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Diffstat (limited to 'runtime/atomic.h')
| -rw-r--r-- | runtime/atomic.h | 63 |
1 files changed, 63 insertions, 0 deletions
diff --git a/runtime/atomic.h b/runtime/atomic.h new file mode 100644 index 00000000..10dbac90 --- /dev/null +++ b/runtime/atomic.h @@ -0,0 +1,63 @@ +/* This header supplies atomic operations. So far, we rely on GCC's + * atomic builtins. During configure, we check if atomic operatons are + * available. If they are not, I am making the necessary provisioning to live without them if + * they are not available. Please note that you should only use the macros + * here if you think you can actually live WITHOUT an explicit atomic operation, + * because in the non-presence of them, we simply do it without atomicitiy. + * Which, for word-aligned data types, usually (but only usually!) should work. + * + * We are using the functions described in + * http:/gcc.gnu.org/onlinedocs/gcc/Atomic-Builtins.html + * + * THESE MACROS MUST ONLY BE USED WITH WORD-SIZED DATA TYPES! + * + * Copyright 2008 Rainer Gerhards and Adiscon GmbH. + * + * This file is part of the rsyslog runtime library. + * + * The rsyslog runtime library is free software: you can redistribute it and/or modify + * it under the terms of the GNU Lesser General Public License as published by + * the Free Software Foundation, either version 3 of the License, or + * (at your option) any later version. + * + * The rsyslog runtime library is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public License + * along with the rsyslog runtime library. If not, see <http://www.gnu.org/licenses/>. + * + * A copy of the GPL can be found in the file "COPYING" in this distribution. + * A copy of the LGPL can be found in the file "COPYING.LESSER" in this distribution. + */ +#include "config.h" /* autotools! */ + +#ifndef INCLUDED_ATOMIC_H +#define INCLUDED_ATOMIC_H + +/* for this release, we disable atomic calls because there seem to be some + * portability problems and we can not fix that without destabilizing the build. + * They simply came in too late. -- rgerhards, 2008-04-02 + */ +#ifdef HAVE_ATOMIC_BUILTINS +# define ATOMIC_INC(data) ((void) __sync_fetch_and_add(&(data), 1)) +# define ATOMIC_DEC_AND_FETCH(data) __sync_sub_and_fetch(&(data), 1) +# define ATOMIC_FETCH_32BIT(data) ((unsigned) __sync_fetch_and_and(&(data), 0xffffffff)) +# define ATOMIC_STORE_1_TO_32BIT(data) __sync_lock_test_and_set(&(data), 1) +#else + /* note that we gained parctical proof that theoretical problems DO occur + * if we do not properly address them. See this blog post for details: + * http://blog.gerhards.net/2009/01/rsyslog-data-race-analysis.html + * The bottom line is that if there are no atomics available, we should NOT + * simply go ahead and do without them - use mutexes or other things. The + * code needs to be checked against all those cases. -- rgerhards, 2009-01-30 + */ +# warning "atomic builtins not available, using nul operations - rsyslogd will probably be racy!" +# define ATOMIC_INC(data) (++(data)) +# define ATOMIC_DEC_AND_FETCH(data) (--(data)) +# define ATOMIC_FETCH_32BIT(data) (data) +# define ATOMIC_STORE_1_TO_32BIT(data) (data) = 1 +#endif + +#endif /* #ifndef INCLUDED_ATOMIC_H */ |