arch/sparc64/lib/debuglocks.c

   1 /* $Id: debuglocks.c,v 1.2 1998/10/13 09:07:27 davem Exp $
   2  * debuglocks.c: Debugging versions of SMP locking primitives.
   3  *
   4  * Copyright (C) 1998 David S. Miller (davem@dm.cobaltmicro.com)
   5  */
   6
   7 #include <linux/kernel.h>
   8 #include <linux/sched.h>
   9 #include <linux/spinlock.h>
  10 #include <asm/system.h>
  11
  12 #ifdef __SMP__
  13
  14 /* To enable this code, just define SPIN_LOCK_DEBUG in asm/spinlock.h */
  15 #ifdef SPIN_LOCK_DEBUG
  16
  17 #define GET_CALLER(PC) __asm__ __volatile__("mov %%i7, %0" : "=r" (PC))
  18
  19 static inline void show (char *str, spinlock_t *lock, unsigned long caller)
  20 {
  21         int cpu = smp_processor_id();
  22
  23         printk("%s(%p) CPU#%d stuck at %08x, owner PC(%08x):CPU(%x)\n",
  24                str, lock, cpu, (unsigned int) caller,
  25                lock->owner_pc, lock->owner_cpu);
  26 }
  27
  28 static inline void show_read (char *str, rwlock_t *lock, unsigned long caller)
  29 {
  30         int cpu = smp_processor_id();
  31
  32         printk("%s(%p) CPU#%d stuck at %08x, writer PC(%08x):CPU(%x)\n",
  33                str, lock, cpu, (unsigned int) caller,
  34                lock->writer_pc, lock->writer_cpu);
  35 }
  36
  37 static inline void show_write (char *str, rwlock_t *lock, unsigned long caller)
  38 {
  39         int cpu = smp_processor_id();
  40
  41         printk("%s(%p) CPU#%d stuck at %08x\n",
  42                str, lock, cpu, (unsigned int) caller);
  43         printk("Writer: PC(%08x):CPU(%x)\n",
  44                lock->writer_pc, lock->writer_cpu);
  45         printk("Readers: 0[%08x] 1[%08x] 2[%08x] 4[%08x]\n",
  46                lock->reader_pc[0], lock->reader_pc[1],
  47                lock->reader_pc[2], lock->reader_pc[3]);
  48 }
  49
  50 #undef INIT_STUCK
  51 #define INIT_STUCK 100000000
  52
  53 void _do_spin_lock(spinlock_t *lock, char *str)
  54 {
  55         unsigned long caller, val;
  56         int stuck = INIT_STUCK;
  57         int cpu = smp_processor_id();
  58
  59         GET_CALLER(caller);
  60 again:
  61         __asm__ __volatile__("ldstub [%1], %0"
  62                              : "=r" (val)
  63                              : "r" (&(lock->lock))
  64                              : "memory");
  65         membar("#StoreLoad | #StoreStore");
  66         if (val) {
  67                 while (lock->lock) {
  68                         if (!--stuck) {
  69                                 show(str, lock, caller);
  70                                 stuck = INIT_STUCK;
  71                         }
  72                         membar("#LoadLoad");
  73                 }
  74                 goto again;
  75         }
  76         lock->owner_pc = ((unsigned int)caller);
  77         lock->owner_cpu = cpu;
  78 }
  79
  80 int _spin_trylock(spinlock_t *lock)
  81 {
  82         unsigned long val, caller;
  83         int cpu = smp_processor_id();
  84
  85         GET_CALLER(caller);
  86         __asm__ __volatile__("ldstub [%1], %0"
  87                              : "=r" (val)
  88                              : "r" (&(lock->lock))
  89                              : "memory");
  90         membar("#StoreLoad | #StoreStore");
  91         if (!val) {
  92                 lock->owner_pc = ((unsigned int)caller);
  93                 lock->owner_cpu = cpu;
  94         }
  95         return val == 0;
  96 }
  97
  98 void _do_spin_unlock(spinlock_t *lock)
  99 {
 100         lock->owner_pc = 0;
 101         lock->owner_cpu = NO_PROC_ID;
 102         membar("#StoreStore | #LoadStore");
 103         lock->lock = 0;
 104 }
 105
 106 /* Keep INIT_STUCK the same... */
 107
 108 void _do_read_lock (rwlock_t *rw, char *str)
 109 {
 110         unsigned long caller, val;
 111         int stuck = INIT_STUCK;
 112         int cpu = smp_processor_id();
 113
 114         GET_CALLER(caller);
 115 wlock_again:
 116         /* Wait for any writer to go away.  */
 117         while (((long)(rw->lock)) < 0) {
 118                 if (!--stuck) {
 119                         show_read(str, rw, caller);
 120                         stuck = INIT_STUCK;
 121                 }
 122                 membar("#LoadLoad");
 123         }
 124         /* Try once to increment the counter.  */
 125         __asm__ __volatile__("
 126         ldx             [%0], %%g5
 127         brlz,a,pn       %%g5, 2f
 128          mov            1, %0
 129         add             %%g5, 1, %%g7
 130         casx            [%0], %%g5, %%g7
 131         sub             %%g5, %%g7, %0
 132 2:"     : "=r" (val)
 133         : "0" (&(rw->lock))
 134         : "g5", "g7", "memory");
 135         membar("#StoreLoad | #StoreStore");
 136         if (val)
 137                 goto wlock_again;
 138         rw->reader_pc[cpu] = ((unsigned int)caller);
 139 }
 140
 141 void _do_read_unlock (rwlock_t *rw, char *str)
 142 {
 143         unsigned long caller, val;
 144         int stuck = INIT_STUCK;
 145         int cpu = smp_processor_id();
 146
 147         GET_CALLER(caller);
 148
 149         /* Drop our identity _first_. */
 150         rw->reader_pc[cpu] = 0;
 151 runlock_again:
 152         /* Spin trying to decrement the counter using casx.  */
 153         __asm__ __volatile__("
 154         ldx     [%0], %%g5
 155         sub     %%g5, 1, %%g7
 156         casx    [%0], %%g5, %%g7
 157         membar  #StoreLoad | #StoreStore
 158         sub     %%g5, %%g7, %0
 159 "       : "=r" (val)
 160         : "0" (&(rw->lock))
 161         : "g5", "g7", "memory");
 162         if (val) {
 163                 if (!--stuck) {
 164                         show_read(str, rw, caller);
 165                         stuck = INIT_STUCK;
 166                 }
 167                 goto runlock_again;
 168         }
 169 }
 170
 171 void _do_write_lock (rwlock_t *rw, char *str)
 172 {
 173         unsigned long caller, val;
 174         int stuck = INIT_STUCK;
 175         int cpu = smp_processor_id();
 176
 177         GET_CALLER(caller);
 178 wlock_again:
 179         /* Spin while there is another writer. */
 180         while (((long)rw->lock) < 0) {
 181                 if (!--stuck) {
 182                         show_write(str, rw, caller);
 183                         stuck = INIT_STUCK;
 184                 }
 185                 membar("#LoadLoad");
 186         }
 187
 188         /* Try to acuire the write bit.  */
 189         __asm__ __volatile__("
 190         mov     1, %%g3
 191         sllx    %%g3, 63, %%g3
 192         ldx     [%0], %%g5
 193         brlz,pn %%g5, 1f
 194          or     %%g5, %%g3, %%g7
 195         casx    [%0], %%g5, %%g7
 196         membar  #StoreLoad | #StoreStore
 197         ba,pt   %%xcc, 2f
 198          sub    %%g5, %%g7, %0
 199 1:      mov     1, %0
 200 2:"     : "=r" (val)
 201         : "0" (&(rw->lock))
 202         : "g3", "g5", "g7", "memory");
 203         if (val) {
 204                 /* We couldn't get the write bit. */
 205                 if (!--stuck) {
 206                         show_write(str, rw, caller);
 207                         stuck = INIT_STUCK;
 208                 }
 209                 goto wlock_again;
 210         }
 211         if ((rw->lock & ((1UL<<63)-1UL)) != 0UL) {
 212                 /* Readers still around, drop the write
 213                  * lock, spin, and try again.
 214                  */
 215                 if (!--stuck) {
 216                         show_write(str, rw, caller);
 217                         stuck = INIT_STUCK;
 218                 }
 219                 __asm__ __volatile__("
 220                 mov     1, %%g3
 221                 sllx    %%g3, 63, %%g3
 222 1:              ldx     [%0], %%g5
 223                 andn    %%g5, %%g3, %%g7
 224                 casx    [%0], %%g5, %%g7
 225                 cmp     %%g5, %%g7
 226                 bne,pn  %%xcc, 1b
 227                  membar #StoreLoad | #StoreStore"
 228                 : /* no outputs */
 229                 : "r" (&(rw->lock))
 230                 : "g3", "g5", "g7", "cc", "memory");
 231                 while(rw->lock != 0) {
 232                         if (!--stuck) {
 233                                 show_write(str, rw, caller);
 234                                 stuck = INIT_STUCK;
 235                         }
 236                         membar("#LoadLoad");
 237                 }
 238                 goto wlock_again;
 239         }
 240
 241         /* We have it, say who we are. */
 242         rw->writer_pc = ((unsigned int)caller);
 243         rw->writer_cpu = cpu;
 244 }
 245
 246 void _do_write_unlock(rwlock_t *rw)
 247 {
 248         unsigned long caller, val;
 249         int stuck = INIT_STUCK;
 250
 251         GET_CALLER(caller);
 252
 253         /* Drop our identity _first_ */
 254         rw->writer_pc = 0;
 255         rw->writer_cpu = NO_PROC_ID;
 256 wlock_again:
 257         __asm__ __volatile__("
 258         mov     1, %%g3
 259         sllx    %%g3, 63, %%g3
 260         ldx     [%0], %%g5
 261         andn    %%g5, %%g3, %%g7
 262         casx    [%0], %%g5, %%g7
 263         membar  #StoreLoad | #StoreStore
 264         sub     %%g5, %%g7, %0
 265 "       : "=r" (val)
 266         : "0" (&(rw->lock))
 267         : "g3", "g5", "g7", "memory");
 268         if (val) {
 269                 if (!--stuck) {
 270                         show_write("write_unlock", rw, caller);
 271                         stuck = INIT_STUCK;
 272                 }
 273                 goto wlock_again;
 274         }
 275 }
 276
 277 #endif /* SPIN_LOCK_DEBUG */
 278 #endif /* __SMP__ */