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 #ifdef CONFIG_PREEMPT
  27         unsigned int break_lock;
  28 #endif
  29 } spinlock_t;
  30
  31 typedef struct {
  32         volatile signed int lock;
  33 #ifdef CONFIG_PREEMPT
  34         unsigned int break_lock;
  35 #endif
  36 } rwlock_t;
  37
  38 #ifdef __KERNEL__
  39 #define SPIN_LOCK_UNLOCKED      (spinlock_t) { 0 }
  40
  41 #define spin_is_locked(x)       ((x)->lock != 0)
  42 #define spin_lock_init(x)       do { *(x) = SPIN_LOCK_UNLOCKED; } while(0)
  43
  44 static __inline__ void _raw_spin_unlock(spinlock_t *lock)
  45 {
  46         __asm__ __volatile__("lwsync    # spin_unlock": : :"memory");
  47         lock->lock = 0;
  48 }
  49
  50 /*
  51  * On a system with shared processors (that is, where a physical
  52  * processor is multiplexed between several virtual processors),
  53  * there is no point spinning on a lock if the holder of the lock
  54  * isn't currently scheduled on a physical processor.  Instead
  55  * we detect this situation and ask the hypervisor to give the
  56  * rest of our timeslice to the lock holder.
  57  *
  58  * So that we can tell which virtual processor is holding a lock,
  59  * we put 0x80000000 | smp_processor_id() in the lock when it is
  60  * held.  Conveniently, we have a word in the paca that holds this
  61  * value.
  62  */
  63
  64 #if defined(CONFIG_PPC_SPLPAR) || defined(CONFIG_PPC_ISERIES)
  65 /* We only yield to the hypervisor if we are in shared processor mode */
  66 #define SHARED_PROCESSOR (get_paca()->lppaca.shared_proc)
  67 extern void __spin_yield(spinlock_t *lock);
  68 extern void __rw_yield(rwlock_t *lock);
  69 #else /* SPLPAR || ISERIES */
  70 #define __spin_yield(x) barrier()
  71 #define __rw_yield(x)   barrier()
  72 #define SHARED_PROCESSOR        0
  73 #endif
  74 extern void spin_unlock_wait(spinlock_t *lock);
  75
  76 /*
  77  * This returns the old value in the lock, so we succeeded
  78  * in getting the lock if the return value is 0.
  79  */
  80 static __inline__ unsigned long __spin_trylock(spinlock_t *lock)
  81 {
  82         unsigned long tmp, tmp2;
  83
  84         __asm__ __volatile__(
  85 "       lwz             %1,%3(13)               # __spin_trylock\n\
  86 1:      lwarx           %0,0,%2\n\
  87         cmpwi           0,%0,0\n\
  88         bne-            2f\n\
  89         stwcx.          %1,0,%2\n\
  90         bne-            1b\n\
  91         isync\n\
  92 2:"     : "=&r" (tmp), "=&r" (tmp2)
  93         : "r" (&lock->lock), "i" (offsetof(struct paca_struct, lock_token))
  94         : "cr0", "memory");
  95
  96         return tmp;
  97 }
  98
  99 static int __inline__ _raw_spin_trylock(spinlock_t *lock)
 100 {
 101         return __spin_trylock(lock) == 0;
 102 }
 103
 104 static void __inline__ _raw_spin_lock(spinlock_t *lock)
 105 {
 106         while (1) {
 107                 if (likely(__spin_trylock(lock) == 0))
 108                         break;
 109                 do {
 110                         HMT_low();
 111                         if (SHARED_PROCESSOR)
 112                                 __spin_yield(lock);
 113                 } while (unlikely(lock->lock != 0));
 114                 HMT_medium();
 115         }
 116 }
 117
 118 static void __inline__ _raw_spin_lock_flags(spinlock_t *lock, unsigned long flags)
 119 {
 120         unsigned long flags_dis;
 121
 122         while (1) {
 123                 if (likely(__spin_trylock(lock) == 0))
 124                         break;
 125                 local_save_flags(flags_dis);
 126                 local_irq_restore(flags);
 127                 do {
 128                         HMT_low();
 129                         if (SHARED_PROCESSOR)
 130                                 __spin_yield(lock);
 131                 } while (unlikely(lock->lock != 0));
 132                 HMT_medium();
 133                 local_irq_restore(flags_dis);
 134         }
 135 }
 136
 137 /*
 138  * Read-write spinlocks, allowing multiple readers
 139  * but only one writer.
 140  *
 141  * NOTE! it is quite common to have readers in interrupts
 142  * but no interrupt writers. For those circumstances we
 143  * can "mix" irq-safe locks - any writer needs to get a
 144  * irq-safe write-lock, but readers can get non-irqsafe
 145  * read-locks.
 146  */
 147 #define RW_LOCK_UNLOCKED (rwlock_t) { 0 }
 148
 149 #define rwlock_init(x)          do { *(x) = RW_LOCK_UNLOCKED; } while(0)
 150
 151 #define read_can_lock(rw)       ((rw)->lock >= 0)
 152 #define write_can_lock(rw)      (!(rw)->lock)
 153
 154 static __inline__ void _raw_write_unlock(rwlock_t *rw)
 155 {
 156         __asm__ __volatile__("lwsync            # write_unlock": : :"memory");
 157         rw->lock = 0;
 158 }
 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(rwlock_t *rw)
 165 {
 166         long tmp;
 167
 168         __asm__ __volatile__(
 169 "1:     lwarx           %0,0,%1         # read_trylock\n\
 170         extsw           %0,%0\n\
 171         addic.          %0,%0,1\n\
 172         ble-            2f\n\
 173         stwcx.          %0,0,%1\n\
 174         bne-            1b\n\
 175         isync\n\
 176 2:"     : "=&r" (tmp)
 177         : "r" (&rw->lock)
 178         : "cr0", "xer", "memory");
 179
 180         return tmp;
 181 }
 182
 183 static int __inline__ _raw_read_trylock(rwlock_t *rw)
 184 {
 185         return __read_trylock(rw) > 0;
 186 }
 187
 188 static void __inline__ _raw_read_lock(rwlock_t *rw)
 189 {
 190         while (1) {
 191                 if (likely(__read_trylock(rw) > 0))
 192                         break;
 193                 do {
 194                         HMT_low();
 195                         if (SHARED_PROCESSOR)
 196                                 __rw_yield(rw);
 197                 } while (unlikely(rw->lock < 0));
 198                 HMT_medium();
 199         }
 200 }
 201
 202 static void __inline__ _raw_read_unlock(rwlock_t *rw)
 203 {
 204         long tmp;
 205
 206         __asm__ __volatile__(
 207         "eieio                          # read_unlock\n\
 208 1:      lwarx           %0,0,%1\n\
 209         addic           %0,%0,-1\n\
 210         stwcx.          %0,0,%1\n\
 211         bne-            1b"
 212         : "=&r"(tmp)
 213         : "r"(&rw->lock)
 214         : "cr0", "memory");
 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 __write_trylock(rwlock_t *rw)
 222 {
 223         long tmp, tmp2;
 224
 225         __asm__ __volatile__(
 226 "       lwz             %1,%3(13)       # write_trylock\n\
 227 1:      lwarx           %0,0,%2\n\
 228         cmpwi           0,%0,0\n\
 229         bne-            2f\n\
 230         stwcx.          %1,0,%2\n\
 231         bne-            1b\n\
 232         isync\n\
 233 2:"     : "=&r" (tmp), "=&r" (tmp2)
 234         : "r" (&rw->lock), "i" (offsetof(struct paca_struct, lock_token))
 235         : "cr0", "memory");
 236
 237         return tmp;
 238 }
 239
 240 static int __inline__ _raw_write_trylock(rwlock_t *rw)
 241 {
 242         return __write_trylock(rw) == 0;
 243 }
 244
 245 static void __inline__ _raw_write_lock(rwlock_t *rw)
 246 {
 247         while (1) {
 248                 if (likely(__write_trylock(rw) == 0))
 249                         break;
 250                 do {
 251                         HMT_low();
 252                         if (SHARED_PROCESSOR)
 253                                 __rw_yield(rw);
 254                 } while (unlikely(rw->lock != 0));
 255                 HMT_medium();
 256         }
 257 }
 258
 259 #endif /* __KERNEL__ */
 260 #endif /* __ASM_SPINLOCK_H */