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 #ifdef CONFIG_PPC64
  32 /* use 0x800000yy when locked, where yy == CPU number */
  33 #ifdef __BIG_ENDIAN__
  34 #define LOCK_TOKEN      (*(u32 *)(&get_paca()->lock_token))
  35 #else
  36 #define LOCK_TOKEN      (*(u32 *)(&get_paca()->paca_index))
  37 #endif
  38 #else
  39 #define LOCK_TOKEN      1
  40 #endif
  41
  42 #if defined(CONFIG_PPC64) && defined(CONFIG_SMP)
  43 #define CLEAR_IO_SYNC   (get_paca()->io_sync = 0)
  44 #define SYNC_IO         do {                                            \
  45                                 if (unlikely(get_paca()->io_sync)) {    \
  46                                         mb();                           \
  47                                         get_paca()->io_sync = 0;        \
  48                                 }                                       \
  49                         } while (0)
  50 #else
  51 #define CLEAR_IO_SYNC
  52 #define SYNC_IO
  53 #endif
  54
  55 #ifdef CONFIG_PPC_PSERIES
  56 #define vcpu_is_preempted vcpu_is_preempted
  57 static inline bool vcpu_is_preempted(int cpu)
  58 {
  59         return !!(be32_to_cpu(lppaca_of(cpu).yield_count) & 1);
  60 }
  61 #endif
  62
  63 static __always_inline int arch_spin_value_unlocked(arch_spinlock_t lock)
  64 {
  65         return lock.slock == 0;
  66 }
  67
  68 static inline int arch_spin_is_locked(arch_spinlock_t *lock)
  69 {
  70         smp_mb();
  71         return !arch_spin_value_unlocked(*lock);
  72 }
  73
  74 /*
  75  * This returns the old value in the lock, so we succeeded
  76  * in getting the lock if the return value is 0.
  77  */
  78 static inline unsigned long __arch_spin_trylock(arch_spinlock_t *lock)
  79 {
  80         unsigned long tmp, token;
  81
  82         token = LOCK_TOKEN;
  83         __asm__ __volatile__(
  84 "1:     " PPC_LWARX(%0,0,%2,1) "\n\
  85         cmpwi           0,%0,0\n\
  86         bne-            2f\n\
  87         stwcx.          %1,0,%2\n\
  88         bne-            1b\n"
  89         PPC_ACQUIRE_BARRIER
  90 "2:"
  91         : "=&r" (tmp)
  92         : "r" (token), "r" (&lock->slock)
  93         : "cr0", "memory");
  94
  95         return tmp;
  96 }
  97
  98 static inline int arch_spin_trylock(arch_spinlock_t *lock)
  99 {
 100         CLEAR_IO_SYNC;
 101         return __arch_spin_trylock(lock) == 0;
 102 }
 103
 104 /*
 105  * On a system with shared processors (that is, where a physical
 106  * processor is multiplexed between several virtual processors),
 107  * there is no point spinning on a lock if the holder of the lock
 108  * isn't currently scheduled on a physical processor.  Instead
 109  * we detect this situation and ask the hypervisor to give the
 110  * rest of our timeslice to the lock holder.
 111  *
 112  * So that we can tell which virtual processor is holding a lock,
 113  * we put 0x80000000 | smp_processor_id() in the lock when it is
 114  * held.  Conveniently, we have a word in the paca that holds this
 115  * value.
 116  */
 117
 118 #if defined(CONFIG_PPC_SPLPAR)
 119 /* We only yield to the hypervisor if we are in shared processor mode */
 120 #define SHARED_PROCESSOR (lppaca_shared_proc(local_paca->lppaca_ptr))
 121 extern void __spin_yield(arch_spinlock_t *lock);
 122 extern void __rw_yield(arch_rwlock_t *lock);
 123 #else /* SPLPAR */
 124 #define __spin_yield(x) barrier()
 125 #define __rw_yield(x)   barrier()
 126 #define SHARED_PROCESSOR        0
 127 #endif
 128
 129 static inline void arch_spin_lock(arch_spinlock_t *lock)
 130 {
 131         CLEAR_IO_SYNC;
 132         while (1) {
 133                 if (likely(__arch_spin_trylock(lock) == 0))
 134                         break;
 135                 do {
 136                         HMT_low();
 137                         if (SHARED_PROCESSOR)
 138                                 __spin_yield(lock);
 139                 } while (unlikely(lock->slock != 0));
 140                 HMT_medium();
 141         }
 142 }
 143
 144 static inline
 145 void arch_spin_lock_flags(arch_spinlock_t *lock, unsigned long flags)
 146 {
 147         unsigned long flags_dis;
 148
 149         CLEAR_IO_SYNC;
 150         while (1) {
 151                 if (likely(__arch_spin_trylock(lock) == 0))
 152                         break;
 153                 local_save_flags(flags_dis);
 154                 local_irq_restore(flags);
 155                 do {
 156                         HMT_low();
 157                         if (SHARED_PROCESSOR)
 158                                 __spin_yield(lock);
 159                 } while (unlikely(lock->slock != 0));
 160                 HMT_medium();
 161                 local_irq_restore(flags_dis);
 162         }
 163 }
 164 #define arch_spin_lock_flags arch_spin_lock_flags
 165
 166 static inline void arch_spin_unlock(arch_spinlock_t *lock)
 167 {
 168         SYNC_IO;
 169         __asm__ __volatile__("# arch_spin_unlock\n\t"
 170                                 PPC_RELEASE_BARRIER: : :"memory");
 171         lock->slock = 0;
 172 }
 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 #ifdef CONFIG_PPC64
 186 #define __DO_SIGN_EXTEND        "extsw  %0,%0\n"
 187 #define WRLOCK_TOKEN            LOCK_TOKEN      /* it's negative */
 188 #else
 189 #define __DO_SIGN_EXTEND
 190 #define WRLOCK_TOKEN            (-1)
 191 #endif
 192
 193 /*
 194  * This returns the old value in the lock + 1,
 195  * so we got a read lock if the return value is > 0.
 196  */
 197 static inline long __arch_read_trylock(arch_rwlock_t *rw)
 198 {
 199         long tmp;
 200
 201         __asm__ __volatile__(
 202 "1:     " PPC_LWARX(%0,0,%1,1) "\n"
 203         __DO_SIGN_EXTEND
 204 "       addic.          %0,%0,1\n\
 205         ble-            2f\n"
 206         PPC405_ERR77(0,%1)
 207 "       stwcx.          %0,0,%1\n\
 208         bne-            1b\n"
 209         PPC_ACQUIRE_BARRIER
 210 "2:"    : "=&r" (tmp)
 211         : "r" (&rw->lock)
 212         : "cr0", "xer", "memory");
 213
 214         return tmp;
 215 }
 216
 217 /*
 218  * This returns the old value in the lock,
 219  * so we got the write lock if the return value is 0.
 220  */
 221 static inline long __arch_write_trylock(arch_rwlock_t *rw)
 222 {
 223         long tmp, token;
 224
 225         token = WRLOCK_TOKEN;
 226         __asm__ __volatile__(
 227 "1:     " PPC_LWARX(%0,0,%2,1) "\n\
 228         cmpwi           0,%0,0\n\
 229         bne-            2f\n"
 230         PPC405_ERR77(0,%1)
 231 "       stwcx.          %1,0,%2\n\
 232         bne-            1b\n"
 233         PPC_ACQUIRE_BARRIER
 234 "2:"    : "=&r" (tmp)
 235         : "r" (token), "r" (&rw->lock)
 236         : "cr0", "memory");
 237
 238         return tmp;
 239 }
 240
 241 static inline void arch_read_lock(arch_rwlock_t *rw)
 242 {
 243         while (1) {
 244                 if (likely(__arch_read_trylock(rw) > 0))
 245                         break;
 246                 do {
 247                         HMT_low();
 248                         if (SHARED_PROCESSOR)
 249                                 __rw_yield(rw);
 250                 } while (unlikely(rw->lock < 0));
 251                 HMT_medium();
 252         }
 253 }
 254
 255 static inline void arch_write_lock(arch_rwlock_t *rw)
 256 {
 257         while (1) {
 258                 if (likely(__arch_write_trylock(rw) == 0))
 259                         break;
 260                 do {
 261                         HMT_low();
 262                         if (SHARED_PROCESSOR)
 263                                 __rw_yield(rw);
 264                 } while (unlikely(rw->lock != 0));
 265                 HMT_medium();
 266         }
 267 }
 268
 269 static inline int arch_read_trylock(arch_rwlock_t *rw)
 270 {
 271         return __arch_read_trylock(rw) > 0;
 272 }
 273
 274 static inline int arch_write_trylock(arch_rwlock_t *rw)
 275 {
 276         return __arch_write_trylock(rw) == 0;
 277 }
 278
 279 static inline void arch_read_unlock(arch_rwlock_t *rw)
 280 {
 281         long tmp;
 282
 283         __asm__ __volatile__(
 284         "# read_unlock\n\t"
 285         PPC_RELEASE_BARRIER
 286 "1:     lwarx           %0,0,%1\n\
 287         addic           %0,%0,-1\n"
 288         PPC405_ERR77(0,%1)
 289 "       stwcx.          %0,0,%1\n\
 290         bne-            1b"
 291         : "=&r"(tmp)
 292         : "r"(&rw->lock)
 293         : "cr0", "xer", "memory");
 294 }
 295
 296 static inline void arch_write_unlock(arch_rwlock_t *rw)
 297 {
 298         __asm__ __volatile__("# write_unlock\n\t"
 299                                 PPC_RELEASE_BARRIER: : :"memory");
 300         rw->lock = 0;
 301 }
 302
 303 #define arch_spin_relax(lock)   __spin_yield(lock)
 304 #define arch_read_relax(lock)   __rw_yield(lock)
 305 #define arch_write_relax(lock)  __rw_yield(lock)
 306
 307 /* See include/linux/spinlock.h */
 308 #define smp_mb__after_spinlock()   smp_mb()
 309
 310 #endif /* __KERNEL__ */
 311 #endif /* __ASM_SPINLOCK_H */