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>
39 #include <sys/lock_profile.h>
40 #include <sys/lockmgr.h>
41 #include <sys/mutex.h>
43 #include <sys/sleepqueue.h>
45 #include <sys/stack.h>
47 #include <sys/sysctl.h>
48 #include <sys/systm.h>
50 #include <machine/cpu.h>
56 CTASSERT(((LK_ADAPTIVE | LK_NOSHARE) & LO_CLASSFLAGS) ==
57 (LK_ADAPTIVE | LK_NOSHARE));
58 CTASSERT(LK_UNLOCKED == (LK_UNLOCKED &
59 ~(LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS)));
61 #define SQ_EXCLUSIVE_QUEUE 0
62 #define SQ_SHARED_QUEUE 1
65 #define _lockmgr_assert(lk, what, file, line)
66 #define TD_LOCKS_INC(td)
67 #define TD_LOCKS_DEC(td)
69 #define TD_LOCKS_INC(td) ((td)->td_locks++)
70 #define TD_LOCKS_DEC(td) ((td)->td_locks--)
72 #define TD_SLOCKS_INC(td) ((td)->td_lk_slocks++)
73 #define TD_SLOCKS_DEC(td) ((td)->td_lk_slocks--)
76 #define STACK_PRINT(lk)
77 #define STACK_SAVE(lk)
78 #define STACK_ZERO(lk)
80 #define STACK_PRINT(lk) stack_print_ddb(&(lk)->lk_stack)
81 #define STACK_SAVE(lk) stack_save(&(lk)->lk_stack)
82 #define STACK_ZERO(lk) stack_zero(&(lk)->lk_stack)
85 #define LOCK_LOG2(lk, string, arg1, arg2) \
86 if (LOCK_LOG_TEST(&(lk)->lock_object, 0)) \
87 CTR2(KTR_LOCK, (string), (arg1), (arg2))
88 #define LOCK_LOG3(lk, string, arg1, arg2, arg3) \
89 if (LOCK_LOG_TEST(&(lk)->lock_object, 0)) \
90 CTR3(KTR_LOCK, (string), (arg1), (arg2), (arg3))
92 #define GIANT_DECLARE \
94 WITNESS_SAVE_DECL(Giant)
95 #define GIANT_RESTORE() do { \
99 WITNESS_RESTORE(&Giant.lock_object, Giant); \
102 #define GIANT_SAVE() do { \
103 if (mtx_owned(&Giant)) { \
104 WITNESS_SAVE(&Giant.lock_object, Giant); \
105 while (mtx_owned(&Giant)) { \
107 mtx_unlock(&Giant); \
112 #define LK_CAN_SHARE(x) \
113 (((x) & LK_SHARE) && (((x) & LK_EXCLUSIVE_WAITERS) == 0 || \
114 ((x) & LK_EXCLUSIVE_SPINNERS) == 0 || \
115 curthread->td_lk_slocks || (curthread->td_pflags & TDP_DEADLKTREAT)))
116 #define LK_TRYOP(x) \
119 #define LK_CAN_WITNESS(x) \
120 (((x) & LK_NOWITNESS) == 0 && !LK_TRYOP(x))
121 #define LK_TRYWIT(x) \
122 (LK_TRYOP(x) ? LOP_TRYLOCK : 0)
124 #define LK_CAN_ADAPT(lk, f) \
125 (((lk)->lock_object.lo_flags & LK_ADAPTIVE) != 0 && \
126 ((f) & LK_SLEEPFAIL) == 0)
128 #define lockmgr_disowned(lk) \
129 (((lk)->lk_lock & ~(LK_FLAGMASK & ~LK_SHARE)) == LK_KERNPROC)
131 #define lockmgr_xlocked(lk) \
132 (((lk)->lk_lock & ~(LK_FLAGMASK & ~LK_SHARE)) == (uintptr_t)curthread)
134 static void assert_lockmgr(struct lock_object *lock, int how);
136 static void db_show_lockmgr(struct lock_object *lock);
138 static void lock_lockmgr(struct lock_object *lock, int how);
140 static int owner_lockmgr(struct lock_object *lock, struct thread **owner);
142 static int unlock_lockmgr(struct lock_object *lock);
144 struct lock_class lock_class_lockmgr = {
145 .lc_name = "lockmgr",
146 .lc_flags = LC_RECURSABLE | LC_SLEEPABLE | LC_SLEEPLOCK | LC_UPGRADABLE,
147 .lc_assert = assert_lockmgr,
149 .lc_ddb_show = db_show_lockmgr,
151 .lc_lock = lock_lockmgr,
152 .lc_unlock = unlock_lockmgr,
154 .lc_owner = owner_lockmgr,
158 #ifdef ADAPTIVE_LOCKMGRS
159 static u_int alk_retries = 10;
160 static u_int alk_loops = 10000;
161 static SYSCTL_NODE(_debug, OID_AUTO, lockmgr, CTLFLAG_RD, NULL,
162 "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);
200 if (queue == SQ_EXCLUSIVE_QUEUE && (flags & LK_SLEEPFAIL) != 0)
203 sleepq_add(&lk->lock_object, NULL, wmesg, SLEEPQ_LK | (catch ?
204 SLEEPQ_INTERRUPTIBLE : 0), queue);
205 if ((flags & LK_TIMELOCK) && timo)
206 sleepq_set_timeout(&lk->lock_object, timo);
209 * Decisional switch for real sleeping.
211 if ((flags & LK_TIMELOCK) && timo && catch)
212 error = sleepq_timedwait_sig(&lk->lock_object, pri);
213 else if ((flags & LK_TIMELOCK) && timo)
214 error = sleepq_timedwait(&lk->lock_object, pri);
216 error = sleepq_wait_sig(&lk->lock_object, pri);
218 sleepq_wait(&lk->lock_object, pri);
220 if ((flags & LK_SLEEPFAIL) && error == 0)
227 wakeupshlk(struct lock *lk, const char *file, int line)
231 int queue, wakeup_swapper;
233 TD_LOCKS_DEC(curthread);
234 TD_SLOCKS_DEC(curthread);
235 WITNESS_UNLOCK(&lk->lock_object, 0, file, line);
236 LOCK_LOG_LOCK("SUNLOCK", &lk->lock_object, 0, 0, file, line);
243 * If there is more than one shared lock held, just drop one
246 if (LK_SHARERS(x) > 1) {
247 if (atomic_cmpset_rel_ptr(&lk->lk_lock, x,
254 * If there are not waiters on the exclusive queue, drop the
257 if ((x & LK_ALL_WAITERS) == 0) {
258 MPASS((x & ~LK_EXCLUSIVE_SPINNERS) ==
260 if (atomic_cmpset_rel_ptr(&lk->lk_lock, x, LK_UNLOCKED))
266 * We should have a sharer with waiters, so enter the hard
267 * path in order to handle wakeups correctly.
269 sleepq_lock(&lk->lock_object);
270 x = lk->lk_lock & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS);
274 * If the lock has exclusive waiters, give them preference in
275 * order to avoid deadlock with shared runners up.
276 * If interruptible sleeps left the exclusive queue empty
277 * avoid a starvation for the threads sleeping on the shared
278 * queue by giving them precedence and cleaning up the
279 * exclusive waiters bit anyway.
280 * Please note that lk_exslpfail count may be lying about
281 * the real number of waiters with the LK_SLEEPFAIL flag on
282 * because they may be used in conjuction with interruptible
283 * sleeps so lk_exslpfail might be considered an 'upper limit'
284 * bound, including the edge cases.
286 realexslp = sleepq_sleepcnt(&lk->lock_object,
288 if ((x & LK_EXCLUSIVE_WAITERS) != 0 && realexslp != 0) {
289 if (lk->lk_exslpfail < realexslp) {
290 lk->lk_exslpfail = 0;
291 queue = SQ_EXCLUSIVE_QUEUE;
292 v |= (x & LK_SHARED_WAITERS);
294 lk->lk_exslpfail = 0;
296 "%s: %p has only LK_SLEEPFAIL sleepers",
299 "%s: %p waking up threads on the exclusive queue",
302 sleepq_broadcast(&lk->lock_object,
303 SLEEPQ_LK, 0, SQ_EXCLUSIVE_QUEUE);
304 queue = SQ_SHARED_QUEUE;
310 * Exclusive waiters sleeping with LK_SLEEPFAIL on
311 * and using interruptible sleeps/timeout may have
312 * left spourious lk_exslpfail counts on, so clean
315 lk->lk_exslpfail = 0;
316 queue = SQ_SHARED_QUEUE;
319 if (!atomic_cmpset_rel_ptr(&lk->lk_lock, LK_SHARERS_LOCK(1) | x,
321 sleepq_release(&lk->lock_object);
324 LOCK_LOG3(lk, "%s: %p waking up threads on the %s queue",
325 __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" :
327 wakeup_swapper |= sleepq_broadcast(&lk->lock_object, SLEEPQ_LK,
329 sleepq_release(&lk->lock_object);
333 lock_profile_release_lock(&lk->lock_object);
334 return (wakeup_swapper);
338 assert_lockmgr(struct lock_object *lock, int what)
341 panic("lockmgr locks do not support assertions");
345 lock_lockmgr(struct lock_object *lock, int how)
348 panic("lockmgr locks do not support sleep interlocking");
352 unlock_lockmgr(struct lock_object *lock)
355 panic("lockmgr locks do not support sleep interlocking");
360 owner_lockmgr(struct lock_object *lock, struct thread **owner)
363 panic("lockmgr locks do not support owner inquiring");
368 lockinit(struct lock *lk, int pri, const char *wmesg, int timo, int flags)
372 MPASS((flags & ~LK_INIT_MASK) == 0);
373 ASSERT_ATOMIC_LOAD_PTR(lk->lk_lock,
374 ("%s: lockmgr not aligned for %s: %p", __func__, wmesg,
377 iflags = LO_SLEEPABLE | LO_UPGRADABLE;
378 if (flags & LK_CANRECURSE)
379 iflags |= LO_RECURSABLE;
380 if ((flags & LK_NODUP) == 0)
382 if (flags & LK_NOPROFILE)
383 iflags |= LO_NOPROFILE;
384 if ((flags & LK_NOWITNESS) == 0)
385 iflags |= LO_WITNESS;
386 if (flags & LK_QUIET)
388 iflags |= flags & (LK_ADAPTIVE | LK_NOSHARE);
390 lk->lk_lock = LK_UNLOCKED;
392 lk->lk_exslpfail = 0;
395 lock_init(&lk->lock_object, &lock_class_lockmgr, wmesg, NULL, iflags);
400 * XXX: Gross hacks to manipulate external lock flags after
401 * initialization. Used for certain vnode and buf locks.
404 lockallowshare(struct lock *lk)
407 lockmgr_assert(lk, KA_XLOCKED);
408 lk->lock_object.lo_flags &= ~LK_NOSHARE;
412 lockallowrecurse(struct lock *lk)
415 lockmgr_assert(lk, KA_XLOCKED);
416 lk->lock_object.lo_flags |= LO_RECURSABLE;
420 lockdisablerecurse(struct lock *lk)
423 lockmgr_assert(lk, KA_XLOCKED);
424 lk->lock_object.lo_flags &= ~LO_RECURSABLE;
428 lockdestroy(struct lock *lk)
431 KASSERT(lk->lk_lock == LK_UNLOCKED, ("lockmgr still held"));
432 KASSERT(lk->lk_recurse == 0, ("lockmgr still recursed"));
433 KASSERT(lk->lk_exslpfail == 0, ("lockmgr still exclusive waiters"));
434 lock_destroy(&lk->lock_object);
438 __lockmgr_args(struct lock *lk, u_int flags, struct lock_object *ilk,
439 const char *wmesg, int pri, int timo, const char *file, int line)
442 struct lock_class *class;
446 int error, ipri, itimo, queue, wakeup_swapper;
447 #ifdef LOCK_PROFILING
448 uint64_t waittime = 0;
451 #ifdef ADAPTIVE_LOCKMGRS
452 volatile struct thread *owner;
453 u_int i, spintries = 0;
457 tid = (uintptr_t)curthread;
458 op = (flags & LK_TYPE_MASK);
459 iwmesg = (wmesg == LK_WMESG_DEFAULT) ? lk->lock_object.lo_name : wmesg;
460 ipri = (pri == LK_PRIO_DEFAULT) ? lk->lk_pri : pri;
461 itimo = (timo == LK_TIMO_DEFAULT) ? lk->lk_timo : timo;
463 MPASS((flags & ~LK_TOTAL_MASK) == 0);
464 KASSERT((op & (op - 1)) == 0,
465 ("%s: Invalid requested operation @ %s:%d", __func__, file, line));
466 KASSERT((flags & (LK_NOWAIT | LK_SLEEPFAIL)) == 0 ||
467 (op != LK_DOWNGRADE && op != LK_RELEASE),
468 ("%s: Invalid flags in regard of the operation desired @ %s:%d",
469 __func__, file, line));
470 KASSERT((flags & LK_INTERLOCK) == 0 || ilk != NULL,
471 ("%s: LK_INTERLOCK passed without valid interlock @ %s:%d",
472 __func__, file, line));
474 class = (flags & LK_INTERLOCK) ? LOCK_CLASS(ilk) : NULL;
475 if (panicstr != NULL) {
476 if (flags & LK_INTERLOCK)
477 class->lc_unlock(ilk);
481 if (lk->lock_object.lo_flags & LK_NOSHARE) {
488 _lockmgr_assert(lk, KA_XLOCKED | KA_NOTRECURSED,
497 if (LK_CAN_WITNESS(flags))
498 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER,
504 * If no other thread has an exclusive lock, or
505 * no exclusive waiter is present, bump the count of
506 * sharers. Since we have to preserve the state of
507 * waiters, if we fail to acquire the shared lock
508 * loop back and retry.
510 if (LK_CAN_SHARE(x)) {
511 if (atomic_cmpset_acq_ptr(&lk->lk_lock, x,
516 lock_profile_obtain_lock_failed(&lk->lock_object,
517 &contested, &waittime);
520 * If the lock is already held by curthread in
521 * exclusive way avoid a deadlock.
523 if (LK_HOLDER(x) == tid) {
525 "%s: %p already held in exclusive mode",
532 * If the lock is expected to not sleep just give up
535 if (LK_TRYOP(flags)) {
536 LOCK_LOG2(lk, "%s: %p fails the try operation",
542 #ifdef ADAPTIVE_LOCKMGRS
544 * If the owner is running on another CPU, spin until
545 * the owner stops running or the state of the lock
546 * changes. We need a double-state handle here
547 * because for a failed acquisition the lock can be
548 * either held in exclusive mode or shared mode
549 * (for the writer starvation avoidance technique).
551 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 &&
552 LK_HOLDER(x) != LK_KERNPROC) {
553 owner = (struct thread *)LK_HOLDER(x);
554 if (LOCK_LOG_TEST(&lk->lock_object, 0))
556 "%s: spinning on %p held by %p",
557 __func__, lk, owner);
560 * If we are holding also an interlock drop it
561 * in order to avoid a deadlock if the lockmgr
562 * owner is adaptively spinning on the
565 if (flags & LK_INTERLOCK) {
566 class->lc_unlock(ilk);
567 flags &= ~LK_INTERLOCK;
570 while (LK_HOLDER(lk->lk_lock) ==
571 (uintptr_t)owner && TD_IS_RUNNING(owner))
575 } else if (LK_CAN_ADAPT(lk, flags) &&
576 (x & LK_SHARE) != 0 && LK_SHARERS(x) &&
577 spintries < alk_retries) {
578 if (flags & LK_INTERLOCK) {
579 class->lc_unlock(ilk);
580 flags &= ~LK_INTERLOCK;
584 for (i = 0; i < alk_loops; i++) {
585 if (LOCK_LOG_TEST(&lk->lock_object, 0))
587 "%s: shared spinning on %p with %u and %u",
588 __func__, lk, spintries, i);
590 if ((x & LK_SHARE) == 0 ||
591 LK_CAN_SHARE(x) != 0)
602 * Acquire the sleepqueue chain lock because we
603 * probabilly will need to manipulate waiters flags.
605 sleepq_lock(&lk->lock_object);
609 * if the lock can be acquired in shared mode, try
612 if (LK_CAN_SHARE(x)) {
613 sleepq_release(&lk->lock_object);
617 #ifdef ADAPTIVE_LOCKMGRS
619 * The current lock owner might have started executing
620 * on another CPU (or the lock could have changed
621 * owner) while we were waiting on the turnstile
622 * chain lock. If so, drop the turnstile lock and try
625 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 &&
626 LK_HOLDER(x) != LK_KERNPROC) {
627 owner = (struct thread *)LK_HOLDER(x);
628 if (TD_IS_RUNNING(owner)) {
629 sleepq_release(&lk->lock_object);
636 * Try to set the LK_SHARED_WAITERS flag. If we fail,
637 * loop back and retry.
639 if ((x & LK_SHARED_WAITERS) == 0) {
640 if (!atomic_cmpset_acq_ptr(&lk->lk_lock, x,
641 x | LK_SHARED_WAITERS)) {
642 sleepq_release(&lk->lock_object);
645 LOCK_LOG2(lk, "%s: %p set shared waiters flag",
650 * As far as we have been unable to acquire the
651 * shared lock and the shared waiters flag is set,
654 error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo,
656 flags &= ~LK_INTERLOCK;
659 "%s: interrupted sleep for %p with %d",
660 __func__, lk, error);
663 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue",
667 lock_profile_obtain_lock_success(&lk->lock_object,
668 contested, waittime, file, line);
669 LOCK_LOG_LOCK("SLOCK", &lk->lock_object, 0, 0, file,
671 WITNESS_LOCK(&lk->lock_object, LK_TRYWIT(flags), file,
673 TD_LOCKS_INC(curthread);
674 TD_SLOCKS_INC(curthread);
679 _lockmgr_assert(lk, KA_SLOCKED, file, line);
681 x = v & LK_ALL_WAITERS;
682 v &= LK_EXCLUSIVE_SPINNERS;
685 * Try to switch from one shared lock to an exclusive one.
686 * We need to preserve waiters flags during the operation.
688 if (atomic_cmpset_ptr(&lk->lk_lock, LK_SHARERS_LOCK(1) | x | v,
690 LOCK_LOG_LOCK("XUPGRADE", &lk->lock_object, 0, 0, file,
692 WITNESS_UPGRADE(&lk->lock_object, LOP_EXCLUSIVE |
693 LK_TRYWIT(flags), file, line);
694 TD_SLOCKS_DEC(curthread);
699 * We have been unable to succeed in upgrading, so just
700 * give up the shared lock.
702 wakeup_swapper |= wakeupshlk(lk, file, line);
706 if (LK_CAN_WITNESS(flags))
707 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER |
708 LOP_EXCLUSIVE, file, line, ilk);
711 * If curthread already holds the lock and this one is
712 * allowed to recurse, simply recurse on it.
714 if (lockmgr_xlocked(lk)) {
715 if ((flags & LK_CANRECURSE) == 0 &&
716 (lk->lock_object.lo_flags & LO_RECURSABLE) == 0) {
719 * If the lock is expected to not panic just
720 * give up and return.
722 if (LK_TRYOP(flags)) {
724 "%s: %p fails the try operation",
729 if (flags & LK_INTERLOCK)
730 class->lc_unlock(ilk);
731 panic("%s: recursing on non recursive lockmgr %s @ %s:%d\n",
732 __func__, iwmesg, file, line);
735 LOCK_LOG2(lk, "%s: %p recursing", __func__, lk);
736 LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0,
737 lk->lk_recurse, file, line);
738 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE |
739 LK_TRYWIT(flags), file, line);
740 TD_LOCKS_INC(curthread);
744 while (!atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED,
746 lock_profile_obtain_lock_failed(&lk->lock_object,
747 &contested, &waittime);
750 * If the lock is expected to not sleep just give up
753 if (LK_TRYOP(flags)) {
754 LOCK_LOG2(lk, "%s: %p fails the try operation",
760 #ifdef ADAPTIVE_LOCKMGRS
762 * If the owner is running on another CPU, spin until
763 * the owner stops running or the state of the lock
767 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 &&
768 LK_HOLDER(x) != LK_KERNPROC) {
769 owner = (struct thread *)LK_HOLDER(x);
770 if (LOCK_LOG_TEST(&lk->lock_object, 0))
772 "%s: spinning on %p held by %p",
773 __func__, lk, owner);
776 * If we are holding also an interlock drop it
777 * in order to avoid a deadlock if the lockmgr
778 * owner is adaptively spinning on the
781 if (flags & LK_INTERLOCK) {
782 class->lc_unlock(ilk);
783 flags &= ~LK_INTERLOCK;
786 while (LK_HOLDER(lk->lk_lock) ==
787 (uintptr_t)owner && TD_IS_RUNNING(owner))
791 } else if (LK_CAN_ADAPT(lk, flags) &&
792 (x & LK_SHARE) != 0 && LK_SHARERS(x) &&
793 spintries < alk_retries) {
794 if ((x & LK_EXCLUSIVE_SPINNERS) == 0 &&
795 !atomic_cmpset_ptr(&lk->lk_lock, x,
796 x | LK_EXCLUSIVE_SPINNERS))
798 if (flags & LK_INTERLOCK) {
799 class->lc_unlock(ilk);
800 flags &= ~LK_INTERLOCK;
804 for (i = 0; i < alk_loops; i++) {
805 if (LOCK_LOG_TEST(&lk->lock_object, 0))
807 "%s: shared spinning on %p with %u and %u",
808 __func__, lk, spintries, i);
810 LK_EXCLUSIVE_SPINNERS) == 0)
821 * Acquire the sleepqueue chain lock because we
822 * probabilly will need to manipulate waiters flags.
824 sleepq_lock(&lk->lock_object);
828 * if the lock has been released while we spun on
829 * the sleepqueue chain lock just try again.
831 if (x == LK_UNLOCKED) {
832 sleepq_release(&lk->lock_object);
836 #ifdef ADAPTIVE_LOCKMGRS
838 * The current lock owner might have started executing
839 * on another CPU (or the lock could have changed
840 * owner) while we were waiting on the turnstile
841 * chain lock. If so, drop the turnstile lock and try
844 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 &&
845 LK_HOLDER(x) != LK_KERNPROC) {
846 owner = (struct thread *)LK_HOLDER(x);
847 if (TD_IS_RUNNING(owner)) {
848 sleepq_release(&lk->lock_object);
855 * The lock can be in the state where there is a
856 * pending queue of waiters, but still no owner.
857 * This happens when the lock is contested and an
858 * owner is going to claim the lock.
859 * If curthread is the one successfully acquiring it
860 * claim lock ownership and return, preserving waiters
863 v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS);
864 if ((x & ~v) == LK_UNLOCKED) {
865 v &= ~LK_EXCLUSIVE_SPINNERS;
866 if (atomic_cmpset_acq_ptr(&lk->lk_lock, x,
868 sleepq_release(&lk->lock_object);
870 "%s: %p claimed by a new writer",
874 sleepq_release(&lk->lock_object);
879 * Try to set the LK_EXCLUSIVE_WAITERS flag. If we
880 * fail, loop back and retry.
882 if ((x & LK_EXCLUSIVE_WAITERS) == 0) {
883 if (!atomic_cmpset_ptr(&lk->lk_lock, x,
884 x | LK_EXCLUSIVE_WAITERS)) {
885 sleepq_release(&lk->lock_object);
888 LOCK_LOG2(lk, "%s: %p set excl waiters flag",
893 * As far as we have been unable to acquire the
894 * exclusive lock and the exclusive waiters flag
895 * is set, we will sleep.
897 error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo,
899 flags &= ~LK_INTERLOCK;
902 "%s: interrupted sleep for %p with %d",
903 __func__, lk, error);
906 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue",
910 lock_profile_obtain_lock_success(&lk->lock_object,
911 contested, waittime, file, line);
912 LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0,
913 lk->lk_recurse, file, line);
914 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE |
915 LK_TRYWIT(flags), file, line);
916 TD_LOCKS_INC(curthread);
921 _lockmgr_assert(lk, KA_XLOCKED | KA_NOTRECURSED, file, line);
922 LOCK_LOG_LOCK("XDOWNGRADE", &lk->lock_object, 0, 0, file, line);
923 WITNESS_DOWNGRADE(&lk->lock_object, 0, file, line);
924 TD_SLOCKS_INC(curthread);
927 * In order to preserve waiters flags, just spin.
931 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0);
933 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x,
934 LK_SHARERS_LOCK(1) | x))
940 _lockmgr_assert(lk, KA_LOCKED, file, line);
943 if ((x & LK_SHARE) == 0) {
946 * As first option, treact the lock as if it has not
948 * Fix-up the tid var if the lock has been disowned.
950 if (LK_HOLDER(x) == LK_KERNPROC)
953 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE,
955 TD_LOCKS_DEC(curthread);
957 LOCK_LOG_LOCK("XUNLOCK", &lk->lock_object, 0,
958 lk->lk_recurse, file, line);
961 * The lock is held in exclusive mode.
962 * If the lock is recursed also, then unrecurse it.
964 if (lockmgr_xlocked(lk) && lockmgr_recursed(lk)) {
965 LOCK_LOG2(lk, "%s: %p unrecursing", __func__,
970 if (tid != LK_KERNPROC)
971 lock_profile_release_lock(&lk->lock_object);
973 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid,
977 sleepq_lock(&lk->lock_object);
982 * If the lock has exclusive waiters, give them
983 * preference in order to avoid deadlock with
985 * If interruptible sleeps left the exclusive queue
986 * empty avoid a starvation for the threads sleeping
987 * on the shared queue by giving them precedence
988 * and cleaning up the exclusive waiters bit anyway.
989 * Please note that lk_exslpfail count may be lying
990 * about the real number of waiters with the
991 * LK_SLEEPFAIL flag on because they may be used in
992 * conjuction with interruptible sleeps so
993 * lk_exslpfail might be considered an 'upper limit'
994 * bound, including the edge cases.
996 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0);
997 realexslp = sleepq_sleepcnt(&lk->lock_object,
999 if ((x & LK_EXCLUSIVE_WAITERS) != 0 && realexslp != 0) {
1000 if (lk->lk_exslpfail < realexslp) {
1001 lk->lk_exslpfail = 0;
1002 queue = SQ_EXCLUSIVE_QUEUE;
1003 v |= (x & LK_SHARED_WAITERS);
1005 lk->lk_exslpfail = 0;
1007 "%s: %p has only LK_SLEEPFAIL sleepers",
1010 "%s: %p waking up threads on the exclusive queue",
1013 sleepq_broadcast(&lk->lock_object,
1014 SLEEPQ_LK, 0, SQ_EXCLUSIVE_QUEUE);
1015 queue = SQ_SHARED_QUEUE;
1020 * Exclusive waiters sleeping with LK_SLEEPFAIL
1021 * on and using interruptible sleeps/timeout
1022 * may have left spourious lk_exslpfail counts
1023 * on, so clean it up anyway.
1025 lk->lk_exslpfail = 0;
1026 queue = SQ_SHARED_QUEUE;
1030 "%s: %p waking up threads on the %s queue",
1031 __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" :
1033 atomic_store_rel_ptr(&lk->lk_lock, v);
1034 wakeup_swapper |= sleepq_broadcast(&lk->lock_object,
1035 SLEEPQ_LK, 0, queue);
1036 sleepq_release(&lk->lock_object);
1039 wakeup_swapper = wakeupshlk(lk, file, line);
1042 if (LK_CAN_WITNESS(flags))
1043 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER |
1044 LOP_EXCLUSIVE, file, line, ilk);
1047 * Trying to drain a lock we already own will result in a
1050 if (lockmgr_xlocked(lk)) {
1051 if (flags & LK_INTERLOCK)
1052 class->lc_unlock(ilk);
1053 panic("%s: draining %s with the lock held @ %s:%d\n",
1054 __func__, iwmesg, file, line);
1057 while (!atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid)) {
1058 lock_profile_obtain_lock_failed(&lk->lock_object,
1059 &contested, &waittime);
1062 * If the lock is expected to not sleep just give up
1065 if (LK_TRYOP(flags)) {
1066 LOCK_LOG2(lk, "%s: %p fails the try operation",
1073 * Acquire the sleepqueue chain lock because we
1074 * probabilly will need to manipulate waiters flags.
1076 sleepq_lock(&lk->lock_object);
1080 * if the lock has been released while we spun on
1081 * the sleepqueue chain lock just try again.
1083 if (x == LK_UNLOCKED) {
1084 sleepq_release(&lk->lock_object);
1088 v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS);
1089 if ((x & ~v) == LK_UNLOCKED) {
1090 v = (x & ~LK_EXCLUSIVE_SPINNERS);
1093 * If interruptible sleeps left the exclusive
1094 * queue empty avoid a starvation for the
1095 * threads sleeping on the shared queue by
1096 * giving them precedence and cleaning up the
1097 * exclusive waiters bit anyway.
1098 * Please note that lk_exslpfail count may be
1099 * lying about the real number of waiters with
1100 * the LK_SLEEPFAIL flag on because they may
1101 * be used in conjuction with interruptible
1102 * sleeps so lk_exslpfail might be considered
1103 * an 'upper limit' bound, including the edge
1106 if (v & LK_EXCLUSIVE_WAITERS) {
1107 queue = SQ_EXCLUSIVE_QUEUE;
1108 v &= ~LK_EXCLUSIVE_WAITERS;
1112 * Exclusive waiters sleeping with
1113 * LK_SLEEPFAIL on and using
1114 * interruptible sleeps/timeout may
1115 * have left spourious lk_exslpfail
1116 * counts on, so clean it up anyway.
1118 MPASS(v & LK_SHARED_WAITERS);
1119 lk->lk_exslpfail = 0;
1120 queue = SQ_SHARED_QUEUE;
1121 v &= ~LK_SHARED_WAITERS;
1123 if (queue == SQ_EXCLUSIVE_QUEUE) {
1125 sleepq_sleepcnt(&lk->lock_object,
1126 SQ_EXCLUSIVE_QUEUE);
1127 if (lk->lk_exslpfail >= realexslp) {
1128 lk->lk_exslpfail = 0;
1129 queue = SQ_SHARED_QUEUE;
1130 v &= ~LK_SHARED_WAITERS;
1131 if (realexslp != 0) {
1133 "%s: %p has only LK_SLEEPFAIL sleepers",
1136 "%s: %p waking up threads on the exclusive queue",
1142 SQ_EXCLUSIVE_QUEUE);
1145 lk->lk_exslpfail = 0;
1147 if (!atomic_cmpset_ptr(&lk->lk_lock, x, v)) {
1148 sleepq_release(&lk->lock_object);
1152 "%s: %p waking up all threads on the %s queue",
1153 __func__, lk, queue == SQ_SHARED_QUEUE ?
1154 "shared" : "exclusive");
1155 wakeup_swapper |= sleepq_broadcast(
1156 &lk->lock_object, SLEEPQ_LK, 0, queue);
1159 * If shared waiters have been woken up we need
1160 * to wait for one of them to acquire the lock
1161 * before to set the exclusive waiters in
1162 * order to avoid a deadlock.
1164 if (queue == SQ_SHARED_QUEUE) {
1165 for (v = lk->lk_lock;
1166 (v & LK_SHARE) && !LK_SHARERS(v);
1173 * Try to set the LK_EXCLUSIVE_WAITERS flag. If we
1174 * fail, loop back and retry.
1176 if ((x & LK_EXCLUSIVE_WAITERS) == 0) {
1177 if (!atomic_cmpset_ptr(&lk->lk_lock, x,
1178 x | LK_EXCLUSIVE_WAITERS)) {
1179 sleepq_release(&lk->lock_object);
1182 LOCK_LOG2(lk, "%s: %p set drain waiters flag",
1187 * As far as we have been unable to acquire the
1188 * exclusive lock and the exclusive waiters flag
1189 * is set, we will sleep.
1191 if (flags & LK_INTERLOCK) {
1192 class->lc_unlock(ilk);
1193 flags &= ~LK_INTERLOCK;
1196 sleepq_add(&lk->lock_object, NULL, iwmesg, SLEEPQ_LK,
1197 SQ_EXCLUSIVE_QUEUE);
1198 sleepq_wait(&lk->lock_object, ipri & PRIMASK);
1200 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue",
1205 lock_profile_obtain_lock_success(&lk->lock_object,
1206 contested, waittime, file, line);
1207 LOCK_LOG_LOCK("DRAIN", &lk->lock_object, 0,
1208 lk->lk_recurse, file, line);
1209 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE |
1210 LK_TRYWIT(flags), file, line);
1211 TD_LOCKS_INC(curthread);
1216 if (flags & LK_INTERLOCK)
1217 class->lc_unlock(ilk);
1218 panic("%s: unknown lockmgr request 0x%x\n", __func__, op);
1221 if (flags & LK_INTERLOCK)
1222 class->lc_unlock(ilk);
1230 _lockmgr_disown(struct lock *lk, const char *file, int line)
1234 tid = (uintptr_t)curthread;
1235 _lockmgr_assert(lk, KA_XLOCKED | KA_NOTRECURSED, file, line);
1238 * If the owner is already LK_KERNPROC just skip the whole operation.
1240 if (LK_HOLDER(lk->lk_lock) != tid)
1242 lock_profile_release_lock(&lk->lock_object);
1243 LOCK_LOG_LOCK("XDISOWN", &lk->lock_object, 0, 0, file, line);
1244 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, file, line);
1245 TD_LOCKS_DEC(curthread);
1249 * In order to preserve waiters flags, just spin.
1253 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0);
1254 x &= LK_ALL_WAITERS;
1255 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x,
1263 lockmgr_printinfo(struct lock *lk)
1268 if (lk->lk_lock == LK_UNLOCKED)
1269 printf("lock type %s: UNLOCKED\n", lk->lock_object.lo_name);
1270 else if (lk->lk_lock & LK_SHARE)
1271 printf("lock type %s: SHARED (count %ju)\n",
1272 lk->lock_object.lo_name,
1273 (uintmax_t)LK_SHARERS(lk->lk_lock));
1275 td = lockmgr_xholder(lk);
1276 printf("lock type %s: EXCL by thread %p (pid %d)\n",
1277 lk->lock_object.lo_name, td, td->td_proc->p_pid);
1281 if (x & LK_EXCLUSIVE_WAITERS)
1282 printf(" with exclusive waiters pending\n");
1283 if (x & LK_SHARED_WAITERS)
1284 printf(" with shared waiters pending\n");
1285 if (x & LK_EXCLUSIVE_SPINNERS)
1286 printf(" with exclusive spinners pending\n");
1292 lockstatus(struct lock *lk)
1301 if ((x & LK_SHARE) == 0) {
1302 if (v == (uintptr_t)curthread || v == LK_KERNPROC)
1306 } else if (x == LK_UNLOCKED)
1312 #ifdef INVARIANT_SUPPORT
1314 FEATURE(invariant_support,
1315 "Support for modules compiled with INVARIANTS option");
1318 #undef _lockmgr_assert
1322 _lockmgr_assert(struct lock *lk, int what, const char *file, int line)
1326 if (panicstr != NULL)
1330 case KA_SLOCKED | KA_NOTRECURSED:
1331 case KA_SLOCKED | KA_RECURSED:
1334 case KA_LOCKED | KA_NOTRECURSED:
1335 case KA_LOCKED | KA_RECURSED:
1339 * We cannot trust WITNESS if the lock is held in exclusive
1340 * mode and a call to lockmgr_disown() happened.
1341 * Workaround this skipping the check if the lock is held in
1342 * exclusive mode even for the KA_LOCKED case.
1344 if (slocked || (lk->lk_lock & LK_SHARE)) {
1345 witness_assert(&lk->lock_object, what, file, line);
1349 if (lk->lk_lock == LK_UNLOCKED ||
1350 ((lk->lk_lock & LK_SHARE) == 0 && (slocked ||
1351 (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk)))))
1352 panic("Lock %s not %slocked @ %s:%d\n",
1353 lk->lock_object.lo_name, slocked ? "share" : "",
1356 if ((lk->lk_lock & LK_SHARE) == 0) {
1357 if (lockmgr_recursed(lk)) {
1358 if (what & KA_NOTRECURSED)
1359 panic("Lock %s recursed @ %s:%d\n",
1360 lk->lock_object.lo_name, file,
1362 } else if (what & KA_RECURSED)
1363 panic("Lock %s not recursed @ %s:%d\n",
1364 lk->lock_object.lo_name, file, line);
1368 case KA_XLOCKED | KA_NOTRECURSED:
1369 case KA_XLOCKED | KA_RECURSED:
1370 if (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk))
1371 panic("Lock %s not exclusively locked @ %s:%d\n",
1372 lk->lock_object.lo_name, file, line);
1373 if (lockmgr_recursed(lk)) {
1374 if (what & KA_NOTRECURSED)
1375 panic("Lock %s recursed @ %s:%d\n",
1376 lk->lock_object.lo_name, file, line);
1377 } else if (what & KA_RECURSED)
1378 panic("Lock %s not recursed @ %s:%d\n",
1379 lk->lock_object.lo_name, file, line);
1382 if (lockmgr_xlocked(lk) || lockmgr_disowned(lk))
1383 panic("Lock %s exclusively locked @ %s:%d\n",
1384 lk->lock_object.lo_name, file, line);
1387 panic("Unknown lockmgr assertion: %d @ %s:%d\n", what, file,
1395 lockmgr_chain(struct thread *td, struct thread **ownerp)
1401 if (LOCK_CLASS(&lk->lock_object) != &lock_class_lockmgr)
1403 db_printf("blocked on lockmgr %s", lk->lock_object.lo_name);
1404 if (lk->lk_lock & LK_SHARE)
1405 db_printf("SHARED (count %ju)\n",
1406 (uintmax_t)LK_SHARERS(lk->lk_lock));
1408 db_printf("EXCL\n");
1409 *ownerp = lockmgr_xholder(lk);
1415 db_show_lockmgr(struct lock_object *lock)
1420 lk = (struct lock *)lock;
1422 db_printf(" state: ");
1423 if (lk->lk_lock == LK_UNLOCKED)
1424 db_printf("UNLOCKED\n");
1425 else if (lk->lk_lock & LK_SHARE)
1426 db_printf("SLOCK: %ju\n", (uintmax_t)LK_SHARERS(lk->lk_lock));
1428 td = lockmgr_xholder(lk);
1429 if (td == (struct thread *)LK_KERNPROC)
1430 db_printf("XLOCK: LK_KERNPROC\n");
1432 db_printf("XLOCK: %p (tid %d, pid %d, \"%s\")\n", td,
1433 td->td_tid, td->td_proc->p_pid,
1434 td->td_proc->p_comm);
1435 if (lockmgr_recursed(lk))
1436 db_printf(" recursed: %d\n", lk->lk_recurse);
1438 db_printf(" waiters: ");
1439 switch (lk->lk_lock & LK_ALL_WAITERS) {
1440 case LK_SHARED_WAITERS:
1441 db_printf("shared\n");
1443 case LK_EXCLUSIVE_WAITERS:
1444 db_printf("exclusive\n");
1446 case LK_ALL_WAITERS:
1447 db_printf("shared and exclusive\n");
1450 db_printf("none\n");
1452 db_printf(" spinners: ");
1453 if (lk->lk_lock & LK_EXCLUSIVE_SPINNERS)
1454 db_printf("exclusive\n");
1456 db_printf("none\n");