libjava/sysdep/alpha/locks.h

// locks.h - Thread synchronization primitives. Alpha implementation.

/* Copyright (C) 2002, 2011  Free Software Foundation

   This file is part of libgcj.

This software is copyrighted work licensed under the terms of the
Libgcj License.  Please consult the file "LIBGCJ_LICENSE" for
details.  */

#ifndef __SYSDEP_LOCKS_H__
#define __SYSDEP_LOCKS_H__

/* Integer type big enough for object address.	*/
typedef size_t obj_addr_t;

// Atomically replace *addr by new_val if it was initially equal to old.
// Return true if the comparison succeeded.
// Assumed to have acquire semantics, i.e. later memory operations
// cannot execute before the compare_and_swap finishes.
inline static bool
compare_and_swap(volatile obj_addr_t *addr,
		 obj_addr_t old,
		 obj_addr_t new_val) 
{
  return __sync_bool_compare_and_swap(addr, old, new_val);
}

// Set *addr to new_val with release semantics, i.e. making sure
// that prior loads and stores complete before this
// assignment.
inline static void
release_set(volatile obj_addr_t *addr, obj_addr_t new_val)
{
  __sync_synchronize();
  *(addr) = new_val;
}

// Compare_and_swap with release semantics instead of acquire semantics.
// On many architecture, the operation makes both guarantees, so the
// implementation can be the same.
inline static bool
compare_and_swap_release(volatile obj_addr_t *addr,
			 obj_addr_t old,
			 obj_addr_t new_val)
{
  return compare_and_swap(addr, old, new_val);
}

// Ensure that subsequent instructions do not execute on stale
// data that was loaded from memory before the barrier.
inline static void
read_barrier()
{
  __asm__ __volatile__("mb" : : : "memory");
}

// Ensure that prior stores to memory are completed with respect to other
// processors.
inline static void
write_barrier()
{
  __asm__ __volatile__("wmb" : : : "memory");
}

#endif