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192 lines
5.8 KiB
C
192 lines
5.8 KiB
C
/* This header supplies atomic operations. So far, we rely on GCC's
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* atomic builtins. During configure, we check if atomic operatons are
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* available. If they are not, I am making the necessary provisioning to live without them if
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* they are not available. Please note that you should only use the macros
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* here if you think you can actually live WITHOUT an explicit atomic operation,
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* because in the non-presence of them, we simply do it without atomicitiy.
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* Which, for word-aligned data types, usually (but only usually!) should work.
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*
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* We are using the functions described in
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* http:/gcc.gnu.org/onlinedocs/gcc/Atomic-Builtins.html
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*
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* THESE MACROS MUST ONLY BE USED WITH WORD-SIZED DATA TYPES!
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*
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* Copyright 2008 Rainer Gerhards and Adiscon GmbH.
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*
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* This file is part of the rsyslog runtime library.
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*
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* The rsyslog runtime library is free software: you can redistribute it and/or modify
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* it under the terms of the GNU Lesser General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* The rsyslog runtime library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public License
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* along with the rsyslog runtime library. If not, see <http://www.gnu.org/licenses/>.
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*
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* A copy of the GPL can be found in the file "COPYING" in this distribution.
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* A copy of the LGPL can be found in the file "COPYING.LESSER" in this distribution.
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*/
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#include "config.h" /* autotools! */
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#ifndef INCLUDED_ATOMIC_H
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#define INCLUDED_ATOMIC_H
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/* for this release, we disable atomic calls because there seem to be some
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* portability problems and we can not fix that without destabilizing the build.
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* They simply came in too late. -- rgerhards, 2008-04-02
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*/
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#ifdef HAVE_ATOMIC_BUILTINS
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# define ATOMIC_INC(data) ((void) __sync_fetch_and_add(&(data), 1))
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# define ATOMIC_INC_AND_FETCH(data) __sync_fetch_and_add(&(data), 1)
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# define ATOMIC_DEC(data) ((void) __sync_sub_and_fetch(&(data), 1))
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# define ATOMIC_DEC_AND_FETCH(data) __sync_sub_and_fetch(&(data), 1)
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# define ATOMIC_FETCH_32BIT(data) ((unsigned) __sync_fetch_and_and(&(data), 0xffffffff))
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# define ATOMIC_STORE_1_TO_32BIT(data) __sync_lock_test_and_set(&(data), 1)
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# define ATOMIC_STORE_0_TO_INT(data) __sync_fetch_and_and(&(data), 0)
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# define ATOMIC_STORE_1_TO_INT(data) __sync_fetch_and_or(&(data), 1)
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# define ATOMIC_STORE_INT_TO_INT(data, val) __sync_fetch_and_or(&(data), (val))
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# define ATOMIC_CAS(data, oldVal, newVal) __sync_bool_compare_and_swap(&(data), (oldVal), (newVal));
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# define ATOMIC_CAS_VAL(data, oldVal, newVal) __sync_val_compare_and_swap(&(data), (oldVal), (newVal));
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#else
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#ifdef HAVE_SEMAPHORE_H
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/* we use POSIX semaphores instead */
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#include "rsyslog.h"
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#include <semaphore.h>
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extern sem_t atomicSem;
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rsRetVal atomicSemInit(void);
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void atomicSemExit(void);
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#if HAVE_TYPEOF
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#define my_typeof(x) typeof(x)
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#else /* sorry, can't determine types, using 'int' */
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#define my_typeof(x) int
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#endif
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# define ATOMIC_SUB(data, val) \
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({ \
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my_typeof(data) tmp; \
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sem_wait(&atomicSem); \
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tmp = data; \
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data -= val; \
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sem_post(&atomicSem); \
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tmp; \
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})
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# define ATOMIC_ADD(data, val) \
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({ \
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my_typeof(data) tmp; \
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sem_wait(&atomicSem); \
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tmp = data; \
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data += val; \
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sem_post(&atomicSem); \
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tmp; \
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})
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# define ATOMIC_INC_AND_FETCH(data) \
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({ \
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my_typeof(data) tmp; \
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sem_wait(&atomicSem); \
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tmp = data; \
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data += 1; \
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sem_post(&atomicSem); \
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tmp; \
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})
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# define ATOMIC_INC(data) ((void) ATOMIC_INC_AND_FETCH(data))
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# define ATOMIC_DEC_AND_FETCH(data) \
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({ \
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sem_wait(&atomicSem); \
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data -= 1; \
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sem_post(&atomicSem); \
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data; \
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})
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# define ATOMIC_DEC(data) ((void) ATOMIC_DEC_AND_FETCH(data))
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# define ATOMIC_FETCH_32BIT(data) ((unsigned) ATOMIC_ADD((data), 0xffffffff))
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# define ATOMIC_STORE_1_TO_32BIT(data) \
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({ \
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my_typeof(data) tmp; \
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sem_wait(&atomicSem); \
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tmp = data; \
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data = 1; \
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sem_post(&atomicSem); \
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tmp; \
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})
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# define ATOMIC_STORE_0_TO_INT(data) \
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({ \
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my_typeof(data) tmp; \
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sem_wait(&atomicSem); \
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tmp = data; \
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data = 0; \
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sem_post(&atomicSem); \
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tmp; \
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})
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# define ATOMIC_STORE_1_TO_INT(data) \
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({ \
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my_typeof(data) tmp; \
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sem_wait(&atomicSem); \
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tmp = data; \
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data = 1; \
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sem_post(&atomicSem); \
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tmp; \
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})
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# define ATOMIC_CAS(data, oldVal, newVal) \
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({ \
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int ret; \
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sem_wait(&atomicSem); \
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if(data != oldVal) ret = 0; \
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else \
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{ \
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data = newVal; \
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ret = 1; \
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} \
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sem_post(&atomicSem); \
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ret; \
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})
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# define ATOMIC_CAS_VAL(data, oldVal, newVal) \
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({ \
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sem_wait(&atomicSem); \
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if(data == oldVal) \
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{ \
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data = newVal; \
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} \
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sem_post(&atomicSem); \
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data; \
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})
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#else /* not HAVE_SEMAPHORE_H */
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/* note that we gained parctical proof that theoretical problems DO occur
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* if we do not properly address them. See this blog post for details:
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* http://blog.gerhards.net/2009/01/rsyslog-data-race-analysis.html
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* The bottom line is that if there are no atomics available, we should NOT
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* simply go ahead and do without them - use mutexes or other things. The
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* code needs to be checked against all those cases. -- rgerhards, 2009-01-30
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*/
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# warning "atomic builtins not available, using nul operations - rsyslogd will probably be racy!"
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# define ATOMIC_INC(data) (++(data))
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# define ATOMIC_DEC(data) (--(data))
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# define ATOMIC_DEC_AND_FETCH(data) (--(data))
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# define ATOMIC_FETCH_32BIT(data) (data)
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# define ATOMIC_STORE_1_TO_32BIT(data) (data) = 1
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# define ATOMIC_STORE_1_TO_INT(data) (data) = 1
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# define ATOMIC_STORE_0_TO_INT(data) (data) = 0
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# define ATOMIC_CAS_VAL(data, oldVal, newVal) (data) = (newVal)
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#endif
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#endif
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#endif /* #ifndef INCLUDED_ATOMIC_H */
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