1 /*-
2 * SPDX-License-Identifier: BSD-3-Clause
3 *
4 * Copyright (c) 1998 Berkeley Software Design, Inc. All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
14 * 3. Berkeley Software Design Inc's name may not be used to endorse or
15 * promote products derived from this software without specific prior
16 * written permission.
17 *
18 * THIS SOFTWARE IS PROVIDED BY BERKELEY SOFTWARE DESIGN INC ``AS IS'' AND
19 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
20 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
21 * ARE DISCLAIMED. IN NO EVENT SHALL BERKELEY SOFTWARE DESIGN INC BE LIABLE
22 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
23 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
24 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
25 * HOWEVER 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
28 * SUCH DAMAGE.
29 *
30 * from BSDI $Id: mutex_witness.c,v 1.1.2.20 2000/04/27 03:10:27 cp Exp $
31 * and BSDI $Id: synch_machdep.c,v 2.3.2.39 2000/04/27 03:10:25 cp Exp $
32 */
33
34 /*
35 * Implementation of turnstiles used to hold queue of threads blocked on
36 * non-sleepable locks. Sleepable locks use condition variables to
37 * implement their queues. Turnstiles differ from a sleep queue in that
38 * turnstile queue's are assigned to a lock held by an owning thread. Thus,
39 * when one thread is enqueued onto a turnstile, it can lend its priority
40 * to the owning thread.
41 *
42 * We wish to avoid bloating locks with an embedded turnstile and we do not
43 * want to use back-pointers in the locks for the same reason. Thus, we
44 * use a similar approach to that of Solaris 7 as described in Solaris
45 * Internals by Jim Mauro and Richard McDougall. Turnstiles are looked up
46 * in a hash table based on the address of the lock. Each entry in the
47 * hash table is a linked-lists of turnstiles and is called a turnstile
48 * chain. Each chain contains a spin mutex that protects all of the
49 * turnstiles in the chain.
50 *
51 * Each time a thread is created, a turnstile is allocated from a UMA zone
52 * and attached to that thread. When a thread blocks on a lock, if it is the
53 * first thread to block, it lends its turnstile to the lock. If the lock
54 * already has a turnstile, then it gives its turnstile to the lock's
55 * turnstile's free list. When a thread is woken up, it takes a turnstile from
56 * the free list if there are any other waiters. If it is the only thread
57 * blocked on the lock, then it reclaims the turnstile associated with the lock
58 * and removes it from the hash table.
59 */
60
61 #include <sys/cdefs.h>
62 #include "opt_ddb.h"
63 #include "opt_turnstile_profiling.h"
64 #include "opt_sched.h"
65
66 #include <sys/param.h>
67 #include <sys/systm.h>
68 #include <sys/kdb.h>
69 #include <sys/kernel.h>
70 #include <sys/ktr.h>
71 #include <sys/lock.h>
72 #include <sys/mutex.h>
73 #include <sys/proc.h>
74 #include <sys/queue.h>
75 #include <sys/sched.h>
76 #include <sys/sdt.h>
77 #include <sys/sysctl.h>
78 #include <sys/turnstile.h>
79
80 #include <vm/uma.h>
81
82 #ifdef DDB
83 #include <ddb/ddb.h>
84 #include <sys/lockmgr.h>
85 #include <sys/sx.h>
86 #endif
87
88 /*
89 * Constants for the hash table of turnstile chains. TC_SHIFT is a magic
90 * number chosen because the sleep queue's use the same value for the
91 * shift. Basically, we ignore the lower 8 bits of the address.
92 * TC_TABLESIZE must be a power of two for TC_MASK to work properly.
93 */
94 #define TC_TABLESIZE 128 /* Must be power of 2. */
95 #define TC_MASK (TC_TABLESIZE - 1)
96 #define TC_SHIFT 8
97 #define TC_HASH(lock) (((uintptr_t)(lock) >> TC_SHIFT) & TC_MASK)
98 #define TC_LOOKUP(lock) &turnstile_chains[TC_HASH(lock)]
99
100 /*
101 * There are three different lists of turnstiles as follows. The list
102 * connected by ts_link entries is a per-thread list of all the turnstiles
103 * attached to locks that we own. This is used to fixup our priority when
104 * a lock is released. The other two lists use the ts_hash entries. The
105 * first of these two is the turnstile chain list that a turnstile is on
106 * when it is attached to a lock. The second list to use ts_hash is the
107 * free list hung off of a turnstile that is attached to a lock.
108 *
109 * Each turnstile contains three lists of threads. The two ts_blocked lists
110 * are linked list of threads blocked on the turnstile's lock. One list is
111 * for exclusive waiters, and the other is for shared waiters. The
112 * ts_pending list is a linked list of threads previously awakened by
113 * turnstile_signal() or turnstile_wait() that are waiting to be put on
114 * the run queue.
115 *
116 * Locking key:
117 * c - turnstile chain lock
118 * q - td_contested lock
119 */
120 struct turnstile {
121 struct mtx ts_lock; /* Spin lock for self. */
122 struct threadqueue ts_blocked[2]; /* (c + q) Blocked threads. */
123 struct threadqueue ts_pending; /* (c) Pending threads. */
124 LIST_ENTRY(turnstile) ts_hash; /* (c) Chain and free list. */
125 LIST_ENTRY(turnstile) ts_link; /* (q) Contested locks. */
126 LIST_HEAD(, turnstile) ts_free; /* (c) Free turnstiles. */
127 struct lock_object *ts_lockobj; /* (c) Lock we reference. */
128 struct thread *ts_owner; /* (c + q) Who owns the lock. */
129 };
130
131 struct turnstile_chain {
132 LIST_HEAD(, turnstile) tc_turnstiles; /* List of turnstiles. */
133 struct mtx tc_lock; /* Spin lock for this chain. */
134 #ifdef TURNSTILE_PROFILING
135 u_int tc_depth; /* Length of tc_queues. */
136 u_int tc_max_depth; /* Max length of tc_queues. */
137 #endif
138 };
139
140 #ifdef TURNSTILE_PROFILING
141 u_int turnstile_max_depth;
142 static SYSCTL_NODE(_debug, OID_AUTO, turnstile, CTLFLAG_RD | CTLFLAG_MPSAFE, 0,
143 "turnstile profiling");
144 static SYSCTL_NODE(_debug_turnstile, OID_AUTO, chains,
145 CTLFLAG_RD | CTLFLAG_MPSAFE, 0,
146 "turnstile chain stats");
147 SYSCTL_UINT(_debug_turnstile, OID_AUTO, max_depth, CTLFLAG_RD,
148 &turnstile_max_depth, 0, "maximum depth achieved of a single chain");
149 #endif
150 static struct mtx td_contested_lock;
151 static struct turnstile_chain turnstile_chains[TC_TABLESIZE];
152 static uma_zone_t turnstile_zone;
153
154 /*
155 * Prototypes for non-exported routines.
156 */
157 static void init_turnstile0(void *dummy);
158 #ifdef TURNSTILE_PROFILING
159 static void init_turnstile_profiling(void *arg);
160 #endif
161 static void propagate_priority(struct thread *td);
162 static int turnstile_adjust_thread(struct turnstile *ts,
163 struct thread *td);
164 static struct thread *turnstile_first_waiter(struct turnstile *ts);
165 static void turnstile_setowner(struct turnstile *ts, struct thread *owner);
166 #ifdef INVARIANTS
167 static void turnstile_dtor(void *mem, int size, void *arg);
168 #endif
169 static int turnstile_init(void *mem, int size, int flags);
170 static void turnstile_fini(void *mem, int size);
171
172 SDT_PROVIDER_DECLARE(sched);
173 SDT_PROBE_DEFINE(sched, , , sleep);
174 SDT_PROBE_DEFINE2(sched, , , wakeup, "struct thread *",
175 "struct proc *");
176
177 static inline void
propagate_unlock_ts(struct turnstile * top,struct turnstile * ts)178 propagate_unlock_ts(struct turnstile *top, struct turnstile *ts)
179 {
180
181 if (ts != top)
182 mtx_unlock_spin(&ts->ts_lock);
183 }
184
185 static inline void
propagate_unlock_td(struct turnstile * top,struct thread * td)186 propagate_unlock_td(struct turnstile *top, struct thread *td)
187 {
188
189 if (td->td_lock != &top->ts_lock)
190 thread_unlock(td);
191 }
192
193 /*
194 * Walks the chain of turnstiles and their owners to propagate the priority
195 * of the thread being blocked to all the threads holding locks that have to
196 * release their locks before this thread can run again.
197 */
198 static void
propagate_priority(struct thread * td)199 propagate_priority(struct thread *td)
200 {
201 struct turnstile *ts, *top;
202 int pri;
203
204 THREAD_LOCK_ASSERT(td, MA_OWNED);
205 pri = td->td_priority;
206 top = ts = td->td_blocked;
207 THREAD_LOCKPTR_ASSERT(td, &ts->ts_lock);
208
209 /*
210 * The original turnstile lock is held across the entire
211 * operation. We only ever lock down the chain so the lock
212 * order is constant.
213 */
214 for (;;) {
215 td = ts->ts_owner;
216
217 if (td == NULL) {
218 /*
219 * This might be a read lock with no owner. There's
220 * not much we can do, so just bail.
221 */
222 propagate_unlock_ts(top, ts);
223 return;
224 }
225
226 /*
227 * Wait for the thread lock to be stable and then only
228 * acquire if it is not the turnstile lock.
229 */
230 thread_lock_block_wait(td);
231 if (td->td_lock != &ts->ts_lock) {
232 thread_lock_flags(td, MTX_DUPOK);
233 propagate_unlock_ts(top, ts);
234 }
235 MPASS(td->td_proc != NULL);
236 MPASS(td->td_proc->p_magic == P_MAGIC);
237
238 /*
239 * If the thread is asleep, then we are probably about
240 * to deadlock. To make debugging this easier, show
241 * backtrace of misbehaving thread and panic to not
242 * leave the kernel deadlocked.
243 */
244 if (TD_IS_SLEEPING(td)) {
245 printf(
246 "Sleeping thread (tid %d, pid %d) owns a non-sleepable lock\n",
247 td->td_tid, td->td_proc->p_pid);
248 kdb_backtrace_thread(td);
249 panic("sleeping thread");
250 }
251
252 /*
253 * If this thread already has higher priority than the
254 * thread that is being blocked, we are finished.
255 */
256 if (td->td_priority <= pri) {
257 propagate_unlock_td(top, td);
258 return;
259 }
260
261 /*
262 * Bump this thread's priority.
263 */
264 sched_lend_prio(td, pri);
265
266 /*
267 * If lock holder is actually running or on the run queue
268 * then we are done.
269 */
270 if (TD_IS_RUNNING(td) || TD_ON_RUNQ(td)) {
271 MPASS(td->td_blocked == NULL);
272 propagate_unlock_td(top, td);
273 return;
274 }
275
276 #ifndef SMP
277 /*
278 * For UP, we check to see if td is curthread (this shouldn't
279 * ever happen however as it would mean we are in a deadlock.)
280 */
281 KASSERT(td != curthread, ("Deadlock detected"));
282 #endif
283
284 /*
285 * If we aren't blocked on a lock, we should be.
286 */
287 KASSERT(TD_ON_LOCK(td), (
288 "thread %d(%s):%d holds %s but isn't blocked on a lock\n",
289 td->td_tid, td->td_name, TD_GET_STATE(td),
290 ts->ts_lockobj->lo_name));
291
292 /*
293 * Pick up the lock that td is blocked on.
294 */
295 ts = td->td_blocked;
296 MPASS(ts != NULL);
297 THREAD_LOCKPTR_ASSERT(td, &ts->ts_lock);
298 /* Resort td on the list if needed. */
299 if (!turnstile_adjust_thread(ts, td)) {
300 propagate_unlock_ts(top, ts);
301 return;
302 }
303 /* The thread lock is released as ts lock above. */
304 }
305 }
306
307 /*
308 * Adjust the thread's position on a turnstile after its priority has been
309 * changed.
310 */
311 static int
turnstile_adjust_thread(struct turnstile * ts,struct thread * td)312 turnstile_adjust_thread(struct turnstile *ts, struct thread *td)
313 {
314 struct thread *td1, *td2;
315 int queue;
316
317 THREAD_LOCK_ASSERT(td, MA_OWNED);
318 MPASS(TD_ON_LOCK(td));
319
320 /*
321 * This thread may not be blocked on this turnstile anymore
322 * but instead might already be woken up on another CPU
323 * that is waiting on the thread lock in turnstile_unpend() to
324 * finish waking this thread up. We can detect this case
325 * by checking to see if this thread has been given a
326 * turnstile by either turnstile_signal() or
327 * turnstile_broadcast(). In this case, treat the thread as
328 * if it was already running.
329 */
330 if (td->td_turnstile != NULL)
331 return (0);
332
333 /*
334 * Check if the thread needs to be moved on the blocked chain.
335 * It needs to be moved if either its priority is lower than
336 * the previous thread or higher than the next thread.
337 */
338 THREAD_LOCKPTR_BLOCKED_ASSERT(td, &ts->ts_lock);
339 td1 = TAILQ_PREV(td, threadqueue, td_lockq);
340 td2 = TAILQ_NEXT(td, td_lockq);
341 if ((td1 != NULL && td->td_priority < td1->td_priority) ||
342 (td2 != NULL && td->td_priority > td2->td_priority)) {
343 /*
344 * Remove thread from blocked chain and determine where
345 * it should be moved to.
346 */
347 queue = td->td_tsqueue;
348 MPASS(queue == TS_EXCLUSIVE_QUEUE || queue == TS_SHARED_QUEUE);
349 mtx_lock_spin(&td_contested_lock);
350 TAILQ_REMOVE(&ts->ts_blocked[queue], td, td_lockq);
351 TAILQ_FOREACH(td1, &ts->ts_blocked[queue], td_lockq) {
352 MPASS(td1->td_proc->p_magic == P_MAGIC);
353 if (td1->td_priority > td->td_priority)
354 break;
355 }
356
357 if (td1 == NULL)
358 TAILQ_INSERT_TAIL(&ts->ts_blocked[queue], td, td_lockq);
359 else
360 TAILQ_INSERT_BEFORE(td1, td, td_lockq);
361 mtx_unlock_spin(&td_contested_lock);
362 if (td1 == NULL)
363 CTR3(KTR_LOCK,
364 "turnstile_adjust_thread: td %d put at tail on [%p] %s",
365 td->td_tid, ts->ts_lockobj, ts->ts_lockobj->lo_name);
366 else
367 CTR4(KTR_LOCK,
368 "turnstile_adjust_thread: td %d moved before %d on [%p] %s",
369 td->td_tid, td1->td_tid, ts->ts_lockobj,
370 ts->ts_lockobj->lo_name);
371 }
372 return (1);
373 }
374
375 /*
376 * Early initialization of turnstiles. This is not done via a SYSINIT()
377 * since this needs to be initialized very early when mutexes are first
378 * initialized.
379 */
380 void
init_turnstiles(void)381 init_turnstiles(void)
382 {
383 int i;
384
385 for (i = 0; i < TC_TABLESIZE; i++) {
386 LIST_INIT(&turnstile_chains[i].tc_turnstiles);
387 mtx_init(&turnstile_chains[i].tc_lock, "turnstile chain",
388 NULL, MTX_SPIN);
389 }
390 mtx_init(&td_contested_lock, "td_contested", NULL, MTX_SPIN);
391 LIST_INIT(&thread0.td_contested);
392 thread0.td_turnstile = NULL;
393 }
394
395 #ifdef TURNSTILE_PROFILING
396 static void
init_turnstile_profiling(void * arg)397 init_turnstile_profiling(void *arg)
398 {
399 struct sysctl_oid *chain_oid;
400 char chain_name[10];
401 int i;
402
403 for (i = 0; i < TC_TABLESIZE; i++) {
404 snprintf(chain_name, sizeof(chain_name), "%d", i);
405 chain_oid = SYSCTL_ADD_NODE(NULL,
406 SYSCTL_STATIC_CHILDREN(_debug_turnstile_chains), OID_AUTO,
407 chain_name, CTLFLAG_RD | CTLFLAG_MPSAFE, NULL,
408 "turnstile chain stats");
409 SYSCTL_ADD_UINT(NULL, SYSCTL_CHILDREN(chain_oid), OID_AUTO,
410 "depth", CTLFLAG_RD, &turnstile_chains[i].tc_depth, 0,
411 NULL);
412 SYSCTL_ADD_UINT(NULL, SYSCTL_CHILDREN(chain_oid), OID_AUTO,
413 "max_depth", CTLFLAG_RD, &turnstile_chains[i].tc_max_depth,
414 0, NULL);
415 }
416 }
417 SYSINIT(turnstile_profiling, SI_SUB_LOCK, SI_ORDER_ANY,
418 init_turnstile_profiling, NULL);
419 #endif
420
421 static void
init_turnstile0(void * dummy)422 init_turnstile0(void *dummy)
423 {
424
425 turnstile_zone = uma_zcreate("TURNSTILE", sizeof(struct turnstile),
426 NULL,
427 #ifdef INVARIANTS
428 turnstile_dtor,
429 #else
430 NULL,
431 #endif
432 turnstile_init, turnstile_fini, UMA_ALIGN_CACHE, UMA_ZONE_NOFREE);
433 thread0.td_turnstile = turnstile_alloc();
434 }
435 SYSINIT(turnstile0, SI_SUB_LOCK, SI_ORDER_ANY, init_turnstile0, NULL);
436
437 /*
438 * Update a thread on the turnstile list after it's priority has been changed.
439 * The old priority is passed in as an argument.
440 */
441 void
turnstile_adjust(struct thread * td,u_char oldpri)442 turnstile_adjust(struct thread *td, u_char oldpri)
443 {
444 struct turnstile *ts;
445
446 MPASS(TD_ON_LOCK(td));
447
448 /*
449 * Pick up the lock that td is blocked on.
450 */
451 ts = td->td_blocked;
452 MPASS(ts != NULL);
453 THREAD_LOCKPTR_BLOCKED_ASSERT(td, &ts->ts_lock);
454 mtx_assert(&ts->ts_lock, MA_OWNED);
455
456 /* Resort the turnstile on the list. */
457 if (!turnstile_adjust_thread(ts, td))
458 return;
459 /*
460 * If our priority was lowered and we are at the head of the
461 * turnstile, then propagate our new priority up the chain.
462 * Note that we currently don't try to revoke lent priorities
463 * when our priority goes up.
464 */
465 MPASS(td->td_tsqueue == TS_EXCLUSIVE_QUEUE ||
466 td->td_tsqueue == TS_SHARED_QUEUE);
467 if (td == TAILQ_FIRST(&ts->ts_blocked[td->td_tsqueue]) &&
468 td->td_priority < oldpri) {
469 propagate_priority(td);
470 }
471 }
472
473 /*
474 * Set the owner of the lock this turnstile is attached to.
475 */
476 static void
turnstile_setowner(struct turnstile * ts,struct thread * owner)477 turnstile_setowner(struct turnstile *ts, struct thread *owner)
478 {
479
480 mtx_assert(&td_contested_lock, MA_OWNED);
481 MPASS(ts->ts_owner == NULL);
482
483 /* A shared lock might not have an owner. */
484 if (owner == NULL)
485 return;
486
487 MPASS(owner->td_proc->p_magic == P_MAGIC);
488 ts->ts_owner = owner;
489 LIST_INSERT_HEAD(&owner->td_contested, ts, ts_link);
490 }
491
492 #ifdef INVARIANTS
493 /*
494 * UMA zone item deallocator.
495 */
496 static void
turnstile_dtor(void * mem,int size,void * arg)497 turnstile_dtor(void *mem, int size, void *arg)
498 {
499 struct turnstile *ts;
500
501 ts = mem;
502 MPASS(TAILQ_EMPTY(&ts->ts_blocked[TS_EXCLUSIVE_QUEUE]));
503 MPASS(TAILQ_EMPTY(&ts->ts_blocked[TS_SHARED_QUEUE]));
504 MPASS(TAILQ_EMPTY(&ts->ts_pending));
505 }
506 #endif
507
508 /*
509 * UMA zone item initializer.
510 */
511 static int
turnstile_init(void * mem,int size,int flags)512 turnstile_init(void *mem, int size, int flags)
513 {
514 struct turnstile *ts;
515
516 bzero(mem, size);
517 ts = mem;
518 TAILQ_INIT(&ts->ts_blocked[TS_EXCLUSIVE_QUEUE]);
519 TAILQ_INIT(&ts->ts_blocked[TS_SHARED_QUEUE]);
520 TAILQ_INIT(&ts->ts_pending);
521 LIST_INIT(&ts->ts_free);
522 mtx_init(&ts->ts_lock, "turnstile lock", NULL, MTX_SPIN);
523 return (0);
524 }
525
526 static void
turnstile_fini(void * mem,int size)527 turnstile_fini(void *mem, int size)
528 {
529 struct turnstile *ts;
530
531 ts = mem;
532 mtx_destroy(&ts->ts_lock);
533 }
534
535 /*
536 * Get a turnstile for a new thread.
537 */
538 struct turnstile *
turnstile_alloc(void)539 turnstile_alloc(void)
540 {
541
542 return (uma_zalloc(turnstile_zone, M_WAITOK));
543 }
544
545 /*
546 * Free a turnstile when a thread is destroyed.
547 */
548 void
turnstile_free(struct turnstile * ts)549 turnstile_free(struct turnstile *ts)
550 {
551
552 uma_zfree(turnstile_zone, ts);
553 }
554
555 /*
556 * Lock the turnstile chain associated with the specified lock.
557 */
558 void
turnstile_chain_lock(struct lock_object * lock)559 turnstile_chain_lock(struct lock_object *lock)
560 {
561 struct turnstile_chain *tc;
562
563 tc = TC_LOOKUP(lock);
564 mtx_lock_spin(&tc->tc_lock);
565 }
566
567 struct turnstile *
turnstile_trywait(struct lock_object * lock)568 turnstile_trywait(struct lock_object *lock)
569 {
570 struct turnstile_chain *tc;
571 struct turnstile *ts;
572
573 tc = TC_LOOKUP(lock);
574 mtx_lock_spin(&tc->tc_lock);
575 LIST_FOREACH(ts, &tc->tc_turnstiles, ts_hash)
576 if (ts->ts_lockobj == lock) {
577 mtx_lock_spin(&ts->ts_lock);
578 return (ts);
579 }
580
581 ts = curthread->td_turnstile;
582 MPASS(ts != NULL);
583 mtx_lock_spin(&ts->ts_lock);
584 KASSERT(ts->ts_lockobj == NULL, ("stale ts_lockobj pointer"));
585 ts->ts_lockobj = lock;
586
587 return (ts);
588 }
589
590 bool
turnstile_lock(struct turnstile * ts,struct lock_object ** lockp,struct thread ** tdp)591 turnstile_lock(struct turnstile *ts, struct lock_object **lockp,
592 struct thread **tdp)
593 {
594 struct turnstile_chain *tc;
595 struct lock_object *lock;
596
597 if ((lock = ts->ts_lockobj) == NULL)
598 return (false);
599 tc = TC_LOOKUP(lock);
600 mtx_lock_spin(&tc->tc_lock);
601 mtx_lock_spin(&ts->ts_lock);
602 if (__predict_false(lock != ts->ts_lockobj)) {
603 mtx_unlock_spin(&tc->tc_lock);
604 mtx_unlock_spin(&ts->ts_lock);
605 return (false);
606 }
607 *lockp = lock;
608 *tdp = ts->ts_owner;
609 return (true);
610 }
611
612 void
turnstile_unlock(struct turnstile * ts,struct lock_object * lock)613 turnstile_unlock(struct turnstile *ts, struct lock_object *lock)
614 {
615 struct turnstile_chain *tc;
616
617 mtx_assert(&ts->ts_lock, MA_OWNED);
618 mtx_unlock_spin(&ts->ts_lock);
619 if (ts == curthread->td_turnstile)
620 ts->ts_lockobj = NULL;
621 tc = TC_LOOKUP(lock);
622 mtx_unlock_spin(&tc->tc_lock);
623 }
624
625 void
turnstile_assert(struct turnstile * ts)626 turnstile_assert(struct turnstile *ts)
627 {
628 MPASS(ts->ts_lockobj == NULL);
629 }
630
631 void
turnstile_cancel(struct turnstile * ts)632 turnstile_cancel(struct turnstile *ts)
633 {
634 struct turnstile_chain *tc;
635 struct lock_object *lock;
636
637 mtx_assert(&ts->ts_lock, MA_OWNED);
638
639 mtx_unlock_spin(&ts->ts_lock);
640 lock = ts->ts_lockobj;
641 if (ts == curthread->td_turnstile)
642 ts->ts_lockobj = NULL;
643 tc = TC_LOOKUP(lock);
644 mtx_unlock_spin(&tc->tc_lock);
645 }
646
647 /*
648 * Look up the turnstile for a lock in the hash table locking the associated
649 * turnstile chain along the way. If no turnstile is found in the hash
650 * table, NULL is returned.
651 */
652 struct turnstile *
turnstile_lookup(struct lock_object * lock)653 turnstile_lookup(struct lock_object *lock)
654 {
655 struct turnstile_chain *tc;
656 struct turnstile *ts;
657
658 tc = TC_LOOKUP(lock);
659 mtx_assert(&tc->tc_lock, MA_OWNED);
660 LIST_FOREACH(ts, &tc->tc_turnstiles, ts_hash)
661 if (ts->ts_lockobj == lock) {
662 mtx_lock_spin(&ts->ts_lock);
663 return (ts);
664 }
665 return (NULL);
666 }
667
668 /*
669 * Unlock the turnstile chain associated with a given lock.
670 */
671 void
turnstile_chain_unlock(struct lock_object * lock)672 turnstile_chain_unlock(struct lock_object *lock)
673 {
674 struct turnstile_chain *tc;
675
676 tc = TC_LOOKUP(lock);
677 mtx_unlock_spin(&tc->tc_lock);
678 }
679
680 /*
681 * Return a pointer to the thread waiting on this turnstile with the
682 * most important priority or NULL if the turnstile has no waiters.
683 */
684 static struct thread *
turnstile_first_waiter(struct turnstile * ts)685 turnstile_first_waiter(struct turnstile *ts)
686 {
687 struct thread *std, *xtd;
688
689 std = TAILQ_FIRST(&ts->ts_blocked[TS_SHARED_QUEUE]);
690 xtd = TAILQ_FIRST(&ts->ts_blocked[TS_EXCLUSIVE_QUEUE]);
691 if (xtd == NULL || (std != NULL && std->td_priority < xtd->td_priority))
692 return (std);
693 return (xtd);
694 }
695
696 /*
697 * Take ownership of a turnstile and adjust the priority of the new
698 * owner appropriately.
699 */
700 void
turnstile_claim(struct turnstile * ts)701 turnstile_claim(struct turnstile *ts)
702 {
703 struct thread *td, *owner;
704 struct turnstile_chain *tc;
705
706 mtx_assert(&ts->ts_lock, MA_OWNED);
707 MPASS(ts != curthread->td_turnstile);
708
709 owner = curthread;
710 mtx_lock_spin(&td_contested_lock);
711 turnstile_setowner(ts, owner);
712 mtx_unlock_spin(&td_contested_lock);
713
714 td = turnstile_first_waiter(ts);
715 MPASS(td != NULL);
716 MPASS(td->td_proc->p_magic == P_MAGIC);
717 THREAD_LOCKPTR_BLOCKED_ASSERT(td, &ts->ts_lock);
718
719 /*
720 * Update the priority of the new owner if needed.
721 */
722 thread_lock(owner);
723 if (td->td_priority < owner->td_priority)
724 sched_lend_prio(owner, td->td_priority);
725 thread_unlock(owner);
726 tc = TC_LOOKUP(ts->ts_lockobj);
727 mtx_unlock_spin(&ts->ts_lock);
728 mtx_unlock_spin(&tc->tc_lock);
729 }
730
731 /*
732 * Block the current thread on the turnstile assicated with 'lock'. This
733 * function will context switch and not return until this thread has been
734 * woken back up. This function must be called with the appropriate
735 * turnstile chain locked and will return with it unlocked.
736 */
737 void
turnstile_wait(struct turnstile * ts,struct thread * owner,int queue)738 turnstile_wait(struct turnstile *ts, struct thread *owner, int queue)
739 {
740 struct turnstile_chain *tc;
741 struct thread *td, *td1;
742 struct lock_object *lock;
743
744 td = curthread;
745 mtx_assert(&ts->ts_lock, MA_OWNED);
746 if (owner)
747 MPASS(owner->td_proc->p_magic == P_MAGIC);
748 MPASS(queue == TS_SHARED_QUEUE || queue == TS_EXCLUSIVE_QUEUE);
749
750 /*
751 * If the lock does not already have a turnstile, use this thread's
752 * turnstile. Otherwise insert the current thread into the
753 * turnstile already in use by this lock.
754 */
755 tc = TC_LOOKUP(ts->ts_lockobj);
756 mtx_assert(&tc->tc_lock, MA_OWNED);
757 if (ts == td->td_turnstile) {
758 #ifdef TURNSTILE_PROFILING
759 tc->tc_depth++;
760 if (tc->tc_depth > tc->tc_max_depth) {
761 tc->tc_max_depth = tc->tc_depth;
762 if (tc->tc_max_depth > turnstile_max_depth)
763 turnstile_max_depth = tc->tc_max_depth;
764 }
765 #endif
766 LIST_INSERT_HEAD(&tc->tc_turnstiles, ts, ts_hash);
767 KASSERT(TAILQ_EMPTY(&ts->ts_pending),
768 ("thread's turnstile has pending threads"));
769 KASSERT(TAILQ_EMPTY(&ts->ts_blocked[TS_EXCLUSIVE_QUEUE]),
770 ("thread's turnstile has exclusive waiters"));
771 KASSERT(TAILQ_EMPTY(&ts->ts_blocked[TS_SHARED_QUEUE]),
772 ("thread's turnstile has shared waiters"));
773 KASSERT(LIST_EMPTY(&ts->ts_free),
774 ("thread's turnstile has a non-empty free list"));
775 MPASS(ts->ts_lockobj != NULL);
776 mtx_lock_spin(&td_contested_lock);
777 TAILQ_INSERT_TAIL(&ts->ts_blocked[queue], td, td_lockq);
778 turnstile_setowner(ts, owner);
779 mtx_unlock_spin(&td_contested_lock);
780 } else {
781 TAILQ_FOREACH(td1, &ts->ts_blocked[queue], td_lockq)
782 if (td1->td_priority > td->td_priority)
783 break;
784 mtx_lock_spin(&td_contested_lock);
785 if (td1 != NULL)
786 TAILQ_INSERT_BEFORE(td1, td, td_lockq);
787 else
788 TAILQ_INSERT_TAIL(&ts->ts_blocked[queue], td, td_lockq);
789 MPASS(owner == ts->ts_owner);
790 mtx_unlock_spin(&td_contested_lock);
791 MPASS(td->td_turnstile != NULL);
792 LIST_INSERT_HEAD(&ts->ts_free, td->td_turnstile, ts_hash);
793 }
794 thread_lock(td);
795 thread_lock_set(td, &ts->ts_lock);
796 td->td_turnstile = NULL;
797
798 /* Save who we are blocked on and switch. */
799 lock = ts->ts_lockobj;
800 td->td_tsqueue = queue;
801 td->td_blocked = ts;
802 td->td_lockname = lock->lo_name;
803 td->td_blktick = ticks;
804 TD_SET_LOCK(td);
805 mtx_unlock_spin(&tc->tc_lock);
806 propagate_priority(td);
807
808 if (LOCK_LOG_TEST(lock, 0))
809 CTR4(KTR_LOCK, "%s: td %d blocked on [%p] %s", __func__,
810 td->td_tid, lock, lock->lo_name);
811
812 SDT_PROBE0(sched, , , sleep);
813
814 THREAD_LOCKPTR_ASSERT(td, &ts->ts_lock);
815 mi_switch(SW_VOL | SWT_TURNSTILE);
816
817 if (LOCK_LOG_TEST(lock, 0))
818 CTR4(KTR_LOCK, "%s: td %d free from blocked on [%p] %s",
819 __func__, td->td_tid, lock, lock->lo_name);
820 }
821
822 /*
823 * Pick the highest priority thread on this turnstile and put it on the
824 * pending list. This must be called with the turnstile chain locked.
825 */
826 int
turnstile_signal(struct turnstile * ts,int queue)827 turnstile_signal(struct turnstile *ts, int queue)
828 {
829 struct turnstile_chain *tc __unused;
830 struct thread *td;
831 int empty;
832
833 MPASS(ts != NULL);
834 mtx_assert(&ts->ts_lock, MA_OWNED);
835 MPASS(curthread->td_proc->p_magic == P_MAGIC);
836 MPASS(ts->ts_owner == curthread || ts->ts_owner == NULL);
837 MPASS(queue == TS_SHARED_QUEUE || queue == TS_EXCLUSIVE_QUEUE);
838
839 /*
840 * Pick the highest priority thread blocked on this lock and
841 * move it to the pending list.
842 */
843 td = TAILQ_FIRST(&ts->ts_blocked[queue]);
844 MPASS(td->td_proc->p_magic == P_MAGIC);
845 mtx_lock_spin(&td_contested_lock);
846 TAILQ_REMOVE(&ts->ts_blocked[queue], td, td_lockq);
847 mtx_unlock_spin(&td_contested_lock);
848 TAILQ_INSERT_TAIL(&ts->ts_pending, td, td_lockq);
849
850 /*
851 * If the turnstile is now empty, remove it from its chain and
852 * give it to the about-to-be-woken thread. Otherwise take a
853 * turnstile from the free list and give it to the thread.
854 */
855 empty = TAILQ_EMPTY(&ts->ts_blocked[TS_EXCLUSIVE_QUEUE]) &&
856 TAILQ_EMPTY(&ts->ts_blocked[TS_SHARED_QUEUE]);
857 if (empty) {
858 tc = TC_LOOKUP(ts->ts_lockobj);
859 mtx_assert(&tc->tc_lock, MA_OWNED);
860 MPASS(LIST_EMPTY(&ts->ts_free));
861 #ifdef TURNSTILE_PROFILING
862 tc->tc_depth--;
863 #endif
864 } else
865 ts = LIST_FIRST(&ts->ts_free);
866 MPASS(ts != NULL);
867 LIST_REMOVE(ts, ts_hash);
868 td->td_turnstile = ts;
869
870 return (empty);
871 }
872
873 /*
874 * Put all blocked threads on the pending list. This must be called with
875 * the turnstile chain locked.
876 */
877 void
turnstile_broadcast(struct turnstile * ts,int queue)878 turnstile_broadcast(struct turnstile *ts, int queue)
879 {
880 struct turnstile_chain *tc __unused;
881 struct turnstile *ts1;
882 struct thread *td;
883
884 MPASS(ts != NULL);
885 mtx_assert(&ts->ts_lock, MA_OWNED);
886 MPASS(curthread->td_proc->p_magic == P_MAGIC);
887 MPASS(ts->ts_owner == curthread || ts->ts_owner == NULL);
888 /*
889 * We must have the chain locked so that we can remove the empty
890 * turnstile from the hash queue.
891 */
892 tc = TC_LOOKUP(ts->ts_lockobj);
893 mtx_assert(&tc->tc_lock, MA_OWNED);
894 MPASS(queue == TS_SHARED_QUEUE || queue == TS_EXCLUSIVE_QUEUE);
895
896 /*
897 * Transfer the blocked list to the pending list.
898 */
899 mtx_lock_spin(&td_contested_lock);
900 TAILQ_CONCAT(&ts->ts_pending, &ts->ts_blocked[queue], td_lockq);
901 mtx_unlock_spin(&td_contested_lock);
902
903 /*
904 * Give a turnstile to each thread. The last thread gets
905 * this turnstile if the turnstile is empty.
906 */
907 TAILQ_FOREACH(td, &ts->ts_pending, td_lockq) {
908 if (LIST_EMPTY(&ts->ts_free)) {
909 MPASS(TAILQ_NEXT(td, td_lockq) == NULL);
910 ts1 = ts;
911 #ifdef TURNSTILE_PROFILING
912 tc->tc_depth--;
913 #endif
914 } else
915 ts1 = LIST_FIRST(&ts->ts_free);
916 MPASS(ts1 != NULL);
917 LIST_REMOVE(ts1, ts_hash);
918 td->td_turnstile = ts1;
919 }
920 }
921
922 static u_char
turnstile_calc_unlend_prio_locked(struct thread * td)923 turnstile_calc_unlend_prio_locked(struct thread *td)
924 {
925 struct turnstile *nts;
926 u_char cp, pri;
927
928 THREAD_LOCK_ASSERT(td, MA_OWNED);
929 mtx_assert(&td_contested_lock, MA_OWNED);
930
931 pri = PRI_MAX;
932 LIST_FOREACH(nts, &td->td_contested, ts_link) {
933 cp = turnstile_first_waiter(nts)->td_priority;
934 if (cp < pri)
935 pri = cp;
936 }
937 return (pri);
938 }
939
940 /*
941 * Wakeup all threads on the pending list and adjust the priority of the
942 * current thread appropriately. This must be called with the turnstile
943 * chain locked.
944 */
945 void
turnstile_unpend(struct turnstile * ts)946 turnstile_unpend(struct turnstile *ts)
947 {
948 TAILQ_HEAD( ,thread) pending_threads;
949 struct thread *td;
950 u_char pri;
951
952 MPASS(ts != NULL);
953 mtx_assert(&ts->ts_lock, MA_OWNED);
954 MPASS(ts->ts_owner == curthread || ts->ts_owner == NULL);
955 MPASS(!TAILQ_EMPTY(&ts->ts_pending));
956
957 /*
958 * Move the list of pending threads out of the turnstile and
959 * into a local variable.
960 */
961 TAILQ_INIT(&pending_threads);
962 TAILQ_CONCAT(&pending_threads, &ts->ts_pending, td_lockq);
963 #ifdef INVARIANTS
964 if (TAILQ_EMPTY(&ts->ts_blocked[TS_EXCLUSIVE_QUEUE]) &&
965 TAILQ_EMPTY(&ts->ts_blocked[TS_SHARED_QUEUE]))
966 ts->ts_lockobj = NULL;
967 #endif
968 /*
969 * Adjust the priority of curthread based on other contested
970 * locks it owns. Don't lower the priority below the base
971 * priority however.
972 */
973 td = curthread;
974 thread_lock(td);
975 mtx_lock_spin(&td_contested_lock);
976 /*
977 * Remove the turnstile from this thread's list of contested locks
978 * since this thread doesn't own it anymore. New threads will
979 * not be blocking on the turnstile until it is claimed by a new
980 * owner. There might not be a current owner if this is a shared
981 * lock.
982 */
983 if (ts->ts_owner != NULL) {
984 ts->ts_owner = NULL;
985 LIST_REMOVE(ts, ts_link);
986 }
987 pri = turnstile_calc_unlend_prio_locked(td);
988 mtx_unlock_spin(&td_contested_lock);
989 sched_unlend_prio(td, pri);
990 thread_unlock(td);
991 /*
992 * Wake up all the pending threads. If a thread is not blocked
993 * on a lock, then it is currently executing on another CPU in
994 * turnstile_wait() or sitting on a run queue waiting to resume
995 * in turnstile_wait(). Set a flag to force it to try to acquire
996 * the lock again instead of blocking.
997 */
998 while (!TAILQ_EMPTY(&pending_threads)) {
999 td = TAILQ_FIRST(&pending_threads);
1000 TAILQ_REMOVE(&pending_threads, td, td_lockq);
1001 SDT_PROBE2(sched, , , wakeup, td, td->td_proc);
1002 thread_lock_block_wait(td);
1003 THREAD_LOCKPTR_ASSERT(td, &ts->ts_lock);
1004 MPASS(td->td_proc->p_magic == P_MAGIC);
1005 MPASS(TD_ON_LOCK(td));
1006 TD_CLR_LOCK(td);
1007 MPASS(TD_CAN_RUN(td));
1008 td->td_blocked = NULL;
1009 td->td_lockname = NULL;
1010 td->td_blktick = 0;
1011 #ifdef INVARIANTS
1012 td->td_tsqueue = 0xff;
1013 #endif
1014 sched_add(td, SRQ_HOLD | SRQ_BORING);
1015 }
1016 mtx_unlock_spin(&ts->ts_lock);
1017 }
1018
1019 /*
1020 * Give up ownership of a turnstile. This must be called with the
1021 * turnstile chain locked.
1022 */
1023 void
turnstile_disown(struct turnstile * ts)1024 turnstile_disown(struct turnstile *ts)
1025 {
1026 struct thread *td;
1027 u_char pri;
1028
1029 MPASS(ts != NULL);
1030 mtx_assert(&ts->ts_lock, MA_OWNED);
1031 MPASS(ts->ts_owner == curthread);
1032 MPASS(TAILQ_EMPTY(&ts->ts_pending));
1033 MPASS(!TAILQ_EMPTY(&ts->ts_blocked[TS_EXCLUSIVE_QUEUE]) ||
1034 !TAILQ_EMPTY(&ts->ts_blocked[TS_SHARED_QUEUE]));
1035
1036 /*
1037 * Remove the turnstile from this thread's list of contested locks
1038 * since this thread doesn't own it anymore. New threads will
1039 * not be blocking on the turnstile until it is claimed by a new
1040 * owner.
1041 */
1042 mtx_lock_spin(&td_contested_lock);
1043 ts->ts_owner = NULL;
1044 LIST_REMOVE(ts, ts_link);
1045 mtx_unlock_spin(&td_contested_lock);
1046
1047 /*
1048 * Adjust the priority of curthread based on other contested
1049 * locks it owns. Don't lower the priority below the base
1050 * priority however.
1051 */
1052 td = curthread;
1053 thread_lock(td);
1054 mtx_unlock_spin(&ts->ts_lock);
1055 mtx_lock_spin(&td_contested_lock);
1056 pri = turnstile_calc_unlend_prio_locked(td);
1057 mtx_unlock_spin(&td_contested_lock);
1058 sched_unlend_prio(td, pri);
1059 thread_unlock(td);
1060 }
1061
1062 /*
1063 * Return the first thread in a turnstile.
1064 */
1065 struct thread *
turnstile_head(struct turnstile * ts,int queue)1066 turnstile_head(struct turnstile *ts, int queue)
1067 {
1068 #ifdef INVARIANTS
1069
1070 MPASS(ts != NULL);
1071 MPASS(queue == TS_SHARED_QUEUE || queue == TS_EXCLUSIVE_QUEUE);
1072 mtx_assert(&ts->ts_lock, MA_OWNED);
1073 #endif
1074 return (TAILQ_FIRST(&ts->ts_blocked[queue]));
1075 }
1076
1077 /*
1078 * Returns true if a sub-queue of a turnstile is empty.
1079 */
1080 int
turnstile_empty(struct turnstile * ts,int queue)1081 turnstile_empty(struct turnstile *ts, int queue)
1082 {
1083 #ifdef INVARIANTS
1084
1085 MPASS(ts != NULL);
1086 MPASS(queue == TS_SHARED_QUEUE || queue == TS_EXCLUSIVE_QUEUE);
1087 mtx_assert(&ts->ts_lock, MA_OWNED);
1088 #endif
1089 return (TAILQ_EMPTY(&ts->ts_blocked[queue]));
1090 }
1091
1092 #ifdef DDB
1093 static void
print_thread(struct thread * td,const char * prefix)1094 print_thread(struct thread *td, const char *prefix)
1095 {
1096
1097 db_printf("%s%p (tid %d, pid %d, \"%s\")\n", prefix, td, td->td_tid,
1098 td->td_proc->p_pid, td->td_name);
1099 }
1100
1101 static void
print_queue(struct threadqueue * queue,const char * header,const char * prefix)1102 print_queue(struct threadqueue *queue, const char *header, const char *prefix)
1103 {
1104 struct thread *td;
1105
1106 db_printf("%s:\n", header);
1107 if (TAILQ_EMPTY(queue)) {
1108 db_printf("%sempty\n", prefix);
1109 return;
1110 }
1111 TAILQ_FOREACH(td, queue, td_lockq) {
1112 print_thread(td, prefix);
1113 }
1114 }
1115
DB_SHOW_COMMAND(turnstile,db_show_turnstile)1116 DB_SHOW_COMMAND(turnstile, db_show_turnstile)
1117 {
1118 struct turnstile_chain *tc;
1119 struct turnstile *ts;
1120 struct lock_object *lock;
1121 int i;
1122
1123 if (!have_addr)
1124 return;
1125
1126 /*
1127 * First, see if there is an active turnstile for the lock indicated
1128 * by the address.
1129 */
1130 lock = (struct lock_object *)addr;
1131 tc = TC_LOOKUP(lock);
1132 LIST_FOREACH(ts, &tc->tc_turnstiles, ts_hash)
1133 if (ts->ts_lockobj == lock)
1134 goto found;
1135
1136 /*
1137 * Second, see if there is an active turnstile at the address
1138 * indicated.
1139 */
1140 for (i = 0; i < TC_TABLESIZE; i++)
1141 LIST_FOREACH(ts, &turnstile_chains[i].tc_turnstiles, ts_hash) {
1142 if (ts == (struct turnstile *)addr)
1143 goto found;
1144 }
1145
1146 db_printf("Unable to locate a turnstile via %p\n", (void *)addr);
1147 return;
1148 found:
1149 lock = ts->ts_lockobj;
1150 db_printf("Lock: %p - (%s) %s\n", lock, LOCK_CLASS(lock)->lc_name,
1151 lock->lo_name);
1152 if (ts->ts_owner)
1153 print_thread(ts->ts_owner, "Lock Owner: ");
1154 else
1155 db_printf("Lock Owner: none\n");
1156 print_queue(&ts->ts_blocked[TS_SHARED_QUEUE], "Shared Waiters", "\t");
1157 print_queue(&ts->ts_blocked[TS_EXCLUSIVE_QUEUE], "Exclusive Waiters",
1158 "\t");
1159 print_queue(&ts->ts_pending, "Pending Threads", "\t");
1160
1161 }
1162
1163 /*
1164 * Show all the threads a particular thread is waiting on based on
1165 * non-spin locks.
1166 */
1167 static void
print_lockchain(struct thread * td,const char * prefix)1168 print_lockchain(struct thread *td, const char *prefix)
1169 {
1170 struct lock_object *lock;
1171 struct lock_class *class;
1172 struct turnstile *ts;
1173 struct thread *owner;
1174
1175 /*
1176 * Follow the chain. We keep walking as long as the thread is
1177 * blocked on a lock that has an owner.
1178 */
1179 while (!db_pager_quit) {
1180 if (td == (void *)LK_KERNPROC) {
1181 db_printf("%sdisowned (LK_KERNPROC)\n", prefix);
1182 return;
1183 }
1184 db_printf("%sthread %d (pid %d, %s) is ", prefix, td->td_tid,
1185 td->td_proc->p_pid, td->td_name);
1186 switch (TD_GET_STATE(td)) {
1187 case TDS_INACTIVE:
1188 db_printf("inactive\n");
1189 return;
1190 case TDS_CAN_RUN:
1191 db_printf("runnable\n");
1192 return;
1193 case TDS_RUNQ:
1194 db_printf("on a run queue\n");
1195 return;
1196 case TDS_RUNNING:
1197 db_printf("running on CPU %d\n", td->td_oncpu);
1198 return;
1199 case TDS_INHIBITED:
1200 if (TD_ON_LOCK(td)) {
1201 ts = td->td_blocked;
1202 lock = ts->ts_lockobj;
1203 class = LOCK_CLASS(lock);
1204 db_printf("blocked on lock %p (%s) \"%s\"\n",
1205 lock, class->lc_name, lock->lo_name);
1206 if (ts->ts_owner == NULL)
1207 return;
1208 td = ts->ts_owner;
1209 break;
1210 } else if (TD_ON_SLEEPQ(td)) {
1211 if (!lockmgr_chain(td, &owner) &&
1212 !sx_chain(td, &owner)) {
1213 db_printf("sleeping on %p \"%s\"\n",
1214 td->td_wchan, td->td_wmesg);
1215 return;
1216 }
1217 if (owner == NULL)
1218 return;
1219 td = owner;
1220 break;
1221 }
1222 db_printf("inhibited: %s\n", KTDSTATE(td));
1223 return;
1224 default:
1225 db_printf("??? (%#x)\n", TD_GET_STATE(td));
1226 return;
1227 }
1228 }
1229 }
1230
DB_SHOW_COMMAND(lockchain,db_show_lockchain)1231 DB_SHOW_COMMAND(lockchain, db_show_lockchain)
1232 {
1233 struct thread *td;
1234
1235 /* Figure out which thread to start with. */
1236 if (have_addr)
1237 td = db_lookup_thread(addr, true);
1238 else
1239 td = kdb_thread;
1240
1241 print_lockchain(td, "");
1242 }
1243 DB_SHOW_ALIAS(sleepchain, db_show_lockchain);
1244
DB_SHOW_ALL_COMMAND(chains,db_show_allchains)1245 DB_SHOW_ALL_COMMAND(chains, db_show_allchains)
1246 {
1247 struct thread *td;
1248 struct proc *p;
1249 int i;
1250
1251 i = 1;
1252 FOREACH_PROC_IN_SYSTEM(p) {
1253 FOREACH_THREAD_IN_PROC(p, td) {
1254 if ((TD_ON_LOCK(td) && LIST_EMPTY(&td->td_contested))
1255 || (TD_IS_INHIBITED(td) && TD_ON_SLEEPQ(td))) {
1256 db_printf("chain %d:\n", i++);
1257 print_lockchain(td, " ");
1258 }
1259 if (db_pager_quit)
1260 return;
1261 }
1262 }
1263 }
1264 DB_SHOW_ALIAS_FLAGS(allchains, db_show_allchains, DB_CMD_MEMSAFE);
1265
1266 static void print_waiters(struct turnstile *ts, int indent);
1267
1268 static void
print_waiter(struct thread * td,int indent)1269 print_waiter(struct thread *td, int indent)
1270 {
1271 struct turnstile *ts;
1272 int i;
1273
1274 if (db_pager_quit)
1275 return;
1276 for (i = 0; i < indent; i++)
1277 db_printf(" ");
1278 print_thread(td, "thread ");
1279 LIST_FOREACH(ts, &td->td_contested, ts_link)
1280 print_waiters(ts, indent + 1);
1281 }
1282
1283 static void
print_waiters(struct turnstile * ts,int indent)1284 print_waiters(struct turnstile *ts, int indent)
1285 {
1286 struct lock_object *lock;
1287 struct lock_class *class;
1288 struct thread *td;
1289 int i;
1290
1291 if (db_pager_quit)
1292 return;
1293 lock = ts->ts_lockobj;
1294 class = LOCK_CLASS(lock);
1295 for (i = 0; i < indent; i++)
1296 db_printf(" ");
1297 db_printf("lock %p (%s) \"%s\"\n", lock, class->lc_name, lock->lo_name);
1298 TAILQ_FOREACH(td, &ts->ts_blocked[TS_EXCLUSIVE_QUEUE], td_lockq)
1299 print_waiter(td, indent + 1);
1300 TAILQ_FOREACH(td, &ts->ts_blocked[TS_SHARED_QUEUE], td_lockq)
1301 print_waiter(td, indent + 1);
1302 TAILQ_FOREACH(td, &ts->ts_pending, td_lockq)
1303 print_waiter(td, indent + 1);
1304 }
1305
DB_SHOW_COMMAND(locktree,db_show_locktree)1306 DB_SHOW_COMMAND(locktree, db_show_locktree)
1307 {
1308 struct lock_object *lock;
1309 struct lock_class *class;
1310 struct turnstile_chain *tc;
1311 struct turnstile *ts;
1312
1313 if (!have_addr)
1314 return;
1315 lock = (struct lock_object *)addr;
1316 tc = TC_LOOKUP(lock);
1317 LIST_FOREACH(ts, &tc->tc_turnstiles, ts_hash)
1318 if (ts->ts_lockobj == lock)
1319 break;
1320 if (ts == NULL) {
1321 class = LOCK_CLASS(lock);
1322 db_printf("lock %p (%s) \"%s\"\n", lock, class->lc_name,
1323 lock->lo_name);
1324 } else
1325 print_waiters(ts, 0);
1326 }
1327 #endif
1328