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// locks.h - Thread synchronization primitives. m68k implementation.
/* Copyright (C) 2006 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 __attribute__ ((aligned (4)));
// 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.
static inline bool
compare_and_swap(volatile obj_addr_t *addr,
obj_addr_t old, obj_addr_t new_val)
{
char result;
__asm__ __volatile__("cas.l %2,%3,%0; seq %1"
: "+m" (*addr), "=d" (result), "+d" (old)
: "d" (new_val)
: "memory");
return (bool) result;
}
// Set *addr to new_val with release semantics, i.e. making sure
// that prior loads and stores complete before this
// assignment.
// On m68k, the hardware shouldn't reorder reads and writes,
// so we just have to convince gcc not to do it either.
static inline void
release_set(volatile obj_addr_t *addr, obj_addr_t new_val)
{
__asm__ __volatile__(" " : : : "memory");
*(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.
static inline 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.
// On m68k, the hardware ensures that reads are properly ordered.
static inline void
read_barrier(void)
{
}
// Ensure that prior stores to memory are completed with respect to other
// processors.
static inline void
write_barrier(void)
{
// m68k does not reorder writes. We just need to ensure that gcc also doesn't.
__asm__ __volatile__(" " : : : "memory");
}
#endif
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