atomic.h

/* 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!
 *
 * Note: this file was obtained at 2015-12-16 from the rsyslog project.
 *
 * Copyright 2008-2015 Rainer Gerhards and Adiscon GmbH.
 *
 * This file is part of the rsyslog runtime library.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *       http://www.apache.org/licenses/LICENSE-2.0
 *       -or-
 *       see COPYING.ASL20 in the source distribution
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
#ifndef FJ_INCLUDED_ATOMIC_H
#define FJ_INCLUDED_ATOMIC_H

#ifdef HAVE_ATOMIC_BUILTINS
#   define ATOMIC_SUB(data, val, phlpmut) __sync_fetch_and_sub(data, val)
#   define ATOMIC_ADD(data, val) __sync_fetch_and_add(&(data), val)
#   define ATOMIC_INC(data, phlpmut) ((void) __sync_fetch_and_add(data, 1))
#   define ATOMIC_INC_AND_FETCH_int(data, phlpmut) __sync_add_and_fetch(data, 1)
#   define ATOMIC_INC_AND_FETCH_unsigned(data, phlpmut) __sync_add_and_fetch(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, phlpmut) ((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, phlpmut) __sync_bool_compare_and_swap(data, (oldVal), (newVal))
#   define ATOMIC_CAS_time_t(data, oldVal, newVal, phlpmut) __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.
     * 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(int *data, int oldVal, int newVal, pthread_mutex_t *phlpmut) {
        int bSuccess;
        pthread_mutex_lock(phlpmut);
        if(*data == oldVal) {
            *data = newVal;
            bSuccess = 1;
        } else {
            bSuccess = 0;
        }
        pthread_mutex_unlock(phlpmut);
        return(bSuccess);
    }

    static inline int
    ATOMIC_CAS_time_t(time_t *data, time_t oldVal, time_t newVal, pthread_mutex_t *phlpmut) {
        int bSuccess;
        pthread_mutex_lock(phlpmut);
        if(*data == oldVal) {
            *data = newVal;
            bSuccess = 1;
        } else {
            bSuccess = 0;
        }
        pthread_mutex_unlock(phlpmut);
        return(bSuccess);
    }


    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_INC_AND_FETCH_int(int *data, pthread_mutex_t *phlpmut) {
        int val;
        pthread_mutex_lock(phlpmut);
        val = ++(*data);
        pthread_mutex_unlock(phlpmut);
        return(val);
    }

    static inline unsigned
    ATOMIC_INC_AND_FETCH_unsigned(unsigned *data, pthread_mutex_t *phlpmut) {
        unsigned val;
        pthread_mutex_lock(phlpmut);
        val = ++(*data);
        pthread_mutex_unlock(phlpmut);
        return(val);
    }

    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);
    }

    static inline int
    ATOMIC_FETCH_32BIT(int *data, pthread_mutex_t *phlpmut) {
        int val;
        pthread_mutex_lock(phlpmut);
        val = (*data);
        pthread_mutex_unlock(phlpmut);
        return(val);
    }

    static inline void
    ATOMIC_SUB(int *data, int val, pthread_mutex_t *phlpmut) {
        pthread_mutex_lock(phlpmut);
        (*data) -= val;
        pthread_mutex_unlock(phlpmut);
    }
#   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_destroy(&(x));

#   define PREFER_ATOMIC_INC(data) ((void) ++data)

#endif

/* we need to handle 64bit atomics seperately as some platforms have
 * 32 bit atomics, but not 64 bit ones... -- rgerhards, 2010-12-01
 */
#if 0 /* currently disabled, we don't need it now and dont' have the data types present */
#ifdef HAVE_ATOMIC_BUILTINS64
#   define ATOMIC_INC_uint64(data, phlpmut) ((void) __sync_fetch_and_add(data, 1))
#   define ATOMIC_DEC_unit64(data, phlpmut) ((void) __sync_sub_and_fetch(data, 1))
#   define ATOMIC_INC_AND_FETCH_uint64(data, phlpmut) __sync_fetch_and_add(data, 1)

#   define DEF_ATOMIC_HELPER_MUT64(x)
#   define INIT_ATOMIC_HELPER_MUT64(x)
#   define DESTROY_ATOMIC_HELPER_MUT64(x)
#else
#   define ATOMIC_INC_uint64(data, phlpmut)  { \
        pthread_mutex_lock(phlpmut); \
        ++(*(data)); \
        pthread_mutex_unlock(phlpmut); \
    }
#   define ATOMIC_DEC_uint64(data, phlpmut)  { \
        pthread_mutex_lock(phlpmut); \
        --(*(data)); \
        pthread_mutex_unlock(phlpmut); \
    }

    static inline unsigned
    ATOMIC_INC_AND_FETCH_uint64(uint64 *data, pthread_mutex_t *phlpmut) {
        uint64 val;
        pthread_mutex_lock(phlpmut);
        val = ++(*data);
        pthread_mutex_unlock(phlpmut);
        return(val);
    }

#   define DEF_ATOMIC_HELPER_MUT64(x)  pthread_mutex_t x;
#   define INIT_ATOMIC_HELPER_MUT64(x) pthread_mutex_init(&(x), NULL)
#   define DESTROY_ATOMIC_HELPER_MUT64(x) pthread_mutex_destroy(&(x))
#endif /* #ifdef HAVE_ATOMIC_BUILTINS64 */
#endif

#endif /* #ifndef INCLUDED_ATOMIC_H */