/*- * Copyright (c) 2006 John Baldwin * 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 #include #include #ifdef _KERNEL #include #include #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 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_WRITE_SPINNER 0x08 #define RW_LOCK_FLAGMASK \ (RW_LOCK_READ | RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS | \ RW_LOCK_WRITE_SPINNER) #define RW_LOCK_WAITERS (RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS) #define RW_OWNER(x) ((x) & ~RW_LOCK_FLAGMASK) #define RW_READERS_SHIFT 4 #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) #define RW_DESTROYED (RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS) #ifdef _KERNEL #define rw_recurse lock_object.lo_data /* 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)); \ else \ lock_profile_obtain_lock_success(&(rw)->lock_object, 0, \ 0, (file), (line)); \ } while (0) /* Release a write lock. */ #define __rw_wunlock(rw, tid, file, line) do { \ uintptr_t _tid = (uintptr_t)(tid); \ \ if ((rw)->rw_recurse) \ (rw)->rw_recurse--; \ else 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. */ #define rw_init(rw, name) rw_init_flags((rw), (name), 0) void rw_init_flags(struct rwlock *rw, const char *name, int opts); void rw_destroy(struct rwlock *rw); void rw_sysinit(void *arg); int rw_wowned(struct rwlock *rw); void _rw_wlock(struct rwlock *rw, const char *file, int line); int _rw_try_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); int _rw_try_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. */ #ifndef LOCK_DEBUG #error LOCK_DEBUG not defined, include before #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_rlock(rw) _rw_try_rlock((rw), LOCK_FILE, LOCK_LINE) #define rw_try_upgrade(rw) _rw_try_upgrade((rw), LOCK_FILE, LOCK_LINE) #define rw_try_wlock(rw) _rw_try_wlock((rw), LOCK_FILE, LOCK_LINE) #define rw_downgrade(rw) _rw_downgrade((rw), LOCK_FILE, LOCK_LINE) #define rw_unlock(rw) do { \ if (rw_wowned(rw)) \ rw_wunlock(rw); \ else \ rw_runlock(rw); \ } while (0) #define rw_sleep(chan, rw, pri, wmesg, timo) \ _sleep((chan), &(rw)->lock_object, (pri), (wmesg), (timo)) #define rw_initialized(rw) lock_initalized(&(rw)->lock_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)) /* * Options passed to rw_init_flags(). */ #define RW_DUPOK 0x01 #define RW_NOPROFILE 0x02 #define RW_NOWITNESS 0x04 #define RW_QUIET 0x08 #define RW_RECURSE 0x10 /* * 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 #define RA_RECURSED LA_RECURSED #define RA_NOTRECURSED LA_NOTRECURSED #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_ */