| // 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. */ |
| |
| /* 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 |
