1690 lines
43 KiB
C
1690 lines
43 KiB
C
/*-
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* SPDX-License-Identifier: BSD-2-Clause-FreeBSD
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*
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* Copyright (c) 2008 Attilio Rao <attilio@FreeBSD.org>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice(s), this list of conditions and the following disclaimer as
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* the first lines of this file unmodified other than the possible
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* addition of one or more copyright notices.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice(s), this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY
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* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE LIABLE FOR ANY
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* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
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* DAMAGE.
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*/
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#include "opt_ddb.h"
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#include "opt_hwpmc_hooks.h"
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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#include <sys/param.h>
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#include <sys/kdb.h>
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#include <sys/ktr.h>
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#include <sys/lock.h>
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#include <sys/lock_profile.h>
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#include <sys/lockmgr.h>
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#include <sys/mutex.h>
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#include <sys/proc.h>
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#include <sys/sleepqueue.h>
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#ifdef DEBUG_LOCKS
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#include <sys/stack.h>
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#endif
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#include <sys/sysctl.h>
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#include <sys/systm.h>
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#include <machine/cpu.h>
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#ifdef DDB
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#include <ddb/ddb.h>
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#endif
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#ifdef HWPMC_HOOKS
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#include <sys/pmckern.h>
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PMC_SOFT_DECLARE( , , lock, failed);
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#endif
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CTASSERT(((LK_ADAPTIVE | LK_NOSHARE) & LO_CLASSFLAGS) ==
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(LK_ADAPTIVE | LK_NOSHARE));
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CTASSERT(LK_UNLOCKED == (LK_UNLOCKED &
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~(LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS)));
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#define SQ_EXCLUSIVE_QUEUE 0
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#define SQ_SHARED_QUEUE 1
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#ifndef INVARIANTS
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#define _lockmgr_assert(lk, what, file, line)
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#endif
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#define TD_SLOCKS_INC(td) ((td)->td_lk_slocks++)
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#define TD_SLOCKS_DEC(td) ((td)->td_lk_slocks--)
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#ifndef DEBUG_LOCKS
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#define STACK_PRINT(lk)
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#define STACK_SAVE(lk)
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#define STACK_ZERO(lk)
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#else
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#define STACK_PRINT(lk) stack_print_ddb(&(lk)->lk_stack)
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#define STACK_SAVE(lk) stack_save(&(lk)->lk_stack)
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#define STACK_ZERO(lk) stack_zero(&(lk)->lk_stack)
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#endif
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#define LOCK_LOG2(lk, string, arg1, arg2) \
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if (LOCK_LOG_TEST(&(lk)->lock_object, 0)) \
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CTR2(KTR_LOCK, (string), (arg1), (arg2))
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#define LOCK_LOG3(lk, string, arg1, arg2, arg3) \
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if (LOCK_LOG_TEST(&(lk)->lock_object, 0)) \
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CTR3(KTR_LOCK, (string), (arg1), (arg2), (arg3))
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#define GIANT_DECLARE \
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int _i = 0; \
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WITNESS_SAVE_DECL(Giant)
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#define GIANT_RESTORE() do { \
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if (_i > 0) { \
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while (_i--) \
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mtx_lock(&Giant); \
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WITNESS_RESTORE(&Giant.lock_object, Giant); \
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} \
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} while (0)
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#define GIANT_SAVE() do { \
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if (mtx_owned(&Giant)) { \
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WITNESS_SAVE(&Giant.lock_object, Giant); \
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while (mtx_owned(&Giant)) { \
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_i++; \
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mtx_unlock(&Giant); \
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} \
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} \
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} while (0)
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#define LK_CAN_SHARE(x, flags) \
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(((x) & LK_SHARE) && \
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(((x) & (LK_EXCLUSIVE_WAITERS | LK_EXCLUSIVE_SPINNERS)) == 0 || \
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(curthread->td_lk_slocks != 0 && !(flags & LK_NODDLKTREAT)) || \
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(curthread->td_pflags & TDP_DEADLKTREAT)))
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#define LK_TRYOP(x) \
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((x) & LK_NOWAIT)
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#define LK_CAN_WITNESS(x) \
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(((x) & LK_NOWITNESS) == 0 && !LK_TRYOP(x))
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#define LK_TRYWIT(x) \
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(LK_TRYOP(x) ? LOP_TRYLOCK : 0)
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#define LK_CAN_ADAPT(lk, f) \
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(((lk)->lock_object.lo_flags & LK_ADAPTIVE) != 0 && \
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((f) & LK_SLEEPFAIL) == 0)
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#define lockmgr_disowned(lk) \
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(((lk)->lk_lock & ~(LK_FLAGMASK & ~LK_SHARE)) == LK_KERNPROC)
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#define lockmgr_xlocked(lk) \
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(((lk)->lk_lock & ~(LK_FLAGMASK & ~LK_SHARE)) == (uintptr_t)curthread)
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static void assert_lockmgr(const struct lock_object *lock, int how);
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#ifdef DDB
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static void db_show_lockmgr(const struct lock_object *lock);
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#endif
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static void lock_lockmgr(struct lock_object *lock, uintptr_t how);
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#ifdef KDTRACE_HOOKS
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static int owner_lockmgr(const struct lock_object *lock,
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struct thread **owner);
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#endif
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static uintptr_t unlock_lockmgr(struct lock_object *lock);
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struct lock_class lock_class_lockmgr = {
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.lc_name = "lockmgr",
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.lc_flags = LC_RECURSABLE | LC_SLEEPABLE | LC_SLEEPLOCK | LC_UPGRADABLE,
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.lc_assert = assert_lockmgr,
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#ifdef DDB
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.lc_ddb_show = db_show_lockmgr,
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#endif
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.lc_lock = lock_lockmgr,
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.lc_unlock = unlock_lockmgr,
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#ifdef KDTRACE_HOOKS
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.lc_owner = owner_lockmgr,
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#endif
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};
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struct lockmgr_wait {
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const char *iwmesg;
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int ipri;
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int itimo;
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};
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static bool __always_inline lockmgr_slock_try(struct lock *lk, uintptr_t *xp,
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int flags);
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static bool __always_inline lockmgr_sunlock_try(struct lock *lk, uintptr_t *xp);
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static void
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lockmgr_exit(u_int flags, struct lock_object *ilk, int wakeup_swapper)
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{
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struct lock_class *class;
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if (flags & LK_INTERLOCK) {
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class = LOCK_CLASS(ilk);
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class->lc_unlock(ilk);
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}
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if (__predict_false(wakeup_swapper))
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kick_proc0();
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}
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static void
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lockmgr_note_shared_acquire(struct lock *lk, int contested,
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uint64_t waittime, const char *file, int line, int flags)
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{
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lock_profile_obtain_lock_success(&lk->lock_object, contested, waittime,
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file, line);
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LOCK_LOG_LOCK("SLOCK", &lk->lock_object, 0, 0, file, line);
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WITNESS_LOCK(&lk->lock_object, LK_TRYWIT(flags), file, line);
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TD_LOCKS_INC(curthread);
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TD_SLOCKS_INC(curthread);
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STACK_SAVE(lk);
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}
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static void
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lockmgr_note_shared_release(struct lock *lk, const char *file, int line)
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{
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lock_profile_release_lock(&lk->lock_object);
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WITNESS_UNLOCK(&lk->lock_object, 0, file, line);
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LOCK_LOG_LOCK("SUNLOCK", &lk->lock_object, 0, 0, file, line);
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TD_LOCKS_DEC(curthread);
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TD_SLOCKS_DEC(curthread);
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}
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static void
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lockmgr_note_exclusive_acquire(struct lock *lk, int contested,
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uint64_t waittime, const char *file, int line, int flags)
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{
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lock_profile_obtain_lock_success(&lk->lock_object, contested, waittime,
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file, line);
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LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0, lk->lk_recurse, file, line);
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WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | LK_TRYWIT(flags), file,
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line);
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TD_LOCKS_INC(curthread);
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STACK_SAVE(lk);
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}
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static void
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lockmgr_note_exclusive_release(struct lock *lk, const char *file, int line)
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{
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lock_profile_release_lock(&lk->lock_object);
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LOCK_LOG_LOCK("XUNLOCK", &lk->lock_object, 0, lk->lk_recurse, file,
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line);
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WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, file, line);
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TD_LOCKS_DEC(curthread);
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}
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static __inline struct thread *
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lockmgr_xholder(const struct lock *lk)
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{
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uintptr_t x;
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x = lk->lk_lock;
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return ((x & LK_SHARE) ? NULL : (struct thread *)LK_HOLDER(x));
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}
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/*
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* It assumes sleepq_lock held and returns with this one unheld.
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* It also assumes the generic interlock is sane and previously checked.
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* If LK_INTERLOCK is specified the interlock is not reacquired after the
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* sleep.
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*/
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static __inline int
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sleeplk(struct lock *lk, u_int flags, struct lock_object *ilk,
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const char *wmesg, int pri, int timo, int queue)
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{
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GIANT_DECLARE;
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struct lock_class *class;
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int catch, error;
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class = (flags & LK_INTERLOCK) ? LOCK_CLASS(ilk) : NULL;
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catch = pri & PCATCH;
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pri &= PRIMASK;
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error = 0;
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LOCK_LOG3(lk, "%s: %p blocking on the %s sleepqueue", __func__, lk,
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(queue == SQ_EXCLUSIVE_QUEUE) ? "exclusive" : "shared");
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if (flags & LK_INTERLOCK)
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class->lc_unlock(ilk);
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if (queue == SQ_EXCLUSIVE_QUEUE && (flags & LK_SLEEPFAIL) != 0)
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lk->lk_exslpfail++;
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GIANT_SAVE();
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sleepq_add(&lk->lock_object, NULL, wmesg, SLEEPQ_LK | (catch ?
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SLEEPQ_INTERRUPTIBLE : 0), queue);
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if ((flags & LK_TIMELOCK) && timo)
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sleepq_set_timeout(&lk->lock_object, timo);
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/*
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* Decisional switch for real sleeping.
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*/
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if ((flags & LK_TIMELOCK) && timo && catch)
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error = sleepq_timedwait_sig(&lk->lock_object, pri);
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else if ((flags & LK_TIMELOCK) && timo)
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error = sleepq_timedwait(&lk->lock_object, pri);
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else if (catch)
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error = sleepq_wait_sig(&lk->lock_object, pri);
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else
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sleepq_wait(&lk->lock_object, pri);
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GIANT_RESTORE();
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if ((flags & LK_SLEEPFAIL) && error == 0)
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error = ENOLCK;
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return (error);
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}
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static __inline int
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wakeupshlk(struct lock *lk, const char *file, int line)
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{
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uintptr_t v, x, orig_x;
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u_int realexslp;
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int queue, wakeup_swapper;
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wakeup_swapper = 0;
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for (;;) {
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x = lk->lk_lock;
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if (lockmgr_sunlock_try(lk, &x))
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break;
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/*
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* We should have a sharer with waiters, so enter the hard
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* path in order to handle wakeups correctly.
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*/
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sleepq_lock(&lk->lock_object);
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orig_x = lk->lk_lock;
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retry_sleepq:
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x = orig_x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS);
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v = LK_UNLOCKED;
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/*
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* If the lock has exclusive waiters, give them preference in
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* order to avoid deadlock with shared runners up.
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* If interruptible sleeps left the exclusive queue empty
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* avoid a starvation for the threads sleeping on the shared
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* queue by giving them precedence and cleaning up the
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* exclusive waiters bit anyway.
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* Please note that lk_exslpfail count may be lying about
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* the real number of waiters with the LK_SLEEPFAIL flag on
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* because they may be used in conjunction with interruptible
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* sleeps so lk_exslpfail might be considered an 'upper limit'
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* bound, including the edge cases.
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*/
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realexslp = sleepq_sleepcnt(&lk->lock_object,
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SQ_EXCLUSIVE_QUEUE);
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if ((x & LK_EXCLUSIVE_WAITERS) != 0 && realexslp != 0) {
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if (lk->lk_exslpfail < realexslp) {
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lk->lk_exslpfail = 0;
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queue = SQ_EXCLUSIVE_QUEUE;
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v |= (x & LK_SHARED_WAITERS);
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} else {
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lk->lk_exslpfail = 0;
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LOCK_LOG2(lk,
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"%s: %p has only LK_SLEEPFAIL sleepers",
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__func__, lk);
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LOCK_LOG2(lk,
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"%s: %p waking up threads on the exclusive queue",
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__func__, lk);
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wakeup_swapper =
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sleepq_broadcast(&lk->lock_object,
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SLEEPQ_LK, 0, SQ_EXCLUSIVE_QUEUE);
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queue = SQ_SHARED_QUEUE;
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}
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} else {
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/*
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* Exclusive waiters sleeping with LK_SLEEPFAIL on
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* and using interruptible sleeps/timeout may have
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* left spourious lk_exslpfail counts on, so clean
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* it up anyway.
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*/
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lk->lk_exslpfail = 0;
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queue = SQ_SHARED_QUEUE;
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}
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if (lockmgr_sunlock_try(lk, &orig_x)) {
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sleepq_release(&lk->lock_object);
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break;
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}
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x |= LK_SHARERS_LOCK(1);
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if (!atomic_fcmpset_rel_ptr(&lk->lk_lock, &x, v)) {
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orig_x = x;
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goto retry_sleepq;
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}
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LOCK_LOG3(lk, "%s: %p waking up threads on the %s queue",
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__func__, lk, queue == SQ_SHARED_QUEUE ? "shared" :
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"exclusive");
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wakeup_swapper |= sleepq_broadcast(&lk->lock_object, SLEEPQ_LK,
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0, queue);
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sleepq_release(&lk->lock_object);
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break;
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}
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lockmgr_note_shared_release(lk, file, line);
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return (wakeup_swapper);
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}
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static void
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assert_lockmgr(const struct lock_object *lock, int what)
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{
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panic("lockmgr locks do not support assertions");
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}
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static void
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lock_lockmgr(struct lock_object *lock, uintptr_t how)
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{
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panic("lockmgr locks do not support sleep interlocking");
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}
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static uintptr_t
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unlock_lockmgr(struct lock_object *lock)
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{
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panic("lockmgr locks do not support sleep interlocking");
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}
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#ifdef KDTRACE_HOOKS
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static int
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owner_lockmgr(const struct lock_object *lock, struct thread **owner)
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{
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panic("lockmgr locks do not support owner inquiring");
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}
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#endif
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void
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lockinit(struct lock *lk, int pri, const char *wmesg, int timo, int flags)
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{
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int iflags;
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MPASS((flags & ~LK_INIT_MASK) == 0);
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ASSERT_ATOMIC_LOAD_PTR(lk->lk_lock,
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("%s: lockmgr not aligned for %s: %p", __func__, wmesg,
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&lk->lk_lock));
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iflags = LO_SLEEPABLE | LO_UPGRADABLE;
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if (flags & LK_CANRECURSE)
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iflags |= LO_RECURSABLE;
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if ((flags & LK_NODUP) == 0)
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iflags |= LO_DUPOK;
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if (flags & LK_NOPROFILE)
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iflags |= LO_NOPROFILE;
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if ((flags & LK_NOWITNESS) == 0)
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iflags |= LO_WITNESS;
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if (flags & LK_QUIET)
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iflags |= LO_QUIET;
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if (flags & LK_IS_VNODE)
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iflags |= LO_IS_VNODE;
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iflags |= flags & (LK_ADAPTIVE | LK_NOSHARE);
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lock_init(&lk->lock_object, &lock_class_lockmgr, wmesg, NULL, iflags);
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lk->lk_lock = LK_UNLOCKED;
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lk->lk_recurse = 0;
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lk->lk_exslpfail = 0;
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lk->lk_timo = timo;
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lk->lk_pri = pri;
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STACK_ZERO(lk);
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}
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|
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/*
|
|
* XXX: Gross hacks to manipulate external lock flags after
|
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* initialization. Used for certain vnode and buf locks.
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|
*/
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|
void
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lockallowshare(struct lock *lk)
|
|
{
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lockmgr_assert(lk, KA_XLOCKED);
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lk->lock_object.lo_flags &= ~LK_NOSHARE;
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}
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|
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void
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lockdisableshare(struct lock *lk)
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{
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lockmgr_assert(lk, KA_XLOCKED);
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lk->lock_object.lo_flags |= LK_NOSHARE;
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}
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|
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void
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lockallowrecurse(struct lock *lk)
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{
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lockmgr_assert(lk, KA_XLOCKED);
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lk->lock_object.lo_flags |= LO_RECURSABLE;
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}
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|
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void
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lockdisablerecurse(struct lock *lk)
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{
|
|
|
|
lockmgr_assert(lk, KA_XLOCKED);
|
|
lk->lock_object.lo_flags &= ~LO_RECURSABLE;
|
|
}
|
|
|
|
void
|
|
lockdestroy(struct lock *lk)
|
|
{
|
|
|
|
KASSERT(lk->lk_lock == LK_UNLOCKED, ("lockmgr still held"));
|
|
KASSERT(lk->lk_recurse == 0, ("lockmgr still recursed"));
|
|
KASSERT(lk->lk_exslpfail == 0, ("lockmgr still exclusive waiters"));
|
|
lock_destroy(&lk->lock_object);
|
|
}
|
|
|
|
static bool __always_inline
|
|
lockmgr_slock_try(struct lock *lk, uintptr_t *xp, int flags)
|
|
{
|
|
|
|
/*
|
|
* If no other thread has an exclusive lock, or
|
|
* no exclusive waiter is present, bump the count of
|
|
* sharers. Since we have to preserve the state of
|
|
* waiters, if we fail to acquire the shared lock
|
|
* loop back and retry.
|
|
*/
|
|
*xp = lk->lk_lock;
|
|
while (LK_CAN_SHARE(*xp, flags)) {
|
|
if (atomic_fcmpset_acq_ptr(&lk->lk_lock, xp,
|
|
*xp + LK_ONE_SHARER)) {
|
|
return (true);
|
|
}
|
|
}
|
|
return (false);
|
|
}
|
|
|
|
static bool __always_inline
|
|
lockmgr_sunlock_try(struct lock *lk, uintptr_t *xp)
|
|
{
|
|
|
|
for (;;) {
|
|
/*
|
|
* If there is more than one shared lock held, just drop one
|
|
* and return.
|
|
*/
|
|
if (LK_SHARERS(*xp) > 1) {
|
|
if (atomic_fcmpset_rel_ptr(&lk->lk_lock, xp,
|
|
*xp - LK_ONE_SHARER))
|
|
return (true);
|
|
continue;
|
|
}
|
|
|
|
/*
|
|
* If there are not waiters on the exclusive queue, drop the
|
|
* lock quickly.
|
|
*/
|
|
if ((*xp & LK_ALL_WAITERS) == 0) {
|
|
MPASS((*xp & ~LK_EXCLUSIVE_SPINNERS) ==
|
|
LK_SHARERS_LOCK(1));
|
|
if (atomic_fcmpset_rel_ptr(&lk->lk_lock, xp,
|
|
LK_UNLOCKED))
|
|
return (true);
|
|
continue;
|
|
}
|
|
break;
|
|
}
|
|
return (false);
|
|
}
|
|
|
|
static __noinline int
|
|
lockmgr_slock_hard(struct lock *lk, u_int flags, struct lock_object *ilk,
|
|
const char *file, int line, struct lockmgr_wait *lwa)
|
|
{
|
|
uintptr_t tid, x;
|
|
int error = 0;
|
|
const char *iwmesg;
|
|
int ipri, itimo;
|
|
|
|
#ifdef LOCK_PROFILING
|
|
uint64_t waittime = 0;
|
|
int contested = 0;
|
|
#endif
|
|
|
|
if (__predict_false(panicstr != NULL))
|
|
goto out;
|
|
|
|
tid = (uintptr_t)curthread;
|
|
|
|
if (LK_CAN_WITNESS(flags))
|
|
WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER,
|
|
file, line, flags & LK_INTERLOCK ? ilk : NULL);
|
|
for (;;) {
|
|
if (lockmgr_slock_try(lk, &x, flags))
|
|
break;
|
|
#ifdef HWPMC_HOOKS
|
|
PMC_SOFT_CALL( , , lock, failed);
|
|
#endif
|
|
lock_profile_obtain_lock_failed(&lk->lock_object,
|
|
&contested, &waittime);
|
|
|
|
/*
|
|
* If the lock is already held by curthread in
|
|
* exclusive way avoid a deadlock.
|
|
*/
|
|
if (LK_HOLDER(x) == tid) {
|
|
LOCK_LOG2(lk,
|
|
"%s: %p already held in exclusive mode",
|
|
__func__, lk);
|
|
error = EDEADLK;
|
|
break;
|
|
}
|
|
|
|
/*
|
|
* If the lock is expected to not sleep just give up
|
|
* and return.
|
|
*/
|
|
if (LK_TRYOP(flags)) {
|
|
LOCK_LOG2(lk, "%s: %p fails the try operation",
|
|
__func__, lk);
|
|
error = EBUSY;
|
|
break;
|
|
}
|
|
|
|
/*
|
|
* Acquire the sleepqueue chain lock because we
|
|
* probabilly will need to manipulate waiters flags.
|
|
*/
|
|
sleepq_lock(&lk->lock_object);
|
|
x = lk->lk_lock;
|
|
retry_sleepq:
|
|
|
|
/*
|
|
* if the lock can be acquired in shared mode, try
|
|
* again.
|
|
*/
|
|
if (LK_CAN_SHARE(x, flags)) {
|
|
sleepq_release(&lk->lock_object);
|
|
continue;
|
|
}
|
|
|
|
/*
|
|
* Try to set the LK_SHARED_WAITERS flag. If we fail,
|
|
* loop back and retry.
|
|
*/
|
|
if ((x & LK_SHARED_WAITERS) == 0) {
|
|
if (!atomic_fcmpset_acq_ptr(&lk->lk_lock, &x,
|
|
x | LK_SHARED_WAITERS)) {
|
|
goto retry_sleepq;
|
|
}
|
|
LOCK_LOG2(lk, "%s: %p set shared waiters flag",
|
|
__func__, lk);
|
|
}
|
|
|
|
if (lwa == NULL) {
|
|
iwmesg = lk->lock_object.lo_name;
|
|
ipri = lk->lk_pri;
|
|
itimo = lk->lk_timo;
|
|
} else {
|
|
iwmesg = lwa->iwmesg;
|
|
ipri = lwa->ipri;
|
|
itimo = lwa->itimo;
|
|
}
|
|
|
|
/*
|
|
* As far as we have been unable to acquire the
|
|
* shared lock and the shared waiters flag is set,
|
|
* we will sleep.
|
|
*/
|
|
error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo,
|
|
SQ_SHARED_QUEUE);
|
|
flags &= ~LK_INTERLOCK;
|
|
if (error) {
|
|
LOCK_LOG3(lk,
|
|
"%s: interrupted sleep for %p with %d",
|
|
__func__, lk, error);
|
|
break;
|
|
}
|
|
LOCK_LOG2(lk, "%s: %p resuming from the sleep queue",
|
|
__func__, lk);
|
|
}
|
|
if (error == 0) {
|
|
#ifdef LOCK_PROFILING
|
|
lockmgr_note_shared_acquire(lk, contested, waittime,
|
|
file, line, flags);
|
|
#else
|
|
lockmgr_note_shared_acquire(lk, 0, 0, file, line,
|
|
flags);
|
|
#endif
|
|
}
|
|
|
|
out:
|
|
lockmgr_exit(flags, ilk, 0);
|
|
return (error);
|
|
}
|
|
|
|
static __noinline int
|
|
lockmgr_xlock_hard(struct lock *lk, u_int flags, struct lock_object *ilk,
|
|
const char *file, int line, struct lockmgr_wait *lwa)
|
|
{
|
|
struct lock_class *class;
|
|
uintptr_t tid, x, v;
|
|
int error = 0;
|
|
const char *iwmesg;
|
|
int ipri, itimo;
|
|
|
|
#ifdef LOCK_PROFILING
|
|
uint64_t waittime = 0;
|
|
int contested = 0;
|
|
#endif
|
|
|
|
if (__predict_false(panicstr != NULL))
|
|
goto out;
|
|
|
|
tid = (uintptr_t)curthread;
|
|
|
|
if (LK_CAN_WITNESS(flags))
|
|
WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER |
|
|
LOP_EXCLUSIVE, file, line, flags & LK_INTERLOCK ?
|
|
ilk : NULL);
|
|
|
|
/*
|
|
* If curthread already holds the lock and this one is
|
|
* allowed to recurse, simply recurse on it.
|
|
*/
|
|
if (lockmgr_xlocked(lk)) {
|
|
if ((flags & LK_CANRECURSE) == 0 &&
|
|
(lk->lock_object.lo_flags & LO_RECURSABLE) == 0) {
|
|
/*
|
|
* If the lock is expected to not panic just
|
|
* give up and return.
|
|
*/
|
|
if (LK_TRYOP(flags)) {
|
|
LOCK_LOG2(lk,
|
|
"%s: %p fails the try operation",
|
|
__func__, lk);
|
|
error = EBUSY;
|
|
goto out;
|
|
}
|
|
if (flags & LK_INTERLOCK) {
|
|
class = LOCK_CLASS(ilk);
|
|
class->lc_unlock(ilk);
|
|
}
|
|
panic("%s: recursing on non recursive lockmgr %p "
|
|
"@ %s:%d\n", __func__, lk, file, line);
|
|
}
|
|
lk->lk_recurse++;
|
|
LOCK_LOG2(lk, "%s: %p recursing", __func__, lk);
|
|
LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0,
|
|
lk->lk_recurse, file, line);
|
|
WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE |
|
|
LK_TRYWIT(flags), file, line);
|
|
TD_LOCKS_INC(curthread);
|
|
goto out;
|
|
}
|
|
|
|
for (;;) {
|
|
if (lk->lk_lock == LK_UNLOCKED &&
|
|
atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid))
|
|
break;
|
|
#ifdef HWPMC_HOOKS
|
|
PMC_SOFT_CALL( , , lock, failed);
|
|
#endif
|
|
lock_profile_obtain_lock_failed(&lk->lock_object,
|
|
&contested, &waittime);
|
|
|
|
/*
|
|
* If the lock is expected to not sleep just give up
|
|
* and return.
|
|
*/
|
|
if (LK_TRYOP(flags)) {
|
|
LOCK_LOG2(lk, "%s: %p fails the try operation",
|
|
__func__, lk);
|
|
error = EBUSY;
|
|
break;
|
|
}
|
|
|
|
/*
|
|
* Acquire the sleepqueue chain lock because we
|
|
* probabilly will need to manipulate waiters flags.
|
|
*/
|
|
sleepq_lock(&lk->lock_object);
|
|
x = lk->lk_lock;
|
|
retry_sleepq:
|
|
|
|
/*
|
|
* if the lock has been released while we spun on
|
|
* the sleepqueue chain lock just try again.
|
|
*/
|
|
if (x == LK_UNLOCKED) {
|
|
sleepq_release(&lk->lock_object);
|
|
continue;
|
|
}
|
|
|
|
/*
|
|
* The lock can be in the state where there is a
|
|
* pending queue of waiters, but still no owner.
|
|
* This happens when the lock is contested and an
|
|
* owner is going to claim the lock.
|
|
* If curthread is the one successfully acquiring it
|
|
* claim lock ownership and return, preserving waiters
|
|
* flags.
|
|
*/
|
|
v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS);
|
|
if ((x & ~v) == LK_UNLOCKED) {
|
|
v &= ~LK_EXCLUSIVE_SPINNERS;
|
|
if (atomic_fcmpset_acq_ptr(&lk->lk_lock, &x,
|
|
tid | v)) {
|
|
sleepq_release(&lk->lock_object);
|
|
LOCK_LOG2(lk,
|
|
"%s: %p claimed by a new writer",
|
|
__func__, lk);
|
|
break;
|
|
}
|
|
goto retry_sleepq;
|
|
}
|
|
|
|
/*
|
|
* Try to set the LK_EXCLUSIVE_WAITERS flag. If we
|
|
* fail, loop back and retry.
|
|
*/
|
|
if ((x & LK_EXCLUSIVE_WAITERS) == 0) {
|
|
if (!atomic_fcmpset_ptr(&lk->lk_lock, &x,
|
|
x | LK_EXCLUSIVE_WAITERS)) {
|
|
goto retry_sleepq;
|
|
}
|
|
LOCK_LOG2(lk, "%s: %p set excl waiters flag",
|
|
__func__, lk);
|
|
}
|
|
|
|
if (lwa == NULL) {
|
|
iwmesg = lk->lock_object.lo_name;
|
|
ipri = lk->lk_pri;
|
|
itimo = lk->lk_timo;
|
|
} else {
|
|
iwmesg = lwa->iwmesg;
|
|
ipri = lwa->ipri;
|
|
itimo = lwa->itimo;
|
|
}
|
|
|
|
/*
|
|
* As far as we have been unable to acquire the
|
|
* exclusive lock and the exclusive waiters flag
|
|
* is set, we will sleep.
|
|
*/
|
|
error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo,
|
|
SQ_EXCLUSIVE_QUEUE);
|
|
flags &= ~LK_INTERLOCK;
|
|
if (error) {
|
|
LOCK_LOG3(lk,
|
|
"%s: interrupted sleep for %p with %d",
|
|
__func__, lk, error);
|
|
break;
|
|
}
|
|
LOCK_LOG2(lk, "%s: %p resuming from the sleep queue",
|
|
__func__, lk);
|
|
}
|
|
if (error == 0) {
|
|
#ifdef LOCK_PROFILING
|
|
lockmgr_note_exclusive_acquire(lk, contested, waittime,
|
|
file, line, flags);
|
|
#else
|
|
lockmgr_note_exclusive_acquire(lk, 0, 0, file, line,
|
|
flags);
|
|
#endif
|
|
}
|
|
|
|
out:
|
|
lockmgr_exit(flags, ilk, 0);
|
|
return (error);
|
|
}
|
|
|
|
static __noinline int
|
|
lockmgr_upgrade(struct lock *lk, u_int flags, struct lock_object *ilk,
|
|
const char *file, int line, struct lockmgr_wait *lwa)
|
|
{
|
|
uintptr_t tid, x, v;
|
|
int error = 0;
|
|
int wakeup_swapper = 0;
|
|
int op;
|
|
|
|
if (__predict_false(panicstr != NULL))
|
|
goto out;
|
|
|
|
tid = (uintptr_t)curthread;
|
|
|
|
_lockmgr_assert(lk, KA_SLOCKED, file, line);
|
|
v = lk->lk_lock;
|
|
x = v & LK_ALL_WAITERS;
|
|
v &= LK_EXCLUSIVE_SPINNERS;
|
|
|
|
/*
|
|
* Try to switch from one shared lock to an exclusive one.
|
|
* We need to preserve waiters flags during the operation.
|
|
*/
|
|
if (atomic_cmpset_ptr(&lk->lk_lock, LK_SHARERS_LOCK(1) | x | v,
|
|
tid | x)) {
|
|
LOCK_LOG_LOCK("XUPGRADE", &lk->lock_object, 0, 0, file,
|
|
line);
|
|
WITNESS_UPGRADE(&lk->lock_object, LOP_EXCLUSIVE |
|
|
LK_TRYWIT(flags), file, line);
|
|
TD_SLOCKS_DEC(curthread);
|
|
goto out;
|
|
}
|
|
|
|
op = flags & LK_TYPE_MASK;
|
|
|
|
/*
|
|
* In LK_TRYUPGRADE mode, do not drop the lock,
|
|
* returning EBUSY instead.
|
|
*/
|
|
if (op == LK_TRYUPGRADE) {
|
|
LOCK_LOG2(lk, "%s: %p failed the nowait upgrade",
|
|
__func__, lk);
|
|
error = EBUSY;
|
|
goto out;
|
|
}
|
|
|
|
/*
|
|
* We have been unable to succeed in upgrading, so just
|
|
* give up the shared lock.
|
|
*/
|
|
wakeup_swapper |= wakeupshlk(lk, file, line);
|
|
error = lockmgr_xlock_hard(lk, flags, ilk, file, line, lwa);
|
|
flags &= ~LK_INTERLOCK;
|
|
out:
|
|
lockmgr_exit(flags, ilk, wakeup_swapper);
|
|
return (error);
|
|
}
|
|
|
|
int
|
|
lockmgr_lock_fast_path(struct lock *lk, u_int flags, struct lock_object *ilk,
|
|
const char *file, int line)
|
|
{
|
|
struct lock_class *class;
|
|
uintptr_t x, tid;
|
|
u_int op;
|
|
bool locked;
|
|
|
|
op = flags & LK_TYPE_MASK;
|
|
locked = false;
|
|
switch (op) {
|
|
case LK_SHARED:
|
|
if (LK_CAN_WITNESS(flags))
|
|
WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER,
|
|
file, line, flags & LK_INTERLOCK ? ilk : NULL);
|
|
if (__predict_false(lk->lock_object.lo_flags & LK_NOSHARE))
|
|
break;
|
|
if (lockmgr_slock_try(lk, &x, flags)) {
|
|
lockmgr_note_shared_acquire(lk, 0, 0,
|
|
file, line, flags);
|
|
locked = true;
|
|
} else {
|
|
return (lockmgr_slock_hard(lk, flags, ilk, file, line,
|
|
NULL));
|
|
}
|
|
break;
|
|
case LK_EXCLUSIVE:
|
|
if (LK_CAN_WITNESS(flags))
|
|
WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER |
|
|
LOP_EXCLUSIVE, file, line, flags & LK_INTERLOCK ?
|
|
ilk : NULL);
|
|
tid = (uintptr_t)curthread;
|
|
if (lk->lk_lock == LK_UNLOCKED &&
|
|
atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid)) {
|
|
lockmgr_note_exclusive_acquire(lk, 0, 0, file, line,
|
|
flags);
|
|
locked = true;
|
|
} else {
|
|
return (lockmgr_xlock_hard(lk, flags, ilk, file, line,
|
|
NULL));
|
|
}
|
|
break;
|
|
case LK_UPGRADE:
|
|
case LK_TRYUPGRADE:
|
|
return (lockmgr_upgrade(lk, flags, ilk, file, line, NULL));
|
|
default:
|
|
break;
|
|
}
|
|
if (__predict_true(locked)) {
|
|
if (__predict_false(flags & LK_INTERLOCK)) {
|
|
class = LOCK_CLASS(ilk);
|
|
class->lc_unlock(ilk);
|
|
}
|
|
return (0);
|
|
} else {
|
|
return (__lockmgr_args(lk, flags, ilk, LK_WMESG_DEFAULT,
|
|
LK_PRIO_DEFAULT, LK_TIMO_DEFAULT, file, line));
|
|
}
|
|
}
|
|
|
|
static __noinline int
|
|
lockmgr_sunlock_hard(struct lock *lk, uintptr_t x, u_int flags, struct lock_object *ilk,
|
|
const char *file, int line)
|
|
|
|
{
|
|
int wakeup_swapper = 0;
|
|
|
|
if (__predict_false(panicstr != NULL))
|
|
goto out;
|
|
|
|
wakeup_swapper = wakeupshlk(lk, file, line);
|
|
|
|
out:
|
|
lockmgr_exit(flags, ilk, wakeup_swapper);
|
|
return (0);
|
|
}
|
|
|
|
static __noinline int
|
|
lockmgr_xunlock_hard(struct lock *lk, uintptr_t x, u_int flags, struct lock_object *ilk,
|
|
const char *file, int line)
|
|
{
|
|
uintptr_t tid, v;
|
|
int wakeup_swapper = 0;
|
|
u_int realexslp;
|
|
int queue;
|
|
|
|
if (__predict_false(panicstr != NULL))
|
|
goto out;
|
|
|
|
tid = (uintptr_t)curthread;
|
|
|
|
/*
|
|
* As first option, treact the lock as if it has not
|
|
* any waiter.
|
|
* Fix-up the tid var if the lock has been disowned.
|
|
*/
|
|
if (LK_HOLDER(x) == LK_KERNPROC)
|
|
tid = LK_KERNPROC;
|
|
else {
|
|
WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, file, line);
|
|
TD_LOCKS_DEC(curthread);
|
|
}
|
|
LOCK_LOG_LOCK("XUNLOCK", &lk->lock_object, 0, lk->lk_recurse, file, line);
|
|
|
|
/*
|
|
* The lock is held in exclusive mode.
|
|
* If the lock is recursed also, then unrecurse it.
|
|
*/
|
|
if (lockmgr_xlocked(lk) && lockmgr_recursed(lk)) {
|
|
LOCK_LOG2(lk, "%s: %p unrecursing", __func__, lk);
|
|
lk->lk_recurse--;
|
|
goto out;
|
|
}
|
|
if (tid != LK_KERNPROC)
|
|
lock_profile_release_lock(&lk->lock_object);
|
|
|
|
if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid, LK_UNLOCKED))
|
|
goto out;
|
|
|
|
sleepq_lock(&lk->lock_object);
|
|
x = lk->lk_lock;
|
|
v = LK_UNLOCKED;
|
|
|
|
/*
|
|
* If the lock has exclusive waiters, give them
|
|
* preference in order to avoid deadlock with
|
|
* shared runners up.
|
|
* If interruptible sleeps left the exclusive queue
|
|
* empty avoid a starvation for the threads sleeping
|
|
* on the shared queue by giving them precedence
|
|
* and cleaning up the exclusive waiters bit anyway.
|
|
* Please note that lk_exslpfail count may be lying
|
|
* about the real number of waiters with the
|
|
* LK_SLEEPFAIL flag on because they may be used in
|
|
* conjunction with interruptible sleeps so
|
|
* lk_exslpfail might be considered an 'upper limit'
|
|
* bound, including the edge cases.
|
|
*/
|
|
MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0);
|
|
realexslp = sleepq_sleepcnt(&lk->lock_object, SQ_EXCLUSIVE_QUEUE);
|
|
if ((x & LK_EXCLUSIVE_WAITERS) != 0 && realexslp != 0) {
|
|
if (lk->lk_exslpfail < realexslp) {
|
|
lk->lk_exslpfail = 0;
|
|
queue = SQ_EXCLUSIVE_QUEUE;
|
|
v |= (x & LK_SHARED_WAITERS);
|
|
} else {
|
|
lk->lk_exslpfail = 0;
|
|
LOCK_LOG2(lk,
|
|
"%s: %p has only LK_SLEEPFAIL sleepers",
|
|
__func__, lk);
|
|
LOCK_LOG2(lk,
|
|
"%s: %p waking up threads on the exclusive queue",
|
|
__func__, lk);
|
|
wakeup_swapper = sleepq_broadcast(&lk->lock_object,
|
|
SLEEPQ_LK, 0, SQ_EXCLUSIVE_QUEUE);
|
|
queue = SQ_SHARED_QUEUE;
|
|
}
|
|
} else {
|
|
|
|
/*
|
|
* Exclusive waiters sleeping with LK_SLEEPFAIL
|
|
* on and using interruptible sleeps/timeout
|
|
* may have left spourious lk_exslpfail counts
|
|
* on, so clean it up anyway.
|
|
*/
|
|
lk->lk_exslpfail = 0;
|
|
queue = SQ_SHARED_QUEUE;
|
|
}
|
|
|
|
LOCK_LOG3(lk, "%s: %p waking up threads on the %s queue",
|
|
__func__, lk, queue == SQ_SHARED_QUEUE ? "shared" :
|
|
"exclusive");
|
|
atomic_store_rel_ptr(&lk->lk_lock, v);
|
|
wakeup_swapper |= sleepq_broadcast(&lk->lock_object, SLEEPQ_LK, 0, queue);
|
|
sleepq_release(&lk->lock_object);
|
|
|
|
out:
|
|
lockmgr_exit(flags, ilk, wakeup_swapper);
|
|
return (0);
|
|
}
|
|
|
|
int
|
|
lockmgr_unlock_fast_path(struct lock *lk, u_int flags, struct lock_object *ilk)
|
|
{
|
|
struct lock_class *class;
|
|
uintptr_t x, tid;
|
|
bool unlocked;
|
|
const char *file;
|
|
int line;
|
|
|
|
file = __FILE__;
|
|
line = __LINE__;
|
|
|
|
_lockmgr_assert(lk, KA_LOCKED, file, line);
|
|
unlocked = false;
|
|
x = lk->lk_lock;
|
|
if (__predict_true(x & LK_SHARE) != 0) {
|
|
if (lockmgr_sunlock_try(lk, &x)) {
|
|
lockmgr_note_shared_release(lk, file, line);
|
|
unlocked = true;
|
|
} else {
|
|
return (lockmgr_sunlock_hard(lk, x, flags, ilk, file, line));
|
|
}
|
|
} else {
|
|
tid = (uintptr_t)curthread;
|
|
if (!lockmgr_recursed(lk) &&
|
|
atomic_cmpset_rel_ptr(&lk->lk_lock, tid, LK_UNLOCKED)) {
|
|
lockmgr_note_exclusive_release(lk, file, line);
|
|
unlocked = true;
|
|
} else {
|
|
return (lockmgr_xunlock_hard(lk, x, flags, ilk, file, line));
|
|
}
|
|
}
|
|
if (__predict_false(flags & LK_INTERLOCK)) {
|
|
class = LOCK_CLASS(ilk);
|
|
class->lc_unlock(ilk);
|
|
}
|
|
return (0);
|
|
}
|
|
|
|
int
|
|
__lockmgr_args(struct lock *lk, u_int flags, struct lock_object *ilk,
|
|
const char *wmesg, int pri, int timo, const char *file, int line)
|
|
{
|
|
GIANT_DECLARE;
|
|
struct lockmgr_wait lwa;
|
|
struct lock_class *class;
|
|
const char *iwmesg;
|
|
uintptr_t tid, v, x;
|
|
u_int op, realexslp;
|
|
int error, ipri, itimo, queue, wakeup_swapper;
|
|
#ifdef LOCK_PROFILING
|
|
uint64_t waittime = 0;
|
|
int contested = 0;
|
|
#endif
|
|
|
|
error = 0;
|
|
tid = (uintptr_t)curthread;
|
|
op = (flags & LK_TYPE_MASK);
|
|
iwmesg = (wmesg == LK_WMESG_DEFAULT) ? lk->lock_object.lo_name : wmesg;
|
|
ipri = (pri == LK_PRIO_DEFAULT) ? lk->lk_pri : pri;
|
|
itimo = (timo == LK_TIMO_DEFAULT) ? lk->lk_timo : timo;
|
|
|
|
lwa.iwmesg = iwmesg;
|
|
lwa.ipri = ipri;
|
|
lwa.itimo = itimo;
|
|
|
|
MPASS((flags & ~LK_TOTAL_MASK) == 0);
|
|
KASSERT((op & (op - 1)) == 0,
|
|
("%s: Invalid requested operation @ %s:%d", __func__, file, line));
|
|
KASSERT((flags & (LK_NOWAIT | LK_SLEEPFAIL)) == 0 ||
|
|
(op != LK_DOWNGRADE && op != LK_RELEASE),
|
|
("%s: Invalid flags in regard of the operation desired @ %s:%d",
|
|
__func__, file, line));
|
|
KASSERT((flags & LK_INTERLOCK) == 0 || ilk != NULL,
|
|
("%s: LK_INTERLOCK passed without valid interlock @ %s:%d",
|
|
__func__, file, line));
|
|
KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(curthread),
|
|
("%s: idle thread %p on lockmgr %s @ %s:%d", __func__, curthread,
|
|
lk->lock_object.lo_name, file, line));
|
|
|
|
class = (flags & LK_INTERLOCK) ? LOCK_CLASS(ilk) : NULL;
|
|
if (panicstr != NULL) {
|
|
if (flags & LK_INTERLOCK)
|
|
class->lc_unlock(ilk);
|
|
return (0);
|
|
}
|
|
|
|
if (lk->lock_object.lo_flags & LK_NOSHARE) {
|
|
switch (op) {
|
|
case LK_SHARED:
|
|
op = LK_EXCLUSIVE;
|
|
break;
|
|
case LK_UPGRADE:
|
|
case LK_TRYUPGRADE:
|
|
case LK_DOWNGRADE:
|
|
_lockmgr_assert(lk, KA_XLOCKED | KA_NOTRECURSED,
|
|
file, line);
|
|
if (flags & LK_INTERLOCK)
|
|
class->lc_unlock(ilk);
|
|
return (0);
|
|
}
|
|
}
|
|
|
|
wakeup_swapper = 0;
|
|
switch (op) {
|
|
case LK_SHARED:
|
|
return (lockmgr_slock_hard(lk, flags, ilk, file, line, &lwa));
|
|
break;
|
|
case LK_UPGRADE:
|
|
case LK_TRYUPGRADE:
|
|
return (lockmgr_upgrade(lk, flags, ilk, file, line, &lwa));
|
|
break;
|
|
case LK_EXCLUSIVE:
|
|
return (lockmgr_xlock_hard(lk, flags, ilk, file, line, &lwa));
|
|
break;
|
|
case LK_DOWNGRADE:
|
|
_lockmgr_assert(lk, KA_XLOCKED, file, line);
|
|
LOCK_LOG_LOCK("XDOWNGRADE", &lk->lock_object, 0, 0, file, line);
|
|
WITNESS_DOWNGRADE(&lk->lock_object, 0, file, line);
|
|
|
|
/*
|
|
* Panic if the lock is recursed.
|
|
*/
|
|
if (lockmgr_xlocked(lk) && lockmgr_recursed(lk)) {
|
|
if (flags & LK_INTERLOCK)
|
|
class->lc_unlock(ilk);
|
|
panic("%s: downgrade a recursed lockmgr %s @ %s:%d\n",
|
|
__func__, iwmesg, file, line);
|
|
}
|
|
TD_SLOCKS_INC(curthread);
|
|
|
|
/*
|
|
* In order to preserve waiters flags, just spin.
|
|
*/
|
|
for (;;) {
|
|
x = lk->lk_lock;
|
|
MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0);
|
|
x &= LK_ALL_WAITERS;
|
|
if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x,
|
|
LK_SHARERS_LOCK(1) | x))
|
|
break;
|
|
cpu_spinwait();
|
|
}
|
|
break;
|
|
case LK_RELEASE:
|
|
_lockmgr_assert(lk, KA_LOCKED, file, line);
|
|
x = lk->lk_lock;
|
|
|
|
if (__predict_true(x & LK_SHARE) != 0) {
|
|
return (lockmgr_sunlock_hard(lk, x, flags, ilk, file, line));
|
|
} else {
|
|
return (lockmgr_xunlock_hard(lk, x, flags, ilk, file, line));
|
|
}
|
|
break;
|
|
case LK_DRAIN:
|
|
if (LK_CAN_WITNESS(flags))
|
|
WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER |
|
|
LOP_EXCLUSIVE, file, line, flags & LK_INTERLOCK ?
|
|
ilk : NULL);
|
|
|
|
/*
|
|
* Trying to drain a lock we already own will result in a
|
|
* deadlock.
|
|
*/
|
|
if (lockmgr_xlocked(lk)) {
|
|
if (flags & LK_INTERLOCK)
|
|
class->lc_unlock(ilk);
|
|
panic("%s: draining %s with the lock held @ %s:%d\n",
|
|
__func__, iwmesg, file, line);
|
|
}
|
|
|
|
for (;;) {
|
|
if (lk->lk_lock == LK_UNLOCKED &&
|
|
atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid))
|
|
break;
|
|
|
|
#ifdef HWPMC_HOOKS
|
|
PMC_SOFT_CALL( , , lock, failed);
|
|
#endif
|
|
lock_profile_obtain_lock_failed(&lk->lock_object,
|
|
&contested, &waittime);
|
|
|
|
/*
|
|
* If the lock is expected to not sleep just give up
|
|
* and return.
|
|
*/
|
|
if (LK_TRYOP(flags)) {
|
|
LOCK_LOG2(lk, "%s: %p fails the try operation",
|
|
__func__, lk);
|
|
error = EBUSY;
|
|
break;
|
|
}
|
|
|
|
/*
|
|
* Acquire the sleepqueue chain lock because we
|
|
* probabilly will need to manipulate waiters flags.
|
|
*/
|
|
sleepq_lock(&lk->lock_object);
|
|
x = lk->lk_lock;
|
|
|
|
/*
|
|
* if the lock has been released while we spun on
|
|
* the sleepqueue chain lock just try again.
|
|
*/
|
|
if (x == LK_UNLOCKED) {
|
|
sleepq_release(&lk->lock_object);
|
|
continue;
|
|
}
|
|
|
|
v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS);
|
|
if ((x & ~v) == LK_UNLOCKED) {
|
|
v = (x & ~LK_EXCLUSIVE_SPINNERS);
|
|
|
|
/*
|
|
* If interruptible sleeps left the exclusive
|
|
* queue empty avoid a starvation for the
|
|
* threads sleeping on the shared queue by
|
|
* giving them precedence and cleaning up the
|
|
* exclusive waiters bit anyway.
|
|
* Please note that lk_exslpfail count may be
|
|
* lying about the real number of waiters with
|
|
* the LK_SLEEPFAIL flag on because they may
|
|
* be used in conjunction with interruptible
|
|
* sleeps so lk_exslpfail might be considered
|
|
* an 'upper limit' bound, including the edge
|
|
* cases.
|
|
*/
|
|
if (v & LK_EXCLUSIVE_WAITERS) {
|
|
queue = SQ_EXCLUSIVE_QUEUE;
|
|
v &= ~LK_EXCLUSIVE_WAITERS;
|
|
} else {
|
|
|
|
/*
|
|
* Exclusive waiters sleeping with
|
|
* LK_SLEEPFAIL on and using
|
|
* interruptible sleeps/timeout may
|
|
* have left spourious lk_exslpfail
|
|
* counts on, so clean it up anyway.
|
|
*/
|
|
MPASS(v & LK_SHARED_WAITERS);
|
|
lk->lk_exslpfail = 0;
|
|
queue = SQ_SHARED_QUEUE;
|
|
v &= ~LK_SHARED_WAITERS;
|
|
}
|
|
if (queue == SQ_EXCLUSIVE_QUEUE) {
|
|
realexslp =
|
|
sleepq_sleepcnt(&lk->lock_object,
|
|
SQ_EXCLUSIVE_QUEUE);
|
|
if (lk->lk_exslpfail >= realexslp) {
|
|
lk->lk_exslpfail = 0;
|
|
queue = SQ_SHARED_QUEUE;
|
|
v &= ~LK_SHARED_WAITERS;
|
|
if (realexslp != 0) {
|
|
LOCK_LOG2(lk,
|
|
"%s: %p has only LK_SLEEPFAIL sleepers",
|
|
__func__, lk);
|
|
LOCK_LOG2(lk,
|
|
"%s: %p waking up threads on the exclusive queue",
|
|
__func__, lk);
|
|
wakeup_swapper =
|
|
sleepq_broadcast(
|
|
&lk->lock_object,
|
|
SLEEPQ_LK, 0,
|
|
SQ_EXCLUSIVE_QUEUE);
|
|
}
|
|
} else
|
|
lk->lk_exslpfail = 0;
|
|
}
|
|
if (!atomic_cmpset_ptr(&lk->lk_lock, x, v)) {
|
|
sleepq_release(&lk->lock_object);
|
|
continue;
|
|
}
|
|
LOCK_LOG3(lk,
|
|
"%s: %p waking up all threads on the %s queue",
|
|
__func__, lk, queue == SQ_SHARED_QUEUE ?
|
|
"shared" : "exclusive");
|
|
wakeup_swapper |= sleepq_broadcast(
|
|
&lk->lock_object, SLEEPQ_LK, 0, queue);
|
|
|
|
/*
|
|
* If shared waiters have been woken up we need
|
|
* to wait for one of them to acquire the lock
|
|
* before to set the exclusive waiters in
|
|
* order to avoid a deadlock.
|
|
*/
|
|
if (queue == SQ_SHARED_QUEUE) {
|
|
for (v = lk->lk_lock;
|
|
(v & LK_SHARE) && !LK_SHARERS(v);
|
|
v = lk->lk_lock)
|
|
cpu_spinwait();
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Try to set the LK_EXCLUSIVE_WAITERS flag. If we
|
|
* fail, loop back and retry.
|
|
*/
|
|
if ((x & LK_EXCLUSIVE_WAITERS) == 0) {
|
|
if (!atomic_cmpset_ptr(&lk->lk_lock, x,
|
|
x | LK_EXCLUSIVE_WAITERS)) {
|
|
sleepq_release(&lk->lock_object);
|
|
continue;
|
|
}
|
|
LOCK_LOG2(lk, "%s: %p set drain waiters flag",
|
|
__func__, lk);
|
|
}
|
|
|
|
/*
|
|
* As far as we have been unable to acquire the
|
|
* exclusive lock and the exclusive waiters flag
|
|
* is set, we will sleep.
|
|
*/
|
|
if (flags & LK_INTERLOCK) {
|
|
class->lc_unlock(ilk);
|
|
flags &= ~LK_INTERLOCK;
|
|
}
|
|
GIANT_SAVE();
|
|
sleepq_add(&lk->lock_object, NULL, iwmesg, SLEEPQ_LK,
|
|
SQ_EXCLUSIVE_QUEUE);
|
|
sleepq_wait(&lk->lock_object, ipri & PRIMASK);
|
|
GIANT_RESTORE();
|
|
LOCK_LOG2(lk, "%s: %p resuming from the sleep queue",
|
|
__func__, lk);
|
|
}
|
|
|
|
if (error == 0) {
|
|
lock_profile_obtain_lock_success(&lk->lock_object,
|
|
contested, waittime, file, line);
|
|
LOCK_LOG_LOCK("DRAIN", &lk->lock_object, 0,
|
|
lk->lk_recurse, file, line);
|
|
WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE |
|
|
LK_TRYWIT(flags), file, line);
|
|
TD_LOCKS_INC(curthread);
|
|
STACK_SAVE(lk);
|
|
}
|
|
break;
|
|
default:
|
|
if (flags & LK_INTERLOCK)
|
|
class->lc_unlock(ilk);
|
|
panic("%s: unknown lockmgr request 0x%x\n", __func__, op);
|
|
}
|
|
|
|
if (flags & LK_INTERLOCK)
|
|
class->lc_unlock(ilk);
|
|
if (wakeup_swapper)
|
|
kick_proc0();
|
|
|
|
return (error);
|
|
}
|
|
|
|
void
|
|
_lockmgr_disown(struct lock *lk, const char *file, int line)
|
|
{
|
|
uintptr_t tid, x;
|
|
|
|
if (SCHEDULER_STOPPED())
|
|
return;
|
|
|
|
tid = (uintptr_t)curthread;
|
|
_lockmgr_assert(lk, KA_XLOCKED, file, line);
|
|
|
|
/*
|
|
* Panic if the lock is recursed.
|
|
*/
|
|
if (lockmgr_xlocked(lk) && lockmgr_recursed(lk))
|
|
panic("%s: disown a recursed lockmgr @ %s:%d\n",
|
|
__func__, file, line);
|
|
|
|
/*
|
|
* If the owner is already LK_KERNPROC just skip the whole operation.
|
|
*/
|
|
if (LK_HOLDER(lk->lk_lock) != tid)
|
|
return;
|
|
lock_profile_release_lock(&lk->lock_object);
|
|
LOCK_LOG_LOCK("XDISOWN", &lk->lock_object, 0, 0, file, line);
|
|
WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, file, line);
|
|
TD_LOCKS_DEC(curthread);
|
|
STACK_SAVE(lk);
|
|
|
|
/*
|
|
* In order to preserve waiters flags, just spin.
|
|
*/
|
|
for (;;) {
|
|
x = lk->lk_lock;
|
|
MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0);
|
|
x &= LK_ALL_WAITERS;
|
|
if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x,
|
|
LK_KERNPROC | x))
|
|
return;
|
|
cpu_spinwait();
|
|
}
|
|
}
|
|
|
|
void
|
|
lockmgr_printinfo(const struct lock *lk)
|
|
{
|
|
struct thread *td;
|
|
uintptr_t x;
|
|
|
|
if (lk->lk_lock == LK_UNLOCKED)
|
|
printf("lock type %s: UNLOCKED\n", lk->lock_object.lo_name);
|
|
else if (lk->lk_lock & LK_SHARE)
|
|
printf("lock type %s: SHARED (count %ju)\n",
|
|
lk->lock_object.lo_name,
|
|
(uintmax_t)LK_SHARERS(lk->lk_lock));
|
|
else {
|
|
td = lockmgr_xholder(lk);
|
|
if (td == (struct thread *)LK_KERNPROC)
|
|
printf("lock type %s: EXCL by KERNPROC\n",
|
|
lk->lock_object.lo_name);
|
|
else
|
|
printf("lock type %s: EXCL by thread %p "
|
|
"(pid %d, %s, tid %d)\n", lk->lock_object.lo_name,
|
|
td, td->td_proc->p_pid, td->td_proc->p_comm,
|
|
td->td_tid);
|
|
}
|
|
|
|
x = lk->lk_lock;
|
|
if (x & LK_EXCLUSIVE_WAITERS)
|
|
printf(" with exclusive waiters pending\n");
|
|
if (x & LK_SHARED_WAITERS)
|
|
printf(" with shared waiters pending\n");
|
|
if (x & LK_EXCLUSIVE_SPINNERS)
|
|
printf(" with exclusive spinners pending\n");
|
|
|
|
STACK_PRINT(lk);
|
|
}
|
|
|
|
int
|
|
lockstatus(const struct lock *lk)
|
|
{
|
|
uintptr_t v, x;
|
|
int ret;
|
|
|
|
ret = LK_SHARED;
|
|
x = lk->lk_lock;
|
|
v = LK_HOLDER(x);
|
|
|
|
if ((x & LK_SHARE) == 0) {
|
|
if (v == (uintptr_t)curthread || v == LK_KERNPROC)
|
|
ret = LK_EXCLUSIVE;
|
|
else
|
|
ret = LK_EXCLOTHER;
|
|
} else if (x == LK_UNLOCKED)
|
|
ret = 0;
|
|
|
|
return (ret);
|
|
}
|
|
|
|
#ifdef INVARIANT_SUPPORT
|
|
|
|
FEATURE(invariant_support,
|
|
"Support for modules compiled with INVARIANTS option");
|
|
|
|
#ifndef INVARIANTS
|
|
#undef _lockmgr_assert
|
|
#endif
|
|
|
|
void
|
|
_lockmgr_assert(const struct lock *lk, int what, const char *file, int line)
|
|
{
|
|
int slocked = 0;
|
|
|
|
if (panicstr != NULL)
|
|
return;
|
|
switch (what) {
|
|
case KA_SLOCKED:
|
|
case KA_SLOCKED | KA_NOTRECURSED:
|
|
case KA_SLOCKED | KA_RECURSED:
|
|
slocked = 1;
|
|
case KA_LOCKED:
|
|
case KA_LOCKED | KA_NOTRECURSED:
|
|
case KA_LOCKED | KA_RECURSED:
|
|
#ifdef WITNESS
|
|
|
|
/*
|
|
* We cannot trust WITNESS if the lock is held in exclusive
|
|
* mode and a call to lockmgr_disown() happened.
|
|
* Workaround this skipping the check if the lock is held in
|
|
* exclusive mode even for the KA_LOCKED case.
|
|
*/
|
|
if (slocked || (lk->lk_lock & LK_SHARE)) {
|
|
witness_assert(&lk->lock_object, what, file, line);
|
|
break;
|
|
}
|
|
#endif
|
|
if (lk->lk_lock == LK_UNLOCKED ||
|
|
((lk->lk_lock & LK_SHARE) == 0 && (slocked ||
|
|
(!lockmgr_xlocked(lk) && !lockmgr_disowned(lk)))))
|
|
panic("Lock %s not %slocked @ %s:%d\n",
|
|
lk->lock_object.lo_name, slocked ? "share" : "",
|
|
file, line);
|
|
|
|
if ((lk->lk_lock & LK_SHARE) == 0) {
|
|
if (lockmgr_recursed(lk)) {
|
|
if (what & KA_NOTRECURSED)
|
|
panic("Lock %s recursed @ %s:%d\n",
|
|
lk->lock_object.lo_name, file,
|
|
line);
|
|
} else if (what & KA_RECURSED)
|
|
panic("Lock %s not recursed @ %s:%d\n",
|
|
lk->lock_object.lo_name, file, line);
|
|
}
|
|
break;
|
|
case KA_XLOCKED:
|
|
case KA_XLOCKED | KA_NOTRECURSED:
|
|
case KA_XLOCKED | KA_RECURSED:
|
|
if (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk))
|
|
panic("Lock %s not exclusively locked @ %s:%d\n",
|
|
lk->lock_object.lo_name, file, line);
|
|
if (lockmgr_recursed(lk)) {
|
|
if (what & KA_NOTRECURSED)
|
|
panic("Lock %s recursed @ %s:%d\n",
|
|
lk->lock_object.lo_name, file, line);
|
|
} else if (what & KA_RECURSED)
|
|
panic("Lock %s not recursed @ %s:%d\n",
|
|
lk->lock_object.lo_name, file, line);
|
|
break;
|
|
case KA_UNLOCKED:
|
|
if (lockmgr_xlocked(lk) || lockmgr_disowned(lk))
|
|
panic("Lock %s exclusively locked @ %s:%d\n",
|
|
lk->lock_object.lo_name, file, line);
|
|
break;
|
|
default:
|
|
panic("Unknown lockmgr assertion: %d @ %s:%d\n", what, file,
|
|
line);
|
|
}
|
|
}
|
|
#endif
|
|
|
|
#ifdef DDB
|
|
int
|
|
lockmgr_chain(struct thread *td, struct thread **ownerp)
|
|
{
|
|
struct lock *lk;
|
|
|
|
lk = td->td_wchan;
|
|
|
|
if (LOCK_CLASS(&lk->lock_object) != &lock_class_lockmgr)
|
|
return (0);
|
|
db_printf("blocked on lockmgr %s", lk->lock_object.lo_name);
|
|
if (lk->lk_lock & LK_SHARE)
|
|
db_printf("SHARED (count %ju)\n",
|
|
(uintmax_t)LK_SHARERS(lk->lk_lock));
|
|
else
|
|
db_printf("EXCL\n");
|
|
*ownerp = lockmgr_xholder(lk);
|
|
|
|
return (1);
|
|
}
|
|
|
|
static void
|
|
db_show_lockmgr(const struct lock_object *lock)
|
|
{
|
|
struct thread *td;
|
|
const struct lock *lk;
|
|
|
|
lk = (const struct lock *)lock;
|
|
|
|
db_printf(" state: ");
|
|
if (lk->lk_lock == LK_UNLOCKED)
|
|
db_printf("UNLOCKED\n");
|
|
else if (lk->lk_lock & LK_SHARE)
|
|
db_printf("SLOCK: %ju\n", (uintmax_t)LK_SHARERS(lk->lk_lock));
|
|
else {
|
|
td = lockmgr_xholder(lk);
|
|
if (td == (struct thread *)LK_KERNPROC)
|
|
db_printf("XLOCK: LK_KERNPROC\n");
|
|
else
|
|
db_printf("XLOCK: %p (tid %d, pid %d, \"%s\")\n", td,
|
|
td->td_tid, td->td_proc->p_pid,
|
|
td->td_proc->p_comm);
|
|
if (lockmgr_recursed(lk))
|
|
db_printf(" recursed: %d\n", lk->lk_recurse);
|
|
}
|
|
db_printf(" waiters: ");
|
|
switch (lk->lk_lock & LK_ALL_WAITERS) {
|
|
case LK_SHARED_WAITERS:
|
|
db_printf("shared\n");
|
|
break;
|
|
case LK_EXCLUSIVE_WAITERS:
|
|
db_printf("exclusive\n");
|
|
break;
|
|
case LK_ALL_WAITERS:
|
|
db_printf("shared and exclusive\n");
|
|
break;
|
|
default:
|
|
db_printf("none\n");
|
|
}
|
|
db_printf(" spinners: ");
|
|
if (lk->lk_lock & LK_EXCLUSIVE_SPINNERS)
|
|
db_printf("exclusive\n");
|
|
else
|
|
db_printf("none\n");
|
|
}
|
|
#endif
|