kernel/spinlock.c

   1 /*
   2  * Copyright (2004) Linus Torvalds
   3  *
   4  * Author: Zwane Mwaikambo <zwane@fsmlabs.com>
   5  *
   6  * Copyright (2004) Ingo Molnar
   7  */
   8
   9 #include <linux/config.h>
  10 #include <linux/linkage.h>
  11 #include <linux/preempt.h>
  12 #include <linux/spinlock.h>
  13 #include <linux/interrupt.h>
  14 #include <linux/module.h>
  15
  16 /*
  17  * Generic declaration of the raw read_trylock() function,
  18  * architectures are supposed to optimize this:
  19  */
  20 int __lockfunc generic_raw_read_trylock(rwlock_t *lock)
  21 {
  22         _raw_read_lock(lock);
  23         return 1;
  24 }
  25 EXPORT_SYMBOL(generic_raw_read_trylock);
  26
  27 int __lockfunc _spin_trylock(spinlock_t *lock)
  28 {
  29         preempt_disable();
  30         if (_raw_spin_trylock(lock))
  31                 return 1;
  32
  33         preempt_enable();
  34         return 0;
  35 }
  36 EXPORT_SYMBOL(_spin_trylock);
  37
  38 int __lockfunc _read_trylock(rwlock_t *lock)
  39 {
  40         preempt_disable();
  41         if (_raw_read_trylock(lock))
  42                 return 1;
  43
  44         preempt_enable();
  45         return 0;
  46 }
  47 EXPORT_SYMBOL(_read_trylock);
  48
  49 int __lockfunc _write_trylock(rwlock_t *lock)
  50 {
  51         preempt_disable();
  52         if (_raw_write_trylock(lock))
  53                 return 1;
  54
  55         preempt_enable();
  56         return 0;
  57 }
  58 EXPORT_SYMBOL(_write_trylock);
  59
  60 #ifndef CONFIG_PREEMPT
  61
  62 void __lockfunc _read_lock(rwlock_t *lock)
  63 {
  64         preempt_disable();
  65         _raw_read_lock(lock);
  66 }
  67 EXPORT_SYMBOL(_read_lock);
  68
  69 unsigned long __lockfunc _spin_lock_irqsave(spinlock_t *lock)
  70 {
  71         unsigned long flags;
  72
  73         local_irq_save(flags);
  74         preempt_disable();
  75         _raw_spin_lock_flags(lock, flags);
  76         return flags;
  77 }
  78 EXPORT_SYMBOL(_spin_lock_irqsave);
  79
  80 void __lockfunc _spin_lock_irq(spinlock_t *lock)
  81 {
  82         local_irq_disable();
  83         preempt_disable();
  84         _raw_spin_lock(lock);
  85 }
  86 EXPORT_SYMBOL(_spin_lock_irq);
  87
  88 void __lockfunc _spin_lock_bh(spinlock_t *lock)
  89 {
  90         local_bh_disable();
  91         preempt_disable();
  92         _raw_spin_lock(lock);
  93 }
  94 EXPORT_SYMBOL(_spin_lock_bh);
  95
  96 unsigned long __lockfunc _read_lock_irqsave(rwlock_t *lock)
  97 {
  98         unsigned long flags;
  99
 100         local_irq_save(flags);
 101         preempt_disable();
 102         _raw_read_lock(lock);
 103         return flags;
 104 }
 105 EXPORT_SYMBOL(_read_lock_irqsave);
 106
 107 void __lockfunc _read_lock_irq(rwlock_t *lock)
 108 {
 109         local_irq_disable();
 110         preempt_disable();
 111         _raw_read_lock(lock);
 112 }
 113 EXPORT_SYMBOL(_read_lock_irq);
 114
 115 void __lockfunc _read_lock_bh(rwlock_t *lock)
 116 {
 117         local_bh_disable();
 118         preempt_disable();
 119         _raw_read_lock(lock);
 120 }
 121 EXPORT_SYMBOL(_read_lock_bh);
 122
 123 unsigned long __lockfunc _write_lock_irqsave(rwlock_t *lock)
 124 {
 125         unsigned long flags;
 126
 127         local_irq_save(flags);
 128         preempt_disable();
 129         _raw_write_lock(lock);
 130         return flags;
 131 }
 132 EXPORT_SYMBOL(_write_lock_irqsave);
 133
 134 void __lockfunc _write_lock_irq(rwlock_t *lock)
 135 {
 136         local_irq_disable();
 137         preempt_disable();
 138         _raw_write_lock(lock);
 139 }
 140 EXPORT_SYMBOL(_write_lock_irq);
 141
 142 void __lockfunc _write_lock_bh(rwlock_t *lock)
 143 {
 144         local_bh_disable();
 145         preempt_disable();
 146         _raw_write_lock(lock);
 147 }
 148 EXPORT_SYMBOL(_write_lock_bh);
 149
 150 void __lockfunc _spin_lock(spinlock_t *lock)
 151 {
 152         preempt_disable();
 153         _raw_spin_lock(lock);
 154 }
 155
 156 EXPORT_SYMBOL(_spin_lock);
 157
 158 void __lockfunc _write_lock(rwlock_t *lock)
 159 {
 160         preempt_disable();
 161         _raw_write_lock(lock);
 162 }
 163
 164 EXPORT_SYMBOL(_write_lock);
 165
 166 #else /* CONFIG_PREEMPT: */
 167
 168 /*
 169  * This could be a long-held lock. We both prepare to spin for a long
 170  * time (making _this_ CPU preemptable if possible), and we also signal
 171  * towards that other CPU that it should break the lock ASAP.
 172  *
 173  * (We do this in a function because inlining it would be excessive.)
 174  */
 175
 176 #define BUILD_LOCK_OPS(op, locktype)                                    \
 177 void __lockfunc _##op##_lock(locktype##_t *lock)                        \
 178 {                                                                       \
 179         preempt_disable();                                              \
 180         for (;;) {                                                      \
 181                 if (likely(_raw_##op##_trylock(lock)))                  \
 182                         break;                                          \
 183                 preempt_enable();                                       \
 184                 if (!(lock)->break_lock)                                \
 185                         (lock)->break_lock = 1;                         \
 186                 while (!op##_can_lock(lock) && (lock)->break_lock)      \
 187                         cpu_relax();                                    \
 188                 preempt_disable();                                      \
 189         }                                                               \
 190         (lock)->break_lock = 0;                                         \
 191 }                                                                       \
 192                                                                         \
 193 EXPORT_SYMBOL(_##op##_lock);                                            \
 194                                                                         \
 195 unsigned long __lockfunc _##op##_lock_irqsave(locktype##_t *lock)       \
 196 {                                                                       \
 197         unsigned long flags;                                            \
 198                                                                         \
 199         preempt_disable();                                              \
 200         for (;;) {                                                      \
 201                 local_irq_save(flags);                                  \
 202                 if (likely(_raw_##op##_trylock(lock)))                  \
 203                         break;                                          \
 204                 local_irq_restore(flags);                               \
 205                                                                         \
 206                 preempt_enable();                                       \
 207                 if (!(lock)->break_lock)                                \
 208                         (lock)->break_lock = 1;                         \
 209                 while (!op##_can_lock(lock) && (lock)->break_lock)      \
 210                         cpu_relax();                                    \
 211                 preempt_disable();                                      \
 212         }                                                               \
 213         (lock)->break_lock = 0;                                         \
 214         return flags;                                                   \
 215 }                                                                       \
 216                                                                         \
 217 EXPORT_SYMBOL(_##op##_lock_irqsave);                                    \
 218                                                                         \
 219 void __lockfunc _##op##_lock_irq(locktype##_t *lock)                    \
 220 {                                                                       \
 221         _##op##_lock_irqsave(lock);                                     \
 222 }                                                                       \
 223                                                                         \
 224 EXPORT_SYMBOL(_##op##_lock_irq);                                        \
 225                                                                         \
 226 void __lockfunc _##op##_lock_bh(locktype##_t *lock)                     \
 227 {                                                                       \
 228         unsigned long flags;                                            \
 229                                                                         \
 230         /*                                                      */      \
 231         /* Careful: we must exclude softirqs too, hence the     */      \
 232         /* irq-disabling. We use the generic preemption-aware   */      \
 233         /* function:                                            */      \
 234         /**/                                                            \
 235         flags = _##op##_lock_irqsave(lock);                             \
 236         local_bh_disable();                                             \
 237         local_irq_restore(flags);                                       \
 238 }                                                                       \
 239                                                                         \
 240 EXPORT_SYMBOL(_##op##_lock_bh)
 241
 242 /*
 243  * Build preemption-friendly versions of the following
 244  * lock-spinning functions:
 245  *
 246  *         _[spin|read|write]_lock()
 247  *         _[spin|read|write]_lock_irq()
 248  *         _[spin|read|write]_lock_irqsave()
 249  *         _[spin|read|write]_lock_bh()
 250  */
 251 BUILD_LOCK_OPS(spin, spinlock);
 252 BUILD_LOCK_OPS(read, rwlock);
 253 BUILD_LOCK_OPS(write, rwlock);
 254
 255 #endif /* CONFIG_PREEMPT */
 256
 257 void __lockfunc _spin_unlock(spinlock_t *lock)
 258 {
 259         _raw_spin_unlock(lock);
 260         preempt_enable();
 261 }
 262 EXPORT_SYMBOL(_spin_unlock);
 263
 264 void __lockfunc _write_unlock(rwlock_t *lock)
 265 {
 266         _raw_write_unlock(lock);
 267         preempt_enable();
 268 }
 269 EXPORT_SYMBOL(_write_unlock);
 270
 271 void __lockfunc _read_unlock(rwlock_t *lock)
 272 {
 273         _raw_read_unlock(lock);
 274         preempt_enable();
 275 }
 276 EXPORT_SYMBOL(_read_unlock);
 277
 278 void __lockfunc _spin_unlock_irqrestore(spinlock_t *lock, unsigned long flags)
 279 {
 280         _raw_spin_unlock(lock);
 281         local_irq_restore(flags);
 282         preempt_enable();
 283 }
 284 EXPORT_SYMBOL(_spin_unlock_irqrestore);
 285
 286 void __lockfunc _spin_unlock_irq(spinlock_t *lock)
 287 {
 288         _raw_spin_unlock(lock);
 289         local_irq_enable();
 290         preempt_enable();
 291 }
 292 EXPORT_SYMBOL(_spin_unlock_irq);
 293
 294 void __lockfunc _spin_unlock_bh(spinlock_t *lock)
 295 {
 296         _raw_spin_unlock(lock);
 297         preempt_enable_no_resched();
 298         local_bh_enable();
 299 }
 300 EXPORT_SYMBOL(_spin_unlock_bh);
 301
 302 void __lockfunc _read_unlock_irqrestore(rwlock_t *lock, unsigned long flags)
 303 {
 304         _raw_read_unlock(lock);
 305         local_irq_restore(flags);
 306         preempt_enable();
 307 }
 308 EXPORT_SYMBOL(_read_unlock_irqrestore);
 309
 310 void __lockfunc _read_unlock_irq(rwlock_t *lock)
 311 {
 312         _raw_read_unlock(lock);
 313         local_irq_enable();
 314         preempt_enable();
 315 }
 316 EXPORT_SYMBOL(_read_unlock_irq);
 317
 318 void __lockfunc _read_unlock_bh(rwlock_t *lock)
 319 {
 320         _raw_read_unlock(lock);
 321         preempt_enable_no_resched();
 322         local_bh_enable();
 323 }
 324 EXPORT_SYMBOL(_read_unlock_bh);
 325
 326 void __lockfunc _write_unlock_irqrestore(rwlock_t *lock, unsigned long flags)
 327 {
 328         _raw_write_unlock(lock);
 329         local_irq_restore(flags);
 330         preempt_enable();
 331 }
 332 EXPORT_SYMBOL(_write_unlock_irqrestore);
 333
 334 void __lockfunc _write_unlock_irq(rwlock_t *lock)
 335 {
 336         _raw_write_unlock(lock);
 337         local_irq_enable();
 338         preempt_enable();
 339 }
 340 EXPORT_SYMBOL(_write_unlock_irq);
 341
 342 void __lockfunc _write_unlock_bh(rwlock_t *lock)
 343 {
 344         _raw_write_unlock(lock);
 345         preempt_enable_no_resched();
 346         local_bh_enable();
 347 }
 348 EXPORT_SYMBOL(_write_unlock_bh);
 349
 350 int __lockfunc _spin_trylock_bh(spinlock_t *lock)
 351 {
 352         local_bh_disable();
 353         preempt_disable();
 354         if (_raw_spin_trylock(lock))
 355                 return 1;
 356
 357         preempt_enable_no_resched();
 358         local_bh_enable();
 359         return 0;
 360 }
 361 EXPORT_SYMBOL(_spin_trylock_bh);
 362
 363 int in_lock_functions(unsigned long addr)
 364 {
 365         /* Linker adds these: start and end of __lockfunc functions */
 366         extern char __lock_text_start[], __lock_text_end[];
 367
 368         return addr >= (unsigned long)__lock_text_start
 369         && addr < (unsigned long)__lock_text_end;
 370 }
 371 EXPORT_SYMBOL(in_lock_functions);