arch/sparc64/kernel/semaphore.c

   1 /* $Id: semaphore.c,v 1.9 2001/11/18 00:12:56 davem Exp $
   2  * semaphore.c: Sparc64 semaphore implementation.
   3  *
   4  * This is basically the PPC semaphore scheme ported to use
   5  * the sparc64 atomic instructions, so see the PPC code for
   6  * credits.
   7  */
   8
   9 #include <linux/sched.h>
  10 #include <linux/errno.h>
  11 #include <linux/init.h>
  12
  13 /*
  14  * Atomically update sem->count.
  15  * This does the equivalent of the following:
  16  *
  17  *      old_count = sem->count;
  18  *      tmp = MAX(old_count, 0) + incr;
  19  *      sem->count = tmp;
  20  *      return old_count;
  21  */
  22 static __inline__ int __sem_update_count(struct semaphore *sem, int incr)
  23 {
  24         int old_count, tmp;
  25
  26         __asm__ __volatile__("\n"
  27 "       ! __sem_update_count old_count(%0) tmp(%1) incr(%4) &sem->count(%3)\n"
  28 "1:     ldsw    [%3], %0\n"
  29 "       mov     %0, %1\n"
  30 "       cmp     %0, 0\n"
  31 "       movl    %%icc, 0, %1\n"
  32 "       add     %1, %4, %1\n"
  33 "       cas     [%3], %0, %1\n"
  34 "       cmp     %0, %1\n"
  35 "       membar  #StoreLoad | #StoreStore\n"
  36 "       bne,pn  %%icc, 1b\n"
  37 "        nop\n"
  38         : "=&r" (old_count), "=&r" (tmp), "=m" (sem->count)
  39         : "r" (&sem->count), "r" (incr), "m" (sem->count)
  40         : "cc");
  41
  42         return old_count;
  43 }
  44
  45 static void __up(struct semaphore *sem)
  46 {
  47         __sem_update_count(sem, 1);
  48         wake_up(&sem->wait);
  49 }
  50
  51 void up(struct semaphore *sem)
  52 {
  53         /* This atomically does:
  54          *      old_val = sem->count;
  55          *      new_val = sem->count + 1;
  56          *      sem->count = new_val;
  57          *      if (old_val < 0)
  58          *              __up(sem);
  59          *
  60          * The (old_val < 0) test is equivalent to
  61          * the more straightforward (new_val <= 0),
  62          * but it is easier to test the former because
  63          * of how the CAS instruction works.
  64          */
  65
  66         __asm__ __volatile__("\n"
  67 "       ! up sem(%0)\n"
  68 "       membar  #StoreLoad | #LoadLoad\n"
  69 "1:     lduw    [%0], %%g1\n"
  70 "       add     %%g1, 1, %%g7\n"
  71 "       cas     [%0], %%g1, %%g7\n"
  72 "       cmp     %%g1, %%g7\n"
  73 "       bne,pn  %%icc, 1b\n"
  74 "        addcc  %%g7, 1, %%g0\n"
  75 "       membar  #StoreLoad | #StoreStore\n"
  76 "       ble,pn  %%icc, 3f\n"
  77 "        nop\n"
  78 "2:\n"
  79 "       .subsection 2\n"
  80 "3:     mov     %0, %%g1\n"
  81 "       save    %%sp, -160, %%sp\n"
  82 "       call    %1\n"
  83 "        mov    %%g1, %%o0\n"
  84 "       ba,pt   %%xcc, 2b\n"
  85 "        restore\n"
  86 "       .previous\n"
  87         : : "r" (sem), "i" (__up)
  88         : "g1", "g2", "g3", "g7", "memory", "cc");
  89 }
  90
  91 static void __sched __down(struct semaphore * sem)
  92 {
  93         struct task_struct *tsk = current;
  94         DECLARE_WAITQUEUE(wait, tsk);
  95
  96         tsk->state = TASK_UNINTERRUPTIBLE;
  97         add_wait_queue_exclusive(&sem->wait, &wait);
  98
  99         while (__sem_update_count(sem, -1) <= 0) {
 100                 schedule();
 101                 tsk->state = TASK_UNINTERRUPTIBLE;
 102         }
 103         remove_wait_queue(&sem->wait, &wait);
 104         tsk->state = TASK_RUNNING;
 105
 106         wake_up(&sem->wait);
 107 }
 108
 109 void __sched down(struct semaphore *sem)
 110 {
 111         might_sleep();
 112         /* This atomically does:
 113          *      old_val = sem->count;
 114          *      new_val = sem->count - 1;
 115          *      sem->count = new_val;
 116          *      if (old_val < 1)
 117          *              __down(sem);
 118          *
 119          * The (old_val < 1) test is equivalent to
 120          * the more straightforward (new_val < 0),
 121          * but it is easier to test the former because
 122          * of how the CAS instruction works.
 123          */
 124
 125         __asm__ __volatile__("\n"
 126 "       ! down sem(%0)\n"
 127 "1:     lduw    [%0], %%g1\n"
 128 "       sub     %%g1, 1, %%g7\n"
 129 "       cas     [%0], %%g1, %%g7\n"
 130 "       cmp     %%g1, %%g7\n"
 131 "       bne,pn  %%icc, 1b\n"
 132 "        cmp    %%g7, 1\n"
 133 "       membar  #StoreLoad | #StoreStore\n"
 134 "       bl,pn   %%icc, 3f\n"
 135 "        nop\n"
 136 "2:\n"
 137 "       .subsection 2\n"
 138 "3:     mov     %0, %%g1\n"
 139 "       save    %%sp, -160, %%sp\n"
 140 "       call    %1\n"
 141 "        mov    %%g1, %%o0\n"
 142 "       ba,pt   %%xcc, 2b\n"
 143 "        restore\n"
 144 "       .previous\n"
 145         : : "r" (sem), "i" (__down)
 146         : "g1", "g2", "g3", "g7", "memory", "cc");
 147 }
 148
 149 int down_trylock(struct semaphore *sem)
 150 {
 151         int ret;
 152
 153         /* This atomically does:
 154          *      old_val = sem->count;
 155          *      new_val = sem->count - 1;
 156          *      if (old_val < 1) {
 157          *              ret = 1;
 158          *      } else {
 159          *              sem->count = new_val;
 160          *              ret = 0;
 161          *      }
 162          *
 163          * The (old_val < 1) test is equivalent to
 164          * the more straightforward (new_val < 0),
 165          * but it is easier to test the former because
 166          * of how the CAS instruction works.
 167          */
 168
 169         __asm__ __volatile__("\n"
 170 "       ! down_trylock sem(%1) ret(%0)\n"
 171 "1:     lduw    [%1], %%g1\n"
 172 "       sub     %%g1, 1, %%g7\n"
 173 "       cmp     %%g1, 1\n"
 174 "       bl,pn   %%icc, 2f\n"
 175 "        mov    1, %0\n"
 176 "       cas     [%1], %%g1, %%g7\n"
 177 "       cmp     %%g1, %%g7\n"
 178 "       bne,pn  %%icc, 1b\n"
 179 "        mov    0, %0\n"
 180 "       membar  #StoreLoad | #StoreStore\n"
 181 "2:\n"
 182         : "=&r" (ret)
 183         : "r" (sem)
 184         : "g1", "g7", "memory", "cc");
 185
 186         return ret;
 187 }
 188
 189 static int __sched __down_interruptible(struct semaphore * sem)
 190 {
 191         int retval = 0;
 192         struct task_struct *tsk = current;
 193         DECLARE_WAITQUEUE(wait, tsk);
 194
 195         tsk->state = TASK_INTERRUPTIBLE;
 196         add_wait_queue_exclusive(&sem->wait, &wait);
 197
 198         while (__sem_update_count(sem, -1) <= 0) {
 199                 if (signal_pending(current)) {
 200                         __sem_update_count(sem, 0);
 201                         retval = -EINTR;
 202                         break;
 203                 }
 204                 schedule();
 205                 tsk->state = TASK_INTERRUPTIBLE;
 206         }
 207         tsk->state = TASK_RUNNING;
 208         remove_wait_queue(&sem->wait, &wait);
 209         wake_up(&sem->wait);
 210         return retval;
 211 }
 212
 213 int __sched down_interruptible(struct semaphore *sem)
 214 {
 215         int ret = 0;
 216
 217         might_sleep();
 218         /* This atomically does:
 219          *      old_val = sem->count;
 220          *      new_val = sem->count - 1;
 221          *      sem->count = new_val;
 222          *      if (old_val < 1)
 223          *              ret = __down_interruptible(sem);
 224          *
 225          * The (old_val < 1) test is equivalent to
 226          * the more straightforward (new_val < 0),
 227          * but it is easier to test the former because
 228          * of how the CAS instruction works.
 229          */
 230
 231         __asm__ __volatile__("\n"
 232 "       ! down_interruptible sem(%2) ret(%0)\n"
 233 "1:     lduw    [%2], %%g1\n"
 234 "       sub     %%g1, 1, %%g7\n"
 235 "       cas     [%2], %%g1, %%g7\n"
 236 "       cmp     %%g1, %%g7\n"
 237 "       bne,pn  %%icc, 1b\n"
 238 "        cmp    %%g7, 1\n"
 239 "       membar  #StoreLoad | #StoreStore\n"
 240 "       bl,pn   %%icc, 3f\n"
 241 "        nop\n"
 242 "2:\n"
 243 "       .subsection 2\n"
 244 "3:     mov     %2, %%g1\n"
 245 "       save    %%sp, -160, %%sp\n"
 246 "       call    %3\n"
 247 "        mov    %%g1, %%o0\n"
 248 "       ba,pt   %%xcc, 2b\n"
 249 "        restore\n"
 250 "       .previous\n"
 251         : "=r" (ret)
 252         : "0" (ret), "r" (sem), "i" (__down_interruptible)
 253         : "g1", "g2", "g3", "g7", "memory", "cc");
 254         return ret;
 255 }