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/* 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.
*/
#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, phlpmut) ((void) __sync_fetch_and_add(data, 1))
# define ATOMIC_INC_AND_FETCH(data) __sync_fetch_and_add(&(data), 1)
# define ATOMIC_DEC(data, phlpmut) ((void) __sync_sub_and_fetch(data, 1))
# define ATOMIC_DEC_AND_FETCH(data, phlpmut) __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)
# define ATOMIC_STORE_0_TO_INT(data, phlpmut) __sync_fetch_and_and(data, 0)
# define ATOMIC_STORE_1_TO_INT(data, phlpmut) __sync_fetch_and_or(data, 1)
# define ATOMIC_STORE_INT_TO_INT(data, val) __sync_fetch_and_or(&(data), (val))
# define ATOMIC_CAS(data, oldVal, newVal) __sync_bool_compare_and_swap(&(data), (oldVal), (newVal));
# define ATOMIC_CAS_VAL(data, oldVal, newVal, phlpmut) __sync_val_compare_and_swap(data, (oldVal), (newVal));
/* functions below are not needed if we have atomics */
# define DEF_ATOMIC_HELPER_MUT(x)
# define INIT_ATOMIC_HELPER_MUT(x)
# define DESTROY_ATOMIC_HELPER_MUT(x)
/* the following operations should preferrably be done atomic, but it is
* not fatal if not -- that means we can live with some missed updates. So be
* sure to use these macros only if that really does not matter!
*/
# define PREFER_ATOMIC_INC(data) ((void) __sync_fetch_and_add(&(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
*/
#include <pthread.h>
# define ATOMIC_INC(data, phlpmut) { \
pthread_mutex_lock(phlpmut); \
++(*(data)); \
pthread_mutex_unlock(phlpmut); \
}
# define ATOMIC_STORE_0_TO_INT(data, hlpmut) { \
pthread_mutex_lock(&hlpmut); \
*(data) = 0; \
pthread_mutex_unlock(&hlpmut); \
}
# define ATOMIC_STORE_1_TO_INT(data, hlpmut) { \
pthread_mutex_lock(&hlpmut); \
*(data) = 1; \
pthread_mutex_unlock(&hlpmut); \
}
static inline int
ATOMIC_CAS_VAL(int *data, int oldVal, int newVal, pthread_mutex_t *phlpmut) {
int val;
pthread_mutex_lock(phlpmut);
if(*data == oldVal) {
*data = newVal;
}
val = *data;
pthread_mutex_unlock(phlpmut);
return(val);
}
# define ATOMIC_DEC(data, phlpmut) { \
pthread_mutex_lock(phlpmut); \
--(*(data)); \
pthread_mutex_unlock(phlpmut); \
}
static inline int
ATOMIC_DEC_AND_FETCH(int *data, pthread_mutex_t *phlpmut) {
int val;
pthread_mutex_lock(phlpmut);
val = --(*data);
pthread_mutex_unlock(phlpmut);
return(val);
}
#if 0
# warning "atomic builtins not available, using nul operations - rsyslogd will probably be racy!"
# define ATOMIC_INC_AND_FETCH(data) (++(data))
# define ATOMIC_FETCH_32BIT(data) (data) // TODO: del
# define ATOMIC_STORE_1_TO_32BIT(data) (data) = 1 // TODO: del
#endif
# define DEF_ATOMIC_HELPER_MUT(x) pthread_mutex_t x
# define INIT_ATOMIC_HELPER_MUT(x) pthread_mutex_init(&(x), NULL)
# define DESTROY_ATOMIC_HELPER_MUT(x) pthread_mutex_init(&(x), NULL)
# define PREFER_ATOMIC_INC(data) ((void) ++data)
#endif
#endif /* #ifndef INCLUDED_ATOMIC_H */
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