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);
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 lockdestroy(struct lock *lk)
403 KASSERT(lk->lk_lock == LK_UNLOCKED, ("lockmgr still held"));
404 KASSERT(lk->lk_recurse == 0, ("lockmgr still recursed"));
405 KASSERT(lk->lk_exslpfail == 0, ("lockmgr still exclusive waiters"));
406 lock_destroy(&lk->lock_object);
410 __lockmgr_args(struct lock *lk, u_int flags, struct lock_object *ilk,
411 const char *wmesg, int pri, int timo, const char *file, int line)
414 struct lock_class *class;
418 int error, ipri, itimo, queue, wakeup_swapper;
419 #ifdef LOCK_PROFILING
420 uint64_t waittime = 0;
423 #ifdef ADAPTIVE_LOCKMGRS
424 volatile struct thread *owner;
425 u_int i, spintries = 0;
429 tid = (uintptr_t)curthread;
430 op = (flags & LK_TYPE_MASK);
431 iwmesg = (wmesg == LK_WMESG_DEFAULT) ? lk->lock_object.lo_name : wmesg;
432 ipri = (pri == LK_PRIO_DEFAULT) ? lk->lk_pri : pri;
433 itimo = (timo == LK_TIMO_DEFAULT) ? lk->lk_timo : timo;
435 MPASS((flags & ~LK_TOTAL_MASK) == 0);
436 KASSERT((op & (op - 1)) == 0,
437 ("%s: Invalid requested operation @ %s:%d", __func__, file, line));
438 KASSERT((flags & (LK_NOWAIT | LK_SLEEPFAIL)) == 0 ||
439 (op != LK_DOWNGRADE && op != LK_RELEASE),
440 ("%s: Invalid flags in regard of the operation desired @ %s:%d",
441 __func__, file, line));
442 KASSERT((flags & LK_INTERLOCK) == 0 || ilk != NULL,
443 ("%s: LK_INTERLOCK passed without valid interlock @ %s:%d",
444 __func__, file, line));
446 class = (flags & LK_INTERLOCK) ? LOCK_CLASS(ilk) : NULL;
447 if (panicstr != NULL) {
448 if (flags & LK_INTERLOCK)
449 class->lc_unlock(ilk);
453 if (op == LK_SHARED && (lk->lock_object.lo_flags & LK_NOSHARE))
459 if (LK_CAN_WITNESS(flags))
460 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER,
466 * If no other thread has an exclusive lock, or
467 * no exclusive waiter is present, bump the count of
468 * sharers. Since we have to preserve the state of
469 * waiters, if we fail to acquire the shared lock
470 * loop back and retry.
472 if (LK_CAN_SHARE(x)) {
473 if (atomic_cmpset_acq_ptr(&lk->lk_lock, x,
478 lock_profile_obtain_lock_failed(&lk->lock_object,
479 &contested, &waittime);
482 * If the lock is already held by curthread in
483 * exclusive way avoid a deadlock.
485 if (LK_HOLDER(x) == tid) {
487 "%s: %p already held in exclusive mode",
494 * If the lock is expected to not sleep just give up
497 if (LK_TRYOP(flags)) {
498 LOCK_LOG2(lk, "%s: %p fails the try operation",
504 #ifdef ADAPTIVE_LOCKMGRS
506 * If the owner is running on another CPU, spin until
507 * the owner stops running or the state of the lock
508 * changes. We need a double-state handle here
509 * because for a failed acquisition the lock can be
510 * either held in exclusive mode or shared mode
511 * (for the writer starvation avoidance technique).
513 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 &&
514 LK_HOLDER(x) != LK_KERNPROC) {
515 owner = (struct thread *)LK_HOLDER(x);
516 if (LOCK_LOG_TEST(&lk->lock_object, 0))
518 "%s: spinning on %p held by %p",
519 __func__, lk, owner);
522 * If we are holding also an interlock drop it
523 * in order to avoid a deadlock if the lockmgr
524 * owner is adaptively spinning on the
527 if (flags & LK_INTERLOCK) {
528 class->lc_unlock(ilk);
529 flags &= ~LK_INTERLOCK;
532 while (LK_HOLDER(lk->lk_lock) ==
533 (uintptr_t)owner && TD_IS_RUNNING(owner))
537 } else if (LK_CAN_ADAPT(lk, flags) &&
538 (x & LK_SHARE) != 0 && LK_SHARERS(x) &&
539 spintries < alk_retries) {
540 if (flags & LK_INTERLOCK) {
541 class->lc_unlock(ilk);
542 flags &= ~LK_INTERLOCK;
546 for (i = 0; i < alk_loops; i++) {
547 if (LOCK_LOG_TEST(&lk->lock_object, 0))
549 "%s: shared spinning on %p with %u and %u",
550 __func__, lk, spintries, i);
552 if ((x & LK_SHARE) == 0 ||
553 LK_CAN_SHARE(x) != 0)
564 * Acquire the sleepqueue chain lock because we
565 * probabilly will need to manipulate waiters flags.
567 sleepq_lock(&lk->lock_object);
571 * if the lock can be acquired in shared mode, try
574 if (LK_CAN_SHARE(x)) {
575 sleepq_release(&lk->lock_object);
579 #ifdef ADAPTIVE_LOCKMGRS
581 * The current lock owner might have started executing
582 * on another CPU (or the lock could have changed
583 * owner) while we were waiting on the turnstile
584 * chain lock. If so, drop the turnstile lock and try
587 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 &&
588 LK_HOLDER(x) != LK_KERNPROC) {
589 owner = (struct thread *)LK_HOLDER(x);
590 if (TD_IS_RUNNING(owner)) {
591 sleepq_release(&lk->lock_object);
598 * Try to set the LK_SHARED_WAITERS flag. If we fail,
599 * loop back and retry.
601 if ((x & LK_SHARED_WAITERS) == 0) {
602 if (!atomic_cmpset_acq_ptr(&lk->lk_lock, x,
603 x | LK_SHARED_WAITERS)) {
604 sleepq_release(&lk->lock_object);
607 LOCK_LOG2(lk, "%s: %p set shared waiters flag",
612 * As far as we have been unable to acquire the
613 * shared lock and the shared waiters flag is set,
616 error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo,
618 flags &= ~LK_INTERLOCK;
621 "%s: interrupted sleep for %p with %d",
622 __func__, lk, error);
625 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue",
629 lock_profile_obtain_lock_success(&lk->lock_object,
630 contested, waittime, file, line);
631 LOCK_LOG_LOCK("SLOCK", &lk->lock_object, 0, 0, file,
633 WITNESS_LOCK(&lk->lock_object, LK_TRYWIT(flags), file,
635 TD_LOCKS_INC(curthread);
636 TD_SLOCKS_INC(curthread);
641 _lockmgr_assert(lk, KA_SLOCKED, file, line);
643 x = v & LK_ALL_WAITERS;
644 v &= LK_EXCLUSIVE_SPINNERS;
647 * Try to switch from one shared lock to an exclusive one.
648 * We need to preserve waiters flags during the operation.
650 if (atomic_cmpset_ptr(&lk->lk_lock, LK_SHARERS_LOCK(1) | x | v,
652 LOCK_LOG_LOCK("XUPGRADE", &lk->lock_object, 0, 0, file,
654 WITNESS_UPGRADE(&lk->lock_object, LOP_EXCLUSIVE |
655 LK_TRYWIT(flags), file, line);
656 TD_SLOCKS_DEC(curthread);
661 * We have been unable to succeed in upgrading, so just
662 * give up the shared lock.
664 wakeup_swapper |= wakeupshlk(lk, file, line);
668 if (LK_CAN_WITNESS(flags))
669 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER |
670 LOP_EXCLUSIVE, file, line, ilk);
673 * If curthread already holds the lock and this one is
674 * allowed to recurse, simply recurse on it.
676 if (lockmgr_xlocked(lk)) {
677 if ((flags & LK_CANRECURSE) == 0 &&
678 (lk->lock_object.lo_flags & LO_RECURSABLE) == 0) {
681 * If the lock is expected to not panic just
682 * give up and return.
684 if (LK_TRYOP(flags)) {
686 "%s: %p fails the try operation",
691 if (flags & LK_INTERLOCK)
692 class->lc_unlock(ilk);
693 panic("%s: recursing on non recursive lockmgr %s @ %s:%d\n",
694 __func__, iwmesg, file, line);
697 LOCK_LOG2(lk, "%s: %p recursing", __func__, lk);
698 LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0,
699 lk->lk_recurse, file, line);
700 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE |
701 LK_TRYWIT(flags), file, line);
702 TD_LOCKS_INC(curthread);
706 while (!atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED,
708 lock_profile_obtain_lock_failed(&lk->lock_object,
709 &contested, &waittime);
712 * If the lock is expected to not sleep just give up
715 if (LK_TRYOP(flags)) {
716 LOCK_LOG2(lk, "%s: %p fails the try operation",
722 #ifdef ADAPTIVE_LOCKMGRS
724 * If the owner is running on another CPU, spin until
725 * the owner stops running or the state of the lock
729 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 &&
730 LK_HOLDER(x) != LK_KERNPROC) {
731 owner = (struct thread *)LK_HOLDER(x);
732 if (LOCK_LOG_TEST(&lk->lock_object, 0))
734 "%s: spinning on %p held by %p",
735 __func__, lk, owner);
738 * If we are holding also an interlock drop it
739 * in order to avoid a deadlock if the lockmgr
740 * owner is adaptively spinning on the
743 if (flags & LK_INTERLOCK) {
744 class->lc_unlock(ilk);
745 flags &= ~LK_INTERLOCK;
748 while (LK_HOLDER(lk->lk_lock) ==
749 (uintptr_t)owner && TD_IS_RUNNING(owner))
753 } else if (LK_CAN_ADAPT(lk, flags) &&
754 (x & LK_SHARE) != 0 && LK_SHARERS(x) &&
755 spintries < alk_retries) {
756 if ((x & LK_EXCLUSIVE_SPINNERS) == 0 &&
757 !atomic_cmpset_ptr(&lk->lk_lock, x,
758 x | LK_EXCLUSIVE_SPINNERS))
760 if (flags & LK_INTERLOCK) {
761 class->lc_unlock(ilk);
762 flags &= ~LK_INTERLOCK;
766 for (i = 0; i < alk_loops; i++) {
767 if (LOCK_LOG_TEST(&lk->lock_object, 0))
769 "%s: shared spinning on %p with %u and %u",
770 __func__, lk, spintries, i);
772 LK_EXCLUSIVE_SPINNERS) == 0)
783 * Acquire the sleepqueue chain lock because we
784 * probabilly will need to manipulate waiters flags.
786 sleepq_lock(&lk->lock_object);
790 * if the lock has been released while we spun on
791 * the sleepqueue chain lock just try again.
793 if (x == LK_UNLOCKED) {
794 sleepq_release(&lk->lock_object);
798 #ifdef ADAPTIVE_LOCKMGRS
800 * The current lock owner might have started executing
801 * on another CPU (or the lock could have changed
802 * owner) while we were waiting on the turnstile
803 * chain lock. If so, drop the turnstile lock and try
806 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 &&
807 LK_HOLDER(x) != LK_KERNPROC) {
808 owner = (struct thread *)LK_HOLDER(x);
809 if (TD_IS_RUNNING(owner)) {
810 sleepq_release(&lk->lock_object);
817 * The lock can be in the state where there is a
818 * pending queue of waiters, but still no owner.
819 * This happens when the lock is contested and an
820 * owner is going to claim the lock.
821 * If curthread is the one successfully acquiring it
822 * claim lock ownership and return, preserving waiters
825 v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS);
826 if ((x & ~v) == LK_UNLOCKED) {
827 v &= ~LK_EXCLUSIVE_SPINNERS;
828 if (atomic_cmpset_acq_ptr(&lk->lk_lock, x,
830 sleepq_release(&lk->lock_object);
832 "%s: %p claimed by a new writer",
836 sleepq_release(&lk->lock_object);
841 * Try to set the LK_EXCLUSIVE_WAITERS flag. If we
842 * fail, loop back and retry.
844 if ((x & LK_EXCLUSIVE_WAITERS) == 0) {
845 if (!atomic_cmpset_ptr(&lk->lk_lock, x,
846 x | LK_EXCLUSIVE_WAITERS)) {
847 sleepq_release(&lk->lock_object);
850 LOCK_LOG2(lk, "%s: %p set excl waiters flag",
855 * As far as we have been unable to acquire the
856 * exclusive lock and the exclusive waiters flag
857 * is set, we will sleep.
859 error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo,
861 flags &= ~LK_INTERLOCK;
864 "%s: interrupted sleep for %p with %d",
865 __func__, lk, error);
868 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue",
872 lock_profile_obtain_lock_success(&lk->lock_object,
873 contested, waittime, file, line);
874 LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0,
875 lk->lk_recurse, file, line);
876 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE |
877 LK_TRYWIT(flags), file, line);
878 TD_LOCKS_INC(curthread);
883 _lockmgr_assert(lk, KA_XLOCKED | KA_NOTRECURSED, file, line);
884 LOCK_LOG_LOCK("XDOWNGRADE", &lk->lock_object, 0, 0, file, line);
885 WITNESS_DOWNGRADE(&lk->lock_object, 0, file, line);
886 TD_SLOCKS_INC(curthread);
889 * In order to preserve waiters flags, just spin.
893 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0);
895 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x,
896 LK_SHARERS_LOCK(1) | x))
902 _lockmgr_assert(lk, KA_LOCKED, file, line);
905 if ((x & LK_SHARE) == 0) {
908 * As first option, treact the lock as if it has not
910 * Fix-up the tid var if the lock has been disowned.
912 if (LK_HOLDER(x) == LK_KERNPROC)
915 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE,
917 TD_LOCKS_DEC(curthread);
919 LOCK_LOG_LOCK("XUNLOCK", &lk->lock_object, 0,
920 lk->lk_recurse, file, line);
923 * The lock is held in exclusive mode.
924 * If the lock is recursed also, then unrecurse it.
926 if (lockmgr_xlocked(lk) && lockmgr_recursed(lk)) {
927 LOCK_LOG2(lk, "%s: %p unrecursing", __func__,
932 if (tid != LK_KERNPROC)
933 lock_profile_release_lock(&lk->lock_object);
935 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid,
939 sleepq_lock(&lk->lock_object);
944 * If the lock has exclusive waiters, give them
945 * preference in order to avoid deadlock with
947 * If interruptible sleeps left the exclusive queue
948 * empty avoid a starvation for the threads sleeping
949 * on the shared queue by giving them precedence
950 * and cleaning up the exclusive waiters bit anyway.
951 * Please note that lk_exslpfail count may be lying
952 * about the real number of waiters with the
953 * LK_SLEEPFAIL flag on because they may be used in
954 * conjuction with interruptible sleeps so
955 * lk_exslpfail might be considered an 'upper limit'
956 * bound, including the edge cases.
958 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0);
959 realexslp = sleepq_sleepcnt(&lk->lock_object,
961 if ((x & LK_EXCLUSIVE_WAITERS) != 0 && realexslp != 0) {
962 if (lk->lk_exslpfail < realexslp) {
963 lk->lk_exslpfail = 0;
964 queue = SQ_EXCLUSIVE_QUEUE;
965 v |= (x & LK_SHARED_WAITERS);
967 lk->lk_exslpfail = 0;
969 "%s: %p has only LK_SLEEPFAIL sleepers",
972 "%s: %p waking up threads on the exclusive queue",
975 sleepq_broadcast(&lk->lock_object,
976 SLEEPQ_LK, 0, SQ_EXCLUSIVE_QUEUE);
977 queue = SQ_SHARED_QUEUE;
982 * Exclusive waiters sleeping with LK_SLEEPFAIL
983 * on and using interruptible sleeps/timeout
984 * may have left spourious lk_exslpfail counts
985 * on, so clean it up anyway.
987 lk->lk_exslpfail = 0;
988 queue = SQ_SHARED_QUEUE;
992 "%s: %p waking up threads on the %s queue",
993 __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" :
995 atomic_store_rel_ptr(&lk->lk_lock, v);
996 wakeup_swapper |= sleepq_broadcast(&lk->lock_object,
997 SLEEPQ_LK, 0, queue);
998 sleepq_release(&lk->lock_object);
1001 wakeup_swapper = wakeupshlk(lk, file, line);
1004 if (LK_CAN_WITNESS(flags))
1005 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER |
1006 LOP_EXCLUSIVE, file, line, ilk);
1009 * Trying to drain a lock we already own will result in a
1012 if (lockmgr_xlocked(lk)) {
1013 if (flags & LK_INTERLOCK)
1014 class->lc_unlock(ilk);
1015 panic("%s: draining %s with the lock held @ %s:%d\n",
1016 __func__, iwmesg, file, line);
1019 while (!atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid)) {
1020 lock_profile_obtain_lock_failed(&lk->lock_object,
1021 &contested, &waittime);
1024 * If the lock is expected to not sleep just give up
1027 if (LK_TRYOP(flags)) {
1028 LOCK_LOG2(lk, "%s: %p fails the try operation",
1035 * Acquire the sleepqueue chain lock because we
1036 * probabilly will need to manipulate waiters flags.
1038 sleepq_lock(&lk->lock_object);
1042 * if the lock has been released while we spun on
1043 * the sleepqueue chain lock just try again.
1045 if (x == LK_UNLOCKED) {
1046 sleepq_release(&lk->lock_object);
1050 v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS);
1051 if ((x & ~v) == LK_UNLOCKED) {
1052 v = (x & ~LK_EXCLUSIVE_SPINNERS);
1055 * If interruptible sleeps left the exclusive
1056 * queue empty avoid a starvation for the
1057 * threads sleeping on the shared queue by
1058 * giving them precedence and cleaning up the
1059 * exclusive waiters bit anyway.
1060 * Please note that lk_exslpfail count may be
1061 * lying about the real number of waiters with
1062 * the LK_SLEEPFAIL flag on because they may
1063 * be used in conjuction with interruptible
1064 * sleeps so lk_exslpfail might be considered
1065 * an 'upper limit' bound, including the edge
1068 if (v & LK_EXCLUSIVE_WAITERS) {
1069 queue = SQ_EXCLUSIVE_QUEUE;
1070 v &= ~LK_EXCLUSIVE_WAITERS;
1074 * Exclusive waiters sleeping with
1075 * LK_SLEEPFAIL on and using
1076 * interruptible sleeps/timeout may
1077 * have left spourious lk_exslpfail
1078 * counts on, so clean it up anyway.
1080 MPASS(v & LK_SHARED_WAITERS);
1081 lk->lk_exslpfail = 0;
1082 queue = SQ_SHARED_QUEUE;
1083 v &= ~LK_SHARED_WAITERS;
1085 if (queue == SQ_EXCLUSIVE_QUEUE) {
1087 sleepq_sleepcnt(&lk->lock_object,
1088 SQ_EXCLUSIVE_QUEUE);
1089 if (lk->lk_exslpfail >= realexslp) {
1090 lk->lk_exslpfail = 0;
1091 queue = SQ_SHARED_QUEUE;
1092 v &= ~LK_SHARED_WAITERS;
1093 if (realexslp != 0) {
1095 "%s: %p has only LK_SLEEPFAIL sleepers",
1098 "%s: %p waking up threads on the exclusive queue",
1104 SQ_EXCLUSIVE_QUEUE);
1107 lk->lk_exslpfail = 0;
1109 if (!atomic_cmpset_ptr(&lk->lk_lock, x, v)) {
1110 sleepq_release(&lk->lock_object);
1114 "%s: %p waking up all threads on the %s queue",
1115 __func__, lk, queue == SQ_SHARED_QUEUE ?
1116 "shared" : "exclusive");
1117 wakeup_swapper |= sleepq_broadcast(
1118 &lk->lock_object, SLEEPQ_LK, 0, queue);
1121 * If shared waiters have been woken up we need
1122 * to wait for one of them to acquire the lock
1123 * before to set the exclusive waiters in
1124 * order to avoid a deadlock.
1126 if (queue == SQ_SHARED_QUEUE) {
1127 for (v = lk->lk_lock;
1128 (v & LK_SHARE) && !LK_SHARERS(v);
1135 * Try to set the LK_EXCLUSIVE_WAITERS flag. If we
1136 * fail, loop back and retry.
1138 if ((x & LK_EXCLUSIVE_WAITERS) == 0) {
1139 if (!atomic_cmpset_ptr(&lk->lk_lock, x,
1140 x | LK_EXCLUSIVE_WAITERS)) {
1141 sleepq_release(&lk->lock_object);
1144 LOCK_LOG2(lk, "%s: %p set drain waiters flag",
1149 * As far as we have been unable to acquire the
1150 * exclusive lock and the exclusive waiters flag
1151 * is set, we will sleep.
1153 if (flags & LK_INTERLOCK) {
1154 class->lc_unlock(ilk);
1155 flags &= ~LK_INTERLOCK;
1158 sleepq_add(&lk->lock_object, NULL, iwmesg, SLEEPQ_LK,
1159 SQ_EXCLUSIVE_QUEUE);
1160 sleepq_wait(&lk->lock_object, ipri & PRIMASK);
1162 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue",
1167 lock_profile_obtain_lock_success(&lk->lock_object,
1168 contested, waittime, file, line);
1169 LOCK_LOG_LOCK("DRAIN", &lk->lock_object, 0,
1170 lk->lk_recurse, file, line);
1171 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE |
1172 LK_TRYWIT(flags), file, line);
1173 TD_LOCKS_INC(curthread);
1178 if (flags & LK_INTERLOCK)
1179 class->lc_unlock(ilk);
1180 panic("%s: unknown lockmgr request 0x%x\n", __func__, op);
1183 if (flags & LK_INTERLOCK)
1184 class->lc_unlock(ilk);
1192 _lockmgr_disown(struct lock *lk, const char *file, int line)
1196 tid = (uintptr_t)curthread;
1197 _lockmgr_assert(lk, KA_XLOCKED | KA_NOTRECURSED, file, line);
1200 * If the owner is already LK_KERNPROC just skip the whole operation.
1202 if (LK_HOLDER(lk->lk_lock) != tid)
1204 lock_profile_release_lock(&lk->lock_object);
1205 LOCK_LOG_LOCK("XDISOWN", &lk->lock_object, 0, 0, file, line);
1206 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, file, line);
1207 TD_LOCKS_DEC(curthread);
1211 * In order to preserve waiters flags, just spin.
1215 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0);
1216 x &= LK_ALL_WAITERS;
1217 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x,
1225 lockmgr_printinfo(struct lock *lk)
1230 if (lk->lk_lock == LK_UNLOCKED)
1231 printf("lock type %s: UNLOCKED\n", lk->lock_object.lo_name);
1232 else if (lk->lk_lock & LK_SHARE)
1233 printf("lock type %s: SHARED (count %ju)\n",
1234 lk->lock_object.lo_name,
1235 (uintmax_t)LK_SHARERS(lk->lk_lock));
1237 td = lockmgr_xholder(lk);
1238 printf("lock type %s: EXCL by thread %p (pid %d)\n",
1239 lk->lock_object.lo_name, td, td->td_proc->p_pid);
1243 if (x & LK_EXCLUSIVE_WAITERS)
1244 printf(" with exclusive waiters pending\n");
1245 if (x & LK_SHARED_WAITERS)
1246 printf(" with shared waiters pending\n");
1247 if (x & LK_EXCLUSIVE_SPINNERS)
1248 printf(" with exclusive spinners pending\n");
1254 lockstatus(struct lock *lk)
1263 if ((x & LK_SHARE) == 0) {
1264 if (v == (uintptr_t)curthread || v == LK_KERNPROC)
1268 } else if (x == LK_UNLOCKED)
1274 #ifdef INVARIANT_SUPPORT
1276 #undef _lockmgr_assert
1280 _lockmgr_assert(struct lock *lk, int what, const char *file, int line)
1284 if (panicstr != NULL)
1288 case KA_SLOCKED | KA_NOTRECURSED:
1289 case KA_SLOCKED | KA_RECURSED:
1292 case KA_LOCKED | KA_NOTRECURSED:
1293 case KA_LOCKED | KA_RECURSED:
1297 * We cannot trust WITNESS if the lock is held in exclusive
1298 * mode and a call to lockmgr_disown() happened.
1299 * Workaround this skipping the check if the lock is held in
1300 * exclusive mode even for the KA_LOCKED case.
1302 if (slocked || (lk->lk_lock & LK_SHARE)) {
1303 witness_assert(&lk->lock_object, what, file, line);
1307 if (lk->lk_lock == LK_UNLOCKED ||
1308 ((lk->lk_lock & LK_SHARE) == 0 && (slocked ||
1309 (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk)))))
1310 panic("Lock %s not %slocked @ %s:%d\n",
1311 lk->lock_object.lo_name, slocked ? "share" : "",
1314 if ((lk->lk_lock & LK_SHARE) == 0) {
1315 if (lockmgr_recursed(lk)) {
1316 if (what & KA_NOTRECURSED)
1317 panic("Lock %s recursed @ %s:%d\n",
1318 lk->lock_object.lo_name, file,
1320 } else if (what & KA_RECURSED)
1321 panic("Lock %s not recursed @ %s:%d\n",
1322 lk->lock_object.lo_name, file, line);
1326 case KA_XLOCKED | KA_NOTRECURSED:
1327 case KA_XLOCKED | KA_RECURSED:
1328 if (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk))
1329 panic("Lock %s not exclusively locked @ %s:%d\n",
1330 lk->lock_object.lo_name, file, line);
1331 if (lockmgr_recursed(lk)) {
1332 if (what & KA_NOTRECURSED)
1333 panic("Lock %s recursed @ %s:%d\n",
1334 lk->lock_object.lo_name, file, line);
1335 } else if (what & KA_RECURSED)
1336 panic("Lock %s not recursed @ %s:%d\n",
1337 lk->lock_object.lo_name, file, line);
1340 if (lockmgr_xlocked(lk) || lockmgr_disowned(lk))
1341 panic("Lock %s exclusively locked @ %s:%d\n",
1342 lk->lock_object.lo_name, file, line);
1345 panic("Unknown lockmgr assertion: %d @ %s:%d\n", what, file,
1353 lockmgr_chain(struct thread *td, struct thread **ownerp)
1359 if (LOCK_CLASS(&lk->lock_object) != &lock_class_lockmgr)
1361 db_printf("blocked on lockmgr %s", lk->lock_object.lo_name);
1362 if (lk->lk_lock & LK_SHARE)
1363 db_printf("SHARED (count %ju)\n",
1364 (uintmax_t)LK_SHARERS(lk->lk_lock));
1366 db_printf("EXCL\n");
1367 *ownerp = lockmgr_xholder(lk);
1373 db_show_lockmgr(struct lock_object *lock)
1378 lk = (struct lock *)lock;
1380 db_printf(" state: ");
1381 if (lk->lk_lock == LK_UNLOCKED)
1382 db_printf("UNLOCKED\n");
1383 else if (lk->lk_lock & LK_SHARE)
1384 db_printf("SLOCK: %ju\n", (uintmax_t)LK_SHARERS(lk->lk_lock));
1386 td = lockmgr_xholder(lk);
1387 if (td == (struct thread *)LK_KERNPROC)
1388 db_printf("XLOCK: LK_KERNPROC\n");
1390 db_printf("XLOCK: %p (tid %d, pid %d, \"%s\")\n", td,
1391 td->td_tid, td->td_proc->p_pid,
1392 td->td_proc->p_comm);
1393 if (lockmgr_recursed(lk))
1394 db_printf(" recursed: %d\n", lk->lk_recurse);
1396 db_printf(" waiters: ");
1397 switch (lk->lk_lock & LK_ALL_WAITERS) {
1398 case LK_SHARED_WAITERS:
1399 db_printf("shared\n");
1401 case LK_EXCLUSIVE_WAITERS:
1402 db_printf("exclusive\n");
1404 case LK_ALL_WAITERS:
1405 db_printf("shared and exclusive\n");
1408 db_printf("none\n");
1410 db_printf(" spinners: ");
1411 if (lk->lk_lock & LK_EXCLUSIVE_SPINNERS)
1412 db_printf("exclusive\n");
1414 db_printf("none\n");