libjava/sysdep/aarch64/locks.h

   1 // locks.h - Thread synchronization primitives. AArch64 implementation.
   2
   3 #ifndef __SYSDEP_LOCKS_H__
   4 #define __SYSDEP_LOCKS_H__
   5
   6 typedef size_t obj_addr_t;      /* Integer type big enough for object   */
   7                                 /* address.                             */
   8
   9 // Atomically replace *addr by new_val if it was initially equal to old.
  10 // Return true if the comparison succeeded.
  11 // Assumed to have acquire semantics, i.e. later memory operations
  12 // cannot execute before the compare_and_swap finishes.
  13 inline static bool
  14 compare_and_swap(volatile obj_addr_t *addr,
  15                  obj_addr_t old,
  16                  obj_addr_t new_val)
  17 {
  18   return __sync_bool_compare_and_swap(addr, old, new_val);
  19 }
  20
  21 // Set *addr to new_val with release semantics, i.e. making sure
  22 // that prior loads and stores complete before this
  23 // assignment.
  24 inline static void
  25 release_set(volatile obj_addr_t *addr, obj_addr_t new_val)
  26 {
  27   __sync_synchronize();
  28   *addr = new_val;
  29 }
  30
  31 // Compare_and_swap with release semantics instead of acquire semantics.
  32 // On many architecture, the operation makes both guarantees, so the
  33 // implementation can be the same.
  34 inline static bool
  35 compare_and_swap_release(volatile obj_addr_t *addr,
  36                          obj_addr_t old,
  37                          obj_addr_t new_val)
  38 {
  39   return __sync_bool_compare_and_swap(addr, old, new_val);
  40 }
  41
  42 // Ensure that subsequent instructions do not execute on stale
  43 // data that was loaded from memory before the barrier.
  44 inline static void
  45 read_barrier()
  46 {
  47   __sync_synchronize();
  48 }
  49
  50 // Ensure that prior stores to memory are completed with respect to other
  51 // processors.
  52 inline static void
  53 write_barrier()
  54 {
  55   __sync_synchronize();
  56 }
  57 #endif