1 /*- 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 * $FreeBSD$ 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 <sys/pcpu.h> 40 #include <sys/lock_profile.h> 41 #include <sys/lockstat.h> 42 #include <machine/atomic.h> 43 #endif 44 45 /* 46 * In general, the sx locks and rwlocks use very similar algorithms. 47 * The main difference in the implementations is how threads are 48 * blocked when a lock is unavailable. For this, sx locks use sleep 49 * queues which do not support priority propagation, and rwlocks use 50 * turnstiles which do. 51 * 52 * The sx_lock field consists of several fields. The low bit 53 * indicates if the lock is locked with a shared or exclusive lock. A 54 * value of 0 indicates an exclusive lock, and a value of 1 indicates 55 * a shared lock. Bit 1 is a boolean indicating if there are any 56 * threads waiting for a shared lock. Bit 2 is a boolean indicating 57 * if there are any threads waiting for an exclusive lock. Bit 3 is a 58 * boolean indicating if an exclusive lock is recursively held. The 59 * rest of the variable's definition is dependent on the value of the 60 * first bit. For an exclusive lock, it is a pointer to the thread 61 * holding the lock, similar to the mtx_lock field of mutexes. For 62 * shared locks, it is a count of read locks that are held. 63 * 64 * When the lock is not locked by any thread, it is encoded as a 65 * shared lock with zero waiters. 66 */ 67 68 #define SX_LOCK_SHARED 0x01 69 #define SX_LOCK_SHARED_WAITERS 0x02 70 #define SX_LOCK_EXCLUSIVE_WAITERS 0x04 71 #define SX_LOCK_RECURSED 0x08 72 #define SX_LOCK_FLAGMASK \ 73 (SX_LOCK_SHARED | SX_LOCK_SHARED_WAITERS | \ 74 SX_LOCK_EXCLUSIVE_WAITERS | SX_LOCK_RECURSED) 75 76 #define SX_OWNER(x) ((x) & ~SX_LOCK_FLAGMASK) 77 #define SX_SHARERS_SHIFT 4 78 #define SX_SHARERS(x) (SX_OWNER(x) >> SX_SHARERS_SHIFT) 79 #define SX_SHARERS_LOCK(x) \ 80 ((x) << SX_SHARERS_SHIFT | SX_LOCK_SHARED) 81 #define SX_ONE_SHARER (1 << SX_SHARERS_SHIFT) 82 83 #define SX_LOCK_UNLOCKED SX_SHARERS_LOCK(0) 84 #define SX_LOCK_DESTROYED \ 85 (SX_LOCK_SHARED_WAITERS | SX_LOCK_EXCLUSIVE_WAITERS) 86 87 #ifdef _KERNEL 88 89 #define sx_recurse lock_object.lo_data 90 91 #define SX_READ_VALUE(sx) ((sx)->sx_lock) 92 93 #define lv_sx_owner(v) \ 94 ((v & SX_LOCK_SHARED) ? NULL : (struct thread *)SX_OWNER(v)) 95 96 /* 97 * Function prototipes. Routines that start with an underscore are not part 98 * of the public interface and are wrappered with a macro. 99 */ 100 void sx_sysinit(void *arg); 101 #define sx_init(sx, desc) sx_init_flags((sx), (desc), 0) 102 void sx_init_flags(struct sx *sx, const char *description, int opts); 103 void sx_destroy(struct sx *sx); 104 int sx_try_slock_(struct sx *sx, const char *file, int line); 105 int sx_try_xlock_(struct sx *sx, const char *file, int line); 106 int sx_try_upgrade_(struct sx *sx, const char *file, int line); 107 void sx_downgrade_(struct sx *sx, const char *file, int line); 108 int _sx_slock(struct sx *sx, int opts, const char *file, int line); 109 int _sx_xlock(struct sx *sx, int opts, const char *file, int line); 110 void _sx_sunlock(struct sx *sx, const char *file, int line); 111 void _sx_xunlock(struct sx *sx, const char *file, int line); 112 int _sx_xlock_hard(struct sx *sx, uintptr_t v, uintptr_t tid, int opts, 113 const char *file, int line); 114 void _sx_xunlock_hard(struct sx *sx, uintptr_t tid, const char *file, int 115 line); 116 #if defined(INVARIANTS) || defined(INVARIANT_SUPPORT) 117 void _sx_assert(const struct sx *sx, int what, const char *file, int line); 118 #endif 119 #ifdef DDB 120 int sx_chain(struct thread *td, struct thread **ownerp); 121 #endif 122 123 struct sx_args { 124 struct sx *sa_sx; 125 const char *sa_desc; 126 int sa_flags; 127 }; 128 129 #define SX_SYSINIT_FLAGS(name, sxa, desc, flags) \ 130 static struct sx_args name##_args = { \ 131 (sxa), \ 132 (desc), \ 133 (flags) \ 134 }; \ 135 SYSINIT(name##_sx_sysinit, SI_SUB_LOCK, SI_ORDER_MIDDLE, \ 136 sx_sysinit, &name##_args); \ 137 SYSUNINIT(name##_sx_sysuninit, SI_SUB_LOCK, SI_ORDER_MIDDLE, \ 138 sx_destroy, (sxa)) 139 140 #define SX_SYSINIT(name, sxa, desc) SX_SYSINIT_FLAGS(name, sxa, desc, 0) 141 142 /* 143 * Full lock operations that are suitable to be inlined in non-debug kernels. 144 * If the lock can't be acquired or released trivially then the work is 145 * deferred to 'tougher' functions. 146 */ 147 148 #if (LOCK_DEBUG == 0) 149 /* Acquire an exclusive lock. */ 150 static __inline int 151 __sx_xlock(struct sx *sx, struct thread *td, int opts, const char *file, 152 int line) 153 { 154 uintptr_t tid = (uintptr_t)td; 155 uintptr_t v = SX_LOCK_UNLOCKED; 156 int error = 0; 157 158 if (__predict_false(LOCKSTAT_PROFILE_ENABLED(sx__acquire) || 159 !atomic_fcmpset_acq_ptr(&sx->sx_lock, &v, tid))) 160 error = _sx_xlock_hard(sx, v, tid, opts, file, line); 161 162 return (error); 163 } 164 165 /* Release an exclusive lock. */ 166 static __inline void 167 __sx_xunlock(struct sx *sx, struct thread *td, const char *file, int line) 168 { 169 uintptr_t tid = (uintptr_t)td; 170 171 if (__predict_false(LOCKSTAT_PROFILE_ENABLED(sx__release) || 172 !atomic_cmpset_rel_ptr(&sx->sx_lock, tid, SX_LOCK_UNLOCKED))) 173 _sx_xunlock_hard(sx, tid, file, line); 174 } 175 #endif 176 177 /* 178 * Public interface for lock operations. 179 */ 180 #ifndef LOCK_DEBUG 181 #error "LOCK_DEBUG not defined, include <sys/lock.h> before <sys/sx.h>" 182 #endif 183 #if (LOCK_DEBUG > 0) || defined(SX_NOINLINE) 184 #define sx_xlock_(sx, file, line) \ 185 (void)_sx_xlock((sx), 0, (file), (line)) 186 #define sx_xlock_sig_(sx, file, line) \ 187 _sx_xlock((sx), SX_INTERRUPTIBLE, (file), (line)) 188 #define sx_xunlock_(sx, file, line) \ 189 _sx_xunlock((sx), (file), (line)) 190 #else 191 #define sx_xlock_(sx, file, line) \ 192 (void)__sx_xlock((sx), curthread, 0, (file), (line)) 193 #define sx_xlock_sig_(sx, file, line) \ 194 __sx_xlock((sx), curthread, SX_INTERRUPTIBLE, (file), (line)) 195 #define sx_xunlock_(sx, file, line) \ 196 __sx_xunlock((sx), curthread, (file), (line)) 197 #endif /* LOCK_DEBUG > 0 || SX_NOINLINE */ 198 #define sx_slock_(sx, file, line) \ 199 (void)_sx_slock((sx), 0, (file), (line)) 200 #define sx_slock_sig_(sx, file, line) \ 201 _sx_slock((sx), SX_INTERRUPTIBLE, (file) , (line)) 202 #define sx_sunlock_(sx, file, line) \ 203 _sx_sunlock((sx), (file), (line)) 204 #define sx_try_slock(sx) sx_try_slock_((sx), LOCK_FILE, LOCK_LINE) 205 #define sx_try_xlock(sx) sx_try_xlock_((sx), LOCK_FILE, LOCK_LINE) 206 #define sx_try_upgrade(sx) sx_try_upgrade_((sx), LOCK_FILE, LOCK_LINE) 207 #define sx_downgrade(sx) sx_downgrade_((sx), LOCK_FILE, LOCK_LINE) 208 #ifdef INVARIANTS 209 #define sx_assert_(sx, what, file, line) \ 210 _sx_assert((sx), (what), (file), (line)) 211 #else 212 #define sx_assert_(sx, what, file, line) (void)0 213 #endif 214 215 #define sx_xlock(sx) sx_xlock_((sx), LOCK_FILE, LOCK_LINE) 216 #define sx_xlock_sig(sx) sx_xlock_sig_((sx), LOCK_FILE, LOCK_LINE) 217 #define sx_xunlock(sx) sx_xunlock_((sx), LOCK_FILE, LOCK_LINE) 218 #define sx_slock(sx) sx_slock_((sx), LOCK_FILE, LOCK_LINE) 219 #define sx_slock_sig(sx) sx_slock_sig_((sx), LOCK_FILE, LOCK_LINE) 220 #define sx_sunlock(sx) sx_sunlock_((sx), LOCK_FILE, LOCK_LINE) 221 #define sx_assert(sx, what) sx_assert_((sx), (what), __FILE__, __LINE__) 222 223 /* 224 * Return a pointer to the owning thread if the lock is exclusively 225 * locked. 226 */ 227 #define sx_xholder(sx) \ 228 ((sx)->sx_lock & SX_LOCK_SHARED ? NULL : \ 229 (struct thread *)SX_OWNER((sx)->sx_lock)) 230 231 #define sx_xlocked(sx) \ 232 (((sx)->sx_lock & ~(SX_LOCK_FLAGMASK & ~SX_LOCK_SHARED)) == \ 233 (uintptr_t)curthread) 234 235 #define sx_unlock_(sx, file, line) do { \ 236 if (sx_xlocked(sx)) \ 237 sx_xunlock_(sx, file, line); \ 238 else \ 239 sx_sunlock_(sx, file, line); \ 240 } while (0) 241 242 #define sx_unlock(sx) sx_unlock_((sx), LOCK_FILE, LOCK_LINE) 243 244 #define sx_sleep(chan, sx, pri, wmesg, timo) \ 245 _sleep((chan), &(sx)->lock_object, (pri), (wmesg), \ 246 tick_sbt * (timo), 0, C_HARDCLOCK) 247 248 /* 249 * Options passed to sx_init_flags(). 250 */ 251 #define SX_DUPOK 0x01 252 #define SX_NOPROFILE 0x02 253 #define SX_NOWITNESS 0x04 254 #define SX_QUIET 0x08 255 #define SX_NOADAPTIVE 0x10 256 #define SX_RECURSE 0x20 257 #define SX_NEW 0x40 258 259 /* 260 * Options passed to sx_*lock_hard(). 261 */ 262 #define SX_INTERRUPTIBLE 0x40 263 264 #if defined(INVARIANTS) || defined(INVARIANT_SUPPORT) 265 #define SA_LOCKED LA_LOCKED 266 #define SA_SLOCKED LA_SLOCKED 267 #define SA_XLOCKED LA_XLOCKED 268 #define SA_UNLOCKED LA_UNLOCKED 269 #define SA_RECURSED LA_RECURSED 270 #define SA_NOTRECURSED LA_NOTRECURSED 271 272 /* Backwards compatibility. */ 273 #define SX_LOCKED LA_LOCKED 274 #define SX_SLOCKED LA_SLOCKED 275 #define SX_XLOCKED LA_XLOCKED 276 #define SX_UNLOCKED LA_UNLOCKED 277 #define SX_RECURSED LA_RECURSED 278 #define SX_NOTRECURSED LA_NOTRECURSED 279 #endif 280 281 #endif /* _KERNEL */ 282 283 #endif /* !_SYS_SX_H_ */ 284