1 // locks.h - Thread synchronization primitives. X86 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,
27 __asm__ __volatile__("lock; cmpxchgl %2, %0; setz %1"
28 : "+m"(*(addr)), "=q"(result)
29 : "r" (new_val), "a"(old)
34 // Set *addr to new_val with release semantics, i.e. making sure
35 // that prior loads and stores complete before this
37 // On X86, the hardware shouldn't reorder reads and writes,
38 // so we just have to convince gcc not to do it either.
40 release_set(volatile obj_addr_t *addr, obj_addr_t new_val)
42 __asm__ __volatile__(" " : : : "memory");
46 // Compare_and_swap with release semantics instead of acquire semantics.
47 // On many architecture, the operation makes both guarantees, so the
48 // implementation can be the same.
50 compare_and_swap_release(volatile obj_addr_t *addr,
54 return compare_and_swap(addr, old, new_val);
57 // Ensure that subsequent instructions do not execute on stale
58 // data that was loaded from memory before the barrier.
59 // On X86, the hardware ensures that reads are properly ordered.
65 // Ensure that prior stores to memory are completed with respect to other
70 // X86 does not reorder writes. We just need to ensure that gcc also doesn't.
71 __asm__ __volatile__(" " : : : "memory");