include/asm-ppc64/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 #include <linux/config.h>
  20 #include <asm/paca.h>
  21 #include <asm/hvcall.h>
  22 #include <asm/iSeries/HvCall.h>
  23
  24 typedef struct {
  25         volatile unsigned int lock;
  26 } spinlock_t;
  27
  28 typedef struct {
  29         volatile signed int lock;
  30 } rwlock_t;
  31
  32 #ifdef __KERNEL__
  33 #define SPIN_LOCK_UNLOCKED      (spinlock_t) { 0 }
  34
  35 #define spin_is_locked(x)       ((x)->lock != 0)
  36 #define spin_lock_init(x)       do { *(x) = SPIN_LOCK_UNLOCKED; } while(0)
  37
  38 static __inline__ void _raw_spin_unlock(spinlock_t *lock)
  39 {
  40         __asm__ __volatile__("lwsync    # spin_unlock": : :"memory");
  41         lock->lock = 0;
  42 }
  43
  44 /*
  45  * On a system with shared processors (that is, where a physical
  46  * processor is multiplexed between several virtual processors),
  47  * there is no point spinning on a lock if the holder of the lock
  48  * isn't currently scheduled on a physical processor.  Instead
  49  * we detect this situation and ask the hypervisor to give the
  50  * rest of our timeslice to the lock holder.
  51  *
  52  * So that we can tell which virtual processor is holding a lock,
  53  * we put 0x80000000 | smp_processor_id() in the lock when it is
  54  * held.  Conveniently, we have a word in the paca that holds this
  55  * value.
  56  */
  57
  58 #if defined(CONFIG_PPC_SPLPAR) || defined(CONFIG_PPC_ISERIES)
  59 /* We only yield to the hypervisor if we are in shared processor mode */
  60 #define SHARED_PROCESSOR (get_paca()->lppaca.xSharedProc)
  61 extern void __spin_yield(spinlock_t *lock);
  62 extern void __rw_yield(rwlock_t *lock);
  63 #else /* SPLPAR || ISERIES */
  64 #define __spin_yield(x) barrier()
  65 #define __rw_yield(x)   barrier()
  66 #define SHARED_PROCESSOR        0
  67 #endif
  68 extern void spin_unlock_wait(spinlock_t *lock);
  69
  70 /*
  71  * This returns the old value in the lock, so we succeeded
  72  * in getting the lock if the return value is 0.
  73  */
  74 static __inline__ unsigned long __spin_trylock(spinlock_t *lock)
  75 {
  76         unsigned long tmp, tmp2;
  77
  78         __asm__ __volatile__(
  79 "       lwz             %1,%3(13)               # __spin_trylock\n\
  80 1:      lwarx           %0,0,%2\n\
  81         cmpwi           0,%0,0\n\
  82         bne-            2f\n\
  83         stwcx.          %1,0,%2\n\
  84         bne-            1b\n\
  85         isync\n\
  86 2:"     : "=&r" (tmp), "=&r" (tmp2)
  87         : "r" (&lock->lock), "i" (offsetof(struct paca_struct, lock_token))
  88         : "cr0", "memory");
  89
  90         return tmp;
  91 }
  92
  93 static int __inline__ _raw_spin_trylock(spinlock_t *lock)
  94 {
  95         return __spin_trylock(lock) == 0;
  96 }
  97
  98 static void __inline__ _raw_spin_lock(spinlock_t *lock)
  99 {
 100         while (1) {
 101                 if (likely(__spin_trylock(lock) == 0))
 102                         break;
 103                 do {
 104                         HMT_low();
 105                         if (SHARED_PROCESSOR)
 106                                 __spin_yield(lock);
 107                 } while (likely(lock->lock != 0));
 108                 HMT_medium();
 109         }
 110 }
 111
 112 static void __inline__ _raw_spin_lock_flags(spinlock_t *lock, unsigned long flags)
 113 {
 114         unsigned long flags_dis;
 115
 116         while (1) {
 117                 if (likely(__spin_trylock(lock) == 0))
 118                         break;
 119                 local_save_flags(flags_dis);
 120                 local_irq_restore(flags);
 121                 do {
 122                         HMT_low();
 123                         if (SHARED_PROCESSOR)
 124                                 __spin_yield(lock);
 125                 } while (likely(lock->lock != 0));
 126                 HMT_medium();
 127                 local_irq_restore(flags_dis);
 128         }
 129 }
 130
 131 /*
 132  * Read-write spinlocks, allowing multiple readers
 133  * but only one writer.
 134  *
 135  * NOTE! it is quite common to have readers in interrupts
 136  * but no interrupt writers. For those circumstances we
 137  * can "mix" irq-safe locks - any writer needs to get a
 138  * irq-safe write-lock, but readers can get non-irqsafe
 139  * read-locks.
 140  */
 141 #define RW_LOCK_UNLOCKED (rwlock_t) { 0 }
 142
 143 #define rwlock_init(x)          do { *(x) = RW_LOCK_UNLOCKED; } while(0)
 144 #define rwlock_is_locked(x)     ((x)->lock)
 145
 146 static __inline__ int is_read_locked(rwlock_t *rw)
 147 {
 148         return rw->lock > 0;
 149 }
 150
 151 static __inline__ int is_write_locked(rwlock_t *rw)
 152 {
 153         return rw->lock < 0;
 154 }
 155
 156 static __inline__ void _raw_write_unlock(rwlock_t *rw)
 157 {
 158         __asm__ __volatile__("lwsync            # write_unlock": : :"memory");
 159         rw->lock = 0;
 160 }
 161
 162 /*
 163  * This returns the old value in the lock + 1,
 164  * so we got a read lock if the return value is > 0.
 165  */
 166 static long __inline__ __read_trylock(rwlock_t *rw)
 167 {
 168         long tmp;
 169
 170         __asm__ __volatile__(
 171 "1:     lwarx           %0,0,%1         # read_trylock\n\
 172         extsw           %0,%0\n\
 173         addic.          %0,%0,1\n\
 174         ble-            2f\n\
 175         stwcx.          %0,0,%1\n\
 176         bne-            1b\n\
 177         isync\n\
 178 2:"     : "=&r" (tmp)
 179         : "r" (&rw->lock)
 180         : "cr0", "xer", "memory");
 181
 182         return tmp;
 183 }
 184
 185 static int __inline__ _raw_read_trylock(rwlock_t *rw)
 186 {
 187         return __read_trylock(rw) > 0;
 188 }
 189
 190 static void __inline__ _raw_read_lock(rwlock_t *rw)
 191 {
 192         while (1) {
 193                 if (likely(__read_trylock(rw) > 0))
 194                         break;
 195                 do {
 196                         HMT_low();
 197                         if (SHARED_PROCESSOR)
 198                                 __rw_yield(rw);
 199                 } while (likely(rw->lock < 0));
 200                 HMT_medium();
 201         }
 202 }
 203
 204 static void __inline__ _raw_read_unlock(rwlock_t *rw)
 205 {
 206         long tmp;
 207
 208         __asm__ __volatile__(
 209         "eieio                          # read_unlock\n\
 210 1:      lwarx           %0,0,%1\n\
 211         addic           %0,%0,-1\n\
 212         stwcx.          %0,0,%1\n\
 213         bne-            1b"
 214         : "=&r"(tmp)
 215         : "r"(&rw->lock)
 216         : "cr0", "memory");
 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 __write_trylock(rwlock_t *rw)
 224 {
 225         long tmp, tmp2;
 226
 227         __asm__ __volatile__(
 228 "       lwz             %1,%3(13)       # write_trylock\n\
 229 1:      lwarx           %0,0,%2\n\
 230         cmpwi           0,%0,0\n\
 231         bne-            2f\n\
 232         stwcx.          %1,0,%2\n\
 233         bne-            1b\n\
 234         isync\n\
 235 2:"     : "=&r" (tmp), "=&r" (tmp2)
 236         : "r" (&rw->lock), "i" (offsetof(struct paca_struct, lock_token))
 237         : "cr0", "memory");
 238
 239         return tmp;
 240 }
 241
 242 static int __inline__ _raw_write_trylock(rwlock_t *rw)
 243 {
 244         return __write_trylock(rw) == 0;
 245 }
 246
 247 static void __inline__ _raw_write_lock(rwlock_t *rw)
 248 {
 249         while (1) {
 250                 if (likely(__write_trylock(rw) == 0))
 251                         break;
 252                 do {
 253                         HMT_low();
 254                         if (SHARED_PROCESSOR)
 255                                 __rw_yield(rw);
 256                 } while (likely(rw->lock != 0));
 257                 HMT_medium();
 258         }
 259 }
 260
 261 #endif /* __KERNEL__ */
 262 #endif /* __ASM_SPINLOCK_H */