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