arch/powerpc/include/asm/spinlock.h

   1 #ifndef __ASM_SPINLOCK_H
   2 #define __ASM_SPINLOCK_H
   3 #ifdef __KERNEL__
   4
   5 /*
   6  * Simple spin lock operations.
   7  *
   8  * Copyright (C) 2001-2004 Paul Mackerras <paulus@au.ibm.com>, IBM
   9  * Copyright (C) 2001 Anton Blanchard <anton@au.ibm.com>, IBM
  10  * Copyright (C) 2002 Dave Engebretsen <engebret@us.ibm.com>, IBM
  11  *      Rework to support virtual processors
  12  *
  13  * Type of int is used as a full 64b word is not necessary.
  14  *
  15  * This program is free software; you can redistribute it and/or
  16  * modify it under the terms of the GNU General Public License
  17  * as published by the Free Software Foundation; either version
  18  * 2 of the License, or (at your option) any later version.
  19  *
  20  * (the type definitions are in asm/spinlock_types.h)
  21  */
  22 #include <linux/irqflags.h>
  23 #ifdef CONFIG_PPC64
  24 #include <asm/paca.h>
  25 #include <asm/hvcall.h>
  26 #endif
  27 #include <asm/asm-compat.h>
  28 #include <asm/synch.h>
  29 #include <asm/ppc-opcode.h>
  30
  31 #define smp_mb__after_unlock_lock()     smp_mb()  /* Full ordering for lock. */
  32
  33 #ifdef CONFIG_PPC64
  34 /* use 0x800000yy when locked, where yy == CPU number */
  35 #ifdef __BIG_ENDIAN__
  36 #define LOCK_TOKEN      (*(u32 *)(&get_paca()->lock_token))
  37 #else
  38 #define LOCK_TOKEN      (*(u32 *)(&get_paca()->paca_index))
  39 #endif
  40 #else
  41 #define LOCK_TOKEN      1
  42 #endif
  43
  44 #if defined(CONFIG_PPC64) && defined(CONFIG_SMP)
  45 #define CLEAR_IO_SYNC   (get_paca()->io_sync = 0)
  46 #define SYNC_IO         do {                                            \
  47                                 if (unlikely(get_paca()->io_sync)) {    \
  48                                         mb();                           \
  49                                         get_paca()->io_sync = 0;        \
  50                                 }                                       \
  51                         } while (0)
  52 #else
  53 #define CLEAR_IO_SYNC
  54 #define SYNC_IO
  55 #endif
  56
  57 static __always_inline int arch_spin_value_unlocked(arch_spinlock_t lock)
  58 {
  59         return lock.slock == 0;
  60 }
  61
  62 static inline int arch_spin_is_locked(arch_spinlock_t *lock)
  63 {
  64         return !arch_spin_value_unlocked(*lock);
  65 }
  66
  67 /*
  68  * This returns the old value in the lock, so we succeeded
  69  * in getting the lock if the return value is 0.
  70  */
  71 static inline unsigned long __arch_spin_trylock(arch_spinlock_t *lock)
  72 {
  73         unsigned long tmp, token;
  74
  75         token = LOCK_TOKEN;
  76         __asm__ __volatile__(
  77 "1:     " PPC_LWARX(%0,0,%2,1) "\n\
  78         cmpwi           0,%0,0\n\
  79         bne-            2f\n\
  80         stwcx.          %1,0,%2\n\
  81         bne-            1b\n"
  82         PPC_ACQUIRE_BARRIER
  83 "2:"
  84         : "=&r" (tmp)
  85         : "r" (token), "r" (&lock->slock)
  86         : "cr0", "memory");
  87
  88         return tmp;
  89 }
  90
  91 static inline int arch_spin_trylock(arch_spinlock_t *lock)
  92 {
  93         CLEAR_IO_SYNC;
  94         return __arch_spin_trylock(lock) == 0;
  95 }
  96
  97 /*
  98  * On a system with shared processors (that is, where a physical
  99  * processor is multiplexed between several virtual processors),
 100  * there is no point spinning on a lock if the holder of the lock
 101  * isn't currently scheduled on a physical processor.  Instead
 102  * we detect this situation and ask the hypervisor to give the
 103  * rest of our timeslice to the lock holder.
 104  *
 105  * So that we can tell which virtual processor is holding a lock,
 106  * we put 0x80000000 | smp_processor_id() in the lock when it is
 107  * held.  Conveniently, we have a word in the paca that holds this
 108  * value.
 109  */
 110
 111 #if defined(CONFIG_PPC_SPLPAR)
 112 /* We only yield to the hypervisor if we are in shared processor mode */
 113 #define SHARED_PROCESSOR (lppaca_shared_proc(local_paca->lppaca_ptr))
 114 extern void __spin_yield(arch_spinlock_t *lock);
 115 extern void __rw_yield(arch_rwlock_t *lock);
 116 #else /* SPLPAR */
 117 #define __spin_yield(x) barrier()
 118 #define __rw_yield(x)   barrier()
 119 #define SHARED_PROCESSOR        0
 120 #endif
 121
 122 static inline void arch_spin_lock(arch_spinlock_t *lock)
 123 {
 124         CLEAR_IO_SYNC;
 125         while (1) {
 126                 if (likely(__arch_spin_trylock(lock) == 0))
 127                         break;
 128                 do {
 129                         HMT_low();
 130                         if (SHARED_PROCESSOR)
 131                                 __spin_yield(lock);
 132                 } while (unlikely(lock->slock != 0));
 133                 HMT_medium();
 134         }
 135 }
 136
 137 static inline
 138 void arch_spin_lock_flags(arch_spinlock_t *lock, unsigned long flags)
 139 {
 140         unsigned long flags_dis;
 141
 142         CLEAR_IO_SYNC;
 143         while (1) {
 144                 if (likely(__arch_spin_trylock(lock) == 0))
 145                         break;
 146                 local_save_flags(flags_dis);
 147                 local_irq_restore(flags);
 148                 do {
 149                         HMT_low();
 150                         if (SHARED_PROCESSOR)
 151                                 __spin_yield(lock);
 152                 } while (unlikely(lock->slock != 0));
 153                 HMT_medium();
 154                 local_irq_restore(flags_dis);
 155         }
 156 }
 157
 158 static inline void arch_spin_unlock(arch_spinlock_t *lock)
 159 {
 160         SYNC_IO;
 161         __asm__ __volatile__("# arch_spin_unlock\n\t"
 162                                 PPC_RELEASE_BARRIER: : :"memory");
 163         lock->slock = 0;
 164 }
 165
 166 #ifdef CONFIG_PPC64
 167 extern void arch_spin_unlock_wait(arch_spinlock_t *lock);
 168 #else
 169 #define arch_spin_unlock_wait(lock) \
 170         do { while (arch_spin_is_locked(lock)) cpu_relax(); } while (0)
 171 #endif
 172
 173 /*
 174  * Read-write spinlocks, allowing multiple readers
 175  * but only one writer.
 176  *
 177  * NOTE! it is quite common to have readers in interrupts
 178  * but no interrupt writers. For those circumstances we
 179  * can "mix" irq-safe locks - any writer needs to get a
 180  * irq-safe write-lock, but readers can get non-irqsafe
 181  * read-locks.
 182  */
 183
 184 #define arch_read_can_lock(rw)          ((rw)->lock >= 0)
 185 #define arch_write_can_lock(rw) (!(rw)->lock)
 186
 187 #ifdef CONFIG_PPC64
 188 #define __DO_SIGN_EXTEND        "extsw  %0,%0\n"
 189 #define WRLOCK_TOKEN            LOCK_TOKEN      /* it's negative */
 190 #else
 191 #define __DO_SIGN_EXTEND
 192 #define WRLOCK_TOKEN            (-1)
 193 #endif
 194
 195 /*
 196  * This returns the old value in the lock + 1,
 197  * so we got a read lock if the return value is > 0.
 198  */
 199 static inline long __arch_read_trylock(arch_rwlock_t *rw)
 200 {
 201         long tmp;
 202
 203         __asm__ __volatile__(
 204 "1:     " PPC_LWARX(%0,0,%1,1) "\n"
 205         __DO_SIGN_EXTEND
 206 "       addic.          %0,%0,1\n\
 207         ble-            2f\n"
 208         PPC405_ERR77(0,%1)
 209 "       stwcx.          %0,0,%1\n\
 210         bne-            1b\n"
 211         PPC_ACQUIRE_BARRIER
 212 "2:"    : "=&r" (tmp)
 213         : "r" (&rw->lock)
 214         : "cr0", "xer", "memory");
 215
 216         return tmp;
 217 }
 218
 219 /*
 220  * This returns the old value in the lock,
 221  * so we got the write lock if the return value is 0.
 222  */
 223 static inline long __arch_write_trylock(arch_rwlock_t *rw)
 224 {
 225         long tmp, token;
 226
 227         token = WRLOCK_TOKEN;
 228         __asm__ __volatile__(
 229 "1:     " PPC_LWARX(%0,0,%2,1) "\n\
 230         cmpwi           0,%0,0\n\
 231         bne-            2f\n"
 232         PPC405_ERR77(0,%1)
 233 "       stwcx.          %1,0,%2\n\
 234         bne-            1b\n"
 235         PPC_ACQUIRE_BARRIER
 236 "2:"    : "=&r" (tmp)
 237         : "r" (token), "r" (&rw->lock)
 238         : "cr0", "memory");
 239
 240         return tmp;
 241 }
 242
 243 static inline void arch_read_lock(arch_rwlock_t *rw)
 244 {
 245         while (1) {
 246                 if (likely(__arch_read_trylock(rw) > 0))
 247                         break;
 248                 do {
 249                         HMT_low();
 250                         if (SHARED_PROCESSOR)
 251                                 __rw_yield(rw);
 252                 } while (unlikely(rw->lock < 0));
 253                 HMT_medium();
 254         }
 255 }
 256
 257 static inline void arch_write_lock(arch_rwlock_t *rw)
 258 {
 259         while (1) {
 260                 if (likely(__arch_write_trylock(rw) == 0))
 261                         break;
 262                 do {
 263                         HMT_low();
 264                         if (SHARED_PROCESSOR)
 265                                 __rw_yield(rw);
 266                 } while (unlikely(rw->lock != 0));
 267                 HMT_medium();
 268         }
 269 }
 270
 271 static inline int arch_read_trylock(arch_rwlock_t *rw)
 272 {
 273         return __arch_read_trylock(rw) > 0;
 274 }
 275
 276 static inline int arch_write_trylock(arch_rwlock_t *rw)
 277 {
 278         return __arch_write_trylock(rw) == 0;
 279 }
 280
 281 static inline void arch_read_unlock(arch_rwlock_t *rw)
 282 {
 283         long tmp;
 284
 285         __asm__ __volatile__(
 286         "# read_unlock\n\t"
 287         PPC_RELEASE_BARRIER
 288 "1:     lwarx           %0,0,%1\n\
 289         addic           %0,%0,-1\n"
 290         PPC405_ERR77(0,%1)
 291 "       stwcx.          %0,0,%1\n\
 292         bne-            1b"
 293         : "=&r"(tmp)
 294         : "r"(&rw->lock)
 295         : "cr0", "xer", "memory");
 296 }
 297
 298 static inline void arch_write_unlock(arch_rwlock_t *rw)
 299 {
 300         __asm__ __volatile__("# write_unlock\n\t"
 301                                 PPC_RELEASE_BARRIER: : :"memory");
 302         rw->lock = 0;
 303 }
 304
 305 #define arch_read_lock_flags(lock, flags) arch_read_lock(lock)
 306 #define arch_write_lock_flags(lock, flags) arch_write_lock(lock)
 307
 308 #define arch_spin_relax(lock)   __spin_yield(lock)
 309 #define arch_read_relax(lock)   __rw_yield(lock)
 310 #define arch_write_relax(lock)  __rw_yield(lock)
 311
 312 #endif /* __KERNEL__ */
 313 #endif /* __ASM_SPINLOCK_H */