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   1 /*
   2  * arch/alpha/lib/dec_and_lock.c
   3  *
   4  * ll/sc version of atomic_dec_and_lock()
   5  *
   6  */
   7
   8 #include <linux/spinlock.h>
   9 #include <asm/atomic.h>
  10
  11   asm (".text                                   \n\
  12         .global _atomic_dec_and_lock            \n\
  13         .ent _atomic_dec_and_lock               \n\
  14         .align  4                               \n\
  15 _atomic_dec_and_lock:                           \n\
  16         .prologue 0                             \n\
  17 1:      ldl_l   $1, 0($16)                      \n\
  18         subl    $1, 1, $1                       \n\
  19         beq     $1, 2f                          \n\
  20         stl_c   $1, 0($16)                      \n\
  21         beq     $1, 4f                          \n\
  22         mb                                      \n\
  23         clr     $0                              \n\
  24         ret                                     \n\
  25 2:      br      $29, 3f                         \n\
  26 3:      ldgp    $29, 0($29)                     \n\
  27         br      $atomic_dec_and_lock_1..ng      \n\
  28         .subsection 2                           \n\
  29 4:      br      1b                              \n\
  30         .previous                               \n\
  31         .end _atomic_dec_and_lock");
  32
  33 static int __attribute_used__
  34 atomic_dec_and_lock_1(atomic_t *atomic, spinlock_t *lock)
  35 {
  36         /* Slow path */
  37         spin_lock(lock);
  38         if (atomic_dec_and_test(atomic))
  39                 return 1;
  40         spin_unlock(lock);
  41         return 0;
  42 }