2 * Copyright (c) 1998 Berkeley Software Design, Inc. All rights reserved.
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
7 * 1. Redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution.
12 * 3. Berkeley Software Design Inc's name may not be used to endorse or
13 * promote products derived from this software without specific prior
16 * THIS SOFTWARE IS PROVIDED BY BERKELEY SOFTWARE DESIGN INC ``AS IS'' AND
17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19 * ARE DISCLAIMED. IN NO EVENT SHALL BERKELEY SOFTWARE DESIGN INC BE LIABLE
20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23 * HOWEVER 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
28 * from BSDI $Id: mutex_witness.c,v 1.1.2.20 2000/04/27 03:10:27 cp Exp $
29 * and BSDI $Id: synch_machdep.c,v 2.3.2.39 2000/04/27 03:10:25 cp Exp $
33 * Implementation of turnstiles used to hold queue of threads blocked on
34 * non-sleepable locks. Sleepable locks use condition variables to
35 * implement their queues. Turnstiles differ from a sleep queue in that
36 * turnstile queue's are assigned to a lock held by an owning thread. Thus,
37 * when one thread is enqueued onto a turnstile, it can lend its priority
38 * to the owning thread.
40 * We wish to avoid bloating locks with an embedded turnstile and we do not
41 * want to use back-pointers in the locks for the same reason. Thus, we
42 * use a similar approach to that of Solaris 7 as described in Solaris
43 * Internals by Jim Mauro and Richard McDougall. Turnstiles are looked up
44 * in a hash table based on the address of the lock. Each entry in the
45 * hash table is a linked-lists of turnstiles and is called a turnstile
46 * chain. Each chain contains a spin mutex that protects all of the
47 * turnstiles in the chain.
49 * Each time a thread is created, a turnstile is allocated from a UMA zone
50 * and attached to that thread. When a thread blocks on a lock, if it is the
51 * first thread to block, it lends its turnstile to the lock. If the lock
52 * already has a turnstile, then it gives its turnstile to the lock's
53 * turnstile's free list. When a thread is woken up, it takes a turnstile from
54 * the free list if there are any other waiters. If it is the only thread
55 * blocked on the lock, then it reclaims the turnstile associated with the lock
56 * and removes it from the hash table.
59 #include <sys/cdefs.h>
60 __FBSDID("$FreeBSD$");
63 #include "opt_turnstile_profiling.h"
64 #include "opt_sched.h"
66 #include <sys/param.h>
67 #include <sys/systm.h>
68 #include <sys/kernel.h>
71 #include <sys/mutex.h>
73 #include <sys/queue.h>
74 #include <sys/sched.h>
75 #include <sys/sysctl.h>
76 #include <sys/turnstile.h>
83 #include <sys/lockmgr.h>
88 * Constants for the hash table of turnstile chains. TC_SHIFT is a magic
89 * number chosen because the sleep queue's use the same value for the
90 * shift. Basically, we ignore the lower 8 bits of the address.
91 * TC_TABLESIZE must be a power of two for TC_MASK to work properly.
93 #define TC_TABLESIZE 128 /* Must be power of 2. */
94 #define TC_MASK (TC_TABLESIZE - 1)
96 #define TC_HASH(lock) (((uintptr_t)(lock) >> TC_SHIFT) & TC_MASK)
97 #define TC_LOOKUP(lock) &turnstile_chains[TC_HASH(lock)]
100 * There are three different lists of turnstiles as follows. The list
101 * connected by ts_link entries is a per-thread list of all the turnstiles
102 * attached to locks that we own. This is used to fixup our priority when
103 * a lock is released. The other two lists use the ts_hash entries. The
104 * first of these two is the turnstile chain list that a turnstile is on
105 * when it is attached to a lock. The second list to use ts_hash is the
106 * free list hung off of a turnstile that is attached to a lock.
108 * Each turnstile contains three lists of threads. The two ts_blocked lists
109 * are linked list of threads blocked on the turnstile's lock. One list is
110 * for exclusive waiters, and the other is for shared waiters. The
111 * ts_pending list is a linked list of threads previously awakened by
112 * turnstile_signal() or turnstile_wait() that are waiting to be put on
116 * c - turnstile chain lock
117 * q - td_contested lock
120 struct mtx ts_lock; /* Spin lock for self. */
121 struct threadqueue ts_blocked[2]; /* (c + q) Blocked threads. */
122 struct threadqueue ts_pending; /* (c) Pending threads. */
123 LIST_ENTRY(turnstile) ts_hash; /* (c) Chain and free list. */
124 LIST_ENTRY(turnstile) ts_link; /* (q) Contested locks. */
125 LIST_HEAD(, turnstile) ts_free; /* (c) Free turnstiles. */
126 struct lock_object *ts_lockobj; /* (c) Lock we reference. */
127 struct thread *ts_owner; /* (c + q) Who owns the lock. */
130 struct turnstile_chain {
131 LIST_HEAD(, turnstile) tc_turnstiles; /* List of turnstiles. */
132 struct mtx tc_lock; /* Spin lock for this chain. */
133 #ifdef TURNSTILE_PROFILING
134 u_int tc_depth; /* Length of tc_queues. */
135 u_int tc_max_depth; /* Max length of tc_queues. */
139 #ifdef TURNSTILE_PROFILING
140 u_int turnstile_max_depth;
141 SYSCTL_NODE(_debug, OID_AUTO, turnstile, CTLFLAG_RD, 0, "turnstile profiling");
142 SYSCTL_NODE(_debug_turnstile, OID_AUTO, chains, CTLFLAG_RD, 0,
143 "turnstile chain stats");
144 SYSCTL_UINT(_debug_turnstile, OID_AUTO, max_depth, CTLFLAG_RD,
145 &turnstile_max_depth, 0, "maxmimum depth achieved of a single chain");
147 static struct mtx td_contested_lock;
148 static struct turnstile_chain turnstile_chains[TC_TABLESIZE];
149 static uma_zone_t turnstile_zone;
152 * Prototypes for non-exported routines.
154 static void init_turnstile0(void *dummy);
155 #ifdef TURNSTILE_PROFILING
156 static void init_turnstile_profiling(void *arg);
158 static void propagate_priority(struct thread *td);
159 static int turnstile_adjust_thread(struct turnstile *ts,
161 static struct thread *turnstile_first_waiter(struct turnstile *ts);
162 static void turnstile_setowner(struct turnstile *ts, struct thread *owner);
164 static void turnstile_dtor(void *mem, int size, void *arg);
166 static int turnstile_init(void *mem, int size, int flags);
167 static void turnstile_fini(void *mem, int size);
170 * Walks the chain of turnstiles and their owners to propagate the priority
171 * of the thread being blocked to all the threads holding locks that have to
172 * release their locks before this thread can run again.
175 propagate_priority(struct thread *td)
177 struct turnstile *ts;
180 THREAD_LOCK_ASSERT(td, MA_OWNED);
181 pri = td->td_priority;
183 THREAD_LOCKPTR_ASSERT(td, &ts->ts_lock);
185 * Grab a recursive lock on this turnstile chain so it stays locked
186 * for the whole operation. The caller expects us to return with
187 * the original lock held. We only ever lock down the chain so
188 * the lock order is constant.
190 mtx_lock_spin(&ts->ts_lock);
196 * This might be a read lock with no owner. There's
197 * not much we can do, so just bail.
199 mtx_unlock_spin(&ts->ts_lock);
203 thread_lock_flags(td, MTX_DUPOK);
204 mtx_unlock_spin(&ts->ts_lock);
205 MPASS(td->td_proc != NULL);
206 MPASS(td->td_proc->p_magic == P_MAGIC);
209 * If the thread is asleep, then we are probably about
210 * to deadlock. To make debugging this easier, just
211 * panic and tell the user which thread misbehaved so
212 * they can hopefully get a stack trace from the truly
213 * misbehaving thread.
215 if (TD_IS_SLEEPING(td)) {
217 "Sleeping thread (tid %d, pid %d) owns a non-sleepable lock\n",
218 td->td_tid, td->td_proc->p_pid);
220 db_trace_thread(td, -1);
222 panic("sleeping thread");
226 * If this thread already has higher priority than the
227 * thread that is being blocked, we are finished.
229 if (td->td_priority <= pri) {
235 * Bump this thread's priority.
237 sched_lend_prio(td, pri);
240 * If lock holder is actually running or on the run queue
243 if (TD_IS_RUNNING(td) || TD_ON_RUNQ(td)) {
244 MPASS(td->td_blocked == NULL);
251 * For UP, we check to see if td is curthread (this shouldn't
252 * ever happen however as it would mean we are in a deadlock.)
254 KASSERT(td != curthread, ("Deadlock detected"));
258 * If we aren't blocked on a lock, we should be.
260 KASSERT(TD_ON_LOCK(td), (
261 "thread %d(%s):%d holds %s but isn't blocked on a lock\n",
262 td->td_tid, td->td_name, td->td_state,
263 ts->ts_lockobj->lo_name));
266 * Pick up the lock that td is blocked on.
270 THREAD_LOCKPTR_ASSERT(td, &ts->ts_lock);
271 /* Resort td on the list if needed. */
272 if (!turnstile_adjust_thread(ts, td)) {
273 mtx_unlock_spin(&ts->ts_lock);
276 /* The thread lock is released as ts lock above. */
281 * Adjust the thread's position on a turnstile after its priority has been
285 turnstile_adjust_thread(struct turnstile *ts, struct thread *td)
287 struct thread *td1, *td2;
290 THREAD_LOCK_ASSERT(td, MA_OWNED);
291 MPASS(TD_ON_LOCK(td));
294 * This thread may not be blocked on this turnstile anymore
295 * but instead might already be woken up on another CPU
296 * that is waiting on the thread lock in turnstile_unpend() to
297 * finish waking this thread up. We can detect this case
298 * by checking to see if this thread has been given a
299 * turnstile by either turnstile_signal() or
300 * turnstile_broadcast(). In this case, treat the thread as
301 * if it was already running.
303 if (td->td_turnstile != NULL)
307 * Check if the thread needs to be moved on the blocked chain.
308 * It needs to be moved if either its priority is lower than
309 * the previous thread or higher than the next thread.
311 THREAD_LOCKPTR_ASSERT(td, &ts->ts_lock);
312 td1 = TAILQ_PREV(td, threadqueue, td_lockq);
313 td2 = TAILQ_NEXT(td, td_lockq);
314 if ((td1 != NULL && td->td_priority < td1->td_priority) ||
315 (td2 != NULL && td->td_priority > td2->td_priority)) {
318 * Remove thread from blocked chain and determine where
319 * it should be moved to.
321 queue = td->td_tsqueue;
322 MPASS(queue == TS_EXCLUSIVE_QUEUE || queue == TS_SHARED_QUEUE);
323 mtx_lock_spin(&td_contested_lock);
324 TAILQ_REMOVE(&ts->ts_blocked[queue], td, td_lockq);
325 TAILQ_FOREACH(td1, &ts->ts_blocked[queue], td_lockq) {
326 MPASS(td1->td_proc->p_magic == P_MAGIC);
327 if (td1->td_priority > td->td_priority)
332 TAILQ_INSERT_TAIL(&ts->ts_blocked[queue], td, td_lockq);
334 TAILQ_INSERT_BEFORE(td1, td, td_lockq);
335 mtx_unlock_spin(&td_contested_lock);
338 "turnstile_adjust_thread: td %d put at tail on [%p] %s",
339 td->td_tid, ts->ts_lockobj, ts->ts_lockobj->lo_name);
342 "turnstile_adjust_thread: td %d moved before %d on [%p] %s",
343 td->td_tid, td1->td_tid, ts->ts_lockobj,
344 ts->ts_lockobj->lo_name);
350 * Early initialization of turnstiles. This is not done via a SYSINIT()
351 * since this needs to be initialized very early when mutexes are first
355 init_turnstiles(void)
359 for (i = 0; i < TC_TABLESIZE; i++) {
360 LIST_INIT(&turnstile_chains[i].tc_turnstiles);
361 mtx_init(&turnstile_chains[i].tc_lock, "turnstile chain",
364 mtx_init(&td_contested_lock, "td_contested", NULL, MTX_SPIN);
365 LIST_INIT(&thread0.td_contested);
366 thread0.td_turnstile = NULL;
369 #ifdef TURNSTILE_PROFILING
371 init_turnstile_profiling(void *arg)
373 struct sysctl_oid *chain_oid;
377 for (i = 0; i < TC_TABLESIZE; i++) {
378 snprintf(chain_name, sizeof(chain_name), "%d", i);
379 chain_oid = SYSCTL_ADD_NODE(NULL,
380 SYSCTL_STATIC_CHILDREN(_debug_turnstile_chains), OID_AUTO,
381 chain_name, CTLFLAG_RD, NULL, "turnstile chain stats");
382 SYSCTL_ADD_UINT(NULL, SYSCTL_CHILDREN(chain_oid), OID_AUTO,
383 "depth", CTLFLAG_RD, &turnstile_chains[i].tc_depth, 0,
385 SYSCTL_ADD_UINT(NULL, SYSCTL_CHILDREN(chain_oid), OID_AUTO,
386 "max_depth", CTLFLAG_RD, &turnstile_chains[i].tc_max_depth,
390 SYSINIT(turnstile_profiling, SI_SUB_LOCK, SI_ORDER_ANY,
391 init_turnstile_profiling, NULL);
395 init_turnstile0(void *dummy)
398 turnstile_zone = uma_zcreate("TURNSTILE", sizeof(struct turnstile),
400 NULL, turnstile_dtor, turnstile_init, turnstile_fini,
403 NULL, NULL, turnstile_init, turnstile_fini, UMA_ALIGN_CACHE, 0);
405 thread0.td_turnstile = turnstile_alloc();
407 SYSINIT(turnstile0, SI_SUB_LOCK, SI_ORDER_ANY, init_turnstile0, NULL);
410 * Update a thread on the turnstile list after it's priority has been changed.
411 * The old priority is passed in as an argument.
414 turnstile_adjust(struct thread *td, u_char oldpri)
416 struct turnstile *ts;
418 MPASS(TD_ON_LOCK(td));
421 * Pick up the lock that td is blocked on.
425 THREAD_LOCKPTR_ASSERT(td, &ts->ts_lock);
426 mtx_assert(&ts->ts_lock, MA_OWNED);
428 /* Resort the turnstile on the list. */
429 if (!turnstile_adjust_thread(ts, td))
432 * If our priority was lowered and we are at the head of the
433 * turnstile, then propagate our new priority up the chain.
434 * Note that we currently don't try to revoke lent priorities
435 * when our priority goes up.
437 MPASS(td->td_tsqueue == TS_EXCLUSIVE_QUEUE ||
438 td->td_tsqueue == TS_SHARED_QUEUE);
439 if (td == TAILQ_FIRST(&ts->ts_blocked[td->td_tsqueue]) &&
440 td->td_priority < oldpri) {
441 propagate_priority(td);
446 * Set the owner of the lock this turnstile is attached to.
449 turnstile_setowner(struct turnstile *ts, struct thread *owner)
452 mtx_assert(&td_contested_lock, MA_OWNED);
453 MPASS(ts->ts_owner == NULL);
455 /* A shared lock might not have an owner. */
459 MPASS(owner->td_proc->p_magic == P_MAGIC);
460 ts->ts_owner = owner;
461 LIST_INSERT_HEAD(&owner->td_contested, ts, ts_link);
466 * UMA zone item deallocator.
469 turnstile_dtor(void *mem, int size, void *arg)
471 struct turnstile *ts;
474 MPASS(TAILQ_EMPTY(&ts->ts_blocked[TS_EXCLUSIVE_QUEUE]));
475 MPASS(TAILQ_EMPTY(&ts->ts_blocked[TS_SHARED_QUEUE]));
476 MPASS(TAILQ_EMPTY(&ts->ts_pending));
481 * UMA zone item initializer.
484 turnstile_init(void *mem, int size, int flags)
486 struct turnstile *ts;
490 TAILQ_INIT(&ts->ts_blocked[TS_EXCLUSIVE_QUEUE]);
491 TAILQ_INIT(&ts->ts_blocked[TS_SHARED_QUEUE]);
492 TAILQ_INIT(&ts->ts_pending);
493 LIST_INIT(&ts->ts_free);
494 mtx_init(&ts->ts_lock, "turnstile lock", NULL, MTX_SPIN | MTX_RECURSE);
499 turnstile_fini(void *mem, int size)
501 struct turnstile *ts;
504 mtx_destroy(&ts->ts_lock);
508 * Get a turnstile for a new thread.
511 turnstile_alloc(void)
514 return (uma_zalloc(turnstile_zone, M_WAITOK));
518 * Free a turnstile when a thread is destroyed.
521 turnstile_free(struct turnstile *ts)
524 uma_zfree(turnstile_zone, ts);
528 * Lock the turnstile chain associated with the specified lock.
531 turnstile_chain_lock(struct lock_object *lock)
533 struct turnstile_chain *tc;
535 tc = TC_LOOKUP(lock);
536 mtx_lock_spin(&tc->tc_lock);
540 turnstile_trywait(struct lock_object *lock)
542 struct turnstile_chain *tc;
543 struct turnstile *ts;
545 tc = TC_LOOKUP(lock);
546 mtx_lock_spin(&tc->tc_lock);
547 LIST_FOREACH(ts, &tc->tc_turnstiles, ts_hash)
548 if (ts->ts_lockobj == lock) {
549 mtx_lock_spin(&ts->ts_lock);
553 ts = curthread->td_turnstile;
555 mtx_lock_spin(&ts->ts_lock);
556 KASSERT(ts->ts_lockobj == NULL, ("stale ts_lockobj pointer"));
557 ts->ts_lockobj = lock;
563 turnstile_cancel(struct turnstile *ts)
565 struct turnstile_chain *tc;
566 struct lock_object *lock;
568 mtx_assert(&ts->ts_lock, MA_OWNED);
570 mtx_unlock_spin(&ts->ts_lock);
571 lock = ts->ts_lockobj;
572 if (ts == curthread->td_turnstile)
573 ts->ts_lockobj = NULL;
574 tc = TC_LOOKUP(lock);
575 mtx_unlock_spin(&tc->tc_lock);
579 * Look up the turnstile for a lock in the hash table locking the associated
580 * turnstile chain along the way. If no turnstile is found in the hash
581 * table, NULL is returned.
584 turnstile_lookup(struct lock_object *lock)
586 struct turnstile_chain *tc;
587 struct turnstile *ts;
589 tc = TC_LOOKUP(lock);
590 mtx_assert(&tc->tc_lock, MA_OWNED);
591 LIST_FOREACH(ts, &tc->tc_turnstiles, ts_hash)
592 if (ts->ts_lockobj == lock) {
593 mtx_lock_spin(&ts->ts_lock);
600 * Unlock the turnstile chain associated with a given lock.
603 turnstile_chain_unlock(struct lock_object *lock)
605 struct turnstile_chain *tc;
607 tc = TC_LOOKUP(lock);
608 mtx_unlock_spin(&tc->tc_lock);
612 * Return a pointer to the thread waiting on this turnstile with the
613 * most important priority or NULL if the turnstile has no waiters.
615 static struct thread *
616 turnstile_first_waiter(struct turnstile *ts)
618 struct thread *std, *xtd;
620 std = TAILQ_FIRST(&ts->ts_blocked[TS_SHARED_QUEUE]);
621 xtd = TAILQ_FIRST(&ts->ts_blocked[TS_EXCLUSIVE_QUEUE]);
622 if (xtd == NULL || (std != NULL && std->td_priority < xtd->td_priority))
628 * Take ownership of a turnstile and adjust the priority of the new
629 * owner appropriately.
632 turnstile_claim(struct turnstile *ts)
634 struct thread *td, *owner;
635 struct turnstile_chain *tc;
637 mtx_assert(&ts->ts_lock, MA_OWNED);
638 MPASS(ts != curthread->td_turnstile);
641 mtx_lock_spin(&td_contested_lock);
642 turnstile_setowner(ts, owner);
643 mtx_unlock_spin(&td_contested_lock);
645 td = turnstile_first_waiter(ts);
647 MPASS(td->td_proc->p_magic == P_MAGIC);
648 THREAD_LOCKPTR_ASSERT(td, &ts->ts_lock);
651 * Update the priority of the new owner if needed.
654 if (td->td_priority < owner->td_priority)
655 sched_lend_prio(owner, td->td_priority);
656 thread_unlock(owner);
657 tc = TC_LOOKUP(ts->ts_lockobj);
658 mtx_unlock_spin(&ts->ts_lock);
659 mtx_unlock_spin(&tc->tc_lock);
663 * Block the current thread on the turnstile assicated with 'lock'. This
664 * function will context switch and not return until this thread has been
665 * woken back up. This function must be called with the appropriate
666 * turnstile chain locked and will return with it unlocked.
669 turnstile_wait(struct turnstile *ts, struct thread *owner, int queue)
671 struct turnstile_chain *tc;
672 struct thread *td, *td1;
673 struct lock_object *lock;
676 mtx_assert(&ts->ts_lock, MA_OWNED);
678 MPASS(owner->td_proc->p_magic == P_MAGIC);
679 MPASS(queue == TS_SHARED_QUEUE || queue == TS_EXCLUSIVE_QUEUE);
682 * If the lock does not already have a turnstile, use this thread's
683 * turnstile. Otherwise insert the current thread into the
684 * turnstile already in use by this lock.
686 tc = TC_LOOKUP(ts->ts_lockobj);
687 if (ts == td->td_turnstile) {
688 mtx_assert(&tc->tc_lock, MA_OWNED);
689 #ifdef TURNSTILE_PROFILING
691 if (tc->tc_depth > tc->tc_max_depth) {
692 tc->tc_max_depth = tc->tc_depth;
693 if (tc->tc_max_depth > turnstile_max_depth)
694 turnstile_max_depth = tc->tc_max_depth;
697 tc = TC_LOOKUP(ts->ts_lockobj);
698 LIST_INSERT_HEAD(&tc->tc_turnstiles, ts, ts_hash);
699 KASSERT(TAILQ_EMPTY(&ts->ts_pending),
700 ("thread's turnstile has pending threads"));
701 KASSERT(TAILQ_EMPTY(&ts->ts_blocked[TS_EXCLUSIVE_QUEUE]),
702 ("thread's turnstile has exclusive waiters"));
703 KASSERT(TAILQ_EMPTY(&ts->ts_blocked[TS_SHARED_QUEUE]),
704 ("thread's turnstile has shared waiters"));
705 KASSERT(LIST_EMPTY(&ts->ts_free),
706 ("thread's turnstile has a non-empty free list"));
707 MPASS(ts->ts_lockobj != NULL);
708 mtx_lock_spin(&td_contested_lock);
709 TAILQ_INSERT_TAIL(&ts->ts_blocked[queue], td, td_lockq);
710 turnstile_setowner(ts, owner);
711 mtx_unlock_spin(&td_contested_lock);
713 TAILQ_FOREACH(td1, &ts->ts_blocked[queue], td_lockq)
714 if (td1->td_priority > td->td_priority)
716 mtx_lock_spin(&td_contested_lock);
718 TAILQ_INSERT_BEFORE(td1, td, td_lockq);
720 TAILQ_INSERT_TAIL(&ts->ts_blocked[queue], td, td_lockq);
721 MPASS(owner == ts->ts_owner);
722 mtx_unlock_spin(&td_contested_lock);
723 MPASS(td->td_turnstile != NULL);
724 LIST_INSERT_HEAD(&ts->ts_free, td->td_turnstile, ts_hash);
727 thread_lock_set(td, &ts->ts_lock);
728 td->td_turnstile = NULL;
730 /* Save who we are blocked on and switch. */
731 lock = ts->ts_lockobj;
732 td->td_tsqueue = queue;
734 td->td_lockname = lock->lo_name;
736 mtx_unlock_spin(&tc->tc_lock);
737 propagate_priority(td);
739 if (LOCK_LOG_TEST(lock, 0))
740 CTR4(KTR_LOCK, "%s: td %d blocked on [%p] %s", __func__,
741 td->td_tid, lock, lock->lo_name);
743 THREAD_LOCKPTR_ASSERT(td, &ts->ts_lock);
744 mi_switch(SW_VOL | SWT_TURNSTILE, NULL);
746 if (LOCK_LOG_TEST(lock, 0))
747 CTR4(KTR_LOCK, "%s: td %d free from blocked on [%p] %s",
748 __func__, td->td_tid, lock, lock->lo_name);
753 * Pick the highest priority thread on this turnstile and put it on the
754 * pending list. This must be called with the turnstile chain locked.
757 turnstile_signal(struct turnstile *ts, int queue)
759 struct turnstile_chain *tc;
764 mtx_assert(&ts->ts_lock, MA_OWNED);
765 MPASS(curthread->td_proc->p_magic == P_MAGIC);
766 MPASS(ts->ts_owner == curthread || ts->ts_owner == NULL);
767 MPASS(queue == TS_SHARED_QUEUE || queue == TS_EXCLUSIVE_QUEUE);
770 * Pick the highest priority thread blocked on this lock and
771 * move it to the pending list.
773 td = TAILQ_FIRST(&ts->ts_blocked[queue]);
774 MPASS(td->td_proc->p_magic == P_MAGIC);
775 mtx_lock_spin(&td_contested_lock);
776 TAILQ_REMOVE(&ts->ts_blocked[queue], td, td_lockq);
777 mtx_unlock_spin(&td_contested_lock);
778 TAILQ_INSERT_TAIL(&ts->ts_pending, td, td_lockq);
781 * If the turnstile is now empty, remove it from its chain and
782 * give it to the about-to-be-woken thread. Otherwise take a
783 * turnstile from the free list and give it to the thread.
785 empty = TAILQ_EMPTY(&ts->ts_blocked[TS_EXCLUSIVE_QUEUE]) &&
786 TAILQ_EMPTY(&ts->ts_blocked[TS_SHARED_QUEUE]);
788 tc = TC_LOOKUP(ts->ts_lockobj);
789 mtx_assert(&tc->tc_lock, MA_OWNED);
790 MPASS(LIST_EMPTY(&ts->ts_free));
791 #ifdef TURNSTILE_PROFILING
795 ts = LIST_FIRST(&ts->ts_free);
797 LIST_REMOVE(ts, ts_hash);
798 td->td_turnstile = ts;
804 * Put all blocked threads on the pending list. This must be called with
805 * the turnstile chain locked.
808 turnstile_broadcast(struct turnstile *ts, int queue)
810 struct turnstile_chain *tc;
811 struct turnstile *ts1;
815 mtx_assert(&ts->ts_lock, MA_OWNED);
816 MPASS(curthread->td_proc->p_magic == P_MAGIC);
817 MPASS(ts->ts_owner == curthread || ts->ts_owner == NULL);
819 * We must have the chain locked so that we can remove the empty
820 * turnstile from the hash queue.
822 tc = TC_LOOKUP(ts->ts_lockobj);
823 mtx_assert(&tc->tc_lock, MA_OWNED);
824 MPASS(queue == TS_SHARED_QUEUE || queue == TS_EXCLUSIVE_QUEUE);
827 * Transfer the blocked list to the pending list.
829 mtx_lock_spin(&td_contested_lock);
830 TAILQ_CONCAT(&ts->ts_pending, &ts->ts_blocked[queue], td_lockq);
831 mtx_unlock_spin(&td_contested_lock);
834 * Give a turnstile to each thread. The last thread gets
835 * this turnstile if the turnstile is empty.
837 TAILQ_FOREACH(td, &ts->ts_pending, td_lockq) {
838 if (LIST_EMPTY(&ts->ts_free)) {
839 MPASS(TAILQ_NEXT(td, td_lockq) == NULL);
841 #ifdef TURNSTILE_PROFILING
845 ts1 = LIST_FIRST(&ts->ts_free);
847 LIST_REMOVE(ts1, ts_hash);
848 td->td_turnstile = ts1;
853 * Wakeup all threads on the pending list and adjust the priority of the
854 * current thread appropriately. This must be called with the turnstile
858 turnstile_unpend(struct turnstile *ts, int owner_type)
860 TAILQ_HEAD( ,thread) pending_threads;
861 struct turnstile *nts;
866 mtx_assert(&ts->ts_lock, MA_OWNED);
867 MPASS(ts->ts_owner == curthread || ts->ts_owner == NULL);
868 MPASS(!TAILQ_EMPTY(&ts->ts_pending));
871 * Move the list of pending threads out of the turnstile and
872 * into a local variable.
874 TAILQ_INIT(&pending_threads);
875 TAILQ_CONCAT(&pending_threads, &ts->ts_pending, td_lockq);
877 if (TAILQ_EMPTY(&ts->ts_blocked[TS_EXCLUSIVE_QUEUE]) &&
878 TAILQ_EMPTY(&ts->ts_blocked[TS_SHARED_QUEUE]))
879 ts->ts_lockobj = NULL;
882 * Adjust the priority of curthread based on other contested
883 * locks it owns. Don't lower the priority below the base
889 mtx_lock_spin(&td_contested_lock);
891 * Remove the turnstile from this thread's list of contested locks
892 * since this thread doesn't own it anymore. New threads will
893 * not be blocking on the turnstile until it is claimed by a new
894 * owner. There might not be a current owner if this is a shared
897 if (ts->ts_owner != NULL) {
899 LIST_REMOVE(ts, ts_link);
901 LIST_FOREACH(nts, &td->td_contested, ts_link) {
902 cp = turnstile_first_waiter(nts)->td_priority;
906 mtx_unlock_spin(&td_contested_lock);
907 sched_unlend_prio(td, pri);
910 * Wake up all the pending threads. If a thread is not blocked
911 * on a lock, then it is currently executing on another CPU in
912 * turnstile_wait() or sitting on a run queue waiting to resume
913 * in turnstile_wait(). Set a flag to force it to try to acquire
914 * the lock again instead of blocking.
916 while (!TAILQ_EMPTY(&pending_threads)) {
917 td = TAILQ_FIRST(&pending_threads);
918 TAILQ_REMOVE(&pending_threads, td, td_lockq);
920 THREAD_LOCKPTR_ASSERT(td, &ts->ts_lock);
921 MPASS(td->td_proc->p_magic == P_MAGIC);
922 MPASS(TD_ON_LOCK(td));
924 MPASS(TD_CAN_RUN(td));
925 td->td_blocked = NULL;
926 td->td_lockname = NULL;
928 td->td_tsqueue = 0xff;
930 sched_add(td, SRQ_BORING);
933 mtx_unlock_spin(&ts->ts_lock);
937 * Give up ownership of a turnstile. This must be called with the
938 * turnstile chain locked.
941 turnstile_disown(struct turnstile *ts)
947 mtx_assert(&ts->ts_lock, MA_OWNED);
948 MPASS(ts->ts_owner == curthread);
949 MPASS(TAILQ_EMPTY(&ts->ts_pending));
950 MPASS(!TAILQ_EMPTY(&ts->ts_blocked[TS_EXCLUSIVE_QUEUE]) ||
951 !TAILQ_EMPTY(&ts->ts_blocked[TS_SHARED_QUEUE]));
954 * Remove the turnstile from this thread's list of contested locks
955 * since this thread doesn't own it anymore. New threads will
956 * not be blocking on the turnstile until it is claimed by a new
959 mtx_lock_spin(&td_contested_lock);
961 LIST_REMOVE(ts, ts_link);
962 mtx_unlock_spin(&td_contested_lock);
965 * Adjust the priority of curthread based on other contested
966 * locks it owns. Don't lower the priority below the base
972 mtx_unlock_spin(&ts->ts_lock);
973 mtx_lock_spin(&td_contested_lock);
974 LIST_FOREACH(ts, &td->td_contested, ts_link) {
975 cp = turnstile_first_waiter(ts)->td_priority;
979 mtx_unlock_spin(&td_contested_lock);
980 sched_unlend_prio(td, pri);
985 * Return the first thread in a turnstile.
988 turnstile_head(struct turnstile *ts, int queue)
993 MPASS(queue == TS_SHARED_QUEUE || queue == TS_EXCLUSIVE_QUEUE);
994 mtx_assert(&ts->ts_lock, MA_OWNED);
996 return (TAILQ_FIRST(&ts->ts_blocked[queue]));
1000 * Returns true if a sub-queue of a turnstile is empty.
1003 turnstile_empty(struct turnstile *ts, int queue)
1008 MPASS(queue == TS_SHARED_QUEUE || queue == TS_EXCLUSIVE_QUEUE);
1009 mtx_assert(&ts->ts_lock, MA_OWNED);
1011 return (TAILQ_EMPTY(&ts->ts_blocked[queue]));
1016 print_thread(struct thread *td, const char *prefix)
1019 db_printf("%s%p (tid %d, pid %d, \"%s\")\n", prefix, td, td->td_tid,
1020 td->td_proc->p_pid, td->td_name[0] != '\0' ? td->td_name :
1025 print_queue(struct threadqueue *queue, const char *header, const char *prefix)
1029 db_printf("%s:\n", header);
1030 if (TAILQ_EMPTY(queue)) {
1031 db_printf("%sempty\n", prefix);
1034 TAILQ_FOREACH(td, queue, td_lockq) {
1035 print_thread(td, prefix);
1039 DB_SHOW_COMMAND(turnstile, db_show_turnstile)
1041 struct turnstile_chain *tc;
1042 struct turnstile *ts;
1043 struct lock_object *lock;
1050 * First, see if there is an active turnstile for the lock indicated
1053 lock = (struct lock_object *)addr;
1054 tc = TC_LOOKUP(lock);
1055 LIST_FOREACH(ts, &tc->tc_turnstiles, ts_hash)
1056 if (ts->ts_lockobj == lock)
1060 * Second, see if there is an active turnstile at the address
1063 for (i = 0; i < TC_TABLESIZE; i++)
1064 LIST_FOREACH(ts, &turnstile_chains[i].tc_turnstiles, ts_hash) {
1065 if (ts == (struct turnstile *)addr)
1069 db_printf("Unable to locate a turnstile via %p\n", (void *)addr);
1072 lock = ts->ts_lockobj;
1073 db_printf("Lock: %p - (%s) %s\n", lock, LOCK_CLASS(lock)->lc_name,
1076 print_thread(ts->ts_owner, "Lock Owner: ");
1078 db_printf("Lock Owner: none\n");
1079 print_queue(&ts->ts_blocked[TS_SHARED_QUEUE], "Shared Waiters", "\t");
1080 print_queue(&ts->ts_blocked[TS_EXCLUSIVE_QUEUE], "Exclusive Waiters",
1082 print_queue(&ts->ts_pending, "Pending Threads", "\t");
1087 * Show all the threads a particular thread is waiting on based on
1088 * non-sleepable and non-spin locks.
1091 print_lockchain(struct thread *td, const char *prefix)
1093 struct lock_object *lock;
1094 struct lock_class *class;
1095 struct turnstile *ts;
1098 * Follow the chain. We keep walking as long as the thread is
1099 * blocked on a turnstile that has an owner.
1101 while (!db_pager_quit) {
1102 db_printf("%sthread %d (pid %d, %s) ", prefix, td->td_tid,
1103 td->td_proc->p_pid, td->td_name[0] != '\0' ? td->td_name :
1105 switch (td->td_state) {
1107 db_printf("is inactive\n");
1110 db_printf("can run\n");
1113 db_printf("is on a run queue\n");
1116 db_printf("running on CPU %d\n", td->td_oncpu);
1119 if (TD_ON_LOCK(td)) {
1120 ts = td->td_blocked;
1121 lock = ts->ts_lockobj;
1122 class = LOCK_CLASS(lock);
1123 db_printf("blocked on lock %p (%s) \"%s\"\n",
1124 lock, class->lc_name, lock->lo_name);
1125 if (ts->ts_owner == NULL)
1130 db_printf("inhibited\n");
1133 db_printf("??? (%#x)\n", td->td_state);
1139 DB_SHOW_COMMAND(lockchain, db_show_lockchain)
1143 /* Figure out which thread to start with. */
1145 td = db_lookup_thread(addr, TRUE);
1149 print_lockchain(td, "");
1152 DB_SHOW_COMMAND(allchains, db_show_allchains)
1159 FOREACH_PROC_IN_SYSTEM(p) {
1160 FOREACH_THREAD_IN_PROC(p, td) {
1161 if (TD_ON_LOCK(td) && LIST_EMPTY(&td->td_contested)) {
1162 db_printf("chain %d:\n", i++);
1163 print_lockchain(td, " ");
1172 * Show all the threads a particular thread is waiting on based on
1176 print_sleepchain(struct thread *td, const char *prefix)
1178 struct thread *owner;
1181 * Follow the chain. We keep walking as long as the thread is
1182 * blocked on a sleep lock that has an owner.
1184 while (!db_pager_quit) {
1185 db_printf("%sthread %d (pid %d, %s) ", prefix, td->td_tid,
1186 td->td_proc->p_pid, td->td_name[0] != '\0' ? td->td_name :
1188 switch (td->td_state) {
1190 db_printf("is inactive\n");
1193 db_printf("can run\n");
1196 db_printf("is on a run queue\n");
1199 db_printf("running on CPU %d\n", td->td_oncpu);
1202 if (TD_ON_SLEEPQ(td)) {
1203 if (lockmgr_chain(td, &owner) ||
1204 sx_chain(td, &owner)) {
1210 db_printf("sleeping on %p \"%s\"\n",
1211 td->td_wchan, td->td_wmesg);
1214 db_printf("inhibited\n");
1217 db_printf("??? (%#x)\n", td->td_state);
1223 DB_SHOW_COMMAND(sleepchain, db_show_sleepchain)
1227 /* Figure out which thread to start with. */
1229 td = db_lookup_thread(addr, TRUE);
1233 print_sleepchain(td, "");
1236 static void print_waiters(struct turnstile *ts, int indent);
1239 print_waiter(struct thread *td, int indent)
1241 struct turnstile *ts;
1246 for (i = 0; i < indent; i++)
1248 print_thread(td, "thread ");
1249 LIST_FOREACH(ts, &td->td_contested, ts_link)
1250 print_waiters(ts, indent + 1);
1254 print_waiters(struct turnstile *ts, int indent)
1256 struct lock_object *lock;
1257 struct lock_class *class;
1263 lock = ts->ts_lockobj;
1264 class = LOCK_CLASS(lock);
1265 for (i = 0; i < indent; i++)
1267 db_printf("lock %p (%s) \"%s\"\n", lock, class->lc_name, lock->lo_name);
1268 TAILQ_FOREACH(td, &ts->ts_blocked[TS_EXCLUSIVE_QUEUE], td_lockq)
1269 print_waiter(td, indent + 1);
1270 TAILQ_FOREACH(td, &ts->ts_blocked[TS_SHARED_QUEUE], td_lockq)
1271 print_waiter(td, indent + 1);
1272 TAILQ_FOREACH(td, &ts->ts_pending, td_lockq)
1273 print_waiter(td, indent + 1);
1276 DB_SHOW_COMMAND(locktree, db_show_locktree)
1278 struct lock_object *lock;
1279 struct lock_class *class;
1280 struct turnstile_chain *tc;
1281 struct turnstile *ts;
1285 lock = (struct lock_object *)addr;
1286 tc = TC_LOOKUP(lock);
1287 LIST_FOREACH(ts, &tc->tc_turnstiles, ts_hash)
1288 if (ts->ts_lockobj == lock)
1291 class = LOCK_CLASS(lock);
1292 db_printf("lock %p (%s) \"%s\"\n", lock, class->lc_name,
1295 print_waiters(ts, 0);