/*-
* Copyright (c) 2006 John Baldwin <jhb@FreeBSD.org>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the author nor the names of any co-contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* $FreeBSD$
*/
#ifndef _SYS_RWLOCK_H_
#define _SYS_RWLOCK_H_
#include <sys/_lock.h>
#include <sys/_rwlock.h>
#ifdef _KERNEL
#include <sys/pcpu.h>
#include <machine/atomic.h>
#endif
/*
* The rw_lock field consists of several fields. The low bit indicates
* if the lock is locked with a read (shared) or write (exclusive) lock.
* A value of 0 indicates a write lock, and a value of 1 indicates a read
* lock. Bit 1 is a boolean indicating if there are any threads waiting
* for a read lock. Bit 2 is a boolean indicating if there are any threads
* waiting for a write lock. The rest of the variable's definition is
* dependent on the value of the first bit. For a write lock, it is a
* pointer to the thread holding the lock, similar to the mtx_lock field of
* mutexes. For read locks, it is a count of read locks that are held.
*
* When the lock is not locked by any thread, it is encoded as a read lock
* with zero waiters.
*
* A note about memory barriers. Write locks need to use the same memory
* barriers as mutexes: _acq when acquiring a write lock and _rel when
* releasing a write lock. Read locks also need to use an _acq barrier when
* acquiring a read lock. However, since read locks do not update any
* locked data (modulo bugs of course), no memory barrier is needed to when
* releasing a read lock.
*/
#define RW_LOCK_READ 0x01
#define RW_LOCK_READ_WAITERS 0x02
#define RW_LOCK_WRITE_WAITERS 0x04
#define RW_LOCK_FLAGMASK \
(RW_LOCK_READ | RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS)
#define RW_OWNER(x) ((x) & ~RW_LOCK_FLAGMASK)
#define RW_READERS_SHIFT 3
#define RW_READERS(x) (RW_OWNER((x)) >> RW_READERS_SHIFT)
#define RW_READERS_LOCK(x) ((x) << RW_READERS_SHIFT | RW_LOCK_READ)
#define RW_ONE_READER (1 << RW_READERS_SHIFT)
#define RW_UNLOCKED RW_READERS_LOCK(0)
#ifdef _KERNEL
/* Very simple operations on rw_lock. */
/* Try to obtain a write lock once. */
#define _rw_write_lock(rw, tid) \
atomic_cmpset_acq_ptr(&(rw)->rw_lock, RW_UNLOCKED, (tid))
/* Release a write lock quickly if there are no waiters. */
#define _rw_write_unlock(rw, tid) \
atomic_cmpset_rel_ptr(&(rw)->rw_lock, (tid), RW_UNLOCKED)
/*
* Full lock operations that are suitable to be inlined in non-debug
* kernels. If the lock cannot be acquired or released trivially then
* the work is deferred to another function.
*/
/* Acquire a write lock. */
#define __rw_wlock(rw, tid, file, line) do { \
uintptr_t _tid = (uintptr_t)(tid); \
\
if (!_rw_write_lock((rw), _tid)) \
_rw_wlock_hard((rw), _tid, (file), (line)); \
} while (0)
/* Release a write lock. */
#define __rw_wunlock(rw, tid, file, line) do { \
uintptr_t _tid = (uintptr_t)(tid); \
\
if (!_rw_write_unlock((rw), _tid)) \
_rw_wunlock_hard((rw), _tid, (file), (line)); \
} while (0)
/*
* Function prototypes. Routines that start with _ are not part of the
* external API and should not be called directly. Wrapper macros should
* be used instead.
*/
void rw_init(struct rwlock *rw, const char *name);
void rw_destroy(struct rwlock *rw);
void rw_sysinit(void *arg);
void _rw_wlock(struct rwlock *rw, const char *file, int line);
void _rw_wunlock(struct rwlock *rw, const char *file, int line);
void _rw_rlock(struct rwlock *rw, const char *file, int line);
void _rw_runlock(struct rwlock *rw, const char *file, int line);
void _rw_wlock_hard(struct rwlock *rw, uintptr_t tid, const char *file,
int line);
void _rw_wunlock_hard(struct rwlock *rw, uintptr_t tid, const char *file,
int line);
int _rw_try_upgrade(struct rwlock *rw, const char *file, int line);
void _rw_downgrade(struct rwlock *rw, const char *file, int line);
#if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
void _rw_assert(struct rwlock *rw, int what, const char *file, int line);
#endif
/*
* Public interface for lock operations.
*
* XXX: Missing try locks.
*/
#ifndef LOCK_DEBUG
#error LOCK_DEBUG not defined, include <sys/lock.h> before <sys/rwlock.h>
#endif
#if LOCK_DEBUG > 0 || defined(RWLOCK_NOINLINE)
#define rw_wlock(rw) _rw_wlock((rw), LOCK_FILE, LOCK_LINE)
#define rw_wunlock(rw) _rw_wunlock((rw), LOCK_FILE, LOCK_LINE)
#else
#define rw_wlock(rw) \
__rw_wlock((rw), curthread, LOCK_FILE, LOCK_LINE)
#define rw_wunlock(rw) \
__rw_wunlock((rw), curthread, LOCK_FILE, LOCK_LINE)
#endif
#define rw_rlock(rw) _rw_rlock((rw), LOCK_FILE, LOCK_LINE)
#define rw_runlock(rw) _rw_runlock((rw), LOCK_FILE, LOCK_LINE)
#define rw_try_upgrade(rw) _rw_try_upgrade((rw), LOCK_FILE, LOCK_LINE)
#define rw_downgrade(rw) _rw_downgrade((rw), LOCK_FILE, LOCK_LINE)
#define rw_initialized(rw) lock_initalized(&(rw)->rw_object)
struct rw_args {
struct rwlock *ra_rw;
const char *ra_desc;
};
#define RW_SYSINIT(name, rw, desc) \
static struct rw_args name##_args = { \
(rw), \
(desc), \
}; \
SYSINIT(name##_rw_sysinit, SI_SUB_LOCK, SI_ORDER_MIDDLE, \
rw_sysinit, &name##_args); \
SYSUNINIT(name##_rw_sysuninit, SI_SUB_LOCK, SI_ORDER_MIDDLE, \
rw_destroy, (rw))
/*
* The INVARIANTS-enabled rw_assert() functionality.
*
* The constants need to be defined for INVARIANT_SUPPORT infrastructure
* support as _rw_assert() itself uses them and the latter implies that
* _rw_assert() must build.
*/
#if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
#define RA_LOCKED LA_LOCKED
#define RA_RLOCKED LA_SLOCKED
#define RA_WLOCKED LA_XLOCKED
#define RA_UNLOCKED LA_UNLOCKED
#endif
#ifdef INVARIANTS
#define rw_assert(rw, what) _rw_assert((rw), (what), LOCK_FILE, LOCK_LINE)
#else
#define rw_assert(rw, what)
#endif
#endif /* _KERNEL */
#endif /* !_SYS_RWLOCK_H_ */
