1/* Copyright (C) 2012-2015 Free Software Foundation, Inc. 2 Contributed by Richard Henderson <rth@redhat.com>. 3 4 This file is part of the GNU Atomic Library (libatomic). 5 6 Libatomic is free software; you can redistribute it and/or modify it 7 under the terms of the GNU General Public License as published by 8 the Free Software Foundation; either version 3 of the License, or 9 (at your option) any later version. 10 11 Libatomic is distributed in the hope that it will be useful, but WITHOUT ANY 12 WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS 13 FOR A PARTICULAR PURPOSE. See the GNU General Public License for 14 more details. 15 16 Under Section 7 of GPL version 3, you are granted additional 17 permissions described in the GCC Runtime Library Exception, version 18 3.1, as published by the Free Software Foundation. 19 20 You should have received a copy of the GNU General Public License and 21 a copy of the GCC Runtime Library Exception along with this program; 22 see the files COPYING3 and COPYING.RUNTIME respectively. If not, see 23 <http://www.gnu.org/licenses/>. */ 24 25#include "libatomic_i.h" 26 27 28/* If we support the builtin, just use it. */ 29#if !DONE && SIZE(HAVE_ATOMIC_TAS) 30bool 31SIZE(libat_test_and_set) (UTYPE *mptr, int smodel) 32{ 33 if (maybe_specialcase_relaxed(smodel)) 34 return __atomic_test_and_set (mptr, __ATOMIC_RELAXED); 35 else if (maybe_specialcase_acqrel(smodel)) 36 return __atomic_test_and_set (mptr, __ATOMIC_ACQ_REL); 37 else 38 return __atomic_test_and_set (mptr, __ATOMIC_SEQ_CST); 39} 40 41#define DONE 1 42#endif /* HAVE_ATOMIC_TAS */ 43 44 45/* If this type is smaller than word-sized, fall back to a word-sized 46 compare-and-swap loop. */ 47#if !DONE && N <= WORDSIZE && defined(atomic_compare_exchange_w) 48bool 49SIZE(libat_test_and_set) (UTYPE *mptr, int smodel) 50{ 51 UWORD wval, woldval, shift, *wptr, t; 52 53 pre_barrier (smodel); 54 55 if (N < WORDSIZE) 56 { 57 wptr = (UWORD *)((uintptr_t)mptr & -WORDSIZE); 58 shift = SIZE(INVERT_MASK); 59 } 60 else 61 { 62 wptr = (UWORD *)mptr; 63 shift = 0; 64 } 65 66 wval = (UWORD)__GCC_ATOMIC_TEST_AND_SET_TRUEVAL << shift; 67 woldval = __atomic_load_n (wptr, __ATOMIC_RELAXED); 68 do 69 { 70 t = woldval | wval; 71 } 72 while (!atomic_compare_exchange_w (wptr, &woldval, t, true, 73 __ATOMIC_RELAXED, __ATOMIC_RELAXED)); 74 75 post_barrier (smodel); 76 return woldval != 0; 77} 78 79#define DONE 1 80#endif /* HAVE_ATOMIC_CAS && N < WORDSIZE */ 81 82 83/* Otherwise, fall back to some sort of protection mechanism. */ 84#if !DONE && N == 1 85bool 86SIZE(libat_test_and_set) (UTYPE *mptr, int smodel) 87{ 88 UTYPE oldval; 89 UWORD magic; 90 91 pre_seq_barrier (smodel); 92 magic = protect_start (mptr); 93 94 oldval = *mptr; 95 *mptr = __GCC_ATOMIC_TEST_AND_SET_TRUEVAL; 96 97 protect_end (mptr, magic); 98 post_seq_barrier (smodel); 99 100 return oldval != 0; 101} 102 103#define DONE 1 104#endif /* N == 1 */ 105 106 107#if !DONE 108bool 109SIZE(libat_test_and_set) (UTYPE *mptr, int smodel UNUSED) 110{ 111 return libat_test_and_set_1 ((U_1 *)mptr, smodel); 112} 113#endif 114 115EXPORT_ALIAS (SIZE(test_and_set)); 116