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_hwpmc_hooks.h"
32 #include "opt_kdtrace.h"
34 #include <sys/cdefs.h>
35 __FBSDID("$FreeBSD$");
37 #include <sys/param.h>
41 #include <sys/lock_profile.h>
42 #include <sys/lockmgr.h>
43 #include <sys/mutex.h>
45 #include <sys/sleepqueue.h>
47 #include <sys/stack.h>
49 #include <sys/sysctl.h>
50 #include <sys/systm.h>
52 #include <machine/cpu.h>
59 #include <sys/pmckern.h>
60 PMC_SOFT_DECLARE( , , lock, failed);
63 CTASSERT(((LK_ADAPTIVE | LK_NOSHARE) & LO_CLASSFLAGS) ==
64 (LK_ADAPTIVE | LK_NOSHARE));
65 CTASSERT(LK_UNLOCKED == (LK_UNLOCKED &
66 ~(LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS)));
68 #define SQ_EXCLUSIVE_QUEUE 0
69 #define SQ_SHARED_QUEUE 1
72 #define _lockmgr_assert(lk, what, file, line)
73 #define TD_LOCKS_INC(td)
74 #define TD_LOCKS_DEC(td)
76 #define TD_LOCKS_INC(td) ((td)->td_locks++)
77 #define TD_LOCKS_DEC(td) ((td)->td_locks--)
79 #define TD_SLOCKS_INC(td) ((td)->td_lk_slocks++)
80 #define TD_SLOCKS_DEC(td) ((td)->td_lk_slocks--)
83 #define STACK_PRINT(lk)
84 #define STACK_SAVE(lk)
85 #define STACK_ZERO(lk)
87 #define STACK_PRINT(lk) stack_print_ddb(&(lk)->lk_stack)
88 #define STACK_SAVE(lk) stack_save(&(lk)->lk_stack)
89 #define STACK_ZERO(lk) stack_zero(&(lk)->lk_stack)
92 #define LOCK_LOG2(lk, string, arg1, arg2) \
93 if (LOCK_LOG_TEST(&(lk)->lock_object, 0)) \
94 CTR2(KTR_LOCK, (string), (arg1), (arg2))
95 #define LOCK_LOG3(lk, string, arg1, arg2, arg3) \
96 if (LOCK_LOG_TEST(&(lk)->lock_object, 0)) \
97 CTR3(KTR_LOCK, (string), (arg1), (arg2), (arg3))
99 #define GIANT_DECLARE \
101 WITNESS_SAVE_DECL(Giant)
102 #define GIANT_RESTORE() do { \
106 WITNESS_RESTORE(&Giant.lock_object, Giant); \
109 #define GIANT_SAVE() do { \
110 if (mtx_owned(&Giant)) { \
111 WITNESS_SAVE(&Giant.lock_object, Giant); \
112 while (mtx_owned(&Giant)) { \
114 mtx_unlock(&Giant); \
119 #define LK_CAN_SHARE(x) \
120 (((x) & LK_SHARE) && (((x) & LK_EXCLUSIVE_WAITERS) == 0 || \
121 ((x) & LK_EXCLUSIVE_SPINNERS) == 0 || \
122 curthread->td_lk_slocks || (curthread->td_pflags & TDP_DEADLKTREAT)))
123 #define LK_TRYOP(x) \
126 #define LK_CAN_WITNESS(x) \
127 (((x) & LK_NOWITNESS) == 0 && !LK_TRYOP(x))
128 #define LK_TRYWIT(x) \
129 (LK_TRYOP(x) ? LOP_TRYLOCK : 0)
131 #define LK_CAN_ADAPT(lk, f) \
132 (((lk)->lock_object.lo_flags & LK_ADAPTIVE) != 0 && \
133 ((f) & LK_SLEEPFAIL) == 0)
135 #define lockmgr_disowned(lk) \
136 (((lk)->lk_lock & ~(LK_FLAGMASK & ~LK_SHARE)) == LK_KERNPROC)
138 #define lockmgr_xlocked(lk) \
139 (((lk)->lk_lock & ~(LK_FLAGMASK & ~LK_SHARE)) == (uintptr_t)curthread)
141 static void assert_lockmgr(const struct lock_object *lock, int how);
143 static void db_show_lockmgr(const struct lock_object *lock);
145 static void lock_lockmgr(struct lock_object *lock, uintptr_t how);
147 static int owner_lockmgr(const struct lock_object *lock,
148 struct thread **owner);
150 static uintptr_t unlock_lockmgr(struct lock_object *lock);
152 struct lock_class lock_class_lockmgr = {
153 .lc_name = "lockmgr",
154 .lc_flags = LC_RECURSABLE | LC_SLEEPABLE | LC_SLEEPLOCK | LC_UPGRADABLE,
155 .lc_assert = assert_lockmgr,
157 .lc_ddb_show = db_show_lockmgr,
159 .lc_lock = lock_lockmgr,
160 .lc_unlock = unlock_lockmgr,
162 .lc_owner = owner_lockmgr,
166 #ifdef ADAPTIVE_LOCKMGRS
167 static u_int alk_retries = 10;
168 static u_int alk_loops = 10000;
169 static SYSCTL_NODE(_debug, OID_AUTO, lockmgr, CTLFLAG_RD, NULL,
170 "lockmgr debugging");
171 SYSCTL_UINT(_debug_lockmgr, OID_AUTO, retries, CTLFLAG_RW, &alk_retries, 0, "");
172 SYSCTL_UINT(_debug_lockmgr, OID_AUTO, loops, CTLFLAG_RW, &alk_loops, 0, "");
175 static __inline struct thread *
176 lockmgr_xholder(const struct lock *lk)
181 return ((x & LK_SHARE) ? NULL : (struct thread *)LK_HOLDER(x));
185 * It assumes sleepq_lock held and returns with this one unheld.
186 * It also assumes the generic interlock is sane and previously checked.
187 * If LK_INTERLOCK is specified the interlock is not reacquired after the
191 sleeplk(struct lock *lk, u_int flags, struct lock_object *ilk,
192 const char *wmesg, int pri, int timo, int queue)
195 struct lock_class *class;
198 class = (flags & LK_INTERLOCK) ? LOCK_CLASS(ilk) : NULL;
199 catch = pri & PCATCH;
203 LOCK_LOG3(lk, "%s: %p blocking on the %s sleepqueue", __func__, lk,
204 (queue == SQ_EXCLUSIVE_QUEUE) ? "exclusive" : "shared");
206 if (flags & LK_INTERLOCK)
207 class->lc_unlock(ilk);
208 if (queue == SQ_EXCLUSIVE_QUEUE && (flags & LK_SLEEPFAIL) != 0)
211 sleepq_add(&lk->lock_object, NULL, wmesg, SLEEPQ_LK | (catch ?
212 SLEEPQ_INTERRUPTIBLE : 0), queue);
213 if ((flags & LK_TIMELOCK) && timo)
214 sleepq_set_timeout(&lk->lock_object, timo);
217 * Decisional switch for real sleeping.
219 if ((flags & LK_TIMELOCK) && timo && catch)
220 error = sleepq_timedwait_sig(&lk->lock_object, pri);
221 else if ((flags & LK_TIMELOCK) && timo)
222 error = sleepq_timedwait(&lk->lock_object, pri);
224 error = sleepq_wait_sig(&lk->lock_object, pri);
226 sleepq_wait(&lk->lock_object, pri);
228 if ((flags & LK_SLEEPFAIL) && error == 0)
235 wakeupshlk(struct lock *lk, const char *file, int line)
239 int queue, wakeup_swapper;
241 WITNESS_UNLOCK(&lk->lock_object, 0, file, line);
242 LOCK_LOG_LOCK("SUNLOCK", &lk->lock_object, 0, 0, file, line);
249 * If there is more than one shared lock held, just drop one
252 if (LK_SHARERS(x) > 1) {
253 if (atomic_cmpset_rel_ptr(&lk->lk_lock, x,
260 * If there are not waiters on the exclusive queue, drop the
263 if ((x & LK_ALL_WAITERS) == 0) {
264 MPASS((x & ~LK_EXCLUSIVE_SPINNERS) ==
266 if (atomic_cmpset_rel_ptr(&lk->lk_lock, x, LK_UNLOCKED))
272 * We should have a sharer with waiters, so enter the hard
273 * path in order to handle wakeups correctly.
275 sleepq_lock(&lk->lock_object);
276 x = lk->lk_lock & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS);
280 * If the lock has exclusive waiters, give them preference in
281 * order to avoid deadlock with shared runners up.
282 * If interruptible sleeps left the exclusive queue empty
283 * avoid a starvation for the threads sleeping on the shared
284 * queue by giving them precedence and cleaning up the
285 * exclusive waiters bit anyway.
286 * Please note that lk_exslpfail count may be lying about
287 * the real number of waiters with the LK_SLEEPFAIL flag on
288 * because they may be used in conjuction with interruptible
289 * sleeps so lk_exslpfail might be considered an 'upper limit'
290 * bound, including the edge cases.
292 realexslp = sleepq_sleepcnt(&lk->lock_object,
294 if ((x & LK_EXCLUSIVE_WAITERS) != 0 && realexslp != 0) {
295 if (lk->lk_exslpfail < realexslp) {
296 lk->lk_exslpfail = 0;
297 queue = SQ_EXCLUSIVE_QUEUE;
298 v |= (x & LK_SHARED_WAITERS);
300 lk->lk_exslpfail = 0;
302 "%s: %p has only LK_SLEEPFAIL sleepers",
305 "%s: %p waking up threads on the exclusive queue",
308 sleepq_broadcast(&lk->lock_object,
309 SLEEPQ_LK, 0, SQ_EXCLUSIVE_QUEUE);
310 queue = SQ_SHARED_QUEUE;
316 * Exclusive waiters sleeping with LK_SLEEPFAIL on
317 * and using interruptible sleeps/timeout may have
318 * left spourious lk_exslpfail counts on, so clean
321 lk->lk_exslpfail = 0;
322 queue = SQ_SHARED_QUEUE;
325 if (!atomic_cmpset_rel_ptr(&lk->lk_lock, LK_SHARERS_LOCK(1) | x,
327 sleepq_release(&lk->lock_object);
330 LOCK_LOG3(lk, "%s: %p waking up threads on the %s queue",
331 __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" :
333 wakeup_swapper |= sleepq_broadcast(&lk->lock_object, SLEEPQ_LK,
335 sleepq_release(&lk->lock_object);
339 lock_profile_release_lock(&lk->lock_object);
340 TD_LOCKS_DEC(curthread);
341 TD_SLOCKS_DEC(curthread);
342 return (wakeup_swapper);
346 assert_lockmgr(const struct lock_object *lock, int what)
349 panic("lockmgr locks do not support assertions");
353 lock_lockmgr(struct lock_object *lock, uintptr_t how)
356 panic("lockmgr locks do not support sleep interlocking");
360 unlock_lockmgr(struct lock_object *lock)
363 panic("lockmgr locks do not support sleep interlocking");
368 owner_lockmgr(const struct lock_object *lock, struct thread **owner)
371 panic("lockmgr locks do not support owner inquiring");
376 lockinit(struct lock *lk, int pri, const char *wmesg, int timo, int flags)
380 MPASS((flags & ~LK_INIT_MASK) == 0);
381 ASSERT_ATOMIC_LOAD_PTR(lk->lk_lock,
382 ("%s: lockmgr not aligned for %s: %p", __func__, wmesg,
385 iflags = LO_SLEEPABLE | LO_UPGRADABLE;
386 if (flags & LK_CANRECURSE)
387 iflags |= LO_RECURSABLE;
388 if ((flags & LK_NODUP) == 0)
390 if (flags & LK_NOPROFILE)
391 iflags |= LO_NOPROFILE;
392 if ((flags & LK_NOWITNESS) == 0)
393 iflags |= LO_WITNESS;
394 if (flags & LK_QUIET)
396 if (flags & LK_IS_VNODE)
397 iflags |= LO_IS_VNODE;
398 iflags |= flags & (LK_ADAPTIVE | LK_NOSHARE);
400 lock_init(&lk->lock_object, &lock_class_lockmgr, wmesg, NULL, iflags);
401 lk->lk_lock = LK_UNLOCKED;
403 lk->lk_exslpfail = 0;
410 * XXX: Gross hacks to manipulate external lock flags after
411 * initialization. Used for certain vnode and buf locks.
414 lockallowshare(struct lock *lk)
417 lockmgr_assert(lk, KA_XLOCKED);
418 lk->lock_object.lo_flags &= ~LK_NOSHARE;
422 lockallowrecurse(struct lock *lk)
425 lockmgr_assert(lk, KA_XLOCKED);
426 lk->lock_object.lo_flags |= LO_RECURSABLE;
430 lockdisablerecurse(struct lock *lk)
433 lockmgr_assert(lk, KA_XLOCKED);
434 lk->lock_object.lo_flags &= ~LO_RECURSABLE;
438 lockdestroy(struct lock *lk)
441 KASSERT(lk->lk_lock == LK_UNLOCKED, ("lockmgr still held"));
442 KASSERT(lk->lk_recurse == 0, ("lockmgr still recursed"));
443 KASSERT(lk->lk_exslpfail == 0, ("lockmgr still exclusive waiters"));
444 lock_destroy(&lk->lock_object);
448 __lockmgr_args(struct lock *lk, u_int flags, struct lock_object *ilk,
449 const char *wmesg, int pri, int timo, const char *file, int line)
452 struct lock_class *class;
456 int error, ipri, itimo, queue, wakeup_swapper;
457 #ifdef LOCK_PROFILING
458 uint64_t waittime = 0;
461 #ifdef ADAPTIVE_LOCKMGRS
462 volatile struct thread *owner;
463 u_int i, spintries = 0;
467 tid = (uintptr_t)curthread;
468 op = (flags & LK_TYPE_MASK);
469 iwmesg = (wmesg == LK_WMESG_DEFAULT) ? lk->lock_object.lo_name : wmesg;
470 ipri = (pri == LK_PRIO_DEFAULT) ? lk->lk_pri : pri;
471 itimo = (timo == LK_TIMO_DEFAULT) ? lk->lk_timo : timo;
473 MPASS((flags & ~LK_TOTAL_MASK) == 0);
474 KASSERT((op & (op - 1)) == 0,
475 ("%s: Invalid requested operation @ %s:%d", __func__, file, line));
476 KASSERT((flags & (LK_NOWAIT | LK_SLEEPFAIL)) == 0 ||
477 (op != LK_DOWNGRADE && op != LK_RELEASE),
478 ("%s: Invalid flags in regard of the operation desired @ %s:%d",
479 __func__, file, line));
480 KASSERT((flags & LK_INTERLOCK) == 0 || ilk != NULL,
481 ("%s: LK_INTERLOCK passed without valid interlock @ %s:%d",
482 __func__, file, line));
483 KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(curthread),
484 ("%s: idle thread %p on lockmgr %s @ %s:%d", __func__, curthread,
485 lk->lock_object.lo_name, file, line));
487 class = (flags & LK_INTERLOCK) ? LOCK_CLASS(ilk) : NULL;
488 if (panicstr != NULL) {
489 if (flags & LK_INTERLOCK)
490 class->lc_unlock(ilk);
494 if (lk->lock_object.lo_flags & LK_NOSHARE) {
502 _lockmgr_assert(lk, KA_XLOCKED | KA_NOTRECURSED,
504 if (flags & LK_INTERLOCK)
505 class->lc_unlock(ilk);
513 if (LK_CAN_WITNESS(flags))
514 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER,
515 file, line, flags & LK_INTERLOCK ? ilk : NULL);
520 * If no other thread has an exclusive lock, or
521 * no exclusive waiter is present, bump the count of
522 * sharers. Since we have to preserve the state of
523 * waiters, if we fail to acquire the shared lock
524 * loop back and retry.
526 if (LK_CAN_SHARE(x)) {
527 if (atomic_cmpset_acq_ptr(&lk->lk_lock, x,
533 PMC_SOFT_CALL( , , lock, failed);
535 lock_profile_obtain_lock_failed(&lk->lock_object,
536 &contested, &waittime);
539 * If the lock is already held by curthread in
540 * exclusive way avoid a deadlock.
542 if (LK_HOLDER(x) == tid) {
544 "%s: %p already held in exclusive mode",
551 * If the lock is expected to not sleep just give up
554 if (LK_TRYOP(flags)) {
555 LOCK_LOG2(lk, "%s: %p fails the try operation",
561 #ifdef ADAPTIVE_LOCKMGRS
563 * If the owner is running on another CPU, spin until
564 * the owner stops running or the state of the lock
565 * changes. We need a double-state handle here
566 * because for a failed acquisition the lock can be
567 * either held in exclusive mode or shared mode
568 * (for the writer starvation avoidance technique).
570 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 &&
571 LK_HOLDER(x) != LK_KERNPROC) {
572 owner = (struct thread *)LK_HOLDER(x);
573 if (LOCK_LOG_TEST(&lk->lock_object, 0))
575 "%s: spinning on %p held by %p",
576 __func__, lk, owner);
579 * If we are holding also an interlock drop it
580 * in order to avoid a deadlock if the lockmgr
581 * owner is adaptively spinning on the
584 if (flags & LK_INTERLOCK) {
585 class->lc_unlock(ilk);
586 flags &= ~LK_INTERLOCK;
589 while (LK_HOLDER(lk->lk_lock) ==
590 (uintptr_t)owner && TD_IS_RUNNING(owner))
594 } else if (LK_CAN_ADAPT(lk, flags) &&
595 (x & LK_SHARE) != 0 && LK_SHARERS(x) &&
596 spintries < alk_retries) {
597 if (flags & LK_INTERLOCK) {
598 class->lc_unlock(ilk);
599 flags &= ~LK_INTERLOCK;
603 for (i = 0; i < alk_loops; i++) {
604 if (LOCK_LOG_TEST(&lk->lock_object, 0))
606 "%s: shared spinning on %p with %u and %u",
607 __func__, lk, spintries, i);
609 if ((x & LK_SHARE) == 0 ||
610 LK_CAN_SHARE(x) != 0)
621 * Acquire the sleepqueue chain lock because we
622 * probabilly will need to manipulate waiters flags.
624 sleepq_lock(&lk->lock_object);
628 * if the lock can be acquired in shared mode, try
631 if (LK_CAN_SHARE(x)) {
632 sleepq_release(&lk->lock_object);
636 #ifdef ADAPTIVE_LOCKMGRS
638 * The current lock owner might have started executing
639 * on another CPU (or the lock could have changed
640 * owner) while we were waiting on the turnstile
641 * chain lock. If so, drop the turnstile lock and try
644 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 &&
645 LK_HOLDER(x) != LK_KERNPROC) {
646 owner = (struct thread *)LK_HOLDER(x);
647 if (TD_IS_RUNNING(owner)) {
648 sleepq_release(&lk->lock_object);
655 * Try to set the LK_SHARED_WAITERS flag. If we fail,
656 * loop back and retry.
658 if ((x & LK_SHARED_WAITERS) == 0) {
659 if (!atomic_cmpset_acq_ptr(&lk->lk_lock, x,
660 x | LK_SHARED_WAITERS)) {
661 sleepq_release(&lk->lock_object);
664 LOCK_LOG2(lk, "%s: %p set shared waiters flag",
669 * As far as we have been unable to acquire the
670 * shared lock and the shared waiters flag is set,
673 error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo,
675 flags &= ~LK_INTERLOCK;
678 "%s: interrupted sleep for %p with %d",
679 __func__, lk, error);
682 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue",
686 lock_profile_obtain_lock_success(&lk->lock_object,
687 contested, waittime, file, line);
688 LOCK_LOG_LOCK("SLOCK", &lk->lock_object, 0, 0, file,
690 WITNESS_LOCK(&lk->lock_object, LK_TRYWIT(flags), file,
692 TD_LOCKS_INC(curthread);
693 TD_SLOCKS_INC(curthread);
699 _lockmgr_assert(lk, KA_SLOCKED, file, line);
701 x = v & LK_ALL_WAITERS;
702 v &= LK_EXCLUSIVE_SPINNERS;
705 * Try to switch from one shared lock to an exclusive one.
706 * We need to preserve waiters flags during the operation.
708 if (atomic_cmpset_ptr(&lk->lk_lock, LK_SHARERS_LOCK(1) | x | v,
710 LOCK_LOG_LOCK("XUPGRADE", &lk->lock_object, 0, 0, file,
712 WITNESS_UPGRADE(&lk->lock_object, LOP_EXCLUSIVE |
713 LK_TRYWIT(flags), file, line);
714 TD_SLOCKS_DEC(curthread);
719 * In LK_TRYUPGRADE mode, do not drop the lock,
720 * returning EBUSY instead.
722 if (op == LK_TRYUPGRADE) {
723 LOCK_LOG2(lk, "%s: %p failed the nowait upgrade",
730 * We have been unable to succeed in upgrading, so just
731 * give up the shared lock.
733 wakeup_swapper |= wakeupshlk(lk, file, line);
737 if (LK_CAN_WITNESS(flags))
738 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER |
739 LOP_EXCLUSIVE, file, line, flags & LK_INTERLOCK ?
743 * If curthread already holds the lock and this one is
744 * allowed to recurse, simply recurse on it.
746 if (lockmgr_xlocked(lk)) {
747 if ((flags & LK_CANRECURSE) == 0 &&
748 (lk->lock_object.lo_flags & LO_RECURSABLE) == 0) {
751 * If the lock is expected to not panic just
752 * give up and return.
754 if (LK_TRYOP(flags)) {
756 "%s: %p fails the try operation",
761 if (flags & LK_INTERLOCK)
762 class->lc_unlock(ilk);
763 panic("%s: recursing on non recursive lockmgr %s @ %s:%d\n",
764 __func__, iwmesg, file, line);
767 LOCK_LOG2(lk, "%s: %p recursing", __func__, lk);
768 LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0,
769 lk->lk_recurse, file, line);
770 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE |
771 LK_TRYWIT(flags), file, line);
772 TD_LOCKS_INC(curthread);
776 while (!atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED,
779 PMC_SOFT_CALL( , , lock, failed);
781 lock_profile_obtain_lock_failed(&lk->lock_object,
782 &contested, &waittime);
785 * If the lock is expected to not sleep just give up
788 if (LK_TRYOP(flags)) {
789 LOCK_LOG2(lk, "%s: %p fails the try operation",
795 #ifdef ADAPTIVE_LOCKMGRS
797 * If the owner is running on another CPU, spin until
798 * the owner stops running or the state of the lock
802 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 &&
803 LK_HOLDER(x) != LK_KERNPROC) {
804 owner = (struct thread *)LK_HOLDER(x);
805 if (LOCK_LOG_TEST(&lk->lock_object, 0))
807 "%s: spinning on %p held by %p",
808 __func__, lk, owner);
811 * If we are holding also an interlock drop it
812 * in order to avoid a deadlock if the lockmgr
813 * owner is adaptively spinning on the
816 if (flags & LK_INTERLOCK) {
817 class->lc_unlock(ilk);
818 flags &= ~LK_INTERLOCK;
821 while (LK_HOLDER(lk->lk_lock) ==
822 (uintptr_t)owner && TD_IS_RUNNING(owner))
826 } else if (LK_CAN_ADAPT(lk, flags) &&
827 (x & LK_SHARE) != 0 && LK_SHARERS(x) &&
828 spintries < alk_retries) {
829 if ((x & LK_EXCLUSIVE_SPINNERS) == 0 &&
830 !atomic_cmpset_ptr(&lk->lk_lock, x,
831 x | LK_EXCLUSIVE_SPINNERS))
833 if (flags & LK_INTERLOCK) {
834 class->lc_unlock(ilk);
835 flags &= ~LK_INTERLOCK;
839 for (i = 0; i < alk_loops; i++) {
840 if (LOCK_LOG_TEST(&lk->lock_object, 0))
842 "%s: shared spinning on %p with %u and %u",
843 __func__, lk, spintries, i);
845 LK_EXCLUSIVE_SPINNERS) == 0)
856 * Acquire the sleepqueue chain lock because we
857 * probabilly will need to manipulate waiters flags.
859 sleepq_lock(&lk->lock_object);
863 * if the lock has been released while we spun on
864 * the sleepqueue chain lock just try again.
866 if (x == LK_UNLOCKED) {
867 sleepq_release(&lk->lock_object);
871 #ifdef ADAPTIVE_LOCKMGRS
873 * The current lock owner might have started executing
874 * on another CPU (or the lock could have changed
875 * owner) while we were waiting on the turnstile
876 * chain lock. If so, drop the turnstile lock and try
879 if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 &&
880 LK_HOLDER(x) != LK_KERNPROC) {
881 owner = (struct thread *)LK_HOLDER(x);
882 if (TD_IS_RUNNING(owner)) {
883 sleepq_release(&lk->lock_object);
890 * The lock can be in the state where there is a
891 * pending queue of waiters, but still no owner.
892 * This happens when the lock is contested and an
893 * owner is going to claim the lock.
894 * If curthread is the one successfully acquiring it
895 * claim lock ownership and return, preserving waiters
898 v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS);
899 if ((x & ~v) == LK_UNLOCKED) {
900 v &= ~LK_EXCLUSIVE_SPINNERS;
901 if (atomic_cmpset_acq_ptr(&lk->lk_lock, x,
903 sleepq_release(&lk->lock_object);
905 "%s: %p claimed by a new writer",
909 sleepq_release(&lk->lock_object);
914 * Try to set the LK_EXCLUSIVE_WAITERS flag. If we
915 * fail, loop back and retry.
917 if ((x & LK_EXCLUSIVE_WAITERS) == 0) {
918 if (!atomic_cmpset_ptr(&lk->lk_lock, x,
919 x | LK_EXCLUSIVE_WAITERS)) {
920 sleepq_release(&lk->lock_object);
923 LOCK_LOG2(lk, "%s: %p set excl waiters flag",
928 * As far as we have been unable to acquire the
929 * exclusive lock and the exclusive waiters flag
930 * is set, we will sleep.
932 error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo,
934 flags &= ~LK_INTERLOCK;
937 "%s: interrupted sleep for %p with %d",
938 __func__, lk, error);
941 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue",
945 lock_profile_obtain_lock_success(&lk->lock_object,
946 contested, waittime, file, line);
947 LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0,
948 lk->lk_recurse, file, line);
949 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE |
950 LK_TRYWIT(flags), file, line);
951 TD_LOCKS_INC(curthread);
956 _lockmgr_assert(lk, KA_XLOCKED, file, line);
957 LOCK_LOG_LOCK("XDOWNGRADE", &lk->lock_object, 0, 0, file, line);
958 WITNESS_DOWNGRADE(&lk->lock_object, 0, file, line);
961 * Panic if the lock is recursed.
963 if (lockmgr_xlocked(lk) && lockmgr_recursed(lk)) {
964 if (flags & LK_INTERLOCK)
965 class->lc_unlock(ilk);
966 panic("%s: downgrade a recursed lockmgr %s @ %s:%d\n",
967 __func__, iwmesg, file, line);
969 TD_SLOCKS_INC(curthread);
972 * In order to preserve waiters flags, just spin.
976 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0);
978 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x,
979 LK_SHARERS_LOCK(1) | x))
985 _lockmgr_assert(lk, KA_LOCKED, file, line);
988 if ((x & LK_SHARE) == 0) {
991 * As first option, treact the lock as if it has not
993 * Fix-up the tid var if the lock has been disowned.
995 if (LK_HOLDER(x) == LK_KERNPROC)
998 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE,
1000 TD_LOCKS_DEC(curthread);
1002 LOCK_LOG_LOCK("XUNLOCK", &lk->lock_object, 0,
1003 lk->lk_recurse, file, line);
1006 * The lock is held in exclusive mode.
1007 * If the lock is recursed also, then unrecurse it.
1009 if (lockmgr_xlocked(lk) && lockmgr_recursed(lk)) {
1010 LOCK_LOG2(lk, "%s: %p unrecursing", __func__,
1015 if (tid != LK_KERNPROC)
1016 lock_profile_release_lock(&lk->lock_object);
1018 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid,
1022 sleepq_lock(&lk->lock_object);
1027 * If the lock has exclusive waiters, give them
1028 * preference in order to avoid deadlock with
1029 * shared runners up.
1030 * If interruptible sleeps left the exclusive queue
1031 * empty avoid a starvation for the threads sleeping
1032 * on the shared queue by giving them precedence
1033 * and cleaning up the exclusive waiters bit anyway.
1034 * Please note that lk_exslpfail count may be lying
1035 * about the real number of waiters with the
1036 * LK_SLEEPFAIL flag on because they may be used in
1037 * conjuction with interruptible sleeps so
1038 * lk_exslpfail might be considered an 'upper limit'
1039 * bound, including the edge cases.
1041 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0);
1042 realexslp = sleepq_sleepcnt(&lk->lock_object,
1043 SQ_EXCLUSIVE_QUEUE);
1044 if ((x & LK_EXCLUSIVE_WAITERS) != 0 && realexslp != 0) {
1045 if (lk->lk_exslpfail < realexslp) {
1046 lk->lk_exslpfail = 0;
1047 queue = SQ_EXCLUSIVE_QUEUE;
1048 v |= (x & LK_SHARED_WAITERS);
1050 lk->lk_exslpfail = 0;
1052 "%s: %p has only LK_SLEEPFAIL sleepers",
1055 "%s: %p waking up threads on the exclusive queue",
1058 sleepq_broadcast(&lk->lock_object,
1059 SLEEPQ_LK, 0, SQ_EXCLUSIVE_QUEUE);
1060 queue = SQ_SHARED_QUEUE;
1065 * Exclusive waiters sleeping with LK_SLEEPFAIL
1066 * on and using interruptible sleeps/timeout
1067 * may have left spourious lk_exslpfail counts
1068 * on, so clean it up anyway.
1070 lk->lk_exslpfail = 0;
1071 queue = SQ_SHARED_QUEUE;
1075 "%s: %p waking up threads on the %s queue",
1076 __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" :
1078 atomic_store_rel_ptr(&lk->lk_lock, v);
1079 wakeup_swapper |= sleepq_broadcast(&lk->lock_object,
1080 SLEEPQ_LK, 0, queue);
1081 sleepq_release(&lk->lock_object);
1084 wakeup_swapper = wakeupshlk(lk, file, line);
1087 if (LK_CAN_WITNESS(flags))
1088 WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER |
1089 LOP_EXCLUSIVE, file, line, flags & LK_INTERLOCK ?
1093 * Trying to drain a lock we already own will result in a
1096 if (lockmgr_xlocked(lk)) {
1097 if (flags & LK_INTERLOCK)
1098 class->lc_unlock(ilk);
1099 panic("%s: draining %s with the lock held @ %s:%d\n",
1100 __func__, iwmesg, file, line);
1103 while (!atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid)) {
1105 PMC_SOFT_CALL( , , lock, failed);
1107 lock_profile_obtain_lock_failed(&lk->lock_object,
1108 &contested, &waittime);
1111 * If the lock is expected to not sleep just give up
1114 if (LK_TRYOP(flags)) {
1115 LOCK_LOG2(lk, "%s: %p fails the try operation",
1122 * Acquire the sleepqueue chain lock because we
1123 * probabilly will need to manipulate waiters flags.
1125 sleepq_lock(&lk->lock_object);
1129 * if the lock has been released while we spun on
1130 * the sleepqueue chain lock just try again.
1132 if (x == LK_UNLOCKED) {
1133 sleepq_release(&lk->lock_object);
1137 v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS);
1138 if ((x & ~v) == LK_UNLOCKED) {
1139 v = (x & ~LK_EXCLUSIVE_SPINNERS);
1142 * If interruptible sleeps left the exclusive
1143 * queue empty avoid a starvation for the
1144 * threads sleeping on the shared queue by
1145 * giving them precedence and cleaning up the
1146 * exclusive waiters bit anyway.
1147 * Please note that lk_exslpfail count may be
1148 * lying about the real number of waiters with
1149 * the LK_SLEEPFAIL flag on because they may
1150 * be used in conjuction with interruptible
1151 * sleeps so lk_exslpfail might be considered
1152 * an 'upper limit' bound, including the edge
1155 if (v & LK_EXCLUSIVE_WAITERS) {
1156 queue = SQ_EXCLUSIVE_QUEUE;
1157 v &= ~LK_EXCLUSIVE_WAITERS;
1161 * Exclusive waiters sleeping with
1162 * LK_SLEEPFAIL on and using
1163 * interruptible sleeps/timeout may
1164 * have left spourious lk_exslpfail
1165 * counts on, so clean it up anyway.
1167 MPASS(v & LK_SHARED_WAITERS);
1168 lk->lk_exslpfail = 0;
1169 queue = SQ_SHARED_QUEUE;
1170 v &= ~LK_SHARED_WAITERS;
1172 if (queue == SQ_EXCLUSIVE_QUEUE) {
1174 sleepq_sleepcnt(&lk->lock_object,
1175 SQ_EXCLUSIVE_QUEUE);
1176 if (lk->lk_exslpfail >= realexslp) {
1177 lk->lk_exslpfail = 0;
1178 queue = SQ_SHARED_QUEUE;
1179 v &= ~LK_SHARED_WAITERS;
1180 if (realexslp != 0) {
1182 "%s: %p has only LK_SLEEPFAIL sleepers",
1185 "%s: %p waking up threads on the exclusive queue",
1191 SQ_EXCLUSIVE_QUEUE);
1194 lk->lk_exslpfail = 0;
1196 if (!atomic_cmpset_ptr(&lk->lk_lock, x, v)) {
1197 sleepq_release(&lk->lock_object);
1201 "%s: %p waking up all threads on the %s queue",
1202 __func__, lk, queue == SQ_SHARED_QUEUE ?
1203 "shared" : "exclusive");
1204 wakeup_swapper |= sleepq_broadcast(
1205 &lk->lock_object, SLEEPQ_LK, 0, queue);
1208 * If shared waiters have been woken up we need
1209 * to wait for one of them to acquire the lock
1210 * before to set the exclusive waiters in
1211 * order to avoid a deadlock.
1213 if (queue == SQ_SHARED_QUEUE) {
1214 for (v = lk->lk_lock;
1215 (v & LK_SHARE) && !LK_SHARERS(v);
1222 * Try to set the LK_EXCLUSIVE_WAITERS flag. If we
1223 * fail, loop back and retry.
1225 if ((x & LK_EXCLUSIVE_WAITERS) == 0) {
1226 if (!atomic_cmpset_ptr(&lk->lk_lock, x,
1227 x | LK_EXCLUSIVE_WAITERS)) {
1228 sleepq_release(&lk->lock_object);
1231 LOCK_LOG2(lk, "%s: %p set drain waiters flag",
1236 * As far as we have been unable to acquire the
1237 * exclusive lock and the exclusive waiters flag
1238 * is set, we will sleep.
1240 if (flags & LK_INTERLOCK) {
1241 class->lc_unlock(ilk);
1242 flags &= ~LK_INTERLOCK;
1245 sleepq_add(&lk->lock_object, NULL, iwmesg, SLEEPQ_LK,
1246 SQ_EXCLUSIVE_QUEUE);
1247 sleepq_wait(&lk->lock_object, ipri & PRIMASK);
1249 LOCK_LOG2(lk, "%s: %p resuming from the sleep queue",
1254 lock_profile_obtain_lock_success(&lk->lock_object,
1255 contested, waittime, file, line);
1256 LOCK_LOG_LOCK("DRAIN", &lk->lock_object, 0,
1257 lk->lk_recurse, file, line);
1258 WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE |
1259 LK_TRYWIT(flags), file, line);
1260 TD_LOCKS_INC(curthread);
1265 if (flags & LK_INTERLOCK)
1266 class->lc_unlock(ilk);
1267 panic("%s: unknown lockmgr request 0x%x\n", __func__, op);
1270 if (flags & LK_INTERLOCK)
1271 class->lc_unlock(ilk);
1279 _lockmgr_disown(struct lock *lk, const char *file, int line)
1283 if (SCHEDULER_STOPPED())
1286 tid = (uintptr_t)curthread;
1287 _lockmgr_assert(lk, KA_XLOCKED, file, line);
1290 * Panic if the lock is recursed.
1292 if (lockmgr_xlocked(lk) && lockmgr_recursed(lk))
1293 panic("%s: disown a recursed lockmgr @ %s:%d\n",
1294 __func__, file, line);
1297 * If the owner is already LK_KERNPROC just skip the whole operation.
1299 if (LK_HOLDER(lk->lk_lock) != tid)
1301 lock_profile_release_lock(&lk->lock_object);
1302 LOCK_LOG_LOCK("XDISOWN", &lk->lock_object, 0, 0, file, line);
1303 WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, file, line);
1304 TD_LOCKS_DEC(curthread);
1308 * In order to preserve waiters flags, just spin.
1312 MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0);
1313 x &= LK_ALL_WAITERS;
1314 if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x,
1322 lockmgr_printinfo(const struct lock *lk)
1327 if (lk->lk_lock == LK_UNLOCKED)
1328 printf("lock type %s: UNLOCKED\n", lk->lock_object.lo_name);
1329 else if (lk->lk_lock & LK_SHARE)
1330 printf("lock type %s: SHARED (count %ju)\n",
1331 lk->lock_object.lo_name,
1332 (uintmax_t)LK_SHARERS(lk->lk_lock));
1334 td = lockmgr_xholder(lk);
1335 printf("lock type %s: EXCL by thread %p "
1336 "(pid %d, %s, tid %d)\n", lk->lock_object.lo_name, td,
1337 td->td_proc->p_pid, td->td_proc->p_comm, td->td_tid);
1341 if (x & LK_EXCLUSIVE_WAITERS)
1342 printf(" with exclusive waiters pending\n");
1343 if (x & LK_SHARED_WAITERS)
1344 printf(" with shared waiters pending\n");
1345 if (x & LK_EXCLUSIVE_SPINNERS)
1346 printf(" with exclusive spinners pending\n");
1352 lockstatus(const struct lock *lk)
1361 if ((x & LK_SHARE) == 0) {
1362 if (v == (uintptr_t)curthread || v == LK_KERNPROC)
1366 } else if (x == LK_UNLOCKED)
1372 #ifdef INVARIANT_SUPPORT
1374 FEATURE(invariant_support,
1375 "Support for modules compiled with INVARIANTS option");
1378 #undef _lockmgr_assert
1382 _lockmgr_assert(const struct lock *lk, int what, const char *file, int line)
1386 if (panicstr != NULL)
1390 case KA_SLOCKED | KA_NOTRECURSED:
1391 case KA_SLOCKED | KA_RECURSED:
1394 case KA_LOCKED | KA_NOTRECURSED:
1395 case KA_LOCKED | KA_RECURSED:
1399 * We cannot trust WITNESS if the lock is held in exclusive
1400 * mode and a call to lockmgr_disown() happened.
1401 * Workaround this skipping the check if the lock is held in
1402 * exclusive mode even for the KA_LOCKED case.
1404 if (slocked || (lk->lk_lock & LK_SHARE)) {
1405 witness_assert(&lk->lock_object, what, file, line);
1409 if (lk->lk_lock == LK_UNLOCKED ||
1410 ((lk->lk_lock & LK_SHARE) == 0 && (slocked ||
1411 (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk)))))
1412 panic("Lock %s not %slocked @ %s:%d\n",
1413 lk->lock_object.lo_name, slocked ? "share" : "",
1416 if ((lk->lk_lock & LK_SHARE) == 0) {
1417 if (lockmgr_recursed(lk)) {
1418 if (what & KA_NOTRECURSED)
1419 panic("Lock %s recursed @ %s:%d\n",
1420 lk->lock_object.lo_name, file,
1422 } else if (what & KA_RECURSED)
1423 panic("Lock %s not recursed @ %s:%d\n",
1424 lk->lock_object.lo_name, file, line);
1428 case KA_XLOCKED | KA_NOTRECURSED:
1429 case KA_XLOCKED | KA_RECURSED:
1430 if (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk))
1431 panic("Lock %s not exclusively locked @ %s:%d\n",
1432 lk->lock_object.lo_name, file, line);
1433 if (lockmgr_recursed(lk)) {
1434 if (what & KA_NOTRECURSED)
1435 panic("Lock %s recursed @ %s:%d\n",
1436 lk->lock_object.lo_name, file, line);
1437 } else if (what & KA_RECURSED)
1438 panic("Lock %s not recursed @ %s:%d\n",
1439 lk->lock_object.lo_name, file, line);
1442 if (lockmgr_xlocked(lk) || lockmgr_disowned(lk))
1443 panic("Lock %s exclusively locked @ %s:%d\n",
1444 lk->lock_object.lo_name, file, line);
1447 panic("Unknown lockmgr assertion: %d @ %s:%d\n", what, file,
1455 lockmgr_chain(struct thread *td, struct thread **ownerp)
1461 if (LOCK_CLASS(&lk->lock_object) != &lock_class_lockmgr)
1463 db_printf("blocked on lockmgr %s", lk->lock_object.lo_name);
1464 if (lk->lk_lock & LK_SHARE)
1465 db_printf("SHARED (count %ju)\n",
1466 (uintmax_t)LK_SHARERS(lk->lk_lock));
1468 db_printf("EXCL\n");
1469 *ownerp = lockmgr_xholder(lk);
1475 db_show_lockmgr(const struct lock_object *lock)
1478 const struct lock *lk;
1480 lk = (const struct lock *)lock;
1482 db_printf(" state: ");
1483 if (lk->lk_lock == LK_UNLOCKED)
1484 db_printf("UNLOCKED\n");
1485 else if (lk->lk_lock & LK_SHARE)
1486 db_printf("SLOCK: %ju\n", (uintmax_t)LK_SHARERS(lk->lk_lock));
1488 td = lockmgr_xholder(lk);
1489 if (td == (struct thread *)LK_KERNPROC)
1490 db_printf("XLOCK: LK_KERNPROC\n");
1492 db_printf("XLOCK: %p (tid %d, pid %d, \"%s\")\n", td,
1493 td->td_tid, td->td_proc->p_pid,
1494 td->td_proc->p_comm);
1495 if (lockmgr_recursed(lk))
1496 db_printf(" recursed: %d\n", lk->lk_recurse);
1498 db_printf(" waiters: ");
1499 switch (lk->lk_lock & LK_ALL_WAITERS) {
1500 case LK_SHARED_WAITERS:
1501 db_printf("shared\n");
1503 case LK_EXCLUSIVE_WAITERS:
1504 db_printf("exclusive\n");
1506 case LK_ALL_WAITERS:
1507 db_printf("shared and exclusive\n");
1510 db_printf("none\n");
1512 db_printf(" spinners: ");
1513 if (lk->lk_lock & LK_EXCLUSIVE_SPINNERS)
1514 db_printf("exclusive\n");
1516 db_printf("none\n");