sx.h revision 168330
1219820Sjeff/*- 2 * Copyright (c) 2007 Attilio Rao <attilio@freebsd.org> 3 * Copyright (c) 2001 Jason Evans <jasone@freebsd.org> 4 * All rights reserved. 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice(s), this list of conditions and the following disclaimer as 11 * the first lines of this file unmodified other than the possible 12 * addition of one or more copyright notices. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice(s), this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY 18 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 19 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 20 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE LIABLE FOR ANY 21 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES 22 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR 23 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER 24 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH 27 * DAMAGE. 28 * 29 * $FreeBSD: head/sys/sys/sx.h 168330 2007-04-03 22:58:21Z kmacy $ 30 */ 31 32#ifndef _SYS_SX_H_ 33#define _SYS_SX_H_ 34 35#include <sys/_lock.h> 36#include <sys/_sx.h> 37 38#ifdef _KERNEL 39#include <machine/atomic.h> 40#endif 41 42/* 43 * In general, the sx locks and rwlocks use very similar algorithms. 44 * The main difference in the implementations is how threads are 45 * blocked when a lock is unavailable. For this, sx locks use sleep 46 * queues which do not support priority propagation, and rwlocks use 47 * turnstiles which do. 48 * 49 * The sx_lock field consists of several fields. The low bit 50 * indicates if the lock is locked with a shared or exclusive lock. A 51 * value of 0 indicates an exclusive lock, and a value of 1 indicates 52 * a shared lock. Bit 1 is a boolean indicating if there are any 53 * threads waiting for a shared lock. Bit 2 is a boolean indicating 54 * if there are any threads waiting for an exclusive lock. Bit 3 is a 55 * boolean indicating if an exclusive lock is recursively held. The 56 * rest of the variable's definition is dependent on the value of the 57 * first bit. For an exclusive lock, it is a pointer to the thread 58 * holding the lock, similar to the mtx_lock field of mutexes. For 59 * shared locks, it is a count of read locks that are held. 60 * 61 * When the lock is not locked by any thread, it is encoded as a 62 * shared lock with zero waiters. 63 * 64 * A note about memory barriers. Exclusive locks need to use the same 65 * memory barriers as mutexes: _acq when acquiring an exclusive lock 66 * and _rel when releasing an exclusive lock. On the other side, 67 * shared lock needs to use an _acq barrier when acquiring the lock 68 * but, since they don't update any locked data, no memory barrier is 69 * needed when releasing a shared lock. 70 */ 71 72#define SX_LOCK_SHARED 0x01 73#define SX_LOCK_SHARED_WAITERS 0x02 74#define SX_LOCK_EXCLUSIVE_WAITERS 0x04 75#define SX_LOCK_RECURSED 0x08 76#define SX_LOCK_FLAGMASK \ 77 (SX_LOCK_SHARED | SX_LOCK_SHARED_WAITERS | \ 78 SX_LOCK_EXCLUSIVE_WAITERS | SX_LOCK_RECURSED) 79 80#define SX_OWNER(x) ((x) & ~SX_LOCK_FLAGMASK) 81#define SX_SHARERS_SHIFT 4 82#define SX_SHARERS(x) (SX_OWNER(x) >> SX_SHARERS_SHIFT) 83#define SX_SHARERS_LOCK(x) \ 84 ((x) << SX_SHARERS_SHIFT | SX_LOCK_SHARED) 85#define SX_ONE_SHARER (1 << SX_SHARERS_SHIFT) 86 87#define SX_LOCK_UNLOCKED SX_SHARERS_LOCK(0) 88 89#ifdef _KERNEL 90 91/* 92 * Full lock operations that are suitable to be inlined in non-debug kernels. 93 * If the lock can't be acquired or released trivially then the work is 94 * deferred to 'tougher' functions. 95 */ 96 97/* Acquire an exclusive lock. */ 98#define __sx_xlock(sx, tid, file, line) do { \ 99 uintptr_t _tid = (uintptr_t)(tid); \ 100 \ 101 if (!atomic_cmpset_acq_ptr(&(sx)->sx_lock, SX_LOCK_UNLOCKED, \ 102 _tid)) { \ 103 _sx_xlock_hard((sx), _tid, (file), (line)); \ 104 } else \ 105 lock_profile_obtain_lock_success(&(sx)->lock_object, 0, \ 106 0, (file), (line)); \ 107} while (0) 108 109/* Release an exclusive lock. */ 110#define __sx_xunlock(sx, tid, file, line) do { \ 111 uintptr_t _tid = (uintptr_t)(tid); \ 112 \ 113 if (!atomic_cmpset_rel_ptr(&(sx)->sx_lock, _tid, \ 114 SX_LOCK_UNLOCKED)) \ 115 _sx_xunlock_hard((sx), _tid, (file), (line)); \ 116} while (0) 117 118/* Acquire a shared lock. */ 119#define __sx_slock(sx, file, line) do { \ 120 uintptr_t x = (sx)->sx_lock; \ 121 \ 122 if (!(x & SX_LOCK_SHARED) || \ 123 !atomic_cmpset_acq_ptr(&(sx)->sx_lock, x, \ 124 x + SX_ONE_SHARER)) { \ 125 _sx_slock_hard((sx), (file), (line)); \ 126 } else \ 127 lock_profile_obtain_lock_success(&(sx)->lock_object, 0, \ 128 0, (file), (line)); \ 129} while (0) 130 131/* 132 * Release a shared lock. We can just drop a single shared lock so 133 * long as we aren't trying to drop the last shared lock when other 134 * threads are waiting for an exclusive lock. This takes advantage of 135 * the fact that an unlocked lock is encoded as a shared lock with a 136 * count of 0. 137 */ 138#define __sx_sunlock(sx, file, line) do { \ 139 uintptr_t x = (sx)->sx_lock; \ 140 \ 141 if (x == (SX_SHARERS_LOCK(1) | SX_LOCK_EXCLUSIVE_WAITERS) || \ 142 !atomic_cmpset_ptr(&(sx)->sx_lock, x, x - SX_ONE_SHARER)) \ 143 _sx_sunlock_hard((sx), (file), (line)); \ 144} while (0) 145 146/* 147 * Function prototipes. Routines that start with an underscore are not part 148 * of the public interface and are wrappered with a macro. 149 */ 150void sx_sysinit(void *arg); 151#define sx_init(sx, desc) sx_init_flags((sx), (desc), 0) 152void sx_init_flags(struct sx *sx, const char *description, int opts); 153void sx_destroy(struct sx *sx); 154void _sx_slock(struct sx *sx, const char *file, int line); 155void _sx_xlock(struct sx *sx, const char *file, int line); 156int _sx_try_slock(struct sx *sx, const char *file, int line); 157int _sx_try_xlock(struct sx *sx, const char *file, int line); 158void _sx_sunlock(struct sx *sx, const char *file, int line); 159void _sx_xunlock(struct sx *sx, const char *file, int line); 160int _sx_try_upgrade(struct sx *sx, const char *file, int line); 161void _sx_downgrade(struct sx *sx, const char *file, int line); 162void _sx_xlock_hard(struct sx *sx, uintptr_t tid, const char *file, int 163 line); 164void _sx_slock_hard(struct sx *sx, const char *file, int line); 165void _sx_xunlock_hard(struct sx *sx, uintptr_t tid, const char *file, int 166 line); 167void _sx_sunlock_hard(struct sx *sx, const char *file, int line); 168#if defined(INVARIANTS) || defined(INVARIANT_SUPPORT) 169void _sx_assert(struct sx *sx, int what, const char *file, int line); 170#endif 171#ifdef DDB 172int sx_chain(struct thread *td, struct thread **ownerp); 173#endif 174 175struct sx_args { 176 struct sx *sa_sx; 177 const char *sa_desc; 178}; 179 180#define SX_SYSINIT(name, sxa, desc) \ 181 static struct sx_args name##_args = { \ 182 (sxa), \ 183 (desc) \ 184 }; \ 185 SYSINIT(name##_sx_sysinit, SI_SUB_LOCK, SI_ORDER_MIDDLE, \ 186 sx_sysinit, &name##_args); \ 187 SYSUNINIT(name##_sx_sysuninit, SI_SUB_LOCK, SI_ORDER_MIDDLE, \ 188 sx_destroy, (sxa)) 189 190/* 191 * Public interface for lock operations. 192 */ 193#ifndef LOCK_DEBUG 194#error "LOCK_DEBUG not defined, include <sys/lock.h> before <sys/sx.h>" 195#endif 196#if (LOCK_DEBUG > 0) || defined(SX_NOINLINE) 197#define sx_xlock(sx) _sx_xlock((sx), LOCK_FILE, LOCK_LINE) 198#define sx_xunlock(sx) _sx_xunlock((sx), LOCK_FILE, LOCK_LINE) 199#define sx_slock(sx) _sx_slock((sx), LOCK_FILE, LOCK_LINE) 200#define sx_sunlock(sx) _sx_sunlock((sx), LOCK_FILE, LOCK_LINE) 201#else 202#define sx_xlock(sx) \ 203 __sx_xlock((sx), curthread, LOCK_FILE, LOCK_LINE) 204#define sx_xunlock(sx) \ 205 __sx_xunlock((sx), curthread, LOCK_FILE, LOCK_LINE) 206#define sx_slock(sx) __sx_slock((sx), LOCK_FILE, LOCK_LINE) 207#define sx_sunlock(sx) __sx_sunlock((sx), LOCK_FILE, LOCK_LINE) 208#endif /* LOCK_DEBUG > 0 || SX_NOINLINE */ 209#define sx_try_slock(sx) _sx_try_slock((sx), LOCK_FILE, LOCK_LINE) 210#define sx_try_xlock(sx) _sx_try_xlock((sx), LOCK_FILE, LOCK_LINE) 211#define sx_try_upgrade(sx) _sx_try_upgrade((sx), LOCK_FILE, LOCK_LINE) 212#define sx_downgrade(sx) _sx_downgrade((sx), LOCK_FILE, LOCK_LINE) 213 214#define sx_xlocked(sx) \ 215 (((sx)->sx_lock & ~(SX_LOCK_FLAGMASK & ~SX_LOCK_SHARED)) == \ 216 (uintptr_t)curthread) 217 218#define sx_unlock(sx) do { \ 219 if (sx_xlocked(sx)) \ 220 sx_xunlock(sx); \ 221 else \ 222 sx_sunlock(sx); \ 223} while (0) 224 225#define sx_sleep(chan, sx, pri, wmesg, timo) \ 226 _sleep((chan), &(sx)->lock_object, (pri), (wmesg), (timo)) 227 228/* 229 * Options passed to sx_init_flags(). 230 */ 231#define SX_DUPOK 0x01 232#define SX_NOPROFILE 0x02 233#define SX_NOWITNESS 0x04 234#define SX_QUIET 0x08 235#define SX_ADAPTIVESPIN 0x10 236 237/* 238 * XXX: These options should be renamed as SA_* 239 */ 240#if defined(INVARIANTS) || defined(INVARIANT_SUPPORT) 241#define SX_LOCKED LA_LOCKED 242#define SX_SLOCKED LA_SLOCKED 243#define SX_XLOCKED LA_XLOCKED 244#define SX_UNLOCKED LA_UNLOCKED 245#define SX_RECURSED LA_RECURSED 246#define SX_NOTRECURSED LA_NOTRECURSED 247#endif 248 249#ifdef INVARIANTS 250#define sx_assert(sx, what) _sx_assert((sx), (what), LOCK_FILE, LOCK_LINE) 251#else 252#define sx_assert(sx, what) 253#endif 254 255#endif /* _KERNEL */ 256 257#endif /* !_SYS_SX_H_ */ 258