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         smp_mb();
  65         return !arch_spin_value_unlocked(*lock);
  66 }
  67
  68 /*
  69  * This returns the old value in the lock, so we succeeded
  70  * in getting the lock if the return value is 0.
  71  */
  72 static inline unsigned long __arch_spin_trylock(arch_spinlock_t *lock)
  73 {
  74         unsigned long tmp, token;
  75
  76         token = LOCK_TOKEN;
  77         __asm__ __volatile__(
  78 "1:     " PPC_LWARX(%0,0,%2,1) "\n\
  79         cmpwi           0,%0,0\n\
  80         bne-            2f\n\
  81         stwcx.          %1,0,%2\n\
  82         bne-            1b\n"
  83         PPC_ACQUIRE_BARRIER
  84 "2:"
  85         : "=&r" (tmp)
  86         : "r" (token), "r" (&lock->slock)
  87         : "cr0", "memory");
  88
  89         return tmp;
  90 }
  91
  92 static inline int arch_spin_trylock(arch_spinlock_t *lock)
  93 {
  94         CLEAR_IO_SYNC;
  95         return __arch_spin_trylock(lock) == 0;
  96 }
  97
  98 /*
  99  * On a system with shared processors (that is, where a physical
 100  * processor is multiplexed between several virtual processors),
 101  * there is no point spinning on a lock if the holder of the lock
 102  * isn't currently scheduled on a physical processor.  Instead
 103  * we detect this situation and ask the hypervisor to give the
 104  * rest of our timeslice to the lock holder.
 105  *
 106  * So that we can tell which virtual processor is holding a lock,
 107  * we put 0x80000000 | smp_processor_id() in the lock when it is
 108  * held.  Conveniently, we have a word in the paca that holds this
 109  * value.
 110  */
 111
 112 #if defined(CONFIG_PPC_SPLPAR)
 113 /* We only yield to the hypervisor if we are in shared processor mode */
 114 #define SHARED_PROCESSOR (lppaca_shared_proc(local_paca->lppaca_ptr))
 115 extern void __spin_yield(arch_spinlock_t *lock);
 116 extern void __rw_yield(arch_rwlock_t *lock);
 117 #else /* SPLPAR */
 118 #define __spin_yield(x) barrier()
 119 #define __rw_yield(x)   barrier()
 120 #define SHARED_PROCESSOR        0
 121 #endif
 122
 123 static inline void arch_spin_lock(arch_spinlock_t *lock)
 124 {
 125         CLEAR_IO_SYNC;
 126         while (1) {
 127                 if (likely(__arch_spin_trylock(lock) == 0))
 128                         break;
 129                 do {
 130                         HMT_low();
 131                         if (SHARED_PROCESSOR)
 132                                 __spin_yield(lock);
 133                 } while (unlikely(lock->slock != 0));
 134                 HMT_medium();
 135         }
 136 }
 137
 138 static inline
 139 void arch_spin_lock_flags(arch_spinlock_t *lock, unsigned long flags)
 140 {
 141         unsigned long flags_dis;
 142
 143         CLEAR_IO_SYNC;
 144         while (1) {
 145                 if (likely(__arch_spin_trylock(lock) == 0))
 146                         break;
 147                 local_save_flags(flags_dis);
 148                 local_irq_restore(flags);
 149                 do {
 150                         HMT_low();
 151                         if (SHARED_PROCESSOR)
 152                                 __spin_yield(lock);
 153                 } while (unlikely(lock->slock != 0));
 154                 HMT_medium();
 155                 local_irq_restore(flags_dis);
 156         }
 157 }
 158
 159 static inline void arch_spin_unlock(arch_spinlock_t *lock)
 160 {
 161         SYNC_IO;
 162         __asm__ __volatile__("# arch_spin_unlock\n\t"
 163                                 PPC_RELEASE_BARRIER: : :"memory");
 164         lock->slock = 0;
 165 }
 166
 167 #ifdef CONFIG_PPC64
 168 extern void arch_spin_unlock_wait(arch_spinlock_t *lock);
 169 #else
 170 #define arch_spin_unlock_wait(lock) \
 171         do { while (arch_spin_is_locked(lock)) cpu_relax(); } while (0)
 172 #endif
 173
 174 /*
 175  * Read-write spinlocks, allowing multiple readers
 176  * but only one writer.
 177  *
 178  * NOTE! it is quite common to have readers in interrupts
 179  * but no interrupt writers. For those circumstances we
 180  * can "mix" irq-safe locks - any writer needs to get a
 181  * irq-safe write-lock, but readers can get non-irqsafe
 182  * read-locks.
 183  */
 184
 185 #define arch_read_can_lock(rw)          ((rw)->lock >= 0)
 186 #define arch_write_can_lock(rw) (!(rw)->lock)
 187
 188 #ifdef CONFIG_PPC64
 189 #define __DO_SIGN_EXTEND        "extsw  %0,%0\n"
 190 #define WRLOCK_TOKEN            LOCK_TOKEN      /* it's negative */
 191 #else
 192 #define __DO_SIGN_EXTEND
 193 #define WRLOCK_TOKEN            (-1)
 194 #endif
 195
 196 /*
 197  * This returns the old value in the lock + 1,
 198  * so we got a read lock if the return value is > 0.
 199  */
 200 static inline long __arch_read_trylock(arch_rwlock_t *rw)
 201 {
 202         long tmp;
 203
 204         __asm__ __volatile__(
 205 "1:     " PPC_LWARX(%0,0,%1,1) "\n"
 206         __DO_SIGN_EXTEND
 207 "       addic.          %0,%0,1\n\
 208         ble-            2f\n"
 209         PPC405_ERR77(0,%1)
 210 "       stwcx.          %0,0,%1\n\
 211         bne-            1b\n"
 212         PPC_ACQUIRE_BARRIER
 213 "2:"    : "=&r" (tmp)
 214         : "r" (&rw->lock)
 215         : "cr0", "xer", "memory");
 216
 217         return tmp;
 218 }
 219
 220 /*
 221  * This returns the old value in the lock,
 222  * so we got the write lock if the return value is 0.
 223  */
 224 static inline long __arch_write_trylock(arch_rwlock_t *rw)
 225 {
 226         long tmp, token;
 227
 228         token = WRLOCK_TOKEN;
 229         __asm__ __volatile__(
 230 "1:     " PPC_LWARX(%0,0,%2,1) "\n\
 231         cmpwi           0,%0,0\n\
 232         bne-            2f\n"
 233         PPC405_ERR77(0,%1)
 234 "       stwcx.          %1,0,%2\n\
 235         bne-            1b\n"
 236         PPC_ACQUIRE_BARRIER
 237 "2:"    : "=&r" (tmp)
 238         : "r" (token), "r" (&rw->lock)
 239         : "cr0", "memory");
 240
 241         return tmp;
 242 }
 243
 244 static inline void arch_read_lock(arch_rwlock_t *rw)
 245 {
 246         while (1) {
 247                 if (likely(__arch_read_trylock(rw) > 0))
 248                         break;
 249                 do {
 250                         HMT_low();
 251                         if (SHARED_PROCESSOR)
 252                                 __rw_yield(rw);
 253                 } while (unlikely(rw->lock < 0));
 254                 HMT_medium();
 255         }
 256 }
 257
 258 static inline void arch_write_lock(arch_rwlock_t *rw)
 259 {
 260         while (1) {
 261                 if (likely(__arch_write_trylock(rw) == 0))
 262                         break;
 263                 do {
 264                         HMT_low();
 265                         if (SHARED_PROCESSOR)
 266                                 __rw_yield(rw);
 267                 } while (unlikely(rw->lock != 0));
 268                 HMT_medium();
 269         }
 270 }
 271
 272 static inline int arch_read_trylock(arch_rwlock_t *rw)
 273 {
 274         return __arch_read_trylock(rw) > 0;
 275 }
 276
 277 static inline int arch_write_trylock(arch_rwlock_t *rw)
 278 {
 279         return __arch_write_trylock(rw) == 0;
 280 }
 281
 282 static inline void arch_read_unlock(arch_rwlock_t *rw)
 283 {
 284         long tmp;
 285
 286         __asm__ __volatile__(
 287         "# read_unlock\n\t"
 288         PPC_RELEASE_BARRIER
 289 "1:     lwarx           %0,0,%1\n\
 290         addic           %0,%0,-1\n"
 291         PPC405_ERR77(0,%1)
 292 "       stwcx.          %0,0,%1\n\
 293         bne-            1b"
 294         : "=&r"(tmp)
 295         : "r"(&rw->lock)
 296         : "cr0", "xer", "memory");
 297 }
 298
 299 static inline void arch_write_unlock(arch_rwlock_t *rw)
 300 {
 301         __asm__ __volatile__("# write_unlock\n\t"
 302                                 PPC_RELEASE_BARRIER: : :"memory");
 303         rw->lock = 0;
 304 }
 305
 306 #define arch_read_lock_flags(lock, flags) arch_read_lock(lock)
 307 #define arch_write_lock_flags(lock, flags) arch_write_lock(lock)
 308
 309 #define arch_spin_relax(lock)   __spin_yield(lock)
 310 #define arch_read_relax(lock)   __rw_yield(lock)
 311 #define arch_write_relax(lock)  __rw_yield(lock)
 312
 313 #endif /* __KERNEL__ */
 314 #endif /* __ASM_SPINLOCK_H */