1 /* 2 * Copyright (c) 2009 The DragonFly Project. All rights reserved. 3 * 4 * This code is derived from software contributed to The DragonFly Project 5 * by Matthew Dillon <dillon@backplane.com> 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in 15 * the documentation and/or other materials provided with the 16 * distribution. 17 * 3. Neither the name of The DragonFly Project nor the names of its 18 * contributors may be used to endorse or promote products derived 19 * from this software without specific, prior written permission. 20 * 21 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 22 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 23 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 24 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 25 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 26 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING, 27 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 28 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED 29 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 30 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 31 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32 * SUCH DAMAGE. 33 */ 34 35 #ifndef _SYS_MUTEX2_H_ 36 #define _SYS_MUTEX2_H_ 37 38 #ifndef _SYS_MUTEX_H_ 39 #include <sys/mutex.h> 40 #endif 41 #ifndef _SYS_THREAD2_H_ 42 #include <sys/thread2.h> 43 #endif 44 #ifndef _SYS_GLOBALDATA_H_ 45 #include <sys/globaldata.h> 46 #endif 47 #include <machine/atomic.h> 48 49 /* 50 * Initialize a new mutex, placing it in an unlocked state with no refs. 51 */ 52 static __inline void 53 mtx_init(mtx_t *mtx, const char *ident) 54 { 55 mtx->mtx_lock = 0; 56 mtx->mtx_owner = NULL; 57 mtx->mtx_exlink = NULL; 58 mtx->mtx_shlink = NULL; 59 mtx->mtx_ident = ident; 60 } 61 62 /* 63 * Initialize a mtx link structure for deeper control over the mutex 64 * operation. 65 */ 66 static __inline void 67 mtx_link_init(mtx_link_t *link) 68 { 69 link->state = MTX_LINK_IDLE; 70 link->callback = NULL; 71 link->arg = NULL; 72 } 73 74 /* 75 * A link structure initialized this way causes mutex operations to not block, 76 * caller must specify a callback. Caller may still abort the mutex via 77 * the link. 78 */ 79 static __inline void 80 mtx_link_init_async(mtx_link_t *link, 81 void (*callback)(mtx_link_t *link, void *arg, int error), 82 void *arg) 83 { 84 link->state = MTX_LINK_IDLE; 85 link->callback = callback; 86 link->arg = arg; 87 } 88 89 /* 90 * Deinitialize a mutex 91 */ 92 static __inline void 93 mtx_uninit(mtx_t *mtx) 94 { 95 /* empty */ 96 } 97 98 /* 99 * Exclusive-lock a mutex, block until acquired or aborted. Recursion 100 * is allowed. 101 * 102 * This version of the function allows the mtx_link to be passed in, thus 103 * giving the caller visibility for the link structure which is required 104 * when calling mtx_abort_ex_link() or when requesting an asynchronous lock. 105 * 106 * The mutex may be aborted at any time while the passed link structure 107 * is valid. 108 */ 109 static __inline int 110 mtx_lock_ex_link(mtx_t *mtx, mtx_link_t *link, int flags, int to) 111 { 112 if (atomic_cmpset_int(&mtx->mtx_lock, 0, MTX_EXCLUSIVE | 1) == 0) 113 return(_mtx_lock_ex_link(mtx, link, flags, to)); 114 mtx->mtx_owner = curthread; 115 link->state = MTX_LINK_ACQUIRED; 116 117 return(0); 118 } 119 120 /* 121 * Short-form exclusive-lock a mutex, block until acquired. Recursion is 122 * allowed. This is equivalent to mtx_lock_ex(mtx, "mtxex", 0, 0). 123 */ 124 static __inline void 125 mtx_lock(mtx_t *mtx) 126 { 127 if (atomic_cmpset_int(&mtx->mtx_lock, 0, MTX_EXCLUSIVE | 1) == 0) { 128 _mtx_lock_ex(mtx, 0, 0); 129 return; 130 } 131 mtx->mtx_owner = curthread; 132 } 133 134 /* 135 * Exclusive-lock a mutex, block until acquired. Recursion is allowed. 136 * 137 * Returns 0 on success, or the tsleep() return code on failure. 138 * An error can only be returned if PCATCH is specified in the flags. 139 */ 140 static __inline int 141 mtx_lock_ex(mtx_t *mtx, int flags, int to) 142 { 143 if (atomic_cmpset_int(&mtx->mtx_lock, 0, MTX_EXCLUSIVE | 1) == 0) 144 return(_mtx_lock_ex(mtx, flags, to)); 145 mtx->mtx_owner = curthread; 146 return(0); 147 } 148 149 static __inline int 150 mtx_lock_ex_quick(mtx_t *mtx) 151 { 152 if (atomic_cmpset_int(&mtx->mtx_lock, 0, MTX_EXCLUSIVE | 1) == 0) 153 return(_mtx_lock_ex_quick(mtx)); 154 mtx->mtx_owner = curthread; 155 return(0); 156 } 157 158 static __inline int 159 mtx_lock_sh_link(mtx_t *mtx, mtx_link_t *link, int flags, int to) 160 { 161 if (atomic_cmpset_int(&mtx->mtx_lock, 0, 1) == 0) 162 return(_mtx_lock_sh_link(mtx, link, flags, to)); 163 link->state = MTX_LINK_ACQUIRED; 164 return(0); 165 } 166 167 /* 168 * Share-lock a mutex, block until acquired. Recursion is allowed. 169 * 170 * Returns 0 on success, or the tsleep() return code on failure. 171 * An error can only be returned if PCATCH is specified in the flags. 172 */ 173 static __inline int 174 mtx_lock_sh(mtx_t *mtx, int flags, int to) 175 { 176 if (atomic_cmpset_int(&mtx->mtx_lock, 0, 1) == 0) 177 return(_mtx_lock_sh(mtx, flags, to)); 178 return(0); 179 } 180 181 static __inline int 182 mtx_lock_sh_quick(mtx_t *mtx) 183 { 184 if (atomic_cmpset_int(&mtx->mtx_lock, 0, 1) == 0) 185 return(_mtx_lock_sh_quick(mtx)); 186 return(0); 187 } 188 189 /* 190 * Short-form exclusive spinlock a mutex. Must be paired with 191 * mtx_spinunlock(). 192 */ 193 static __inline void 194 mtx_spinlock(mtx_t *mtx) 195 { 196 globaldata_t gd = mycpu; 197 198 /* 199 * Predispose a hard critical section 200 */ 201 ++gd->gd_curthread->td_critcount; 202 cpu_ccfence(); 203 ++gd->gd_spinlocks; 204 205 /* 206 * If we cannot get it trivially get it the hard way. 207 * 208 * Note that mtx_owner will be set twice if we fail to get it 209 * trivially, but there's no point conditionalizing it as a 210 * conditional will be slower. 211 */ 212 if (atomic_cmpset_int(&mtx->mtx_lock, 0, MTX_EXCLUSIVE | 1) == 0) 213 _mtx_spinlock(mtx); 214 mtx->mtx_owner = gd->gd_curthread; 215 } 216 217 static __inline int 218 mtx_spinlock_try(mtx_t *mtx) 219 { 220 globaldata_t gd = mycpu; 221 222 /* 223 * Predispose a hard critical section 224 */ 225 ++gd->gd_curthread->td_critcount; 226 cpu_ccfence(); 227 ++gd->gd_spinlocks; 228 229 /* 230 * If we cannot get it trivially call _mtx_spinlock_try(). This 231 * function will clean up the hard critical section if it fails. 232 */ 233 if (atomic_cmpset_int(&mtx->mtx_lock, 0, MTX_EXCLUSIVE | 1) == 0) 234 return(_mtx_spinlock_try(mtx)); 235 mtx->mtx_owner = gd->gd_curthread; 236 return (0); 237 } 238 239 /* 240 * Short-form exclusive-lock a mutex, spin until acquired. Recursion is 241 * allowed. This form is identical to mtx_spinlock_ex(). 242 * 243 * Attempt to exclusive-lock a mutex, return 0 on success and 244 * EAGAIN on failure. 245 */ 246 static __inline int 247 mtx_lock_ex_try(mtx_t *mtx) 248 { 249 if (atomic_cmpset_int(&mtx->mtx_lock, 0, MTX_EXCLUSIVE | 1) == 0) 250 return (_mtx_lock_ex_try(mtx)); 251 mtx->mtx_owner = curthread; 252 return (0); 253 } 254 255 /* 256 * Attempt to share-lock a mutex, return 0 on success and 257 * EAGAIN on failure. 258 */ 259 static __inline int 260 mtx_lock_sh_try(mtx_t *mtx) 261 { 262 if (atomic_cmpset_int(&mtx->mtx_lock, 0, 1) == 0) 263 return (_mtx_lock_sh_try(mtx)); 264 return (0); 265 } 266 267 /* 268 * If the lock is held exclusively it must be owned by the caller. If the 269 * lock is already a shared lock this operation is a NOP. A panic will 270 * occur if the lock is not held either shared or exclusive. 271 * 272 * The exclusive count is converted to a shared count. 273 */ 274 static __inline void 275 mtx_downgrade(mtx_t *mtx) 276 { 277 mtx->mtx_owner = NULL; 278 if (atomic_cmpset_int(&mtx->mtx_lock, MTX_EXCLUSIVE | 1, 1) == 0) 279 _mtx_downgrade(mtx); 280 } 281 282 /* 283 * Upgrade a shared lock to an exclusive lock. The upgrade will fail if 284 * the shared lock has a count other then 1. Optimize the most likely case 285 * but note that a single cmpset can fail due to WANTED races. 286 * 287 * If the lock is held exclusively it must be owned by the caller and 288 * this function will simply return without doing anything. A panic will 289 * occur if the lock is held exclusively by someone other then the caller. 290 * 291 * Returns 0 on success, EDEADLK on failure. 292 */ 293 static __inline int 294 mtx_upgrade_try(mtx_t *mtx) 295 { 296 if (atomic_cmpset_int(&mtx->mtx_lock, 1, MTX_EXCLUSIVE | 1)) 297 return(0); 298 return (_mtx_upgrade_try(mtx)); 299 } 300 301 /* 302 * Optimized unlock cases. 303 * 304 * NOTE: mtx_unlock() handles any type of mutex: exclusive, shared, and 305 * both blocking and spin methods. 306 * 307 * The mtx_unlock_ex/sh() forms are optimized for exclusive or shared 308 * mutexes and produce less code, but it is ok for code to just use 309 * mtx_unlock() and, in fact, if code uses the short-form mtx_lock() 310 * or mtx_spinlock() to lock it should also use mtx_unlock() to unlock. 311 */ 312 static __inline void 313 mtx_unlock(mtx_t *mtx) 314 { 315 u_int lock = mtx->mtx_lock; 316 317 if (lock == (MTX_EXCLUSIVE | 1)) { 318 mtx->mtx_owner = NULL; 319 if (atomic_cmpset_int(&mtx->mtx_lock, lock, 0) == 0) 320 _mtx_unlock(mtx); 321 } else if (lock == 1) { 322 if (atomic_cmpset_int(&mtx->mtx_lock, lock, 0) == 0) 323 _mtx_unlock(mtx); 324 } else { 325 _mtx_unlock(mtx); 326 } 327 } 328 329 static __inline void 330 mtx_unlock_ex(mtx_t *mtx) 331 { 332 u_int lock = mtx->mtx_lock; 333 334 if (lock == (MTX_EXCLUSIVE | 1)) { 335 mtx->mtx_owner = NULL; 336 if (atomic_cmpset_int(&mtx->mtx_lock, lock, 0) == 0) 337 _mtx_unlock(mtx); 338 } else { 339 _mtx_unlock(mtx); 340 } 341 } 342 343 static __inline void 344 mtx_unlock_sh(mtx_t *mtx) 345 { 346 if (atomic_cmpset_int(&mtx->mtx_lock, 1, 0) == 0) 347 _mtx_unlock(mtx); 348 } 349 350 /* 351 * NOTE: spinlocks are exclusive-only 352 */ 353 static __inline void 354 mtx_spinunlock(mtx_t *mtx) 355 { 356 globaldata_t gd = mycpu; 357 358 mtx_unlock(mtx); 359 360 --gd->gd_spinlocks; 361 cpu_ccfence(); 362 --gd->gd_curthread->td_critcount; 363 } 364 365 /* 366 * Return TRUE (non-zero) if the mutex is locked shared or exclusive by 367 * anyone, including the owner. 368 */ 369 static __inline int 370 mtx_islocked(mtx_t *mtx) 371 { 372 return(mtx->mtx_lock != 0); 373 } 374 375 /* 376 * Return TRUE (non-zero) if the mutex is locked exclusively by anyone, 377 * including the owner. Returns FALSE (0) if the mutex is unlocked or 378 * if it is locked shared by one or more entities. 379 * 380 * A caller wishing to check whether a lock is owned exclusively by it 381 * should use mtx_owned(). 382 */ 383 static __inline int 384 mtx_islocked_ex(mtx_t *mtx) 385 { 386 return((mtx->mtx_lock & MTX_EXCLUSIVE) != 0); 387 } 388 389 /* 390 * Return TRUE (non-zero) if the mutex is not locked. 391 */ 392 static __inline int 393 mtx_notlocked(mtx_t *mtx) 394 { 395 return(mtx->mtx_lock == 0); 396 } 397 398 /* 399 * Return TRUE (non-zero) if the mutex is not locked exclusively. 400 * The mutex may in an unlocked or shared lock state. 401 */ 402 static __inline int 403 mtx_notlocked_ex(mtx_t *mtx) 404 { 405 return((mtx->mtx_lock & MTX_EXCLUSIVE) != 0); 406 } 407 408 /* 409 * Return TRUE (non-zero) if the mutex is exclusively locked by 410 * the caller. 411 */ 412 static __inline int 413 mtx_owned(mtx_t *mtx) 414 { 415 return((mtx->mtx_lock & MTX_EXCLUSIVE) && mtx->mtx_owner == curthread); 416 } 417 418 /* 419 * Return TRUE (non-zero) if the mutex is not exclusively locked by 420 * the caller. 421 */ 422 static __inline int 423 mtx_notowned(mtx_t *mtx) 424 { 425 return((mtx->mtx_lock & MTX_EXCLUSIVE) == 0 || 426 mtx->mtx_owner != curthread); 427 } 428 429 /* 430 * Return the shared or exclusive lock count. A return value of 0 431 * indicate that the mutex is not locked. 432 * 433 * NOTE: If the mutex is held exclusively by someone other then the 434 * caller the lock count for the other owner is still returned. 435 */ 436 static __inline 437 int 438 mtx_lockrefs(mtx_t *mtx) 439 { 440 return(mtx->mtx_lock & MTX_MASK); 441 } 442 443 /* 444 * Lock must held and will be released on return. Returns state 445 * which can be passed to mtx_lock_temp_restore() to return the 446 * lock to its previous state. 447 */ 448 static __inline 449 mtx_state_t 450 mtx_lock_temp_release(mtx_t *mtx) 451 { 452 mtx_state_t state; 453 454 state = (mtx->mtx_lock & MTX_EXCLUSIVE); 455 mtx_unlock(mtx); 456 457 return state; 458 } 459 460 /* 461 * Restore the previous state of a lock released with 462 * mtx_lock_temp_release() or mtx_lock_upgrade(). 463 */ 464 static __inline 465 void 466 mtx_lock_temp_restore(mtx_t *mtx, mtx_state_t state) 467 { 468 if (state & MTX_EXCLUSIVE) 469 mtx_lock_ex_quick(mtx); 470 else 471 mtx_lock_sh_quick(mtx); 472 } 473 474 #endif 475