include/asm-powerpc/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 #ifdef CONFIG_PPC64
  23 #include <asm/paca.h>
  24 #include <asm/hvcall.h>
  25 #include <asm/iseries/hv_call.h>
  26 #endif
  27 #include <asm/asm-compat.h>
  28 #include <asm/synch.h>
  29
  30 #define __raw_spin_is_locked(x)         ((x)->slock != 0)
  31
  32 #ifdef CONFIG_PPC64
  33 /* use 0x800000yy when locked, where yy == CPU number */
  34 #define LOCK_TOKEN      (*(u32 *)(&get_paca()->lock_token))
  35 #else
  36 #define LOCK_TOKEN      1
  37 #endif
  38
  39 #if defined(CONFIG_PPC64) && defined(CONFIG_SMP)
  40 #define CLEAR_IO_SYNC   (get_paca()->io_sync = 0)
  41 #define SYNC_IO         do {                                            \
  42                                 if (unlikely(get_paca()->io_sync)) {    \
  43                                         mb();                           \
  44                                         get_paca()->io_sync = 0;        \
  45                                 }                                       \
  46                         } while (0)
  47 #else
  48 #define CLEAR_IO_SYNC
  49 #define SYNC_IO
  50 #endif
  51
  52 /*
  53  * This returns the old value in the lock, so we succeeded
  54  * in getting the lock if the return value is 0.
  55  */
  56 static __inline__ unsigned long __spin_trylock(raw_spinlock_t *lock)
  57 {
  58         unsigned long tmp, token;
  59
  60         token = LOCK_TOKEN;
  61         __asm__ __volatile__(
  62 "1:     lwarx           %0,0,%2\n\
  63         cmpwi           0,%0,0\n\
  64         bne-            2f\n\
  65         stwcx.          %1,0,%2\n\
  66         bne-            1b\n\
  67         isync\n\
  68 2:"     : "=&r" (tmp)
  69         : "r" (token), "r" (&lock->slock)
  70         : "cr0", "memory");
  71
  72         return tmp;
  73 }
  74
  75 static int __inline__ __raw_spin_trylock(raw_spinlock_t *lock)
  76 {
  77         CLEAR_IO_SYNC;
  78         return __spin_trylock(lock) == 0;
  79 }
  80
  81 /*
  82  * On a system with shared processors (that is, where a physical
  83  * processor is multiplexed between several virtual processors),
  84  * there is no point spinning on a lock if the holder of the lock
  85  * isn't currently scheduled on a physical processor.  Instead
  86  * we detect this situation and ask the hypervisor to give the
  87  * rest of our timeslice to the lock holder.
  88  *
  89  * So that we can tell which virtual processor is holding a lock,
  90  * we put 0x80000000 | smp_processor_id() in the lock when it is
  91  * held.  Conveniently, we have a word in the paca that holds this
  92  * value.
  93  */
  94
  95 #if defined(CONFIG_PPC_SPLPAR) || defined(CONFIG_PPC_ISERIES)
  96 /* We only yield to the hypervisor if we are in shared processor mode */
  97 #define SHARED_PROCESSOR (get_lppaca()->shared_proc)
  98 extern void __spin_yield(raw_spinlock_t *lock);
  99 extern void __rw_yield(raw_rwlock_t *lock);
 100 #else /* SPLPAR || ISERIES */
 101 #define __spin_yield(x) barrier()
 102 #define __rw_yield(x)   barrier()
 103 #define SHARED_PROCESSOR        0
 104 #endif
 105
 106 static void __inline__ __raw_spin_lock(raw_spinlock_t *lock)
 107 {
 108         CLEAR_IO_SYNC;
 109         while (1) {
 110                 if (likely(__spin_trylock(lock) == 0))
 111                         break;
 112                 do {
 113                         HMT_low();
 114                         if (SHARED_PROCESSOR)
 115                                 __spin_yield(lock);
 116                 } while (unlikely(lock->slock != 0));
 117                 HMT_medium();
 118         }
 119 }
 120
 121 static void __inline__ __raw_spin_lock_flags(raw_spinlock_t *lock, unsigned long flags)
 122 {
 123         unsigned long flags_dis;
 124
 125         CLEAR_IO_SYNC;
 126         while (1) {
 127                 if (likely(__spin_trylock(lock) == 0))
 128                         break;
 129                 local_save_flags(flags_dis);
 130                 local_irq_restore(flags);
 131                 do {
 132                         HMT_low();
 133                         if (SHARED_PROCESSOR)
 134                                 __spin_yield(lock);
 135                 } while (unlikely(lock->slock != 0));
 136                 HMT_medium();
 137                 local_irq_restore(flags_dis);
 138         }
 139 }
 140
 141 static __inline__ void __raw_spin_unlock(raw_spinlock_t *lock)
 142 {
 143         SYNC_IO;
 144         __asm__ __volatile__("# __raw_spin_unlock\n\t"
 145                                 LWSYNC_ON_SMP: : :"memory");
 146         lock->slock = 0;
 147 }
 148
 149 #ifdef CONFIG_PPC64
 150 extern void __raw_spin_unlock_wait(raw_spinlock_t *lock);
 151 #else
 152 #define __raw_spin_unlock_wait(lock) \
 153         do { while (__raw_spin_is_locked(lock)) cpu_relax(); } while (0)
 154 #endif
 155
 156 /*
 157  * Read-write spinlocks, allowing multiple readers
 158  * but only one writer.
 159  *
 160  * NOTE! it is quite common to have readers in interrupts
 161  * but no interrupt writers. For those circumstances we
 162  * can "mix" irq-safe locks - any writer needs to get a
 163  * irq-safe write-lock, but readers can get non-irqsafe
 164  * read-locks.
 165  */
 166
 167 #define __raw_read_can_lock(rw)         ((rw)->lock >= 0)
 168 #define __raw_write_can_lock(rw)        (!(rw)->lock)
 169
 170 #ifdef CONFIG_PPC64
 171 #define __DO_SIGN_EXTEND        "extsw  %0,%0\n"
 172 #define WRLOCK_TOKEN            LOCK_TOKEN      /* it's negative */
 173 #else
 174 #define __DO_SIGN_EXTEND
 175 #define WRLOCK_TOKEN            (-1)
 176 #endif
 177
 178 /*
 179  * This returns the old value in the lock + 1,
 180  * so we got a read lock if the return value is > 0.
 181  */
 182 static long __inline__ __read_trylock(raw_rwlock_t *rw)
 183 {
 184         long tmp;
 185
 186         __asm__ __volatile__(
 187 "1:     lwarx           %0,0,%1\n"
 188         __DO_SIGN_EXTEND
 189 "       addic.          %0,%0,1\n\
 190         ble-            2f\n"
 191         PPC405_ERR77(0,%1)
 192 "       stwcx.          %0,0,%1\n\
 193         bne-            1b\n\
 194         isync\n\
 195 2:"     : "=&r" (tmp)
 196         : "r" (&rw->lock)
 197         : "cr0", "xer", "memory");
 198
 199         return tmp;
 200 }
 201
 202 /*
 203  * This returns the old value in the lock,
 204  * so we got the write lock if the return value is 0.
 205  */
 206 static __inline__ long __write_trylock(raw_rwlock_t *rw)
 207 {
 208         long tmp, token;
 209
 210         token = WRLOCK_TOKEN;
 211         __asm__ __volatile__(
 212 "1:     lwarx           %0,0,%2\n\
 213         cmpwi           0,%0,0\n\
 214         bne-            2f\n"
 215         PPC405_ERR77(0,%1)
 216 "       stwcx.          %1,0,%2\n\
 217         bne-            1b\n\
 218         isync\n\
 219 2:"     : "=&r" (tmp)
 220         : "r" (token), "r" (&rw->lock)
 221         : "cr0", "memory");
 222
 223         return tmp;
 224 }
 225
 226 static void __inline__ __raw_read_lock(raw_rwlock_t *rw)
 227 {
 228         while (1) {
 229                 if (likely(__read_trylock(rw) > 0))
 230                         break;
 231                 do {
 232                         HMT_low();
 233                         if (SHARED_PROCESSOR)
 234                                 __rw_yield(rw);
 235                 } while (unlikely(rw->lock < 0));
 236                 HMT_medium();
 237         }
 238 }
 239
 240 static void __inline__ __raw_write_lock(raw_rwlock_t *rw)
 241 {
 242         while (1) {
 243                 if (likely(__write_trylock(rw) == 0))
 244                         break;
 245                 do {
 246                         HMT_low();
 247                         if (SHARED_PROCESSOR)
 248                                 __rw_yield(rw);
 249                 } while (unlikely(rw->lock != 0));
 250                 HMT_medium();
 251         }
 252 }
 253
 254 static int __inline__ __raw_read_trylock(raw_rwlock_t *rw)
 255 {
 256         return __read_trylock(rw) > 0;
 257 }
 258
 259 static int __inline__ __raw_write_trylock(raw_rwlock_t *rw)
 260 {
 261         return __write_trylock(rw) == 0;
 262 }
 263
 264 static void __inline__ __raw_read_unlock(raw_rwlock_t *rw)
 265 {
 266         long tmp;
 267
 268         __asm__ __volatile__(
 269         "# read_unlock\n\t"
 270         LWSYNC_ON_SMP
 271 "1:     lwarx           %0,0,%1\n\
 272         addic           %0,%0,-1\n"
 273         PPC405_ERR77(0,%1)
 274 "       stwcx.          %0,0,%1\n\
 275         bne-            1b"
 276         : "=&r"(tmp)
 277         : "r"(&rw->lock)
 278         : "cr0", "memory");
 279 }
 280
 281 static __inline__ void __raw_write_unlock(raw_rwlock_t *rw)
 282 {
 283         __asm__ __volatile__("# write_unlock\n\t"
 284                                 LWSYNC_ON_SMP: : :"memory");
 285         rw->lock = 0;
 286 }
 287
 288 #define _raw_spin_relax(lock)   __spin_yield(lock)
 289 #define _raw_read_relax(lock)   __rw_yield(lock)
 290 #define _raw_write_relax(lock)  __rw_yield(lock)
 291
 292 #endif /* __KERNEL__ */
 293 #endif /* __ASM_SPINLOCK_H */