include/asm-powerpc/spinlock.h

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