mirror of git://gcc.gnu.org/git/gcc.git
134 lines
3.5 KiB
C
134 lines
3.5 KiB
C
// locks.h - Thread synchronization primitives. ARM implementation.
|
|
|
|
/* Copyright (C) 2007 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__
|
|
|
|
typedef size_t obj_addr_t; /* Integer type big enough for object */
|
|
/* address. */
|
|
#if (__ARM_EABI__ && __linux)
|
|
|
|
// 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 __sync_bool_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 X86, the hardware ensures that reads are properly ordered.
|
|
inline static void
|
|
read_barrier()
|
|
{
|
|
__sync_synchronize();
|
|
}
|
|
|
|
// Ensure that prior stores to memory are completed with respect to other
|
|
// processors.
|
|
inline static void
|
|
write_barrier()
|
|
{
|
|
__sync_synchronize();
|
|
}
|
|
|
|
#else
|
|
|
|
/* Atomic compare and exchange. These sequences are not actually
|
|
atomic; there is a race if *ADDR != OLD_VAL and we are preempted
|
|
between the two swaps. However, they are very close to atomic, and
|
|
are the best that a pre-ARMv6 implementation can do without
|
|
operating system support. LinuxThreads has been using these
|
|
sequences for many years. */
|
|
|
|
inline static bool
|
|
compare_and_swap(volatile obj_addr_t *addr,
|
|
obj_addr_t old_val,
|
|
obj_addr_t new_val)
|
|
{
|
|
volatile obj_addr_t result, tmp;
|
|
__asm__ ("\n"
|
|
"0: ldr %[tmp],[%[addr]]\n"
|
|
" cmp %[tmp],%[old_val]\n"
|
|
" movne %[result],#0\n"
|
|
" bne 1f\n"
|
|
" swp %[result],%[new_val],[%[addr]]\n"
|
|
" cmp %[tmp],%[result]\n"
|
|
" swpne %[tmp],%[result],[%[addr]]\n"
|
|
" bne 0b\n"
|
|
" mov %[result],#1\n"
|
|
"1:"
|
|
: [result] "=&r" (result), [tmp] "=&r" (tmp)
|
|
: [addr] "r" (addr), [new_val] "r" (new_val), [old_val] "r" (old_val)
|
|
: "cc", "memory");
|
|
|
|
return result;
|
|
}
|
|
|
|
inline static void
|
|
release_set(volatile obj_addr_t *addr, obj_addr_t new_val)
|
|
{
|
|
__asm__ __volatile__("" : : : "memory");
|
|
*(addr) = new_val;
|
|
}
|
|
|
|
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__("" : : : "memory");
|
|
}
|
|
|
|
// Ensure that prior stores to memory are completed with respect to other
|
|
// processors.
|
|
inline static void
|
|
write_barrier()
|
|
{
|
|
__asm__ __volatile__("" : : : "memory");
|
|
}
|
|
|
|
#endif
|
|
#endif
|