atexit.h

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#pragma once
/*
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program 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 General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
 */
 
/** Functions to help with cleanup
 *
 * Simplifies cleaning up thread local and global resources
 *
 * @file lib/util/atexit.h
 *
 * @copyright 2020-2022 Arran Cudbard-Bell (a.cudbardb@freeradius.org)
 * @copyright 2013-2016 The FreeRADIUS server project
 */
RCSIDH(atexit_h, "$Id: 0b1721146657499c29e423cbfcebad73f41bdec4 $")
 
#include <stdbool.h>
#include <stdatomic.h>
#include <pthread.h>
#include <freeradius-devel/util/talloc.h>
 
#ifdef __cplusplus
extern "C" {
#endif
 
/** Destructor callback
 *
 * @param[in] uctx      to free.
 * @return
 *      - 0 on success.
 *      - -1 on failure.
 */
typedef int(*fr_atexit_t)(void *uctx);
 
int fr_atexit_global_setup(void);
 
int _atexit_global(char const *file, int line, fr_atexit_t func, void const *uctx);
 
/** Add a free function to the global free list
 *
 * @param[in] _func to call.
 * @param[in] _uctx to pass to func.
 * @return
 *      - 0 on success.
 *      - -1 on failure.
 */
#define fr_atexit_global(_func, _uctx) _atexit_global(__FILE__, __LINE__, _func, _uctx)
 
unsigned int    fr_atexit_global_disarm(bool uctx_scope, fr_atexit_t func, void const *uctx);
 
void            fr_atexit_global_disarm_all(void);
 
int             fr_atexit_global_trigger_all(void);
 
int             fr_atexit_trigger(bool uctx_scope, fr_atexit_t func, void const *uctx);
 
bool            fr_atexit_is_exiting(void);
 
#ifdef HAVE_PTHREADS
/*
 *      Because GCC only added support in 2013 *sigh*
 */
#ifdef TLS_STORAGE_CLASS
#  define _Thread_local TLS_STORAGE_CLASS
#endif
 
/*
 *  Stop complaints of...:
 *
 *    error: the address of 'x' will always evaluate as 'true' [-Werror=address]
 *
 *  ...when functions are tested directly in the fr_atexit_global_once macro
 */
static inline int _fr_atexit_global_once_funcs(fr_atexit_t init_func, fr_atexit_t free_func, void *uctx)
{
        if (init_func) if (init_func(uctx) < 0) return -1;
        if (free_func) fr_atexit_global(free_func, uctx);
 
        return 0;
}
 
/** A generic function to free talloc chunks.  Compatible with the fr_atexit_t type
 *
 * @param[in] to_free   talloc chunk to free.
 * @return the return code returned by talloc_free.
 */
static inline int fr_atexit_talloc_free(void *to_free)
{
        return talloc_free(to_free);
}
 
/** Setup pair of global init/free functions, returning errors from the specified init function
 *
 * Simplifies setting up data structures the first time a given function
 * is called.
 *
 * Should be used in the body of the function before any initialisation
 * dependent code.
 *
 * Will not share init status outside of the function.
 *
 * @param[out] _ret             A pointer to where to write the result
 *                              of the init function if called.
 * @param[in] _init             function to call. Will be called once
 *                              during the process lifetime.
 *                              May be NULL.
 * @param[in] _free             function to call. Will be called once
 *                              at exit.
 *                              May be NULL.
 *                              Pass fr_atexit_talloc_free if _uctx is
 *                              just a talloc chunk and no special logic
 *                              is needed.
 * @param[in] _uctx             data to be passed to free function.
 */
#define fr_atexit_global_once_ret(_ret, _init, _free, _uctx) \
do { \
        static atomic_bool      _init_done = false; \
        static pthread_mutex_t  _init_mutex = PTHREAD_MUTEX_INITIALIZER; \
        void *_our_uctx = _uctx; /* stop _uctx being evaluated multiple times, it may be a call to malloc() */ \
        *(_ret) = 0; \
        if (unlikely(!atomic_load(&_init_done))) { \
                pthread_mutex_lock(&_init_mutex); \
                if (!atomic_load(&_init_done)) { \
                        if (_fr_atexit_global_once_funcs(_init, _free, _our_uctx) < 0) { \
                                *(_ret) = -1; \
                        } \
                        atomic_store(&_init_done, true); \
                } \
                pthread_mutex_unlock(&_init_mutex); \
        } \
} while (0)
 
/** Setup pair of global init/free functions
 *
 * Simplifies setting up data structures the first time a given function
 * is called.
 *
 * Should be used in the body of the function before any initialisation
 * dependent code.
 *
 * Will not share init status outside of the function.
 *
 * @param[in] _init             function to call. Will be called once
 *                              during the process lifetime.
 *                              May be NULL.
 * @param[in] _free             function to call. Will be called once
 *                              at exit.
 *                              May be NULL.
 *                              Pass fr_atexit_talloc_free if _uctx is
 *                              just a talloc chunk and no special logic
 *                              is needed.
 * @param[in] _uctx             data to be passed to free function.
 */
#define fr_atexit_global_once(_init, _free, _uctx) \
        fr_atexit_global_once_ret(&(int){ 0 }, _init, _free, _uctx)
 
/** Set a destructor for thread local storage to free the memory on thread exit
 *
 * @note Pointers to thread local storage seem to become unusable as threads are
 *      destroyed.  So we need to store the address of the memory to free, not
 *      the address of the thread local variable.
 *
 * @param[in] _name             Name of variable e.g. 'my_tls'.
 * @param[in] _free             Destructor, called when the thread exits to clean up any data.
 *                              Pass fr_atexit_talloc_free if _uctx is
 *                              just a talloc chunk and no special logic
 *                              is needed.
 * @param[in] _uctx             Memory to free.
 */
#  define fr_atexit_thread_local(_name, _free, _uctx) \
do { \
        void *_our_uctx = _uctx; /* stop _uctx being evaluated multiple times, it may be a call to malloc() */ \
        _fr_atexit_thread_local(__FILE__, __LINE__, _free, _our_uctx); \
        _name = _our_uctx; \
} while (0)
 
int             _fr_atexit_thread_local(char const *file, int line,
                                        fr_atexit_t func, void const *uctx);
 
unsigned int    fr_atexit_thread_local_disarm(bool uctx_scope, fr_atexit_t func, void const *uctx);
 
void            fr_atexit_thread_local_disarm_all(void);
 
int             fr_atexit_thread_trigger_all(void);
 
bool            fr_atexit_thread_is_exiting(void);
 
/*
 *      If we're building without threading support,
 *      all this becomes much easier, and we just map
 *      all thread local cleanup entries to the global
 *      list.
 */
#else
/*
 *      Don't emit a _Thread_local_storage qualifier
 */
#  define __Thread_local
#  define fr_atexit_global_once(_init, _free, _uctx) \
do { \
        static bool _init_done = false; \
        void * _our_uctx = _uctx; /* stop _uctx being evaluated multiple times, it may be a call to malloc() */ \
        if (unlikely(!_init_done)) { \
                _init(_our_uctx); \
                fr_atexit_global(_free, _our_uctx); \
                _init_done = true; \
        } \
} while(0);
#  define fr_atexit_thread_local(_name, _free, _uctx) \
do { \
        static bool _init_done = false; \
        void * _our_uctx = _uctx; /* stop _uctx being evaluated multiple times, it may be a call to malloc() */ \
        if (unlikely(!_init_done)) { \
                fr_atexit_global(_free, _our_uctx); \
                _init_done = true; \
        } \
        _name = _our_uctx; \
} while(0);
#  define fr_atexit_thread_local_disarm(...)            fr_atexit_global_disarm(__VA_ARGS__)
#  define fr_atexit_thread_local_disarm_all(...)        fr_atexit_global_disarm_all(__VA_ARGS__)
#  define fr_atexit_thread_trigger_all(...)
#endif
 
#ifdef __cplusplus
}
#endif