(&tidhash_lock);
1018 }
1019
1020 void
1021 tidhash_remove(struct thread *td)
1022 {
1023 rw_wlock(&tidhash_lock);
1024 LIST_REMOVE(td, td_hash);
1025 rw_wunlock(&tidhash_lock);
1026 }
Cache object: e39ae3d6c698dca09ca416a147890b43
|