ddce63ca73
in order to avoid, on architectures which doesn't have strong ordered writes, CPU instructions reordering. Diagnosed by: fabio Reviewed by: jhb Tested by: Giovanni Trematerra <giovanni dot trematerra at gmail dot com>
295 lines
10 KiB
C
295 lines
10 KiB
C
/*-
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* Copyright (c) 2007 Attilio Rao <attilio@freebsd.org>
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* Copyright (c) 2001 Jason Evans <jasone@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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* $FreeBSD$
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*/
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#ifndef _SYS_SX_H_
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#define _SYS_SX_H_
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#include <sys/_lock.h>
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#include <sys/_sx.h>
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#ifdef _KERNEL
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#include <sys/pcpu.h>
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#include <sys/lock_profile.h>
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#include <sys/lockstat.h>
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#include <machine/atomic.h>
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#endif
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/*
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* In general, the sx locks and rwlocks use very similar algorithms.
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* The main difference in the implementations is how threads are
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* blocked when a lock is unavailable. For this, sx locks use sleep
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* queues which do not support priority propagation, and rwlocks use
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* turnstiles which do.
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*
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* The sx_lock field consists of several fields. The low bit
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* indicates if the lock is locked with a shared or exclusive lock. A
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* value of 0 indicates an exclusive lock, and a value of 1 indicates
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* a shared lock. Bit 1 is a boolean indicating if there are any
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* threads waiting for a shared lock. Bit 2 is a boolean indicating
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* if there are any threads waiting for an exclusive lock. Bit 3 is a
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* boolean indicating if an exclusive lock is recursively held. The
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* rest of the variable's definition is dependent on the value of the
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* first bit. For an exclusive lock, it is a pointer to the thread
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* holding the lock, similar to the mtx_lock field of mutexes. For
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* shared locks, it is a count of read locks that are held.
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*
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* When the lock is not locked by any thread, it is encoded as a
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* shared lock with zero waiters.
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*/
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#define SX_LOCK_SHARED 0x01
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#define SX_LOCK_SHARED_WAITERS 0x02
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#define SX_LOCK_EXCLUSIVE_WAITERS 0x04
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#define SX_LOCK_RECURSED 0x08
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#define SX_LOCK_FLAGMASK \
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(SX_LOCK_SHARED | SX_LOCK_SHARED_WAITERS | \
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SX_LOCK_EXCLUSIVE_WAITERS | SX_LOCK_RECURSED)
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#define SX_OWNER(x) ((x) & ~SX_LOCK_FLAGMASK)
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#define SX_SHARERS_SHIFT 4
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#define SX_SHARERS(x) (SX_OWNER(x) >> SX_SHARERS_SHIFT)
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#define SX_SHARERS_LOCK(x) \
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((x) << SX_SHARERS_SHIFT | SX_LOCK_SHARED)
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#define SX_ONE_SHARER (1 << SX_SHARERS_SHIFT)
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#define SX_LOCK_UNLOCKED SX_SHARERS_LOCK(0)
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#define SX_LOCK_DESTROYED \
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(SX_LOCK_SHARED_WAITERS | SX_LOCK_EXCLUSIVE_WAITERS)
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#ifdef _KERNEL
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/*
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* Function prototipes. Routines that start with an underscore are not part
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* of the public interface and are wrappered with a macro.
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*/
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void sx_sysinit(void *arg);
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#define sx_init(sx, desc) sx_init_flags((sx), (desc), 0)
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void sx_init_flags(struct sx *sx, const char *description, int opts);
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void sx_destroy(struct sx *sx);
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int _sx_slock(struct sx *sx, int opts, const char *file, int line);
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int _sx_xlock(struct sx *sx, int opts, const char *file, int line);
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int _sx_try_slock(struct sx *sx, const char *file, int line);
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int _sx_try_xlock(struct sx *sx, const char *file, int line);
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void _sx_sunlock(struct sx *sx, const char *file, int line);
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void _sx_xunlock(struct sx *sx, const char *file, int line);
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int _sx_try_upgrade(struct sx *sx, const char *file, int line);
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void _sx_downgrade(struct sx *sx, const char *file, int line);
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int _sx_xlock_hard(struct sx *sx, uintptr_t tid, int opts,
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const char *file, int line);
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int _sx_slock_hard(struct sx *sx, int opts, const char *file, int line);
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void _sx_xunlock_hard(struct sx *sx, uintptr_t tid, const char *file, int
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line);
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void _sx_sunlock_hard(struct sx *sx, const char *file, int line);
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#if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
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void _sx_assert(struct sx *sx, int what, const char *file, int line);
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#endif
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#ifdef DDB
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int sx_chain(struct thread *td, struct thread **ownerp);
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#endif
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struct sx_args {
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struct sx *sa_sx;
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const char *sa_desc;
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};
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#define SX_SYSINIT(name, sxa, desc) \
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static struct sx_args name##_args = { \
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(sxa), \
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(desc) \
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}; \
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SYSINIT(name##_sx_sysinit, SI_SUB_LOCK, SI_ORDER_MIDDLE, \
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sx_sysinit, &name##_args); \
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SYSUNINIT(name##_sx_sysuninit, SI_SUB_LOCK, SI_ORDER_MIDDLE, \
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sx_destroy, (sxa))
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/*
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* Full lock operations that are suitable to be inlined in non-debug kernels.
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* If the lock can't be acquired or released trivially then the work is
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* deferred to 'tougher' functions.
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*/
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/* Acquire an exclusive lock. */
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static __inline int
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__sx_xlock(struct sx *sx, struct thread *td, int opts, const char *file,
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int line)
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{
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uintptr_t tid = (uintptr_t)td;
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int error = 0;
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if (!atomic_cmpset_acq_ptr(&sx->sx_lock, SX_LOCK_UNLOCKED, tid))
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error = _sx_xlock_hard(sx, tid, opts, file, line);
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else
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LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(LS_SX_XLOCK_ACQUIRE,
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sx, 0, 0, file, line);
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return (error);
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}
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/* Release an exclusive lock. */
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static __inline void
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__sx_xunlock(struct sx *sx, struct thread *td, const char *file, int line)
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{
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uintptr_t tid = (uintptr_t)td;
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if (!atomic_cmpset_rel_ptr(&sx->sx_lock, tid, SX_LOCK_UNLOCKED))
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_sx_xunlock_hard(sx, tid, file, line);
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}
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/* Acquire a shared lock. */
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static __inline int
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__sx_slock(struct sx *sx, int opts, const char *file, int line)
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{
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uintptr_t x = sx->sx_lock;
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int error = 0;
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if (!(x & SX_LOCK_SHARED) ||
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!atomic_cmpset_acq_ptr(&sx->sx_lock, x, x + SX_ONE_SHARER))
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error = _sx_slock_hard(sx, opts, file, line);
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else
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LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(LS_SX_SLOCK_ACQUIRE, sx, 0,
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0, file, line);
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return (error);
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}
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/*
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* Release a shared lock. We can just drop a single shared lock so
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* long as we aren't trying to drop the last shared lock when other
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* threads are waiting for an exclusive lock. This takes advantage of
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* the fact that an unlocked lock is encoded as a shared lock with a
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* count of 0.
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*/
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static __inline void
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__sx_sunlock(struct sx *sx, const char *file, int line)
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{
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uintptr_t x = sx->sx_lock;
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if (x == (SX_SHARERS_LOCK(1) | SX_LOCK_EXCLUSIVE_WAITERS) ||
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!atomic_cmpset_rel_ptr(&sx->sx_lock, x, x - SX_ONE_SHARER))
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_sx_sunlock_hard(sx, file, line);
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}
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/*
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* Public interface for lock operations.
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*/
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#ifndef LOCK_DEBUG
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#error "LOCK_DEBUG not defined, include <sys/lock.h> before <sys/sx.h>"
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#endif
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#if (LOCK_DEBUG > 0) || defined(SX_NOINLINE)
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#define sx_xlock(sx) (void)_sx_xlock((sx), 0, LOCK_FILE, LOCK_LINE)
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#define sx_xlock_sig(sx) \
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_sx_xlock((sx), SX_INTERRUPTIBLE, LOCK_FILE, LOCK_LINE)
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#define sx_xunlock(sx) _sx_xunlock((sx), LOCK_FILE, LOCK_LINE)
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#define sx_slock(sx) (void)_sx_slock((sx), 0, LOCK_FILE, LOCK_LINE)
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#define sx_slock_sig(sx) \
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_sx_slock((sx), SX_INTERRUPTIBLE, LOCK_FILE, LOCK_LINE)
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#define sx_sunlock(sx) _sx_sunlock((sx), LOCK_FILE, LOCK_LINE)
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#else
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#define sx_xlock(sx) \
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(void)__sx_xlock((sx), curthread, 0, LOCK_FILE, LOCK_LINE)
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#define sx_xlock_sig(sx) \
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__sx_xlock((sx), curthread, SX_INTERRUPTIBLE, LOCK_FILE, LOCK_LINE)
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#define sx_xunlock(sx) \
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__sx_xunlock((sx), curthread, LOCK_FILE, LOCK_LINE)
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#define sx_slock(sx) (void)__sx_slock((sx), 0, LOCK_FILE, LOCK_LINE)
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#define sx_slock_sig(sx) \
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__sx_slock((sx), SX_INTERRUPTIBLE, LOCK_FILE, LOCK_LINE)
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#define sx_sunlock(sx) __sx_sunlock((sx), LOCK_FILE, LOCK_LINE)
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#endif /* LOCK_DEBUG > 0 || SX_NOINLINE */
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#define sx_try_slock(sx) _sx_try_slock((sx), LOCK_FILE, LOCK_LINE)
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#define sx_try_xlock(sx) _sx_try_xlock((sx), LOCK_FILE, LOCK_LINE)
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#define sx_try_upgrade(sx) _sx_try_upgrade((sx), LOCK_FILE, LOCK_LINE)
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#define sx_downgrade(sx) _sx_downgrade((sx), LOCK_FILE, LOCK_LINE)
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/*
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* Return a pointer to the owning thread if the lock is exclusively
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* locked.
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*/
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#define sx_xholder(sx) \
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((sx)->sx_lock & SX_LOCK_SHARED ? NULL : \
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(struct thread *)SX_OWNER((sx)->sx_lock))
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#define sx_xlocked(sx) \
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(((sx)->sx_lock & ~(SX_LOCK_FLAGMASK & ~SX_LOCK_SHARED)) == \
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(uintptr_t)curthread)
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#define sx_unlock(sx) do { \
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if (sx_xlocked(sx)) \
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sx_xunlock(sx); \
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else \
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sx_sunlock(sx); \
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} while (0)
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#define sx_sleep(chan, sx, pri, wmesg, timo) \
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_sleep((chan), &(sx)->lock_object, (pri), (wmesg), (timo))
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/*
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* Options passed to sx_init_flags().
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*/
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#define SX_DUPOK 0x01
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#define SX_NOPROFILE 0x02
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#define SX_NOWITNESS 0x04
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#define SX_QUIET 0x08
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#define SX_NOADAPTIVE 0x10
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#define SX_RECURSE 0x20
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/*
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* Options passed to sx_*lock_hard().
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*/
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#define SX_INTERRUPTIBLE 0x40
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#if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
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#define SA_LOCKED LA_LOCKED
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#define SA_SLOCKED LA_SLOCKED
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#define SA_XLOCKED LA_XLOCKED
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#define SA_UNLOCKED LA_UNLOCKED
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#define SA_RECURSED LA_RECURSED
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#define SA_NOTRECURSED LA_NOTRECURSED
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/* Backwards compatability. */
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#define SX_LOCKED LA_LOCKED
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#define SX_SLOCKED LA_SLOCKED
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#define SX_XLOCKED LA_XLOCKED
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#define SX_UNLOCKED LA_UNLOCKED
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#define SX_RECURSED LA_RECURSED
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#define SX_NOTRECURSED LA_NOTRECURSED
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#endif
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#ifdef INVARIANTS
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#define sx_assert(sx, what) _sx_assert((sx), (what), LOCK_FILE, LOCK_LINE)
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#else
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#define sx_assert(sx, what) (void)0
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#endif
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#endif /* _KERNEL */
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#endif /* !_SYS_SX_H_ */
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