1 /* locks.h - Thread synchronization primitives. X86/x86-64 implementation.
3 Copyright (C) 2002 Free Software Foundation
5 This file is part of libgcj.
7 This software is copyrighted work licensed under the terms of the
8 Libgcj License. Please consult the file "LIBGCJ_LICENSE" for
11 #ifndef __SYSDEP_LOCKS_H__
12 #define __SYSDEP_LOCKS_H__
14 typedef size_t obj_addr_t
; /* Integer type big enough for object */
17 // Atomically replace *addr by new_val if it was initially equal to old.
18 // Return true if the comparison succeeded.
19 // Assumed to have acquire semantics, i.e. later memory operations
20 // cannot execute before the compare_and_swap finishes.
22 compare_and_swap(volatile obj_addr_t
*addr
,
28 __asm__
__volatile__("lock; cmpxchgq %2, %0; setz %1"
29 : "=m"(*(addr
)), "=q"(result
)
30 : "r" (new_val
), "a"(old
), "m"(*addr
)
33 __asm__
__volatile__("lock; cmpxchgl %2, %0; setz %1"
34 : "=m"(*addr
), "=q"(result
)
35 : "r" (new_val
), "a"(old
), "m"(*addr
)
41 // Set *addr to new_val with release semantics, i.e. making sure
42 // that prior loads and stores complete before this
44 // On X86/x86-64, the hardware shouldn't reorder reads and writes,
45 // so we just have to convince gcc not to do it either.
47 release_set(volatile obj_addr_t
*addr
, obj_addr_t new_val
)
49 __asm__
__volatile__(" " : : : "memory");
53 // Compare_and_swap with release semantics instead of acquire semantics.
54 // On many architecture, the operation makes both guarantees, so the
55 // implementation can be the same.
57 compare_and_swap_release(volatile obj_addr_t
*addr
,
61 return compare_and_swap(addr
, old
, new_val
);
64 // Ensure that subsequent instructions do not execute on stale
65 // data that was loaded from memory before the barrier.
66 // On X86/x86-64, the hardware ensures that reads are properly ordered.
72 // Ensure that prior stores to memory are completed with respect to other
77 /* x86-64/X86 does not reorder writes. We just need to ensure that
79 __asm__
__volatile__(" " : : : "memory");