1 /*-
2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
3 *
4 * Copyright (C) 2001 Julian Elischer <julian@freebsd.org>.
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 * notice(s), this list of conditions and the following disclaimer as
12 * the first lines of this file unmodified other than the possible
13 * addition of one or more copyright notices.
14 * 2. Redistributions in binary form must reproduce the above copyright
15 * notice(s), this list of conditions and the following disclaimer in the
16 * documentation and/or other materials provided with the distribution.
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY
19 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
20 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
21 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE LIABLE FOR ANY
22 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
23 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
24 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
25 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
26 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
27 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
28 * DAMAGE.
29 */
30
31 #include "opt_witness.h"
32 #include "opt_hwpmc_hooks.h"
33
34 #include <sys/cdefs.h>
35 __FBSDID("$FreeBSD: releng/12.0/sys/kern/kern_thread.c 338436 2018-09-02 21:16:43Z kib $");
36
37 #include <sys/param.h>
38 #include <sys/systm.h>
39 #include <sys/kernel.h>
40 #include <sys/lock.h>
41 #include <sys/mutex.h>
42 #include <sys/proc.h>
43 #include <sys/rangelock.h>
44 #include <sys/resourcevar.h>
45 #include <sys/sdt.h>
46 #include <sys/smp.h>
47 #include <sys/sched.h>
48 #include <sys/sleepqueue.h>
49 #include <sys/selinfo.h>
50 #include <sys/syscallsubr.h>
51 #include <sys/sysent.h>
52 #include <sys/turnstile.h>
53 #include <sys/ktr.h>
54 #include <sys/rwlock.h>
55 #include <sys/umtx.h>
56 #include <sys/vmmeter.h>
57 #include <sys/cpuset.h>
58 #ifdef HWPMC_HOOKS
59 #include <sys/pmckern.h>
60 #endif
61
62 #include <security/audit/audit.h>
63
64 #include <vm/vm.h>
65 #include <vm/vm_extern.h>
66 #include <vm/uma.h>
67 #include <sys/eventhandler.h>
68
69 /*
70 * Asserts below verify the stability of struct thread and struct proc
71 * layout, as exposed by KBI to modules. On head, the KBI is allowed
72 * to drift, change to the structures must be accompanied by the
73 * assert update.
74 *
75 * On the stable branches after KBI freeze, conditions must not be
76 * violated. Typically new fields are moved to the end of the
77 * structures.
78 */
79 #ifdef __amd64__
80 _Static_assert(offsetof(struct thread, td_flags) == 0xfc,
81 "struct thread KBI td_flags");
82 _Static_assert(offsetof(struct thread, td_pflags) == 0x104,
83 "struct thread KBI td_pflags");
84 _Static_assert(offsetof(struct thread, td_frame) == 0x470,
85 "struct thread KBI td_frame");
86 _Static_assert(offsetof(struct thread, td_emuldata) == 0x528,
87 "struct thread KBI td_emuldata");
88 _Static_assert(offsetof(struct proc, p_flag) == 0xb0,
89 "struct proc KBI p_flag");
90 _Static_assert(offsetof(struct proc, p_pid) == 0xbc,
91 "struct proc KBI p_pid");
92 _Static_assert(offsetof(struct proc, p_filemon) == 0x3d0,
93 "struct proc KBI p_filemon");
94 _Static_assert(offsetof(struct proc, p_comm) == 0x3e4,
95 "struct proc KBI p_comm");
96 _Static_assert(offsetof(struct proc, p_emuldata) == 0x4b8,
97 "struct proc KBI p_emuldata");
98 #endif
99 #ifdef __i386__
100 _Static_assert(offsetof(struct thread, td_flags) == 0x98,
101 "struct thread KBI td_flags");
102 _Static_assert(offsetof(struct thread, td_pflags) == 0xa0,
103 "struct thread KBI td_pflags");
104 _Static_assert(offsetof(struct thread, td_frame) == 0x2e8,
105 "struct thread KBI td_frame");
106 _Static_assert(offsetof(struct thread, td_emuldata) == 0x334,
107 "struct thread KBI td_emuldata");
108 _Static_assert(offsetof(struct proc, p_flag) == 0x68,
109 "struct proc KBI p_flag");
110 _Static_assert(offsetof(struct proc, p_pid) == 0x74,
111 "struct proc KBI p_pid");
112 _Static_assert(offsetof(struct proc, p_filemon) == 0x27c,
113 "struct proc KBI p_filemon");
114 _Static_assert(offsetof(struct proc, p_comm) == 0x28c,
115 "struct proc KBI p_comm");
116 _Static_assert(offsetof(struct proc, p_emuldata) == 0x318,
117 "struct proc KBI p_emuldata");
118 #endif
119
120 SDT_PROVIDER_DECLARE(proc);
121 SDT_PROBE_DEFINE(proc, , , lwp__exit);
122
123 /*
124 * thread related storage.
125 */
126 static uma_zone_t thread_zone;
127
128 TAILQ_HEAD(, thread) zombie_threads = TAILQ_HEAD_INITIALIZER(zombie_threads);
129 static struct mtx zombie_lock;
130 MTX_SYSINIT(zombie_lock, &zombie_lock, "zombie lock", MTX_SPIN);
131
132 static void thread_zombie(struct thread *);
133 static int thread_unsuspend_one(struct thread *td, struct proc *p,
134 bool boundary);
135
136 #define TID_BUFFER_SIZE 1024
137
138 struct mtx tid_lock;
139 static struct unrhdr *tid_unrhdr;
140 static lwpid_t tid_buffer[TID_BUFFER_SIZE];
141 static int tid_head, tid_tail;
142 static MALLOC_DEFINE(M_TIDHASH, "tidhash", "thread hash");
143
144 struct tidhashhead *tidhashtbl;
145 u_long tidhash;
146 struct rwlock tidhash_lock;
147
148 EVENTHANDLER_LIST_DEFINE(thread_ctor);
149 EVENTHANDLER_LIST_DEFINE(thread_dtor);
150 EVENTHANDLER_LIST_DEFINE(thread_init);
151 EVENTHANDLER_LIST_DEFINE(thread_fini);
152
153 static lwpid_t
154 tid_alloc(void)
155 {
156 lwpid_t tid;
157
158 tid = alloc_unr(tid_unrhdr);
159 if (tid != -1)
160 return (tid);
161 mtx_lock(&tid_lock);
162 if (tid_head == tid_tail) {
163 mtx_unlock(&tid_lock);
164 return (-1);
165 }
166 tid = tid_buffer[tid_head];
167 tid_head = (tid_head + 1) % TID_BUFFER_SIZE;
168 mtx_unlock(&tid_lock);
169 return (tid);
170 }
171
172 static void
173 tid_free(lwpid_t tid)
174 {
175 lwpid_t tmp_tid = -1;
176
177 mtx_lock(&tid_lock);
178 if ((tid_tail + 1) % TID_BUFFER_SIZE == tid_head) {
179 tmp_tid = tid_buffer[tid_head];
180 tid_head = (tid_head + 1) % TID_BUFFER_SIZE;
181 }
182 tid_buffer[tid_tail] = tid;
183 tid_tail = (tid_tail + 1) % TID_BUFFER_SIZE;
184 mtx_unlock(&tid_lock);
185 if (tmp_tid != -1)
186 free_unr(tid_unrhdr, tmp_tid);
187 }
188
189 /*
190 * Prepare a thread for use.
191 */
192 static int
193 thread_ctor(void *mem, int size, void *arg, int flags)
194 {
195 struct thread *td;
196
197 td = (struct thread *)mem;
198 td->td_state = TDS_INACTIVE;
199 td->td_oncpu = NOCPU;
200
201 td->td_tid = tid_alloc();
202
203 /*
204 * Note that td_critnest begins life as 1 because the thread is not
205 * running and is thereby implicitly waiting to be on the receiving
206 * end of a context switch.
207 */
208 td->td_critnest = 1;
209 td->td_lend_user_pri = PRI_MAX;
210 EVENTHANDLER_DIRECT_INVOKE(thread_ctor, td);
211 #ifdef AUDIT
212 audit_thread_alloc(td);
213 #endif
214 umtx_thread_alloc(td);
215 return (0);
216 }
217
218 /*
219 * Reclaim a thread after use.
220 */
221 static void
222 thread_dtor(void *mem, int size, void *arg)
223 {
224 struct thread *td;
225
226 td = (struct thread *)mem;
227
228 #ifdef INVARIANTS
229 /* Verify that this thread is in a safe state to free. */
230 switch (td->td_state) {
231 case TDS_INHIBITED:
232 case TDS_RUNNING:
233 case TDS_CAN_RUN:
234 case TDS_RUNQ:
235 /*
236 * We must never unlink a thread that is in one of
237 * these states, because it is currently active.
238 */
239 panic("bad state for thread unlinking");
240 /* NOTREACHED */
241 case TDS_INACTIVE:
242 break;
243 default:
244 panic("bad thread state");
245 /* NOTREACHED */
246 }
247 #endif
248 #ifdef AUDIT
249 audit_thread_free(td);
250 #endif
251 /* Free all OSD associated to this thread. */
252 osd_thread_exit(td);
253 td_softdep_cleanup(td);
254 MPASS(td->td_su == NULL);
255
256 EVENTHANDLER_DIRECT_INVOKE(thread_dtor, td);
257 tid_free(td->td_tid);
258 }
259
260 /*
261 * Initialize type-stable parts of a thread (when newly created).
262 */
263 static int
264 thread_init(void *mem, int size, int flags)
265 {
266 struct thread *td;
267
268 td = (struct thread *)mem;
269
270 td->td_sleepqueue = sleepq_alloc();
271 td->td_turnstile = turnstile_alloc();
272 td->td_rlqe = NULL;
273 EVENTHANDLER_DIRECT_INVOKE(thread_init, td);
274 umtx_thread_init(td);
275 td->td_kstack = 0;
276 td->td_sel = NULL;
277 return (0);
278 }
279
280 /*
281 * Tear down type-stable parts of a thread (just before being discarded).
282 */
283 static void
284 thread_fini(void *mem, int size)
285 {
286 struct thread *td;
287
288 td = (struct thread *)mem;
289 EVENTHANDLER_DIRECT_INVOKE(thread_fini, td);
290 rlqentry_free(td->td_rlqe);
291 turnstile_free(td->td_turnstile);
292 sleepq_free(td->td_sleepqueue);
293 umtx_thread_fini(td);
294 seltdfini(td);
295 }
296
297 /*
298 * For a newly created process,
299 * link up all the structures and its initial threads etc.
300 * called from:
301 * {arch}/{arch}/machdep.c {arch}_init(), init386() etc.
302 * proc_dtor() (should go away)
303 * proc_init()
304 */
305 void
306 proc_linkup0(struct proc *p, struct thread *td)
307 {
308 TAILQ_INIT(&p->p_threads); /* all threads in proc */
309 proc_linkup(p, td);
310 }
311
312 void
313 proc_linkup(struct proc *p, struct thread *td)
314 {
315
316 sigqueue_init(&p->p_sigqueue, p);
317 p->p_ksi = ksiginfo_alloc(1);
318 if (p->p_ksi != NULL) {
319 /* XXX p_ksi may be null if ksiginfo zone is not ready */
320 p->p_ksi->ksi_flags = KSI_EXT | KSI_INS;
321 }
322 LIST_INIT(&p->p_mqnotifier);
323 p->p_numthreads = 0;
324 thread_link(td, p);
325 }
326
327 /*
328 * Initialize global thread allocation resources.
329 */
330 void
331 threadinit(void)
332 {
333
334 mtx_init(&tid_lock, "TID lock", NULL, MTX_DEF);
335
336 /*
337 * pid_max cannot be greater than PID_MAX.
338 * leave one number for thread0.
339 */
340 tid_unrhdr = new_unrhdr(PID_MAX + 2, INT_MAX, &tid_lock);
341
342 thread_zone = uma_zcreate("THREAD", sched_sizeof_thread(),
343 thread_ctor, thread_dtor, thread_init, thread_fini,
344 32 - 1, UMA_ZONE_NOFREE);
345 tidhashtbl = hashinit(maxproc / 2, M_TIDHASH, &tidhash);
346 rw_init(&tidhash_lock, "tidhash");
347 }
348
349 /*
350 * Place an unused thread on the zombie list.
351 * Use the slpq as that must be unused by now.
352 */
353 void
354 thread_zombie(struct thread *td)
355 {
356 mtx_lock_spin(&zombie_lock);
357 TAILQ_INSERT_HEAD(&zombie_threads, td, td_slpq);
358 mtx_unlock_spin(&zombie_lock);
359 }
360
361 /*
362 * Release a thread that has exited after cpu_throw().
363 */
364 void
365 thread_stash(struct thread *td)
366 {
367 atomic_subtract_rel_int(&td->td_proc->p_exitthreads, 1);
368 thread_zombie(td);
369 }
370
371 /*
372 * Reap zombie resources.
373 */
374 void
375 thread_reap(void)
376 {
377 struct thread *td_first, *td_next;
378
379 /*
380 * Don't even bother to lock if none at this instant,
381 * we really don't care about the next instant.
382 */
383 if (!TAILQ_EMPTY(&zombie_threads)) {
384 mtx_lock_spin(&zombie_lock);
385 td_first = TAILQ_FIRST(&zombie_threads);
386 if (td_first)
387 TAILQ_INIT(&zombie_threads);
388 mtx_unlock_spin(&zombie_lock);
389 while (td_first) {
390 td_next = TAILQ_NEXT(td_first, td_slpq);
391 thread_cow_free(td_first);
392 thread_free(td_first);
393 td_first = td_next;
394 }
395 }
396 }
397
398 /*
399 * Allocate a thread.
400 */
401 struct thread *
402 thread_alloc(int pages)
403 {
404 struct thread *td;
405
406 thread_reap(); /* check if any zombies to get */
407
408 td = (struct thread *)uma_zalloc(thread_zone, M_WAITOK);
409 KASSERT(td->td_kstack == 0, ("thread_alloc got thread with kstack"));
410 if (!vm_thread_new(td, pages)) {
411 uma_zfree(thread_zone, td);
412 return (NULL);
413 }
414 cpu_thread_alloc(td);
415 return (td);
416 }
417
418 int
419 thread_alloc_stack(struct thread *td, int pages)
420 {
421
422 KASSERT(td->td_kstack == 0,
423 ("thread_alloc_stack called on a thread with kstack"));
424 if (!vm_thread_new(td, pages))
425 return (0);
426 cpu_thread_alloc(td);
427 return (1);
428 }
429
430 /*
431 * Deallocate a thread.
432 */
433 void
434 thread_free(struct thread *td)
435 {
436
437 lock_profile_thread_exit(td);
438 if (td->td_cpuset)
439 cpuset_rel(td->td_cpuset);
440 td->td_cpuset = NULL;
441 cpu_thread_free(td);
442 if (td->td_kstack != 0)
443 vm_thread_dispose(td);
444 callout_drain(&td->td_slpcallout);
445 uma_zfree(thread_zone, td);
446 }
447
448 void
449 thread_cow_get_proc(struct thread *newtd, struct proc *p)
450 {
451
452 PROC_LOCK_ASSERT(p, MA_OWNED);
453 newtd->td_ucred = crhold(p->p_ucred);
454 newtd->td_limit = lim_hold(p->p_limit);
455 newtd->td_cowgen = p->p_cowgen;
456 }
457
458 void
459 thread_cow_get(struct thread *newtd, struct thread *td)
460 {
461
462 newtd->td_ucred = crhold(td->td_ucred);
463 newtd->td_limit = lim_hold(td->td_limit);
464 newtd->td_cowgen = td->td_cowgen;
465 }
466
467 void
468 thread_cow_free(struct thread *td)
469 {
470
471 if (td->td_ucred != NULL)
472 crfree(td->td_ucred);
473 if (td->td_limit != NULL)
474 lim_free(td->td_limit);
475 }
476
477 void
478 thread_cow_update(struct thread *td)
479 {
480 struct proc *p;
481 struct ucred *oldcred;
482 struct plimit *oldlimit;
483
484 p = td->td_proc;
485 oldcred = NULL;
486 oldlimit = NULL;
487 PROC_LOCK(p);
488 if (td->td_ucred != p->p_ucred) {
489 oldcred = td->td_ucred;
490 td->td_ucred = crhold(p->p_ucred);
491 }
492 if (td->td_limit != p->p_limit) {
493 oldlimit = td->td_limit;
494 td->td_limit = lim_hold(p->p_limit);
495 }
496 td->td_cowgen = p->p_cowgen;
497 PROC_UNLOCK(p);
498 if (oldcred != NULL)
499 crfree(oldcred);
500 if (oldlimit != NULL)
501 lim_free(oldlimit);
502 }
503
504 /*
505 * Discard the current thread and exit from its context.
506 * Always called with scheduler locked.
507 *
508 * Because we can't free a thread while we're operating under its context,
509 * push the current thread into our CPU's deadthread holder. This means
510 * we needn't worry about someone else grabbing our context before we
511 * do a cpu_throw().
512 */
513 void
514 thread_exit(void)
515 {
516 uint64_t runtime, new_switchtime;
517 struct thread *td;
518 struct thread *td2;
519 struct proc *p;
520 int wakeup_swapper;
521
522 td = curthread;
523 p = td->td_proc;
524
525 PROC_SLOCK_ASSERT(p, MA_OWNED);
526 mtx_assert(&Giant, MA_NOTOWNED);
527
528 PROC_LOCK_ASSERT(p, MA_OWNED);
529 KASSERT(p != NULL, ("thread exiting without a process"));
530 CTR3(KTR_PROC, "thread_exit: thread %p (pid %ld, %s)", td,
531 (long)p->p_pid, td->td_name);
532 SDT_PROBE0(proc, , , lwp__exit);
533 KASSERT(TAILQ_EMPTY(&td->td_sigqueue.sq_list), ("signal pending"));
534
535 /*
536 * drop FPU & debug register state storage, or any other
537 * architecture specific resources that
538 * would not be on a new untouched process.
539 */
540 cpu_thread_exit(td);
541
542 /*
543 * The last thread is left attached to the process
544 * So that the whole bundle gets recycled. Skip
545 * all this stuff if we never had threads.
546 * EXIT clears all sign of other threads when
547 * it goes to single threading, so the last thread always
548 * takes the short path.
549 */
550 if (p->p_flag & P_HADTHREADS) {
551 if (p->p_numthreads > 1) {
552 atomic_add_int(&td->td_proc->p_exitthreads, 1);
553 thread_unlink(td);
554 td2 = FIRST_THREAD_IN_PROC(p);
555 sched_exit_thread(td2, td);
556
557 /*
558 * The test below is NOT true if we are the
559 * sole exiting thread. P_STOPPED_SINGLE is unset
560 * in exit1() after it is the only survivor.
561 */
562 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
563 if (p->p_numthreads == p->p_suspcount) {
564 thread_lock(p->p_singlethread);
565 wakeup_swapper = thread_unsuspend_one(
566 p->p_singlethread, p, false);
567 thread_unlock(p->p_singlethread);
568 if (wakeup_swapper)
569 kick_proc0();
570 }
571 }
572
573 PCPU_SET(deadthread, td);
574 } else {
575 /*
576 * The last thread is exiting.. but not through exit()
577 */
578 panic ("thread_exit: Last thread exiting on its own");
579 }
580 }
581 #ifdef HWPMC_HOOKS
582 /*
583 * If this thread is part of a process that is being tracked by hwpmc(4),
584 * inform the module of the thread's impending exit.
585 */
586 if (PMC_PROC_IS_USING_PMCS(td->td_proc)) {
587 PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_OUT);
588 PMC_CALL_HOOK_UNLOCKED(td, PMC_FN_THR_EXIT, NULL);
589 } else if (PMC_SYSTEM_SAMPLING_ACTIVE())
590 PMC_CALL_HOOK_UNLOCKED(td, PMC_FN_THR_EXIT_LOG, NULL);
591 #endif
592 PROC_UNLOCK(p);
593 PROC_STATLOCK(p);
594 thread_lock(td);
595 PROC_SUNLOCK(p);
596
597 /* Do the same timestamp bookkeeping that mi_switch() would do. */
598 new_switchtime = cpu_ticks();
599 runtime = new_switchtime - PCPU_GET(switchtime);
600 td->td_runtime += runtime;
601 td->td_incruntime += runtime;
602 PCPU_SET(switchtime, new_switchtime);
603 PCPU_SET(switchticks, ticks);
604 VM_CNT_INC(v_swtch);
605
606 /* Save our resource usage in our process. */
607 td->td_ru.ru_nvcsw++;
608 ruxagg(p, td);
609 rucollect(&p->p_ru, &td->td_ru);
610 PROC_STATUNLOCK(p);
611
612 td->td_state = TDS_INACTIVE;
613 #ifdef WITNESS
614 witness_thread_exit(td);
615 #endif
616 CTR1(KTR_PROC, "thread_exit: cpu_throw() thread %p", td);
617 sched_throw(td);
618 panic("I'm a teapot!");
619 /* NOTREACHED */
620 }
621
622 /*
623 * Do any thread specific cleanups that may be needed in wait()
624 * called with Giant, proc and schedlock not held.
625 */
626 void
627 thread_wait(struct proc *p)
628 {
629 struct thread *td;
630
631 mtx_assert(&Giant, MA_NOTOWNED);
632 KASSERT(p->p_numthreads == 1, ("multiple threads in thread_wait()"));
633 KASSERT(p->p_exitthreads == 0, ("p_exitthreads leaking"));
634 td = FIRST_THREAD_IN_PROC(p);
635 /* Lock the last thread so we spin until it exits cpu_throw(). */
636 thread_lock(td);
637 thread_unlock(td);
638 lock_profile_thread_exit(td);
639 cpuset_rel(td->td_cpuset);
640 td->td_cpuset = NULL;
641 cpu_thread_clean(td);
642 thread_cow_free(td);
643 callout_drain(&td->td_slpcallout);
644 thread_reap(); /* check for zombie threads etc. */
645 }
646
647 /*
648 * Link a thread to a process.
649 * set up anything that needs to be initialized for it to
650 * be used by the process.
651 */
652 void
653 thread_link(struct thread *td, struct proc *p)
654 {
655
656 /*
657 * XXX This can't be enabled because it's called for proc0 before
658 * its lock has been created.
659 * PROC_LOCK_ASSERT(p, MA_OWNED);
660 */
661 td->td_state = TDS_INACTIVE;
662 td->td_proc = p;
663 td->td_flags = TDF_INMEM;
664
665 LIST_INIT(&td->td_contested);
666 LIST_INIT(&td->td_lprof[0]);
667 LIST_INIT(&td->td_lprof[1]);
668 sigqueue_init(&td->td_sigqueue, p);
669 callout_init(&td->td_slpcallout, 1);
670 TAILQ_INSERT_TAIL(&p->p_threads, td, td_plist);
671 p->p_numthreads++;
672 }
673
674 /*
675 * Called from:
676 * thread_exit()
677 */
678 void
679 thread_unlink(struct thread *td)
680 {
681 struct proc *p = td->td_proc;
682
683 PROC_LOCK_ASSERT(p, MA_OWNED);
684 TAILQ_REMOVE(&p->p_threads, td, td_plist);
685 p->p_numthreads--;
686 /* could clear a few other things here */
687 /* Must NOT clear links to proc! */
688 }
689
690 static int
691 calc_remaining(struct proc *p, int mode)
692 {
693 int remaining;
694
695 PROC_LOCK_ASSERT(p, MA_OWNED);
696 PROC_SLOCK_ASSERT(p, MA_OWNED);
697 if (mode == SINGLE_EXIT)
698 remaining = p->p_numthreads;
699 else if (mode == SINGLE_BOUNDARY)
700 remaining = p->p_numthreads - p->p_boundary_count;
701 else if (mode == SINGLE_NO_EXIT || mode == SINGLE_ALLPROC)
702 remaining = p->p_numthreads - p->p_suspcount;
703 else
704 panic("calc_remaining: wrong mode %d", mode);
705 return (remaining);
706 }
707
708 static int
709 remain_for_mode(int mode)
710 {
711
712 return (mode == SINGLE_ALLPROC ? 0 : 1);
713 }
714
715 static int
716 weed_inhib(int mode, struct thread *td2, struct proc *p)
717 {
718 int wakeup_swapper;
719
720 PROC_LOCK_ASSERT(p, MA_OWNED);
721 PROC_SLOCK_ASSERT(p, MA_OWNED);
722 THREAD_LOCK_ASSERT(td2, MA_OWNED);
723
724 wakeup_swapper = 0;
725 switch (mode) {
726 case SINGLE_EXIT:
727 if (TD_IS_SUSPENDED(td2))
728 wakeup_swapper |= thread_unsuspend_one(td2, p, true);
729 if (TD_ON_SLEEPQ(td2) && (td2->td_flags & TDF_SINTR) != 0)
730 wakeup_swapper |= sleepq_abort(td2, EINTR);
731 break;
732 case SINGLE_BOUNDARY:
733 case SINGLE_NO_EXIT:
734 if (TD_IS_SUSPENDED(td2) && (td2->td_flags & TDF_BOUNDARY) == 0)
735 wakeup_swapper |= thread_unsuspend_one(td2, p, false);
736 if (TD_ON_SLEEPQ(td2) && (td2->td_flags & TDF_SINTR) != 0)
737 wakeup_swapper |= sleepq_abort(td2, ERESTART);
738 break;
739 case SINGLE_ALLPROC:
740 /*
741 * ALLPROC suspend tries to avoid spurious EINTR for
742 * threads sleeping interruptable, by suspending the
743 * thread directly, similarly to sig_suspend_threads().
744 * Since such sleep is not performed at the user
745 * boundary, TDF_BOUNDARY flag is not set, and TDF_ALLPROCSUSP
746 * is used to avoid immediate un-suspend.
747 */
748 if (TD_IS_SUSPENDED(td2) && (td2->td_flags & (TDF_BOUNDARY |
749 TDF_ALLPROCSUSP)) == 0)
750 wakeup_swapper |= thread_unsuspend_one(td2, p, false);
751 if (TD_ON_SLEEPQ(td2) && (td2->td_flags & TDF_SINTR) != 0) {
752 if ((td2->td_flags & TDF_SBDRY) == 0) {
753 thread_suspend_one(td2);
754 td2->td_flags |= TDF_ALLPROCSUSP;
755 } else {
756 wakeup_swapper |= sleepq_abort(td2, ERESTART);
757 }
758 }
759 break;
760 }
761 return (wakeup_swapper);
762 }
763
764 /*
765 * Enforce single-threading.
766 *
767 * Returns 1 if the caller must abort (another thread is waiting to
768 * exit the process or similar). Process is locked!
769 * Returns 0 when you are successfully the only thread running.
770 * A process has successfully single threaded in the suspend mode when
771 * There are no threads in user mode. Threads in the kernel must be
772 * allowed to continue until they get to the user boundary. They may even
773 * copy out their return values and data before suspending. They may however be
774 * accelerated in reaching the user boundary as we will wake up
775 * any sleeping threads that are interruptable. (PCATCH).
776 */
777 int
778 thread_single(struct proc *p, int mode)
779 {
780 struct thread *td;
781 struct thread *td2;
782 int remaining, wakeup_swapper;
783
784 td = curthread;
785 KASSERT(mode == SINGLE_EXIT || mode == SINGLE_BOUNDARY ||
786 mode == SINGLE_ALLPROC || mode == SINGLE_NO_EXIT,
787 ("invalid mode %d", mode));
788 /*
789 * If allowing non-ALLPROC singlethreading for non-curproc
790 * callers, calc_remaining() and remain_for_mode() should be
791 * adjusted to also account for td->td_proc != p. For now
792 * this is not implemented because it is not used.
793 */
794 KASSERT((mode == SINGLE_ALLPROC && td->td_proc != p) ||
795 (mode != SINGLE_ALLPROC && td->td_proc == p),
796 ("mode %d proc %p curproc %p", mode, p, td->td_proc));
797 mtx_assert(&Giant, MA_NOTOWNED);
798 PROC_LOCK_ASSERT(p, MA_OWNED);
799
800 if ((p->p_flag & P_HADTHREADS) == 0 && mode != SINGLE_ALLPROC)
801 return (0);
802
803 /* Is someone already single threading? */
804 if (p->p_singlethread != NULL && p->p_singlethread != td)
805 return (1);
806
807 if (mode == SINGLE_EXIT) {
808 p->p_flag |= P_SINGLE_EXIT;
809 p->p_flag &= ~P_SINGLE_BOUNDARY;
810 } else {
811 p->p_flag &= ~P_SINGLE_EXIT;
812 if (mode == SINGLE_BOUNDARY)
813 p->p_flag |= P_SINGLE_BOUNDARY;
814 else
815 p->p_flag &= ~P_SINGLE_BOUNDARY;
816 }
817 if (mode == SINGLE_ALLPROC)
818 p->p_flag |= P_TOTAL_STOP;
819 p->p_flag |= P_STOPPED_SINGLE;
820 PROC_SLOCK(p);
821 p->p_singlethread = td;
822 remaining = calc_remaining(p, mode);
823 while (remaining != remain_for_mode(mode)) {
824 if (P_SHOULDSTOP(p) != P_STOPPED_SINGLE)
825 goto stopme;
826 wakeup_swapper = 0;
827 FOREACH_THREAD_IN_PROC(p, td2) {
828 if (td2 == td)
829 continue;
830 thread_lock(td2);
831 td2->td_flags |= TDF_ASTPENDING | TDF_NEEDSUSPCHK;
832 if (TD_IS_INHIBITED(td2)) {
833 wakeup_swapper |= weed_inhib(mode, td2, p);
834 #ifdef SMP
835 } else if (TD_IS_RUNNING(td2) && td != td2) {
836 forward_signal(td2);
837 #endif
838 }
839 thread_unlock(td2);
840 }
841 if (wakeup_swapper)
842 kick_proc0();
843 remaining = calc_remaining(p, mode);
844
845 /*
846 * Maybe we suspended some threads.. was it enough?
847 */
848 if (remaining == remain_for_mode(mode))
849 break;
850
851 stopme:
852 /*
853 * Wake us up when everyone else has suspended.
854 * In the mean time we suspend as well.
855 */
856 thread_suspend_switch(td, p);
857 remaining = calc_remaining(p, mode);
858 }
859 if (mode == SINGLE_EXIT) {
860 /*
861 * Convert the process to an unthreaded process. The
862 * SINGLE_EXIT is called by exit1() or execve(), in
863 * both cases other threads must be retired.
864 */
865 KASSERT(p->p_numthreads == 1, ("Unthreading with >1 threads"));
866 p->p_singlethread = NULL;
867 p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT | P_HADTHREADS);
868
869 /*
870 * Wait for any remaining threads to exit cpu_throw().
871 */
872 while (p->p_exitthreads != 0) {
873 PROC_SUNLOCK(p);
874 PROC_UNLOCK(p);
875 sched_relinquish(td);
876 PROC_LOCK(p);
877 PROC_SLOCK(p);
878 }
879 } else if (mode == SINGLE_BOUNDARY) {
880 /*
881 * Wait until all suspended threads are removed from
882 * the processors. The thread_suspend_check()
883 * increments p_boundary_count while it is still
884 * running, which makes it possible for the execve()
885 * to destroy vmspace while our other threads are
886 * still using the address space.
887 *
888 * We lock the thread, which is only allowed to
889 * succeed after context switch code finished using
890 * the address space.
891 */
892 FOREACH_THREAD_IN_PROC(p, td2) {
893 if (td2 == td)
894 continue;
895 thread_lock(td2);
896 KASSERT((td2->td_flags & TDF_BOUNDARY) != 0,
897 ("td %p not on boundary", td2));
898 KASSERT(TD_IS_SUSPENDED(td2),
899 ("td %p is not suspended", td2));
900 thread_unlock(td2);
901 }
902 }
903 PROC_SUNLOCK(p);
904 return (0);
905 }
906
907 bool
908 thread_suspend_check_needed(void)
909 {
910 struct proc *p;
911 struct thread *td;
912
913 td = curthread;
914 p = td->td_proc;
915 PROC_LOCK_ASSERT(p, MA_OWNED);
916 return (P_SHOULDSTOP(p) || ((p->p_flag & P_TRACED) != 0 &&
917 (td->td_dbgflags & TDB_SUSPEND) != 0));
918 }
919
920 /*
921 * Called in from locations that can safely check to see
922 * whether we have to suspend or at least throttle for a
923 * single-thread event (e.g. fork).
924 *
925 * Such locations include userret().
926 * If the "return_instead" argument is non zero, the thread must be able to
927 * accept 0 (caller may continue), or 1 (caller must abort) as a result.
928 *
929 * The 'return_instead' argument tells the function if it may do a
930 * thread_exit() or suspend, or whether the caller must abort and back
931 * out instead.
932 *
933 * If the thread that set the single_threading request has set the
934 * P_SINGLE_EXIT bit in the process flags then this call will never return
935 * if 'return_instead' is false, but will exit.
936 *
937 * P_SINGLE_EXIT | return_instead == 0| return_instead != 0
938 *---------------+--------------------+---------------------
939 * 0 | returns 0 | returns 0 or 1
940 * | when ST ends | immediately
941 *---------------+--------------------+---------------------
942 * 1 | thread exits | returns 1
943 * | | immediately
944 * 0 = thread_exit() or suspension ok,
945 * other = return error instead of stopping the thread.
946 *
947 * While a full suspension is under effect, even a single threading
948 * thread would be suspended if it made this call (but it shouldn't).
949 * This call should only be made from places where
950 * thread_exit() would be safe as that may be the outcome unless
951 * return_instead is set.
952 */
953 int
954 thread_suspend_check(int return_instead)
955 {
956 struct thread *td;
957 struct proc *p;
958 int wakeup_swapper;
959
960 td = curthread;
961 p = td->td_proc;
962 mtx_assert(&Giant, MA_NOTOWNED);
963 PROC_LOCK_ASSERT(p, MA_OWNED);
964 while (thread_suspend_check_needed()) {
965 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
966 KASSERT(p->p_singlethread != NULL,
967 ("singlethread not set"));
968 /*
969 * The only suspension in action is a
970 * single-threading. Single threader need not stop.
971 * It is safe to access p->p_singlethread unlocked
972 * because it can only be set to our address by us.
973 */
974 if (p->p_singlethread == td)
975 return (0); /* Exempt from stopping. */
976 }
977 if ((p->p_flag & P_SINGLE_EXIT) && return_instead)
978 return (EINTR);
979
980 /* Should we goto user boundary if we didn't come from there? */
981 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE &&
982 (p->p_flag & P_SINGLE_BOUNDARY) && return_instead)
983 return (ERESTART);
984
985 /*
986 * Ignore suspend requests if they are deferred.
987 */
988 if ((td->td_flags & TDF_SBDRY) != 0) {
989 KASSERT(return_instead,
990 ("TDF_SBDRY set for unsafe thread_suspend_check"));
991 KASSERT((td->td_flags & (TDF_SEINTR | TDF_SERESTART)) !=
992 (TDF_SEINTR | TDF_SERESTART),
993 ("both TDF_SEINTR and TDF_SERESTART"));
994 return (TD_SBDRY_INTR(td) ? TD_SBDRY_ERRNO(td) : 0);
995 }
996
997 /*
998 * If the process is waiting for us to exit,
999 * this thread should just suicide.
1000 * Assumes that P_SINGLE_EXIT implies P_STOPPED_SINGLE.
1001 */
1002 if ((p->p_flag & P_SINGLE_EXIT) && (p->p_singlethread != td)) {
1003 PROC_UNLOCK(p);
1004
1005 /*
1006 * Allow Linux emulation layer to do some work
1007 * before thread suicide.
1008 */
1009 if (__predict_false(p->p_sysent->sv_thread_detach != NULL))
1010 (p->p_sysent->sv_thread_detach)(td);
1011 umtx_thread_exit(td);
1012 kern_thr_exit(td);
1013 panic("stopped thread did not exit");
1014 }
1015
1016 PROC_SLOCK(p);
1017 thread_stopped(p);
1018 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
1019 if (p->p_numthreads == p->p_suspcount + 1) {
1020 thread_lock(p->p_singlethread);
1021 wakeup_swapper = thread_unsuspend_one(
1022 p->p_singlethread, p, false);
1023 thread_unlock(p->p_singlethread);
1024 if (wakeup_swapper)
1025 kick_proc0();
1026 }
1027 }
1028 PROC_UNLOCK(p);
1029 thread_lock(td);
1030 /*
1031 * When a thread suspends, it just
1032 * gets taken off all queues.
1033 */
1034 thread_suspend_one(td);
1035 if (return_instead == 0) {
1036 p->p_boundary_count++;
1037 td->td_flags |= TDF_BOUNDARY;
1038 }
1039 PROC_SUNLOCK(p);
1040 mi_switch(SW_INVOL | SWT_SUSPEND, NULL);
1041 thread_unlock(td);
1042 PROC_LOCK(p);
1043 }
1044 return (0);
1045 }
1046
1047 void
1048 thread_suspend_switch(struct thread *td, struct proc *p)
1049 {
1050
1051 KASSERT(!TD_IS_SUSPENDED(td), ("already suspended"));
1052 PROC_LOCK_ASSERT(p, MA_OWNED);
1053 PROC_SLOCK_ASSERT(p, MA_OWNED);
1054 /*
1055 * We implement thread_suspend_one in stages here to avoid
1056 * dropping the proc lock while the thread lock is owned.
1057 */
1058 if (p == td->td_proc) {
1059 thread_stopped(p);
1060 p->p_suspcount++;
1061 }
1062 PROC_UNLOCK(p);
1063 thread_lock(td);
1064 td->td_flags &= ~TDF_NEEDSUSPCHK;
1065 TD_SET_SUSPENDED(td);
1066 sched_sleep(td, 0);
1067 PROC_SUNLOCK(p);
1068 DROP_GIANT();
1069 mi_switch(SW_VOL | SWT_SUSPEND, NULL);
1070 thread_unlock(td);
1071 PICKUP_GIANT();
1072 PROC_LOCK(p);
1073 PROC_SLOCK(p);
1074 }
1075
1076 void
1077 thread_suspend_one(struct thread *td)
1078 {
1079 struct proc *p;
1080
1081 p = td->td_proc;
1082 PROC_SLOCK_ASSERT(p, MA_OWNED);
1083 THREAD_LOCK_ASSERT(td, MA_OWNED);
1084 KASSERT(!TD_IS_SUSPENDED(td), ("already suspended"));
1085 p->p_suspcount++;
1086 td->td_flags &= ~TDF_NEEDSUSPCHK;
1087 TD_SET_SUSPENDED(td);
1088 sched_sleep(td, 0);
1089 }
1090
1091 static int
1092 thread_unsuspend_one(struct thread *td, struct proc *p, bool boundary)
1093 {
1094
1095 THREAD_LOCK_ASSERT(td, MA_OWNED);
1096 KASSERT(TD_IS_SUSPENDED(td), ("Thread not suspended"));
1097 TD_CLR_SUSPENDED(td);
1098 td->td_flags &= ~TDF_ALLPROCSUSP;
1099 if (td->td_proc == p) {
1100 PROC_SLOCK_ASSERT(p, MA_OWNED);
1101 p->p_suspcount--;
1102 if (boundary && (td->td_flags & TDF_BOUNDARY) != 0) {
1103 td->td_flags &= ~TDF_BOUNDARY;
1104 p->p_boundary_count--;
1105 }
1106 }
1107 return (setrunnable(td));
1108 }
1109
1110 /*
1111 * Allow all threads blocked by single threading to continue running.
1112 */
1113 void
1114 thread_unsuspend(struct proc *p)
1115 {
1116 struct thread *td;
1117 int wakeup_swapper;
1118
1119 PROC_LOCK_ASSERT(p, MA_OWNED);
1120 PROC_SLOCK_ASSERT(p, MA_OWNED);
1121 wakeup_swapper = 0;
1122 if (!P_SHOULDSTOP(p)) {
1123 FOREACH_THREAD_IN_PROC(p, td) {
1124 thread_lock(td);
1125 if (TD_IS_SUSPENDED(td)) {
1126 wakeup_swapper |= thread_unsuspend_one(td, p,
1127 true);
1128 }
1129 thread_unlock(td);
1130 }
1131 } else if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE &&
1132 p->p_numthreads == p->p_suspcount) {
1133 /*
1134 * Stopping everything also did the job for the single
1135 * threading request. Now we've downgraded to single-threaded,
1136 * let it continue.
1137 */
1138 if (p->p_singlethread->td_proc == p) {
1139 thread_lock(p->p_singlethread);
1140 wakeup_swapper = thread_unsuspend_one(
1141 p->p_singlethread, p, false);
1142 thread_unlock(p->p_singlethread);
1143 }
1144 }
1145 if (wakeup_swapper)
1146 kick_proc0();
1147 }
1148
1149 /*
1150 * End the single threading mode..
1151 */
1152 void
1153 thread_single_end(struct proc *p, int mode)
1154 {
1155 struct thread *td;
1156 int wakeup_swapper;
1157
1158 KASSERT(mode == SINGLE_EXIT || mode == SINGLE_BOUNDARY ||
1159 mode == SINGLE_ALLPROC || mode == SINGLE_NO_EXIT,
1160 ("invalid mode %d", mode));
1161 PROC_LOCK_ASSERT(p, MA_OWNED);
1162 KASSERT((mode == SINGLE_ALLPROC && (p->p_flag & P_TOTAL_STOP) != 0) ||
1163 (mode != SINGLE_ALLPROC && (p->p_flag & P_TOTAL_STOP) == 0),
1164 ("mode %d does not match P_TOTAL_STOP", mode));
1165 KASSERT(mode == SINGLE_ALLPROC || p->p_singlethread == curthread,
1166 ("thread_single_end from other thread %p %p",
1167 curthread, p->p_singlethread));
1168 KASSERT(mode != SINGLE_BOUNDARY ||
1169 (p->p_flag & P_SINGLE_BOUNDARY) != 0,
1170 ("mis-matched SINGLE_BOUNDARY flags %x", p->p_flag));
1171 p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT | P_SINGLE_BOUNDARY |
1172 P_TOTAL_STOP);
1173 PROC_SLOCK(p);
1174 p->p_singlethread = NULL;
1175 wakeup_swapper = 0;
1176 /*
1177 * If there are other threads they may now run,
1178 * unless of course there is a blanket 'stop order'
1179 * on the process. The single threader must be allowed
1180 * to continue however as this is a bad place to stop.
1181 */
1182 if (p->p_numthreads != remain_for_mode(mode) && !P_SHOULDSTOP(p)) {
1183 FOREACH_THREAD_IN_PROC(p, td) {
1184 thread_lock(td);
1185 if (TD_IS_SUSPENDED(td)) {
1186 wakeup_swapper |= thread_unsuspend_one(td, p,
1187 mode == SINGLE_BOUNDARY);
1188 }
1189 thread_unlock(td);
1190 }
1191 }
1192 KASSERT(mode != SINGLE_BOUNDARY || p->p_boundary_count == 0,
1193 ("inconsistent boundary count %d", p->p_boundary_count));
1194 PROC_SUNLOCK(p);
1195 if (wakeup_swapper)
1196 kick_proc0();
1197 }
1198
1199 struct thread *
1200 thread_find(struct proc *p, lwpid_t tid)
1201 {
1202 struct thread *td;
1203
1204 PROC_LOCK_ASSERT(p, MA_OWNED);
1205 FOREACH_THREAD_IN_PROC(p, td) {
1206 if (td->td_tid == tid)
1207 break;
1208 }
1209 return (td);
1210 }
1211
1212 /* Locate a thread by number; return with proc lock held. */
1213 struct thread *
1214 tdfind(lwpid_t tid, pid_t pid)
1215 {
1216 #define RUN_THRESH 16
1217 struct thread *td;
1218 int run = 0;
1219
1220 rw_rlock(&tidhash_lock);
1221 LIST_FOREACH(td, TIDHASH(tid), td_hash) {
1222 if (td->td_tid == tid) {
1223 if (pid != -1 && td->td_proc->p_pid != pid) {
1224 td = NULL;
1225 break;
1226 }
1227 PROC_LOCK(td->td_proc);
1228 if (td->td_proc->p_state == PRS_NEW) {
1229 PROC_UNLOCK(td->td_proc);
1230 td = NULL;
1231 break;
1232 }
1233 if (run > RUN_THRESH) {
1234 if (rw_try_upgrade(&tidhash_lock)) {
1235 LIST_REMOVE(td, td_hash);
1236 LIST_INSERT_HEAD(TIDHASH(td->td_tid),
1237 td, td_hash);
1238 rw_wunlock(&tidhash_lock);
1239 return (td);
1240 }
1241 }
1242 break;
1243 }
1244 run++;
1245 }
1246 rw_runlock(&tidhash_lock);
1247 return (td);
1248 }
1249
1250 void
1251 tidhash_add(struct thread *td)
1252 {
1253 rw_wlock(&tidhash_lock);
1254 LIST_INSERT_HEAD(TIDHASH(td->td_tid), td, td_hash);
1255 rw_wunlock(&tidhash_lock);
1256 }
1257
1258 void
1259 tidhash_remove(struct thread *td)
1260 {
1261 rw_wlock(&tidhash_lock);
1262 LIST_REMOVE(td, td_hash);
1263 rw_wunlock(&tidhash_lock);
1264 }
Cache object: c13e00d5d5d66f9415bee1f4695eaba7
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