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_rel_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_rel_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_rel_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);
337 ASSERT_ATOMIC_LOAD_PTR(lk->lk_lock,
338 ("%s: lockmgr not aligned for %s: %p", __func__, wmesg,
341 iflags = LO_SLEEPABLE | LO_UPGRADABLE;
342 if (flags & LK_CANRECURSE)
343 iflags |= LO_RECURSABLE;
344 if ((flags & LK_NODUP) == 0)
346 if (flags & LK_NOPROFILE)
347 iflags |= LO_NOPROFILE;
348 if ((flags & LK_NOWITNESS) == 0)
349 iflags |= LO_WITNESS;
350 if (flags & LK_QUIET)
352 iflags |= flags & (LK_ADAPTIVE | LK_NOSHARE);
354 lk->lk_lock = LK_UNLOCKED;
358 lock_init(&lk->lock_object, &lock_class_lockmgr, wmesg, NULL, iflags);
363 lockdestroy(struct lock *lk)
366 KASSERT(lk->lk_lock == LK_UNLOCKED, ("lockmgr still held"));
367 KASSERT(lk->lk_recurse == 0, ("lockmgr still recursed"));
368 lock_destroy(&lk->lock_object);
372 __lockmgr_args(struct lock *lk, u_int flags, struct lock_object *ilk,
373 const char *wmesg, int pri, int timo, const char *file, int line)
376 struct lock_class *class;
380 int error, ipri, itimo, queue, wakeup_swapper;
381 #ifdef LOCK_PROFILING
382 uint64_t waittime = 0;
385 #ifdef ADAPTIVE_LOCKMGRS
386 volatile struct thread *owner;
387 u_int i, spintries = 0;
391 tid = (uintptr_t)curthread;
392 op = (flags & LK_TYPE_MASK);
393 iwmesg = (wmesg == LK_WMESG_DEFAULT) ? lk->lock_object.lo_name : wmesg;
394 ipri = (pri == LK_PRIO_DEFAULT) ? lk->lk_pri : pri;
395 itimo = (timo == LK_TIMO_DEFAULT) ? lk->lk_timo : timo;
397 MPASS((flags & ~LK_TOTAL_MASK) == 0);
398 KASSERT((op & (op - 1)) == 0,
399 ("%s: Invalid requested operation @ %s:%d", __func__, file, line));
400 KASSERT((flags & (LK_NOWAIT | LK_SLEEPFAIL)) == 0 ||
401 (op != LK_DOWNGRADE && op != LK_RELEASE),
402 ("%s: Invalid flags in regard of the operation desired @ %s:%d",
403 __func__, file, line));
404 KASSERT((flags & LK_INTERLOCK) == 0 || ilk != NULL,
405 ("%s: LK_INTERLOCK passed without valid interlock @ %s:%d",
406 __func__, file, line));
408 class = (flags & LK_INTERLOCK) ? LOCK_CLASS(ilk) : NULL;
409 if (panicstr != NULL) {
410 if (flags & LK_INTERLOCK)
411 class->lc_unlock(ilk);
415 if (op == LK_SHARED && (lk->lock_object.lo_flags & LK_NOSHARE))
421 if (LK_CAN_WITNESS(flags))
422 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER,
428 * If no other thread has an exclusive lock, or
429 * no exclusive waiter is present, bump the count of
430 * sharers. Since we have to preserve the state of
431 * waiters, if we fail to acquire the shared lock
432 * loop back and retry.
434 if (LK_CAN_SHARE(x)) {
435 if (atomic_cmpset_acq_ptr(&lk->lk_lock, x,
440 lock_profile_obtain_lock_failed(&lk->lock_object,
441 &contested, &waittime);
444 * If the lock is already held by curthread in
445 * exclusive way avoid a deadlock.
447 if (LK_HOLDER(x) == tid) {
449 "%s: %p already held in exclusive mode",
456 * If the lock is expected to not sleep just give up
459 if (LK_TRYOP(flags)) {
460 LOCK_LOG2(lk, "%s: %p fails the try operation",
466 #ifdef ADAPTIVE_LOCKMGRS
468 * If the owner is running on another CPU, spin until
469 * the owner stops running or the state of the lock
470 * changes. We need a double-state handle here
471 * because for a failed acquisition the lock can be
472 * either held in exclusive mode or shared mode
473 * (for the writer starvation avoidance technique).
475 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 &&
476 LK_HOLDER(x) != LK_KERNPROC) {
477 owner = (struct thread *)LK_HOLDER(x);
478 if (LOCK_LOG_TEST(&lk->lock_object, 0))
480 "%s: spinning on %p held by %p",
481 __func__, lk, owner);
484 * If we are holding also an interlock drop it
485 * in order to avoid a deadlock if the lockmgr
486 * owner is adaptively spinning on the
489 if (flags & LK_INTERLOCK) {
490 class->lc_unlock(ilk);
491 flags &= ~LK_INTERLOCK;
494 while (LK_HOLDER(lk->lk_lock) ==
495 (uintptr_t)owner && TD_IS_RUNNING(owner))
499 } else if (LK_CAN_ADAPT(lk, flags) &&
500 (x & LK_SHARE) != 0 && LK_SHARERS(x) &&
501 spintries < alk_retries) {
502 if (flags & LK_INTERLOCK) {
503 class->lc_unlock(ilk);
504 flags &= ~LK_INTERLOCK;
508 for (i = 0; i < alk_loops; i++) {
509 if (LOCK_LOG_TEST(&lk->lock_object, 0))
511 "%s: shared spinning on %p with %u and %u",
512 __func__, lk, spintries, i);
514 if ((x & LK_SHARE) == 0 ||
515 LK_CAN_SHARE(x) != 0)
526 * Acquire the sleepqueue chain lock because we
527 * probabilly will need to manipulate waiters flags.
529 sleepq_lock(&lk->lock_object);
533 * if the lock can be acquired in shared mode, try
536 if (LK_CAN_SHARE(x)) {
537 sleepq_release(&lk->lock_object);
541 #ifdef ADAPTIVE_LOCKMGRS
543 * The current lock owner might have started executing
544 * on another CPU (or the lock could have changed
545 * owner) while we were waiting on the turnstile
546 * chain lock. If so, drop the turnstile lock and try
549 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 &&
550 LK_HOLDER(x) != LK_KERNPROC) {
551 owner = (struct thread *)LK_HOLDER(x);
552 if (TD_IS_RUNNING(owner)) {
553 sleepq_release(&lk->lock_object);
560 * Try to set the LK_SHARED_WAITERS flag. If we fail,
561 * loop back and retry.
563 if ((x & LK_SHARED_WAITERS) == 0) {
564 if (!atomic_cmpset_acq_ptr(&lk->lk_lock, x,
565 x | LK_SHARED_WAITERS)) {
566 sleepq_release(&lk->lock_object);
569 LOCK_LOG2(lk, "%s: %p set shared waiters flag",
574 * As far as we have been unable to acquire the
575 * shared lock and the shared waiters flag is set,
578 error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo,
580 flags &= ~LK_INTERLOCK;
583 "%s: interrupted sleep for %p with %d",
584 __func__, lk, error);
587 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue",
591 lock_profile_obtain_lock_success(&lk->lock_object,
592 contested, waittime, file, line);
593 LOCK_LOG_LOCK("SLOCK", &lk->lock_object, 0, 0, file,
595 WITNESS_LOCK(&lk->lock_object, LK_TRYWIT(flags), file,
597 TD_LOCKS_INC(curthread);
598 TD_SLOCKS_INC(curthread);
603 _lockmgr_assert(lk, KA_SLOCKED, file, line);
605 x = v & LK_ALL_WAITERS;
606 v &= LK_EXCLUSIVE_SPINNERS;
609 * Try to switch from one shared lock to an exclusive one.
610 * We need to preserve waiters flags during the operation.
612 if (atomic_cmpset_ptr(&lk->lk_lock, LK_SHARERS_LOCK(1) | x | v,
614 LOCK_LOG_LOCK("XUPGRADE", &lk->lock_object, 0, 0, file,
616 WITNESS_UPGRADE(&lk->lock_object, LOP_EXCLUSIVE |
617 LK_TRYWIT(flags), file, line);
618 TD_SLOCKS_DEC(curthread);
623 * We have been unable to succeed in upgrading, so just
624 * give up the shared lock.
626 wakeup_swapper |= wakeupshlk(lk, file, line);
630 if (LK_CAN_WITNESS(flags))
631 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER |
632 LOP_EXCLUSIVE, file, line, ilk);
635 * If curthread already holds the lock and this one is
636 * allowed to recurse, simply recurse on it.
638 if (lockmgr_xlocked(lk)) {
639 if ((flags & LK_CANRECURSE) == 0 &&
640 (lk->lock_object.lo_flags & LO_RECURSABLE) == 0) {
643 * If the lock is expected to not panic just
644 * give up and return.
646 if (LK_TRYOP(flags)) {
648 "%s: %p fails the try operation",
653 if (flags & LK_INTERLOCK)
654 class->lc_unlock(ilk);
655 panic("%s: recursing on non recursive lockmgr %s @ %s:%d\n",
656 __func__, iwmesg, file, line);
659 LOCK_LOG2(lk, "%s: %p recursing", __func__, lk);
660 LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0,
661 lk->lk_recurse, file, line);
662 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE |
663 LK_TRYWIT(flags), file, line);
664 TD_LOCKS_INC(curthread);
668 while (!atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED,
670 lock_profile_obtain_lock_failed(&lk->lock_object,
671 &contested, &waittime);
674 * If the lock is expected to not sleep just give up
677 if (LK_TRYOP(flags)) {
678 LOCK_LOG2(lk, "%s: %p fails the try operation",
684 #ifdef ADAPTIVE_LOCKMGRS
686 * If the owner is running on another CPU, spin until
687 * the owner stops running or the state of the lock
691 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 &&
692 LK_HOLDER(x) != LK_KERNPROC) {
693 owner = (struct thread *)LK_HOLDER(x);
694 if (LOCK_LOG_TEST(&lk->lock_object, 0))
696 "%s: spinning on %p held by %p",
697 __func__, lk, owner);
700 * If we are holding also an interlock drop it
701 * in order to avoid a deadlock if the lockmgr
702 * owner is adaptively spinning on the
705 if (flags & LK_INTERLOCK) {
706 class->lc_unlock(ilk);
707 flags &= ~LK_INTERLOCK;
710 while (LK_HOLDER(lk->lk_lock) ==
711 (uintptr_t)owner && TD_IS_RUNNING(owner))
715 } else if (LK_CAN_ADAPT(lk, flags) &&
716 (x & LK_SHARE) != 0 && LK_SHARERS(x) &&
717 spintries < alk_retries) {
718 if ((x & LK_EXCLUSIVE_SPINNERS) == 0 &&
719 !atomic_cmpset_ptr(&lk->lk_lock, x,
720 x | LK_EXCLUSIVE_SPINNERS))
722 if (flags & LK_INTERLOCK) {
723 class->lc_unlock(ilk);
724 flags &= ~LK_INTERLOCK;
728 for (i = 0; i < alk_loops; i++) {
729 if (LOCK_LOG_TEST(&lk->lock_object, 0))
731 "%s: shared spinning on %p with %u and %u",
732 __func__, lk, spintries, i);
734 LK_EXCLUSIVE_SPINNERS) == 0)
745 * Acquire the sleepqueue chain lock because we
746 * probabilly will need to manipulate waiters flags.
748 sleepq_lock(&lk->lock_object);
752 * if the lock has been released while we spun on
753 * the sleepqueue chain lock just try again.
755 if (x == LK_UNLOCKED) {
756 sleepq_release(&lk->lock_object);
760 #ifdef ADAPTIVE_LOCKMGRS
762 * The current lock owner might have started executing
763 * on another CPU (or the lock could have changed
764 * owner) while we were waiting on the turnstile
765 * chain lock. If so, drop the turnstile lock and try
768 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 &&
769 LK_HOLDER(x) != LK_KERNPROC) {
770 owner = (struct thread *)LK_HOLDER(x);
771 if (TD_IS_RUNNING(owner)) {
772 sleepq_release(&lk->lock_object);
779 * The lock can be in the state where there is a
780 * pending queue of waiters, but still no owner.
781 * This happens when the lock is contested and an
782 * owner is going to claim the lock.
783 * If curthread is the one successfully acquiring it
784 * claim lock ownership and return, preserving waiters
787 v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS);
788 if ((x & ~v) == LK_UNLOCKED) {
789 v &= ~LK_EXCLUSIVE_SPINNERS;
790 if (atomic_cmpset_acq_ptr(&lk->lk_lock, x,
792 sleepq_release(&lk->lock_object);
794 "%s: %p claimed by a new writer",
798 sleepq_release(&lk->lock_object);
803 * Try to set the LK_EXCLUSIVE_WAITERS flag. If we
804 * fail, loop back and retry.
806 if ((x & LK_EXCLUSIVE_WAITERS) == 0) {
807 if (!atomic_cmpset_ptr(&lk->lk_lock, x,
808 x | LK_EXCLUSIVE_WAITERS)) {
809 sleepq_release(&lk->lock_object);
812 LOCK_LOG2(lk, "%s: %p set excl waiters flag",
817 * As far as we have been unable to acquire the
818 * exclusive lock and the exclusive waiters flag
819 * is set, we will sleep.
821 error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo,
823 flags &= ~LK_INTERLOCK;
826 "%s: interrupted sleep for %p with %d",
827 __func__, lk, error);
830 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue",
834 lock_profile_obtain_lock_success(&lk->lock_object,
835 contested, waittime, file, line);
836 LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0,
837 lk->lk_recurse, file, line);
838 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE |
839 LK_TRYWIT(flags), file, line);
840 TD_LOCKS_INC(curthread);
845 _lockmgr_assert(lk, KA_XLOCKED | KA_NOTRECURSED, file, line);
846 LOCK_LOG_LOCK("XDOWNGRADE", &lk->lock_object, 0, 0, file, line);
847 WITNESS_DOWNGRADE(&lk->lock_object, 0, file, line);
848 TD_SLOCKS_INC(curthread);
851 * In order to preserve waiters flags, just spin.
855 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0);
857 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x,
858 LK_SHARERS_LOCK(1) | x))
864 _lockmgr_assert(lk, KA_LOCKED, file, line);
867 if ((x & LK_SHARE) == 0) {
870 * As first option, treact the lock as if it has not
872 * Fix-up the tid var if the lock has been disowned.
874 if (LK_HOLDER(x) == LK_KERNPROC)
877 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE,
879 TD_LOCKS_DEC(curthread);
881 LOCK_LOG_LOCK("XUNLOCK", &lk->lock_object, 0,
882 lk->lk_recurse, file, line);
885 * The lock is held in exclusive mode.
886 * If the lock is recursed also, then unrecurse it.
888 if (lockmgr_xlocked(lk) && lockmgr_recursed(lk)) {
889 LOCK_LOG2(lk, "%s: %p unrecursing", __func__,
894 if (tid != LK_KERNPROC)
895 lock_profile_release_lock(&lk->lock_object);
897 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid,
901 sleepq_lock(&lk->lock_object);
906 * If the lock has exclusive waiters, give them
907 * preference in order to avoid deadlock with
910 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0);
911 if (x & LK_EXCLUSIVE_WAITERS) {
912 queue = SQ_EXCLUSIVE_QUEUE;
913 v |= (x & LK_SHARED_WAITERS);
915 MPASS((x & LK_ALL_WAITERS) ==
917 queue = SQ_SHARED_QUEUE;
921 "%s: %p waking up threads on the %s queue",
922 __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" :
924 atomic_store_rel_ptr(&lk->lk_lock, v);
925 wakeup_swapper = sleepq_broadcast(&lk->lock_object,
926 SLEEPQ_LK, 0, queue);
927 sleepq_release(&lk->lock_object);
930 wakeup_swapper = wakeupshlk(lk, file, line);
933 if (LK_CAN_WITNESS(flags))
934 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER |
935 LOP_EXCLUSIVE, file, line, ilk);
938 * Trying to drain a lock we already own will result in a
941 if (lockmgr_xlocked(lk)) {
942 if (flags & LK_INTERLOCK)
943 class->lc_unlock(ilk);
944 panic("%s: draining %s with the lock held @ %s:%d\n",
945 __func__, iwmesg, file, line);
948 while (!atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid)) {
949 lock_profile_obtain_lock_failed(&lk->lock_object,
950 &contested, &waittime);
953 * If the lock is expected to not sleep just give up
956 if (LK_TRYOP(flags)) {
957 LOCK_LOG2(lk, "%s: %p fails the try operation",
964 * Acquire the sleepqueue chain lock because we
965 * probabilly will need to manipulate waiters flags.
967 sleepq_lock(&lk->lock_object);
971 * if the lock has been released while we spun on
972 * the sleepqueue chain lock just try again.
974 if (x == LK_UNLOCKED) {
975 sleepq_release(&lk->lock_object);
979 v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS);
980 if ((x & ~v) == LK_UNLOCKED) {
981 v = (x & ~LK_EXCLUSIVE_SPINNERS);
982 if (v & LK_EXCLUSIVE_WAITERS) {
983 queue = SQ_EXCLUSIVE_QUEUE;
984 v &= ~LK_EXCLUSIVE_WAITERS;
986 MPASS(v & LK_SHARED_WAITERS);
987 queue = SQ_SHARED_QUEUE;
988 v &= ~LK_SHARED_WAITERS;
990 if (!atomic_cmpset_ptr(&lk->lk_lock, x, v)) {
991 sleepq_release(&lk->lock_object);
995 "%s: %p waking up all threads on the %s queue",
996 __func__, lk, queue == SQ_SHARED_QUEUE ?
997 "shared" : "exclusive");
998 wakeup_swapper |= sleepq_broadcast(
999 &lk->lock_object, SLEEPQ_LK, 0, queue);
1002 * If shared waiters have been woken up we need
1003 * to wait for one of them to acquire the lock
1004 * before to set the exclusive waiters in
1005 * order to avoid a deadlock.
1007 if (queue == SQ_SHARED_QUEUE) {
1008 for (v = lk->lk_lock;
1009 (v & LK_SHARE) && !LK_SHARERS(v);
1016 * Try to set the LK_EXCLUSIVE_WAITERS flag. If we
1017 * fail, loop back and retry.
1019 if ((x & LK_EXCLUSIVE_WAITERS) == 0) {
1020 if (!atomic_cmpset_ptr(&lk->lk_lock, x,
1021 x | LK_EXCLUSIVE_WAITERS)) {
1022 sleepq_release(&lk->lock_object);
1025 LOCK_LOG2(lk, "%s: %p set drain waiters flag",
1030 * As far as we have been unable to acquire the
1031 * exclusive lock and the exclusive waiters flag
1032 * is set, we will sleep.
1034 if (flags & LK_INTERLOCK) {
1035 class->lc_unlock(ilk);
1036 flags &= ~LK_INTERLOCK;
1039 sleepq_add(&lk->lock_object, NULL, iwmesg, SLEEPQ_LK,
1040 SQ_EXCLUSIVE_QUEUE);
1041 sleepq_wait(&lk->lock_object, ipri & PRIMASK);
1043 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue",
1048 lock_profile_obtain_lock_success(&lk->lock_object,
1049 contested, waittime, file, line);
1050 LOCK_LOG_LOCK("DRAIN", &lk->lock_object, 0,
1051 lk->lk_recurse, file, line);
1052 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE |
1053 LK_TRYWIT(flags), file, line);
1054 TD_LOCKS_INC(curthread);
1059 if (flags & LK_INTERLOCK)
1060 class->lc_unlock(ilk);
1061 panic("%s: unknown lockmgr request 0x%x\n", __func__, op);
1064 if (flags & LK_INTERLOCK)
1065 class->lc_unlock(ilk);
1073 _lockmgr_disown(struct lock *lk, const char *file, int line)
1077 tid = (uintptr_t)curthread;
1078 _lockmgr_assert(lk, KA_XLOCKED | KA_NOTRECURSED, file, line);
1081 * If the owner is already LK_KERNPROC just skip the whole operation.
1083 if (LK_HOLDER(lk->lk_lock) != tid)
1085 lock_profile_release_lock(&lk->lock_object);
1086 LOCK_LOG_LOCK("XDISOWN", &lk->lock_object, 0, 0, file, line);
1087 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, file, line);
1088 TD_LOCKS_DEC(curthread);
1092 * In order to preserve waiters flags, just spin.
1096 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0);
1097 x &= LK_ALL_WAITERS;
1098 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x,
1106 lockmgr_printinfo(struct lock *lk)
1111 if (lk->lk_lock == LK_UNLOCKED)
1112 printf("lock type %s: UNLOCKED\n", lk->lock_object.lo_name);
1113 else if (lk->lk_lock & LK_SHARE)
1114 printf("lock type %s: SHARED (count %ju)\n",
1115 lk->lock_object.lo_name,
1116 (uintmax_t)LK_SHARERS(lk->lk_lock));
1118 td = lockmgr_xholder(lk);
1119 printf("lock type %s: EXCL by thread %p (pid %d)\n",
1120 lk->lock_object.lo_name, td, td->td_proc->p_pid);
1124 if (x & LK_EXCLUSIVE_WAITERS)
1125 printf(" with exclusive waiters pending\n");
1126 if (x & LK_SHARED_WAITERS)
1127 printf(" with shared waiters pending\n");
1128 if (x & LK_EXCLUSIVE_SPINNERS)
1129 printf(" with exclusive spinners pending\n");
1135 lockstatus(struct lock *lk)
1144 if ((x & LK_SHARE) == 0) {
1145 if (v == (uintptr_t)curthread || v == LK_KERNPROC)
1149 } else if (x == LK_UNLOCKED)
1155 #ifdef INVARIANT_SUPPORT
1157 #undef _lockmgr_assert
1161 _lockmgr_assert(struct lock *lk, int what, const char *file, int line)
1165 if (panicstr != NULL)
1169 case KA_SLOCKED | KA_NOTRECURSED:
1170 case KA_SLOCKED | KA_RECURSED:
1173 case KA_LOCKED | KA_NOTRECURSED:
1174 case KA_LOCKED | KA_RECURSED:
1178 * We cannot trust WITNESS if the lock is held in exclusive
1179 * mode and a call to lockmgr_disown() happened.
1180 * Workaround this skipping the check if the lock is held in
1181 * exclusive mode even for the KA_LOCKED case.
1183 if (slocked || (lk->lk_lock & LK_SHARE)) {
1184 witness_assert(&lk->lock_object, what, file, line);
1188 if (lk->lk_lock == LK_UNLOCKED ||
1189 ((lk->lk_lock & LK_SHARE) == 0 && (slocked ||
1190 (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk)))))
1191 panic("Lock %s not %slocked @ %s:%d\n",
1192 lk->lock_object.lo_name, slocked ? "share" : "",
1195 if ((lk->lk_lock & LK_SHARE) == 0) {
1196 if (lockmgr_recursed(lk)) {
1197 if (what & KA_NOTRECURSED)
1198 panic("Lock %s recursed @ %s:%d\n",
1199 lk->lock_object.lo_name, file,
1201 } else if (what & KA_RECURSED)
1202 panic("Lock %s not recursed @ %s:%d\n",
1203 lk->lock_object.lo_name, file, line);
1207 case KA_XLOCKED | KA_NOTRECURSED:
1208 case KA_XLOCKED | KA_RECURSED:
1209 if (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk))
1210 panic("Lock %s not exclusively locked @ %s:%d\n",
1211 lk->lock_object.lo_name, file, line);
1212 if (lockmgr_recursed(lk)) {
1213 if (what & KA_NOTRECURSED)
1214 panic("Lock %s recursed @ %s:%d\n",
1215 lk->lock_object.lo_name, file, line);
1216 } else if (what & KA_RECURSED)
1217 panic("Lock %s not recursed @ %s:%d\n",
1218 lk->lock_object.lo_name, file, line);
1221 if (lockmgr_xlocked(lk) || lockmgr_disowned(lk))
1222 panic("Lock %s exclusively locked @ %s:%d\n",
1223 lk->lock_object.lo_name, file, line);
1226 panic("Unknown lockmgr assertion: %d @ %s:%d\n", what, file,
1234 lockmgr_chain(struct thread *td, struct thread **ownerp)
1240 if (LOCK_CLASS(&lk->lock_object) != &lock_class_lockmgr)
1242 db_printf("blocked on lockmgr %s", lk->lock_object.lo_name);
1243 if (lk->lk_lock & LK_SHARE)
1244 db_printf("SHARED (count %ju)\n",
1245 (uintmax_t)LK_SHARERS(lk->lk_lock));
1247 db_printf("EXCL\n");
1248 *ownerp = lockmgr_xholder(lk);
1254 db_show_lockmgr(struct lock_object *lock)
1259 lk = (struct lock *)lock;
1261 db_printf(" state: ");
1262 if (lk->lk_lock == LK_UNLOCKED)
1263 db_printf("UNLOCKED\n");
1264 else if (lk->lk_lock & LK_SHARE)
1265 db_printf("SLOCK: %ju\n", (uintmax_t)LK_SHARERS(lk->lk_lock));
1267 td = lockmgr_xholder(lk);
1268 if (td == (struct thread *)LK_KERNPROC)
1269 db_printf("XLOCK: LK_KERNPROC\n");
1271 db_printf("XLOCK: %p (tid %d, pid %d, \"%s\")\n", td,
1272 td->td_tid, td->td_proc->p_pid,
1273 td->td_proc->p_comm);
1274 if (lockmgr_recursed(lk))
1275 db_printf(" recursed: %d\n", lk->lk_recurse);
1277 db_printf(" waiters: ");
1278 switch (lk->lk_lock & LK_ALL_WAITERS) {
1279 case LK_SHARED_WAITERS:
1280 db_printf("shared\n");
1282 case LK_EXCLUSIVE_WAITERS:
1283 db_printf("exclusive\n");
1285 case LK_ALL_WAITERS:
1286 db_printf("shared and exclusive\n");
1289 db_printf("none\n");
1291 db_printf(" spinners: ");
1292 if (lk->lk_lock & LK_EXCLUSIVE_SPINNERS)
1293 db_printf("exclusive\n");
1295 db_printf("none\n");