2 * Copyright (c) 2008 Attilio Rao <attilio@FreeBSD.org>
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
8 * 1. Redistributions of source code must retain the above copyright
9 * notice(s), this list of conditions and the following disclaimer as
10 * the first lines of this file unmodified other than the possible
11 * addition of one or more copyright notices.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice(s), this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
16 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY
17 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
18 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
19 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE LIABLE FOR ANY
20 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
21 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
22 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
23 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
29 #include "opt_adaptive_lockmgrs.h"
31 #include "opt_kdtrace.h"
33 #include <sys/cdefs.h>
34 __FBSDID("$FreeBSD$");
36 #include <sys/param.h>
38 #include <sys/linker_set.h>
40 #include <sys/lock_profile.h>
41 #include <sys/lockmgr.h>
42 #include <sys/mutex.h>
44 #include <sys/sleepqueue.h>
46 #include <sys/stack.h>
48 #include <sys/sysctl.h>
49 #include <sys/systm.h>
51 #include <machine/cpu.h>
57 CTASSERT(((LK_ADAPTIVE | LK_NOSHARE) & LO_CLASSFLAGS) ==
58 (LK_ADAPTIVE | LK_NOSHARE));
59 CTASSERT(LK_UNLOCKED == (LK_UNLOCKED &
60 ~(LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS)));
62 #define SQ_EXCLUSIVE_QUEUE 0
63 #define SQ_SHARED_QUEUE 1
66 #define _lockmgr_assert(lk, what, file, line)
67 #define TD_LOCKS_INC(td)
68 #define TD_LOCKS_DEC(td)
70 #define TD_LOCKS_INC(td) ((td)->td_locks++)
71 #define TD_LOCKS_DEC(td) ((td)->td_locks--)
73 #define TD_SLOCKS_INC(td) ((td)->td_lk_slocks++)
74 #define TD_SLOCKS_DEC(td) ((td)->td_lk_slocks--)
77 #define STACK_PRINT(lk)
78 #define STACK_SAVE(lk)
79 #define STACK_ZERO(lk)
81 #define STACK_PRINT(lk) stack_print_ddb(&(lk)->lk_stack)
82 #define STACK_SAVE(lk) stack_save(&(lk)->lk_stack)
83 #define STACK_ZERO(lk) stack_zero(&(lk)->lk_stack)
86 #define LOCK_LOG2(lk, string, arg1, arg2) \
87 if (LOCK_LOG_TEST(&(lk)->lock_object, 0)) \
88 CTR2(KTR_LOCK, (string), (arg1), (arg2))
89 #define LOCK_LOG3(lk, string, arg1, arg2, arg3) \
90 if (LOCK_LOG_TEST(&(lk)->lock_object, 0)) \
91 CTR3(KTR_LOCK, (string), (arg1), (arg2), (arg3))
93 #define GIANT_DECLARE \
95 WITNESS_SAVE_DECL(Giant)
96 #define GIANT_RESTORE() do { \
100 WITNESS_RESTORE(&Giant.lock_object, Giant); \
103 #define GIANT_SAVE() do { \
104 if (mtx_owned(&Giant)) { \
105 WITNESS_SAVE(&Giant.lock_object, Giant); \
106 while (mtx_owned(&Giant)) { \
108 mtx_unlock(&Giant); \
113 #define LK_CAN_SHARE(x) \
114 (((x) & LK_SHARE) && (((x) & LK_EXCLUSIVE_WAITERS) == 0 || \
115 ((x) & LK_EXCLUSIVE_SPINNERS) == 0 || \
116 curthread->td_lk_slocks || (curthread->td_pflags & TDP_DEADLKTREAT)))
117 #define LK_TRYOP(x) \
120 #define LK_CAN_WITNESS(x) \
121 (((x) & LK_NOWITNESS) == 0 && !LK_TRYOP(x))
122 #define LK_TRYWIT(x) \
123 (LK_TRYOP(x) ? LOP_TRYLOCK : 0)
125 #define LK_CAN_ADAPT(lk, f) \
126 (((lk)->lock_object.lo_flags & LK_ADAPTIVE) != 0 && \
127 ((f) & LK_SLEEPFAIL) == 0)
129 #define lockmgr_disowned(lk) \
130 (((lk)->lk_lock & ~(LK_FLAGMASK & ~LK_SHARE)) == LK_KERNPROC)
132 #define lockmgr_xlocked(lk) \
133 (((lk)->lk_lock & ~(LK_FLAGMASK & ~LK_SHARE)) == (uintptr_t)curthread)
135 static void assert_lockmgr(struct lock_object *lock, int how);
137 static void db_show_lockmgr(struct lock_object *lock);
139 static void lock_lockmgr(struct lock_object *lock, int how);
141 static int owner_lockmgr(struct lock_object *lock, struct thread **owner);
143 static int unlock_lockmgr(struct lock_object *lock);
145 struct lock_class lock_class_lockmgr = {
146 .lc_name = "lockmgr",
147 .lc_flags = LC_RECURSABLE | LC_SLEEPABLE | LC_SLEEPLOCK | LC_UPGRADABLE,
148 .lc_assert = assert_lockmgr,
150 .lc_ddb_show = db_show_lockmgr,
152 .lc_lock = lock_lockmgr,
153 .lc_unlock = unlock_lockmgr,
155 .lc_owner = owner_lockmgr,
159 #ifdef ADAPTIVE_LOCKMGRS
160 static u_int alk_retries = 10;
161 static u_int alk_loops = 10000;
162 SYSCTL_NODE(_debug, OID_AUTO, lockmgr, CTLFLAG_RD, NULL, "lockmgr debugging");
163 SYSCTL_UINT(_debug_lockmgr, OID_AUTO, retries, CTLFLAG_RW, &alk_retries, 0, "");
164 SYSCTL_UINT(_debug_lockmgr, OID_AUTO, loops, CTLFLAG_RW, &alk_loops, 0, "");
167 static __inline struct thread *
168 lockmgr_xholder(struct lock *lk)
173 return ((x & LK_SHARE) ? NULL : (struct thread *)LK_HOLDER(x));
177 * It assumes sleepq_lock held and returns with this one unheld.
178 * It also assumes the generic interlock is sane and previously checked.
179 * If LK_INTERLOCK is specified the interlock is not reacquired after the
183 sleeplk(struct lock *lk, u_int flags, struct lock_object *ilk,
184 const char *wmesg, int pri, int timo, int queue)
187 struct lock_class *class;
190 class = (flags & LK_INTERLOCK) ? LOCK_CLASS(ilk) : NULL;
191 catch = pri & PCATCH;
195 LOCK_LOG3(lk, "%s: %p blocking on the %s sleepqueue", __func__, lk,
196 (queue == SQ_EXCLUSIVE_QUEUE) ? "exclusive" : "shared");
198 if (flags & LK_INTERLOCK)
199 class->lc_unlock(ilk);
201 sleepq_add(&lk->lock_object, NULL, wmesg, SLEEPQ_LK | (catch ?
202 SLEEPQ_INTERRUPTIBLE : 0), queue);
203 if ((flags & LK_TIMELOCK) && timo)
204 sleepq_set_timeout(&lk->lock_object, timo);
207 * Decisional switch for real sleeping.
209 if ((flags & LK_TIMELOCK) && timo && catch)
210 error = sleepq_timedwait_sig(&lk->lock_object, pri);
211 else if ((flags & LK_TIMELOCK) && timo)
212 error = sleepq_timedwait(&lk->lock_object, pri);
214 error = sleepq_wait_sig(&lk->lock_object, pri);
216 sleepq_wait(&lk->lock_object, pri);
218 if ((flags & LK_SLEEPFAIL) && error == 0)
225 wakeupshlk(struct lock *lk, const char *file, int line)
228 int queue, wakeup_swapper;
230 TD_LOCKS_DEC(curthread);
231 TD_SLOCKS_DEC(curthread);
232 WITNESS_UNLOCK(&lk->lock_object, 0, file, line);
233 LOCK_LOG_LOCK("SUNLOCK", &lk->lock_object, 0, 0, file, line);
240 * If there is more than one shared lock held, just drop one
243 if (LK_SHARERS(x) > 1) {
244 if (atomic_cmpset_ptr(&lk->lk_lock, x,
251 * If there are not waiters on the exclusive queue, drop the
254 if ((x & LK_ALL_WAITERS) == 0) {
255 MPASS((x & ~LK_EXCLUSIVE_SPINNERS) ==
257 if (atomic_cmpset_ptr(&lk->lk_lock, x, LK_UNLOCKED))
263 * We should have a sharer with waiters, so enter the hard
264 * path in order to handle wakeups correctly.
266 sleepq_lock(&lk->lock_object);
267 x = lk->lk_lock & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS);
271 * If the lock has exclusive waiters, give them preference in
272 * order to avoid deadlock with shared runners up.
274 if (x & LK_EXCLUSIVE_WAITERS) {
275 queue = SQ_EXCLUSIVE_QUEUE;
276 v |= (x & LK_SHARED_WAITERS);
278 MPASS((x & ~LK_EXCLUSIVE_SPINNERS) ==
280 queue = SQ_SHARED_QUEUE;
283 if (!atomic_cmpset_ptr(&lk->lk_lock, LK_SHARERS_LOCK(1) | x,
285 sleepq_release(&lk->lock_object);
288 LOCK_LOG3(lk, "%s: %p waking up threads on the %s queue",
289 __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" :
291 wakeup_swapper = sleepq_broadcast(&lk->lock_object, SLEEPQ_LK,
293 sleepq_release(&lk->lock_object);
297 lock_profile_release_lock(&lk->lock_object);
298 return (wakeup_swapper);
302 assert_lockmgr(struct lock_object *lock, int what)
305 panic("lockmgr locks do not support assertions");
309 lock_lockmgr(struct lock_object *lock, int how)
312 panic("lockmgr locks do not support sleep interlocking");
316 unlock_lockmgr(struct lock_object *lock)
319 panic("lockmgr locks do not support sleep interlocking");
324 owner_lockmgr(struct lock_object *lock, struct thread **owner)
327 panic("lockmgr locks do not support owner inquiring");
332 lockinit(struct lock *lk, int pri, const char *wmesg, int timo, int flags)
336 MPASS((flags & ~LK_INIT_MASK) == 0);
338 iflags = LO_SLEEPABLE | LO_UPGRADABLE;
339 if (flags & LK_CANRECURSE)
340 iflags |= LO_RECURSABLE;
341 if ((flags & LK_NODUP) == 0)
343 if (flags & LK_NOPROFILE)
344 iflags |= LO_NOPROFILE;
345 if ((flags & LK_NOWITNESS) == 0)
346 iflags |= LO_WITNESS;
347 if (flags & LK_QUIET)
349 iflags |= flags & (LK_ADAPTIVE | LK_NOSHARE);
351 lk->lk_lock = LK_UNLOCKED;
355 lock_init(&lk->lock_object, &lock_class_lockmgr, wmesg, NULL, iflags);
360 lockdestroy(struct lock *lk)
363 KASSERT(lk->lk_lock == LK_UNLOCKED, ("lockmgr still held"));
364 KASSERT(lk->lk_recurse == 0, ("lockmgr still recursed"));
365 lock_destroy(&lk->lock_object);
369 __lockmgr_args(struct lock *lk, u_int flags, struct lock_object *ilk,
370 const char *wmesg, int pri, int timo, const char *file, int line)
373 struct lock_class *class;
377 int error, ipri, itimo, queue, wakeup_swapper;
378 #ifdef LOCK_PROFILING
379 uint64_t waittime = 0;
382 #ifdef ADAPTIVE_LOCKMGRS
383 volatile struct thread *owner;
384 u_int i, spintries = 0;
388 tid = (uintptr_t)curthread;
389 op = (flags & LK_TYPE_MASK);
390 iwmesg = (wmesg == LK_WMESG_DEFAULT) ? lk->lock_object.lo_name : wmesg;
391 ipri = (pri == LK_PRIO_DEFAULT) ? lk->lk_pri : pri;
392 itimo = (timo == LK_TIMO_DEFAULT) ? lk->lk_timo : timo;
394 MPASS((flags & ~LK_TOTAL_MASK) == 0);
395 KASSERT((op & (op - 1)) == 0,
396 ("%s: Invalid requested operation @ %s:%d", __func__, file, line));
397 KASSERT((flags & (LK_NOWAIT | LK_SLEEPFAIL)) == 0 ||
398 (op != LK_DOWNGRADE && op != LK_RELEASE),
399 ("%s: Invalid flags in regard of the operation desired @ %s:%d",
400 __func__, file, line));
401 KASSERT((flags & LK_INTERLOCK) == 0 || ilk != NULL,
402 ("%s: LK_INTERLOCK passed without valid interlock @ %s:%d",
403 __func__, file, line));
405 class = (flags & LK_INTERLOCK) ? LOCK_CLASS(ilk) : NULL;
406 if (panicstr != NULL) {
407 if (flags & LK_INTERLOCK)
408 class->lc_unlock(ilk);
412 if (op == LK_SHARED && (lk->lock_object.lo_flags & LK_NOSHARE))
418 if (LK_CAN_WITNESS(flags))
419 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER,
425 * If no other thread has an exclusive lock, or
426 * no exclusive waiter is present, bump the count of
427 * sharers. Since we have to preserve the state of
428 * waiters, if we fail to acquire the shared lock
429 * loop back and retry.
431 if (LK_CAN_SHARE(x)) {
432 if (atomic_cmpset_acq_ptr(&lk->lk_lock, x,
437 lock_profile_obtain_lock_failed(&lk->lock_object,
438 &contested, &waittime);
441 * If the lock is already held by curthread in
442 * exclusive way avoid a deadlock.
444 if (LK_HOLDER(x) == tid) {
446 "%s: %p already held in exclusive mode",
453 * If the lock is expected to not sleep just give up
456 if (LK_TRYOP(flags)) {
457 LOCK_LOG2(lk, "%s: %p fails the try operation",
463 #ifdef ADAPTIVE_LOCKMGRS
465 * If the owner is running on another CPU, spin until
466 * the owner stops running or the state of the lock
469 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 &&
470 LK_HOLDER(x) != LK_KERNPROC) {
471 owner = (struct thread *)LK_HOLDER(x);
472 if (LOCK_LOG_TEST(&lk->lock_object, 0))
474 "%s: spinning on %p held by %p",
475 __func__, lk, owner);
478 * If we are holding also an interlock drop it
479 * in order to avoid a deadlock if the lockmgr
480 * owner is adaptively spinning on the
483 if (flags & LK_INTERLOCK) {
484 class->lc_unlock(ilk);
485 flags &= ~LK_INTERLOCK;
488 while (LK_HOLDER(lk->lk_lock) ==
489 (uintptr_t)owner && TD_IS_RUNNING(owner))
491 } else if (LK_CAN_ADAPT(lk, flags) &&
492 (x & LK_SHARE) !=0 && LK_SHARERS(x) &&
493 spintries < alk_retries) {
494 if (flags & LK_INTERLOCK) {
495 class->lc_unlock(ilk);
496 flags &= ~LK_INTERLOCK;
500 for (i = 0; i < alk_loops; i++) {
501 if (LOCK_LOG_TEST(&lk->lock_object, 0))
503 "%s: shared spinning on %p with %u and %u",
504 __func__, lk, spintries, i);
506 if ((x & LK_SHARE) == 0 ||
507 LK_CAN_SHARE(x) != 0)
517 * Acquire the sleepqueue chain lock because we
518 * probabilly will need to manipulate waiters flags.
520 sleepq_lock(&lk->lock_object);
524 * if the lock can be acquired in shared mode, try
527 if (LK_CAN_SHARE(x)) {
528 sleepq_release(&lk->lock_object);
532 #ifdef ADAPTIVE_LOCKMGRS
534 * The current lock owner might have started executing
535 * on another CPU (or the lock could have changed
536 * owner) while we were waiting on the turnstile
537 * chain lock. If so, drop the turnstile lock and try
540 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 &&
541 LK_HOLDER(x) != LK_KERNPROC) {
542 owner = (struct thread *)LK_HOLDER(x);
543 if (TD_IS_RUNNING(owner)) {
544 sleepq_release(&lk->lock_object);
551 * Try to set the LK_SHARED_WAITERS flag. If we fail,
552 * loop back and retry.
554 if ((x & LK_SHARED_WAITERS) == 0) {
555 if (!atomic_cmpset_acq_ptr(&lk->lk_lock, x,
556 x | LK_SHARED_WAITERS)) {
557 sleepq_release(&lk->lock_object);
560 LOCK_LOG2(lk, "%s: %p set shared waiters flag",
565 * As far as we have been unable to acquire the
566 * shared lock and the shared waiters flag is set,
569 error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo,
571 flags &= ~LK_INTERLOCK;
574 "%s: interrupted sleep for %p with %d",
575 __func__, lk, error);
578 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue",
582 lock_profile_obtain_lock_success(&lk->lock_object,
583 contested, waittime, file, line);
584 LOCK_LOG_LOCK("SLOCK", &lk->lock_object, 0, 0, file,
586 WITNESS_LOCK(&lk->lock_object, LK_TRYWIT(flags), file,
588 TD_LOCKS_INC(curthread);
589 TD_SLOCKS_INC(curthread);
594 _lockmgr_assert(lk, KA_SLOCKED, file, line);
596 x = v & LK_ALL_WAITERS;
597 v &= LK_EXCLUSIVE_SPINNERS;
600 * Try to switch from one shared lock to an exclusive one.
601 * We need to preserve waiters flags during the operation.
603 if (atomic_cmpset_ptr(&lk->lk_lock, LK_SHARERS_LOCK(1) | x | v,
605 LOCK_LOG_LOCK("XUPGRADE", &lk->lock_object, 0, 0, file,
607 WITNESS_UPGRADE(&lk->lock_object, LOP_EXCLUSIVE |
608 LK_TRYWIT(flags), file, line);
609 TD_SLOCKS_DEC(curthread);
614 * We have been unable to succeed in upgrading, so just
615 * give up the shared lock.
617 wakeup_swapper |= wakeupshlk(lk, file, line);
621 if (LK_CAN_WITNESS(flags))
622 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER |
623 LOP_EXCLUSIVE, file, line, ilk);
626 * If curthread already holds the lock and this one is
627 * allowed to recurse, simply recurse on it.
629 if (lockmgr_xlocked(lk)) {
630 if ((flags & LK_CANRECURSE) == 0 &&
631 (lk->lock_object.lo_flags & LO_RECURSABLE) == 0) {
634 * If the lock is expected to not panic just
635 * give up and return.
637 if (LK_TRYOP(flags)) {
639 "%s: %p fails the try operation",
644 if (flags & LK_INTERLOCK)
645 class->lc_unlock(ilk);
646 panic("%s: recursing on non recursive lockmgr %s @ %s:%d\n",
647 __func__, iwmesg, file, line);
650 LOCK_LOG2(lk, "%s: %p recursing", __func__, lk);
651 LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0,
652 lk->lk_recurse, file, line);
653 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE |
654 LK_TRYWIT(flags), file, line);
655 TD_LOCKS_INC(curthread);
659 while (!atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED,
661 lock_profile_obtain_lock_failed(&lk->lock_object,
662 &contested, &waittime);
665 * If the lock is expected to not sleep just give up
668 if (LK_TRYOP(flags)) {
669 LOCK_LOG2(lk, "%s: %p fails the try operation",
675 #ifdef ADAPTIVE_LOCKMGRS
677 * If the owner is running on another CPU, spin until
678 * the owner stops running or the state of the lock
682 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 &&
683 LK_HOLDER(x) != LK_KERNPROC) {
684 owner = (struct thread *)LK_HOLDER(x);
685 if (LOCK_LOG_TEST(&lk->lock_object, 0))
687 "%s: spinning on %p held by %p",
688 __func__, lk, owner);
691 * If we are holding also an interlock drop it
692 * in order to avoid a deadlock if the lockmgr
693 * owner is adaptively spinning on the
696 if (flags & LK_INTERLOCK) {
697 class->lc_unlock(ilk);
698 flags &= ~LK_INTERLOCK;
701 while (LK_HOLDER(lk->lk_lock) ==
702 (uintptr_t)owner && TD_IS_RUNNING(owner))
704 } else if (LK_CAN_ADAPT(lk, flags) &&
705 (x & LK_SHARE) != 0 && LK_SHARERS(x) &&
706 spintries < alk_retries) {
707 if ((x & LK_EXCLUSIVE_SPINNERS) == 0 &&
708 !atomic_cmpset_ptr(&lk->lk_lock, x,
709 x | LK_EXCLUSIVE_SPINNERS))
711 if (flags & LK_INTERLOCK) {
712 class->lc_unlock(ilk);
713 flags &= ~LK_INTERLOCK;
717 for (i = 0; i < alk_loops; i++) {
718 if (LOCK_LOG_TEST(&lk->lock_object, 0))
720 "%s: shared spinning on %p with %u and %u",
721 __func__, lk, spintries, i);
723 LK_EXCLUSIVE_SPINNERS) == 0)
733 * Acquire the sleepqueue chain lock because we
734 * probabilly will need to manipulate waiters flags.
736 sleepq_lock(&lk->lock_object);
740 * if the lock has been released while we spun on
741 * the sleepqueue chain lock just try again.
743 if (x == LK_UNLOCKED) {
744 sleepq_release(&lk->lock_object);
748 #ifdef ADAPTIVE_LOCKMGRS
750 * The current lock owner might have started executing
751 * on another CPU (or the lock could have changed
752 * owner) while we were waiting on the turnstile
753 * chain lock. If so, drop the turnstile lock and try
756 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 &&
757 LK_HOLDER(x) != LK_KERNPROC) {
758 owner = (struct thread *)LK_HOLDER(x);
759 if (TD_IS_RUNNING(owner)) {
760 sleepq_release(&lk->lock_object);
767 * The lock can be in the state where there is a
768 * pending queue of waiters, but still no owner.
769 * This happens when the lock is contested and an
770 * owner is going to claim the lock.
771 * If curthread is the one successfully acquiring it
772 * claim lock ownership and return, preserving waiters
775 v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS);
776 if ((x & ~v) == LK_UNLOCKED) {
777 v &= ~LK_EXCLUSIVE_SPINNERS;
778 if (atomic_cmpset_acq_ptr(&lk->lk_lock, x,
780 sleepq_release(&lk->lock_object);
782 "%s: %p claimed by a new writer",
786 sleepq_release(&lk->lock_object);
791 * Try to set the LK_EXCLUSIVE_WAITERS flag. If we
792 * fail, loop back and retry.
794 if ((x & LK_EXCLUSIVE_WAITERS) == 0) {
795 if (!atomic_cmpset_ptr(&lk->lk_lock, x,
796 x | LK_EXCLUSIVE_WAITERS)) {
797 sleepq_release(&lk->lock_object);
800 LOCK_LOG2(lk, "%s: %p set excl waiters flag",
805 * As far as we have been unable to acquire the
806 * exclusive lock and the exclusive waiters flag
807 * is set, we will sleep.
809 error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo,
811 flags &= ~LK_INTERLOCK;
814 "%s: interrupted sleep for %p with %d",
815 __func__, lk, error);
818 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue",
822 lock_profile_obtain_lock_success(&lk->lock_object,
823 contested, waittime, file, line);
824 LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0,
825 lk->lk_recurse, file, line);
826 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE |
827 LK_TRYWIT(flags), file, line);
828 TD_LOCKS_INC(curthread);
833 _lockmgr_assert(lk, KA_XLOCKED | KA_NOTRECURSED, file, line);
834 LOCK_LOG_LOCK("XDOWNGRADE", &lk->lock_object, 0, 0, file, line);
835 WITNESS_DOWNGRADE(&lk->lock_object, 0, file, line);
836 TD_SLOCKS_INC(curthread);
839 * In order to preserve waiters flags, just spin.
843 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0);
845 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x,
846 LK_SHARERS_LOCK(1) | x))
852 _lockmgr_assert(lk, KA_LOCKED, file, line);
855 if ((x & LK_SHARE) == 0) {
858 * As first option, treact the lock as if it has not
860 * Fix-up the tid var if the lock has been disowned.
862 if (LK_HOLDER(x) == LK_KERNPROC)
865 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE,
867 TD_LOCKS_DEC(curthread);
869 LOCK_LOG_LOCK("XUNLOCK", &lk->lock_object, 0,
870 lk->lk_recurse, file, line);
873 * The lock is held in exclusive mode.
874 * If the lock is recursed also, then unrecurse it.
876 if (lockmgr_xlocked(lk) && lockmgr_recursed(lk)) {
877 LOCK_LOG2(lk, "%s: %p unrecursing", __func__,
882 if (tid != LK_KERNPROC)
883 lock_profile_release_lock(&lk->lock_object);
885 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid,
889 sleepq_lock(&lk->lock_object);
894 * If the lock has exclusive waiters, give them
895 * preference in order to avoid deadlock with
898 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0);
899 if (x & LK_EXCLUSIVE_WAITERS) {
900 queue = SQ_EXCLUSIVE_QUEUE;
901 v |= (x & LK_SHARED_WAITERS);
903 MPASS((x & LK_ALL_WAITERS) ==
905 queue = SQ_SHARED_QUEUE;
909 "%s: %p waking up threads on the %s queue",
910 __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" :
912 atomic_store_rel_ptr(&lk->lk_lock, v);
913 wakeup_swapper = sleepq_broadcast(&lk->lock_object,
914 SLEEPQ_LK, 0, queue);
915 sleepq_release(&lk->lock_object);
918 wakeup_swapper = wakeupshlk(lk, file, line);
921 if (LK_CAN_WITNESS(flags))
922 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER |
923 LOP_EXCLUSIVE, file, line, ilk);
926 * Trying to drain a lock we already own will result in a
929 if (lockmgr_xlocked(lk)) {
930 if (flags & LK_INTERLOCK)
931 class->lc_unlock(ilk);
932 panic("%s: draining %s with the lock held @ %s:%d\n",
933 __func__, iwmesg, file, line);
936 while (!atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid)) {
937 lock_profile_obtain_lock_failed(&lk->lock_object,
938 &contested, &waittime);
941 * If the lock is expected to not sleep just give up
944 if (LK_TRYOP(flags)) {
945 LOCK_LOG2(lk, "%s: %p fails the try operation",
952 * Acquire the sleepqueue chain lock because we
953 * probabilly will need to manipulate waiters flags.
955 sleepq_lock(&lk->lock_object);
959 * if the lock has been released while we spun on
960 * the sleepqueue chain lock just try again.
962 if (x == LK_UNLOCKED) {
963 sleepq_release(&lk->lock_object);
967 v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS);
968 if ((x & ~v) == LK_UNLOCKED) {
969 v = (x & ~LK_EXCLUSIVE_SPINNERS);
970 if (v & LK_EXCLUSIVE_WAITERS) {
971 queue = SQ_EXCLUSIVE_QUEUE;
972 v &= ~LK_EXCLUSIVE_WAITERS;
974 MPASS(v & LK_SHARED_WAITERS);
975 queue = SQ_SHARED_QUEUE;
976 v &= ~LK_SHARED_WAITERS;
978 if (!atomic_cmpset_ptr(&lk->lk_lock, x, v)) {
979 sleepq_release(&lk->lock_object);
983 "%s: %p waking up all threads on the %s queue",
984 __func__, lk, queue == SQ_SHARED_QUEUE ?
985 "shared" : "exclusive");
986 wakeup_swapper |= sleepq_broadcast(
987 &lk->lock_object, SLEEPQ_LK, 0, queue);
990 * If shared waiters have been woken up we need
991 * to wait for one of them to acquire the lock
992 * before to set the exclusive waiters in
993 * order to avoid a deadlock.
995 if (queue == SQ_SHARED_QUEUE) {
996 for (v = lk->lk_lock;
997 (v & LK_SHARE) && !LK_SHARERS(v);
1004 * Try to set the LK_EXCLUSIVE_WAITERS flag. If we
1005 * fail, loop back and retry.
1007 if ((x & LK_EXCLUSIVE_WAITERS) == 0) {
1008 if (!atomic_cmpset_ptr(&lk->lk_lock, x,
1009 x | LK_EXCLUSIVE_WAITERS)) {
1010 sleepq_release(&lk->lock_object);
1013 LOCK_LOG2(lk, "%s: %p set drain waiters flag",
1018 * As far as we have been unable to acquire the
1019 * exclusive lock and the exclusive waiters flag
1020 * is set, we will sleep.
1022 if (flags & LK_INTERLOCK) {
1023 class->lc_unlock(ilk);
1024 flags &= ~LK_INTERLOCK;
1027 sleepq_add(&lk->lock_object, NULL, iwmesg, SLEEPQ_LK,
1028 SQ_EXCLUSIVE_QUEUE);
1029 sleepq_wait(&lk->lock_object, ipri & PRIMASK);
1031 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue",
1036 lock_profile_obtain_lock_success(&lk->lock_object,
1037 contested, waittime, file, line);
1038 LOCK_LOG_LOCK("DRAIN", &lk->lock_object, 0,
1039 lk->lk_recurse, file, line);
1040 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE |
1041 LK_TRYWIT(flags), file, line);
1042 TD_LOCKS_INC(curthread);
1047 if (flags & LK_INTERLOCK)
1048 class->lc_unlock(ilk);
1049 panic("%s: unknown lockmgr request 0x%x\n", __func__, op);
1052 if (flags & LK_INTERLOCK)
1053 class->lc_unlock(ilk);
1061 _lockmgr_disown(struct lock *lk, const char *file, int line)
1065 tid = (uintptr_t)curthread;
1066 _lockmgr_assert(lk, KA_XLOCKED | KA_NOTRECURSED, file, line);
1069 * If the owner is already LK_KERNPROC just skip the whole operation.
1071 if (LK_HOLDER(lk->lk_lock) != tid)
1073 lock_profile_release_lock(&lk->lock_object);
1074 LOCK_LOG_LOCK("XDISOWN", &lk->lock_object, 0, 0, file, line);
1075 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, file, line);
1076 TD_LOCKS_DEC(curthread);
1079 * In order to preserve waiters flags, just spin.
1083 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0);
1084 x &= LK_ALL_WAITERS;
1085 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x,
1093 lockmgr_printinfo(struct lock *lk)
1098 if (lk->lk_lock == LK_UNLOCKED)
1099 printf("lock type %s: UNLOCKED\n", lk->lock_object.lo_name);
1100 else if (lk->lk_lock & LK_SHARE)
1101 printf("lock type %s: SHARED (count %ju)\n",
1102 lk->lock_object.lo_name,
1103 (uintmax_t)LK_SHARERS(lk->lk_lock));
1105 td = lockmgr_xholder(lk);
1106 printf("lock type %s: EXCL by thread %p (pid %d)\n",
1107 lk->lock_object.lo_name, td, td->td_proc->p_pid);
1111 if (x & LK_EXCLUSIVE_WAITERS)
1112 printf(" with exclusive waiters pending\n");
1113 if (x & LK_SHARED_WAITERS)
1114 printf(" with shared waiters pending\n");
1115 if (x & LK_EXCLUSIVE_SPINNERS)
1116 printf(" with exclusive spinners pending\n");
1122 lockstatus(struct lock *lk)
1131 if ((x & LK_SHARE) == 0) {
1132 if (v == (uintptr_t)curthread || v == LK_KERNPROC)
1136 } else if (x == LK_UNLOCKED)
1142 #ifdef INVARIANT_SUPPORT
1144 #undef _lockmgr_assert
1148 _lockmgr_assert(struct lock *lk, int what, const char *file, int line)
1152 if (panicstr != NULL)
1156 case KA_SLOCKED | KA_NOTRECURSED:
1157 case KA_SLOCKED | KA_RECURSED:
1160 case KA_LOCKED | KA_NOTRECURSED:
1161 case KA_LOCKED | KA_RECURSED:
1165 * We cannot trust WITNESS if the lock is held in exclusive
1166 * mode and a call to lockmgr_disown() happened.
1167 * Workaround this skipping the check if the lock is held in
1168 * exclusive mode even for the KA_LOCKED case.
1170 if (slocked || (lk->lk_lock & LK_SHARE)) {
1171 witness_assert(&lk->lock_object, what, file, line);
1175 if (lk->lk_lock == LK_UNLOCKED ||
1176 ((lk->lk_lock & LK_SHARE) == 0 && (slocked ||
1177 (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk)))))
1178 panic("Lock %s not %slocked @ %s:%d\n",
1179 lk->lock_object.lo_name, slocked ? "share" : "",
1182 if ((lk->lk_lock & LK_SHARE) == 0) {
1183 if (lockmgr_recursed(lk)) {
1184 if (what & KA_NOTRECURSED)
1185 panic("Lock %s recursed @ %s:%d\n",
1186 lk->lock_object.lo_name, file,
1188 } else if (what & KA_RECURSED)
1189 panic("Lock %s not recursed @ %s:%d\n",
1190 lk->lock_object.lo_name, file, line);
1194 case KA_XLOCKED | KA_NOTRECURSED:
1195 case KA_XLOCKED | KA_RECURSED:
1196 if (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk))
1197 panic("Lock %s not exclusively locked @ %s:%d\n",
1198 lk->lock_object.lo_name, file, line);
1199 if (lockmgr_recursed(lk)) {
1200 if (what & KA_NOTRECURSED)
1201 panic("Lock %s recursed @ %s:%d\n",
1202 lk->lock_object.lo_name, file, line);
1203 } else if (what & KA_RECURSED)
1204 panic("Lock %s not recursed @ %s:%d\n",
1205 lk->lock_object.lo_name, file, line);
1208 if (lockmgr_xlocked(lk) || lockmgr_disowned(lk))
1209 panic("Lock %s exclusively locked @ %s:%d\n",
1210 lk->lock_object.lo_name, file, line);
1213 panic("Unknown lockmgr assertion: %d @ %s:%d\n", what, file,
1221 lockmgr_chain(struct thread *td, struct thread **ownerp)
1227 if (LOCK_CLASS(&lk->lock_object) != &lock_class_lockmgr)
1229 db_printf("blocked on lockmgr %s", lk->lock_object.lo_name);
1230 if (lk->lk_lock & LK_SHARE)
1231 db_printf("SHARED (count %ju)\n",
1232 (uintmax_t)LK_SHARERS(lk->lk_lock));
1234 db_printf("EXCL\n");
1235 *ownerp = lockmgr_xholder(lk);
1241 db_show_lockmgr(struct lock_object *lock)
1246 lk = (struct lock *)lock;
1248 db_printf(" state: ");
1249 if (lk->lk_lock == LK_UNLOCKED)
1250 db_printf("UNLOCKED\n");
1251 else if (lk->lk_lock & LK_SHARE)
1252 db_printf("SLOCK: %ju\n", (uintmax_t)LK_SHARERS(lk->lk_lock));
1254 td = lockmgr_xholder(lk);
1255 if (td == (struct thread *)LK_KERNPROC)
1256 db_printf("XLOCK: LK_KERNPROC\n");
1258 db_printf("XLOCK: %p (tid %d, pid %d, \"%s\")\n", td,
1259 td->td_tid, td->td_proc->p_pid,
1260 td->td_proc->p_comm);
1261 if (lockmgr_recursed(lk))
1262 db_printf(" recursed: %d\n", lk->lk_recurse);
1264 db_printf(" waiters: ");
1265 switch (lk->lk_lock & LK_ALL_WAITERS) {
1266 case LK_SHARED_WAITERS:
1267 db_printf("shared\n");
1269 case LK_EXCLUSIVE_WAITERS:
1270 db_printf("exclusive\n");
1272 case LK_ALL_WAITERS:
1273 db_printf("shared and exclusive\n");
1276 db_printf("none\n");
1278 db_printf(" spinners: ");
1279 if (lk->lk_lock & LK_EXCLUSIVE_SPINNERS)
1280 db_printf("exclusive\n");
1282 db_printf("none\n");