/*- * Copyright (c) 2007 Attilio Rao * Copyright (c) 2001 Jason Evans * 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(s), this list of conditions and the following disclaimer as * the first lines of this file unmodified other than the possible * addition of one or more copyright notices. * 2. Redistributions in binary form must reproduce the above copyright * notice(s), this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``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 COPYRIGHT HOLDER(S) 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_SX_H_ #define _SYS_SX_H_ #include #include #ifdef _KERNEL #include #include #include #include #endif /* * In general, the sx locks and rwlocks use very similar algorithms. * The main difference in the implementations is how threads are * blocked when a lock is unavailable. For this, sx locks use sleep * queues which do not support priority propagation, and rwlocks use * turnstiles which do. * * The sx_lock field consists of several fields. The low bit * indicates if the lock is locked with a shared or exclusive lock. A * value of 0 indicates an exclusive lock, and a value of 1 indicates * a shared lock. Bit 1 is a boolean indicating if there are any * threads waiting for a shared lock. Bit 2 is a boolean indicating * if there are any threads waiting for an exclusive lock. Bit 3 is a * boolean indicating if an exclusive lock is recursively held. The * rest of the variable's definition is dependent on the value of the * first bit. For an exclusive lock, it is a pointer to the thread * holding the lock, similar to the mtx_lock field of mutexes. For * shared 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 * shared lock with zero waiters. */ #define SX_LOCK_SHARED 0x01 #define SX_LOCK_SHARED_WAITERS 0x02 #define SX_LOCK_EXCLUSIVE_WAITERS 0x04 #define SX_LOCK_RECURSED 0x08 #define SX_LOCK_FLAGMASK \ (SX_LOCK_SHARED | SX_LOCK_SHARED_WAITERS | \ SX_LOCK_EXCLUSIVE_WAITERS | SX_LOCK_RECURSED) #define SX_OWNER(x) ((x) & ~SX_LOCK_FLAGMASK) #define SX_SHARERS_SHIFT 4 #define SX_SHARERS(x) (SX_OWNER(x) >> SX_SHARERS_SHIFT) #define SX_SHARERS_LOCK(x) \ ((x) << SX_SHARERS_SHIFT | SX_LOCK_SHARED) #define SX_ONE_SHARER (1 << SX_SHARERS_SHIFT) #define SX_LOCK_UNLOCKED SX_SHARERS_LOCK(0) #define SX_LOCK_DESTROYED \ (SX_LOCK_SHARED_WAITERS | SX_LOCK_EXCLUSIVE_WAITERS) #ifdef _KERNEL /* * Function prototipes. Routines that start with an underscore are not part * of the public interface and are wrappered with a macro. */ void sx_sysinit(void *arg); #define sx_init(sx, desc) sx_init_flags((sx), (desc), 0) void sx_init_flags(struct sx *sx, const char *description, int opts); void sx_destroy(struct sx *sx); int sx_try_slock_(struct sx *sx, const char *file, int line); int sx_try_xlock_(struct sx *sx, const char *file, int line); int sx_try_upgrade_(struct sx *sx, const char *file, int line); void sx_downgrade_(struct sx *sx, const char *file, int line); int _sx_slock(struct sx *sx, int opts, const char *file, int line); int _sx_xlock(struct sx *sx, int opts, const char *file, int line); void _sx_sunlock(struct sx *sx, const char *file, int line); void _sx_xunlock(struct sx *sx, const char *file, int line); int _sx_xlock_hard(struct sx *sx, uintptr_t tid, int opts, const char *file, int line); int _sx_slock_hard(struct sx *sx, int opts, const char *file, int line); void _sx_xunlock_hard(struct sx *sx, uintptr_t tid, const char *file, int line); void _sx_sunlock_hard(struct sx *sx, const char *file, int line); #if defined(INVARIANTS) || defined(INVARIANT_SUPPORT) void _sx_assert(const struct sx *sx, int what, const char *file, int line); #endif #ifdef DDB int sx_chain(struct thread *td, struct thread **ownerp); #endif struct sx_args { struct sx *sa_sx; const char *sa_desc; int sa_flags; }; #define SX_SYSINIT_FLAGS(name, sxa, desc, flags) \ static struct sx_args name##_args = { \ (sxa), \ (desc), \ (flags) \ }; \ SYSINIT(name##_sx_sysinit, SI_SUB_LOCK, SI_ORDER_MIDDLE, \ sx_sysinit, &name##_args); \ SYSUNINIT(name##_sx_sysuninit, SI_SUB_LOCK, SI_ORDER_MIDDLE, \ sx_destroy, (sxa)) #define SX_SYSINIT(name, sxa, desc) SX_SYSINIT_FLAGS(name, sxa, desc, 0) /* * Full lock operations that are suitable to be inlined in non-debug kernels. * If the lock can't be acquired or released trivially then the work is * deferred to 'tougher' functions. */ /* Acquire an exclusive lock. */ static __inline int __sx_xlock(struct sx *sx, struct thread *td, int opts, const char *file, int line) { uintptr_t tid = (uintptr_t)td; int error = 0; if (!atomic_cmpset_acq_ptr(&sx->sx_lock, SX_LOCK_UNLOCKED, tid)) error = _sx_xlock_hard(sx, tid, opts, file, line); else LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(LS_SX_XLOCK_ACQUIRE, sx, 0, 0, file, line); return (error); } /* Release an exclusive lock. */ static __inline void __sx_xunlock(struct sx *sx, struct thread *td, const char *file, int line) { uintptr_t tid = (uintptr_t)td; if (!atomic_cmpset_rel_ptr(&sx->sx_lock, tid, SX_LOCK_UNLOCKED)) _sx_xunlock_hard(sx, tid, file, line); } /* Acquire a shared lock. */ static __inline int __sx_slock(struct sx *sx, int opts, const char *file, int line) { uintptr_t x = sx->sx_lock; int error = 0; if (!(x & SX_LOCK_SHARED) || !atomic_cmpset_acq_ptr(&sx->sx_lock, x, x + SX_ONE_SHARER)) error = _sx_slock_hard(sx, opts, file, line); else LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(LS_SX_SLOCK_ACQUIRE, sx, 0, 0, file, line); return (error); } /* * Release a shared lock. We can just drop a single shared lock so * long as we aren't trying to drop the last shared lock when other * threads are waiting for an exclusive lock. This takes advantage of * the fact that an unlocked lock is encoded as a shared lock with a * count of 0. */ static __inline void __sx_sunlock(struct sx *sx, const char *file, int line) { uintptr_t x = sx->sx_lock; if (x == (SX_SHARERS_LOCK(1) | SX_LOCK_EXCLUSIVE_WAITERS) || !atomic_cmpset_rel_ptr(&sx->sx_lock, x, x - SX_ONE_SHARER)) _sx_sunlock_hard(sx, file, line); } /* * Public interface for lock operations. */ #ifndef LOCK_DEBUG #error "LOCK_DEBUG not defined, include before " #endif #if (LOCK_DEBUG > 0) || defined(SX_NOINLINE) #define sx_xlock_(sx, file, line) \ (void)_sx_xlock((sx), 0, (file), (line)) #define sx_xlock_sig_(sx, file, line) \ _sx_xlock((sx), SX_INTERRUPTIBLE, (file), (line)) #define sx_xunlock_(sx, file, line) \ _sx_xunlock((sx), (file), (line)) #define sx_slock_(sx, file, line) \ (void)_sx_slock((sx), 0, (file), (line)) #define sx_slock_sig_(sx, file, line) \ _sx_slock((sx), SX_INTERRUPTIBLE, (file) , (line)) #define sx_sunlock_(sx, file, line) \ _sx_sunlock((sx), (file), (line)) #else #define sx_xlock_(sx, file, line) \ (void)__sx_xlock((sx), curthread, 0, (file), (line)) #define sx_xlock_sig_(sx, file, line) \ __sx_xlock((sx), curthread, SX_INTERRUPTIBLE, (file), (line)) #define sx_xunlock_(sx, file, line) \ __sx_xunlock((sx), curthread, (file), (line)) #define sx_slock_(sx, file, line) \ (void)__sx_slock((sx), 0, (file), (line)) #define sx_slock_sig_(sx, file, line) \ __sx_slock((sx), SX_INTERRUPTIBLE, (file), (line)) #define sx_sunlock_(sx, file, line) \ __sx_sunlock((sx), (file), (line)) #endif /* LOCK_DEBUG > 0 || SX_NOINLINE */ #define sx_try_slock(sx) sx_try_slock_((sx), LOCK_FILE, LOCK_LINE) #define sx_try_xlock(sx) sx_try_xlock_((sx), LOCK_FILE, LOCK_LINE) #define sx_try_upgrade(sx) sx_try_upgrade_((sx), LOCK_FILE, LOCK_LINE) #define sx_downgrade(sx) sx_downgrade_((sx), LOCK_FILE, LOCK_LINE) #ifdef INVARIANTS #define sx_assert_(sx, what, file, line) \ _sx_assert((sx), (what), (file), (line)) #else #define sx_assert_(sx, what, file, line) (void)0 #endif #define sx_xlock(sx) sx_xlock_((sx), LOCK_FILE, LOCK_LINE) #define sx_xlock_sig(sx) sx_xlock_sig_((sx), LOCK_FILE, LOCK_LINE) #define sx_xunlock(sx) sx_xunlock_((sx), LOCK_FILE, LOCK_LINE) #define sx_slock(sx) sx_slock_((sx), LOCK_FILE, LOCK_LINE) #define sx_slock_sig(sx) sx_slock_sig_((sx), LOCK_FILE, LOCK_LINE) #define sx_sunlock(sx) sx_sunlock_((sx), LOCK_FILE, LOCK_LINE) #define sx_assert(sx, what) sx_assert_((sx), (what), __FILE__, __LINE__) /* * Return a pointer to the owning thread if the lock is exclusively * locked. */ #define sx_xholder(sx) \ ((sx)->sx_lock & SX_LOCK_SHARED ? NULL : \ (struct thread *)SX_OWNER((sx)->sx_lock)) #define sx_xlocked(sx) \ (((sx)->sx_lock & ~(SX_LOCK_FLAGMASK & ~SX_LOCK_SHARED)) == \ (uintptr_t)curthread) #define sx_unlock_(sx, file, line) do { \ if (sx_xlocked(sx)) \ sx_xunlock_(sx, file, line); \ else \ sx_sunlock_(sx, file, line); \ } while (0) #define sx_unlock(sx) sx_unlock_((sx), LOCK_FILE, LOCK_LINE) #define sx_sleep(chan, sx, pri, wmesg, timo) \ _sleep((chan), &(sx)->lock_object, (pri), (wmesg), (timo)) /* * Options passed to sx_init_flags(). */ #define SX_DUPOK 0x01 #define SX_NOPROFILE 0x02 #define SX_NOWITNESS 0x04 #define SX_QUIET 0x08 #define SX_NOADAPTIVE 0x10 #define SX_RECURSE 0x20 /* * Options passed to sx_*lock_hard(). */ #define SX_INTERRUPTIBLE 0x40 #if defined(INVARIANTS) || defined(INVARIANT_SUPPORT) #define SA_LOCKED LA_LOCKED #define SA_SLOCKED LA_SLOCKED #define SA_XLOCKED LA_XLOCKED #define SA_UNLOCKED LA_UNLOCKED #define SA_RECURSED LA_RECURSED #define SA_NOTRECURSED LA_NOTRECURSED /* Backwards compatability. */ #define SX_LOCKED LA_LOCKED #define SX_SLOCKED LA_SLOCKED #define SX_XLOCKED LA_XLOCKED #define SX_UNLOCKED LA_UNLOCKED #define SX_RECURSED LA_RECURSED #define SX_NOTRECURSED LA_NOTRECURSED #endif #endif /* _KERNEL */ #endif /* !_SYS_SX_H_ */