1 /* 2 * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com) 3 * 4 * This program is free software; you can redistribute it and/or modify 5 * it under the terms of the GNU General Public License version 2 as 6 * published by the Free Software Foundation. 7 */ 8 9 #ifndef __ASM_SPINLOCK_H 10 #define __ASM_SPINLOCK_H 11 12 #include <asm/spinlock_types.h> 13 #include <asm/processor.h> 14 #include <asm/barrier.h> 15 16 #define arch_spin_is_locked(x) ((x)->slock != __ARCH_SPIN_LOCK_UNLOCKED__) 17 #define arch_spin_lock_flags(lock, flags) arch_spin_lock(lock) 18 19 static inline void arch_spin_unlock_wait(arch_spinlock_t *lock) 20 { 21 smp_cond_load_acquire(&lock->slock, !VAL); 22 } 23 24 #ifdef CONFIG_ARC_HAS_LLSC 25 26 static inline void arch_spin_lock(arch_spinlock_t *lock) 27 { 28 unsigned int val; 29 30 smp_mb(); 31 32 __asm__ __volatile__( 33 "1: llock %[val], [%[slock]] \n" 34 " breq %[val], %[LOCKED], 1b \n" /* spin while LOCKED */ 35 " scond %[LOCKED], [%[slock]] \n" /* acquire */ 36 " bnz 1b \n" 37 " \n" 38 : [val] "=&r" (val) 39 : [slock] "r" (&(lock->slock)), 40 [LOCKED] "r" (__ARCH_SPIN_LOCK_LOCKED__) 41 : "memory", "cc"); 42 43 smp_mb(); 44 } 45 46 /* 1 - lock taken successfully */ 47 static inline int arch_spin_trylock(arch_spinlock_t *lock) 48 { 49 unsigned int val, got_it = 0; 50 51 smp_mb(); 52 53 __asm__ __volatile__( 54 "1: llock %[val], [%[slock]] \n" 55 " breq %[val], %[LOCKED], 4f \n" /* already LOCKED, just bail */ 56 " scond %[LOCKED], [%[slock]] \n" /* acquire */ 57 " bnz 1b \n" 58 " mov %[got_it], 1 \n" 59 "4: \n" 60 " \n" 61 : [val] "=&r" (val), 62 [got_it] "+&r" (got_it) 63 : [slock] "r" (&(lock->slock)), 64 [LOCKED] "r" (__ARCH_SPIN_LOCK_LOCKED__) 65 : "memory", "cc"); 66 67 smp_mb(); 68 69 return got_it; 70 } 71 72 static inline void arch_spin_unlock(arch_spinlock_t *lock) 73 { 74 smp_mb(); 75 76 lock->slock = __ARCH_SPIN_LOCK_UNLOCKED__; 77 78 smp_mb(); 79 } 80 81 /* 82 * Read-write spinlocks, allowing multiple readers but only one writer. 83 * Unfair locking as Writers could be starved indefinitely by Reader(s) 84 */ 85 86 static inline void arch_read_lock(arch_rwlock_t *rw) 87 { 88 unsigned int val; 89 90 smp_mb(); 91 92 /* 93 * zero means writer holds the lock exclusively, deny Reader. 94 * Otherwise grant lock to first/subseq reader 95 * 96 * if (rw->counter > 0) { 97 * rw->counter--; 98 * ret = 1; 99 * } 100 */ 101 102 __asm__ __volatile__( 103 "1: llock %[val], [%[rwlock]] \n" 104 " brls %[val], %[WR_LOCKED], 1b\n" /* <= 0: spin while write locked */ 105 " sub %[val], %[val], 1 \n" /* reader lock */ 106 " scond %[val], [%[rwlock]] \n" 107 " bnz 1b \n" 108 " \n" 109 : [val] "=&r" (val) 110 : [rwlock] "r" (&(rw->counter)), 111 [WR_LOCKED] "ir" (0) 112 : "memory", "cc"); 113 114 smp_mb(); 115 } 116 117 /* 1 - lock taken successfully */ 118 static inline int arch_read_trylock(arch_rwlock_t *rw) 119 { 120 unsigned int val, got_it = 0; 121 122 smp_mb(); 123 124 __asm__ __volatile__( 125 "1: llock %[val], [%[rwlock]] \n" 126 " brls %[val], %[WR_LOCKED], 4f\n" /* <= 0: already write locked, bail */ 127 " sub %[val], %[val], 1 \n" /* counter-- */ 128 " scond %[val], [%[rwlock]] \n" 129 " bnz 1b \n" /* retry if collided with someone */ 130 " mov %[got_it], 1 \n" 131 " \n" 132 "4: ; --- done --- \n" 133 134 : [val] "=&r" (val), 135 [got_it] "+&r" (got_it) 136 : [rwlock] "r" (&(rw->counter)), 137 [WR_LOCKED] "ir" (0) 138 : "memory", "cc"); 139 140 smp_mb(); 141 142 return got_it; 143 } 144 145 static inline void arch_write_lock(arch_rwlock_t *rw) 146 { 147 unsigned int val; 148 149 smp_mb(); 150 151 /* 152 * If reader(s) hold lock (lock < __ARCH_RW_LOCK_UNLOCKED__), 153 * deny writer. Otherwise if unlocked grant to writer 154 * Hence the claim that Linux rwlocks are unfair to writers. 155 * (can be starved for an indefinite time by readers). 156 * 157 * if (rw->counter == __ARCH_RW_LOCK_UNLOCKED__) { 158 * rw->counter = 0; 159 * ret = 1; 160 * } 161 */ 162 163 __asm__ __volatile__( 164 "1: llock %[val], [%[rwlock]] \n" 165 " brne %[val], %[UNLOCKED], 1b \n" /* while !UNLOCKED spin */ 166 " mov %[val], %[WR_LOCKED] \n" 167 " scond %[val], [%[rwlock]] \n" 168 " bnz 1b \n" 169 " \n" 170 : [val] "=&r" (val) 171 : [rwlock] "r" (&(rw->counter)), 172 [UNLOCKED] "ir" (__ARCH_RW_LOCK_UNLOCKED__), 173 [WR_LOCKED] "ir" (0) 174 : "memory", "cc"); 175 176 smp_mb(); 177 } 178 179 /* 1 - lock taken successfully */ 180 static inline int arch_write_trylock(arch_rwlock_t *rw) 181 { 182 unsigned int val, got_it = 0; 183 184 smp_mb(); 185 186 __asm__ __volatile__( 187 "1: llock %[val], [%[rwlock]] \n" 188 " brne %[val], %[UNLOCKED], 4f \n" /* !UNLOCKED, bail */ 189 " mov %[val], %[WR_LOCKED] \n" 190 " scond %[val], [%[rwlock]] \n" 191 " bnz 1b \n" /* retry if collided with someone */ 192 " mov %[got_it], 1 \n" 193 " \n" 194 "4: ; --- done --- \n" 195 196 : [val] "=&r" (val), 197 [got_it] "+&r" (got_it) 198 : [rwlock] "r" (&(rw->counter)), 199 [UNLOCKED] "ir" (__ARCH_RW_LOCK_UNLOCKED__), 200 [WR_LOCKED] "ir" (0) 201 : "memory", "cc"); 202 203 smp_mb(); 204 205 return got_it; 206 } 207 208 static inline void arch_read_unlock(arch_rwlock_t *rw) 209 { 210 unsigned int val; 211 212 smp_mb(); 213 214 /* 215 * rw->counter++; 216 */ 217 __asm__ __volatile__( 218 "1: llock %[val], [%[rwlock]] \n" 219 " add %[val], %[val], 1 \n" 220 " scond %[val], [%[rwlock]] \n" 221 " bnz 1b \n" 222 " \n" 223 : [val] "=&r" (val) 224 : [rwlock] "r" (&(rw->counter)) 225 : "memory", "cc"); 226 227 smp_mb(); 228 } 229 230 static inline void arch_write_unlock(arch_rwlock_t *rw) 231 { 232 smp_mb(); 233 234 rw->counter = __ARCH_RW_LOCK_UNLOCKED__; 235 236 smp_mb(); 237 } 238 239 #else /* !CONFIG_ARC_HAS_LLSC */ 240 241 static inline void arch_spin_lock(arch_spinlock_t *lock) 242 { 243 unsigned int val = __ARCH_SPIN_LOCK_LOCKED__; 244 245 /* 246 * This smp_mb() is technically superfluous, we only need the one 247 * after the lock for providing the ACQUIRE semantics. 248 * However doing the "right" thing was regressing hackbench 249 * so keeping this, pending further investigation 250 */ 251 smp_mb(); 252 253 __asm__ __volatile__( 254 "1: ex %0, [%1] \n" 255 " breq %0, %2, 1b \n" 256 : "+&r" (val) 257 : "r"(&(lock->slock)), "ir"(__ARCH_SPIN_LOCK_LOCKED__) 258 : "memory"); 259 260 /* 261 * ACQUIRE barrier to ensure load/store after taking the lock 262 * don't "bleed-up" out of the critical section (leak-in is allowed) 263 * http://www.spinics.net/lists/kernel/msg2010409.html 264 * 265 * ARCv2 only has load-load, store-store and all-all barrier 266 * thus need the full all-all barrier 267 */ 268 smp_mb(); 269 } 270 271 /* 1 - lock taken successfully */ 272 static inline int arch_spin_trylock(arch_spinlock_t *lock) 273 { 274 unsigned int val = __ARCH_SPIN_LOCK_LOCKED__; 275 276 smp_mb(); 277 278 __asm__ __volatile__( 279 "1: ex %0, [%1] \n" 280 : "+r" (val) 281 : "r"(&(lock->slock)) 282 : "memory"); 283 284 smp_mb(); 285 286 return (val == __ARCH_SPIN_LOCK_UNLOCKED__); 287 } 288 289 static inline void arch_spin_unlock(arch_spinlock_t *lock) 290 { 291 unsigned int val = __ARCH_SPIN_LOCK_UNLOCKED__; 292 293 /* 294 * RELEASE barrier: given the instructions avail on ARCv2, full barrier 295 * is the only option 296 */ 297 smp_mb(); 298 299 __asm__ __volatile__( 300 " ex %0, [%1] \n" 301 : "+r" (val) 302 : "r"(&(lock->slock)) 303 : "memory"); 304 305 /* 306 * superfluous, but keeping for now - see pairing version in 307 * arch_spin_lock above 308 */ 309 smp_mb(); 310 } 311 312 /* 313 * Read-write spinlocks, allowing multiple readers but only one writer. 314 * Unfair locking as Writers could be starved indefinitely by Reader(s) 315 * 316 * The spinlock itself is contained in @counter and access to it is 317 * serialized with @lock_mutex. 318 */ 319 320 /* 1 - lock taken successfully */ 321 static inline int arch_read_trylock(arch_rwlock_t *rw) 322 { 323 int ret = 0; 324 unsigned long flags; 325 326 local_irq_save(flags); 327 arch_spin_lock(&(rw->lock_mutex)); 328 329 /* 330 * zero means writer holds the lock exclusively, deny Reader. 331 * Otherwise grant lock to first/subseq reader 332 */ 333 if (rw->counter > 0) { 334 rw->counter--; 335 ret = 1; 336 } 337 338 arch_spin_unlock(&(rw->lock_mutex)); 339 local_irq_restore(flags); 340 341 smp_mb(); 342 return ret; 343 } 344 345 /* 1 - lock taken successfully */ 346 static inline int arch_write_trylock(arch_rwlock_t *rw) 347 { 348 int ret = 0; 349 unsigned long flags; 350 351 local_irq_save(flags); 352 arch_spin_lock(&(rw->lock_mutex)); 353 354 /* 355 * If reader(s) hold lock (lock < __ARCH_RW_LOCK_UNLOCKED__), 356 * deny writer. Otherwise if unlocked grant to writer 357 * Hence the claim that Linux rwlocks are unfair to writers. 358 * (can be starved for an indefinite time by readers). 359 */ 360 if (rw->counter == __ARCH_RW_LOCK_UNLOCKED__) { 361 rw->counter = 0; 362 ret = 1; 363 } 364 arch_spin_unlock(&(rw->lock_mutex)); 365 local_irq_restore(flags); 366 367 return ret; 368 } 369 370 static inline void arch_read_lock(arch_rwlock_t *rw) 371 { 372 while (!arch_read_trylock(rw)) 373 cpu_relax(); 374 } 375 376 static inline void arch_write_lock(arch_rwlock_t *rw) 377 { 378 while (!arch_write_trylock(rw)) 379 cpu_relax(); 380 } 381 382 static inline void arch_read_unlock(arch_rwlock_t *rw) 383 { 384 unsigned long flags; 385 386 local_irq_save(flags); 387 arch_spin_lock(&(rw->lock_mutex)); 388 rw->counter++; 389 arch_spin_unlock(&(rw->lock_mutex)); 390 local_irq_restore(flags); 391 } 392 393 static inline void arch_write_unlock(arch_rwlock_t *rw) 394 { 395 unsigned long flags; 396 397 local_irq_save(flags); 398 arch_spin_lock(&(rw->lock_mutex)); 399 rw->counter = __ARCH_RW_LOCK_UNLOCKED__; 400 arch_spin_unlock(&(rw->lock_mutex)); 401 local_irq_restore(flags); 402 } 403 404 #endif 405 406 #define arch_read_can_lock(x) ((x)->counter > 0) 407 #define arch_write_can_lock(x) ((x)->counter == __ARCH_RW_LOCK_UNLOCKED__) 408 409 #define arch_read_lock_flags(lock, flags) arch_read_lock(lock) 410 #define arch_write_lock_flags(lock, flags) arch_write_lock(lock) 411 412 #define arch_spin_relax(lock) cpu_relax() 413 #define arch_read_relax(lock) cpu_relax() 414 #define arch_write_relax(lock) cpu_relax() 415 416 #endif /* __ASM_SPINLOCK_H */ 417