Sat Aug 6 00:39:32 2011

Asterisk developer's documentation


sched.h

Go to the documentation of this file.
00001 /*
00002  * Asterisk -- An open source telephony toolkit.
00003  *
00004  * Copyright (C) 1999 - 2005, Digium, Inc.
00005  *
00006  * Mark Spencer <markster@digium.com>
00007  *
00008  * See http://www.asterisk.org for more information about
00009  * the Asterisk project. Please do not directly contact
00010  * any of the maintainers of this project for assistance;
00011  * the project provides a web site, mailing lists and IRC
00012  * channels for your use.
00013  *
00014  * This program is free software, distributed under the terms of
00015  * the GNU General Public License Version 2. See the LICENSE file
00016  * at the top of the source tree.
00017  */
00018 
00019 /*! \file
00020  * \brief Scheduler Routines (derived from cheops)
00021  */
00022 
00023 #ifndef _ASTERISK_SCHED_H
00024 #define _ASTERISK_SCHED_H
00025 
00026 #if defined(__cplusplus) || defined(c_plusplus)
00027 extern "C" {
00028 #endif
00029 
00030 /*! \brief Max num of schedule structs
00031  * \note The max number of schedule structs to keep around
00032  * for use.  Undefine to disable schedule structure
00033  * caching. (Only disable this on very low memory
00034  * machines)
00035  */
00036 #define SCHED_MAX_CACHE 128
00037 
00038 /*! \brief a loop construct to ensure that
00039  * the scheduled task get deleted. The idea is that
00040  * if we loop attempting to remove the scheduled task,
00041  * then whatever callback had been running will complete
00042  * and reinsert the task into the scheduler.
00043  *
00044  * Since macro expansion essentially works like pass-by-name
00045  * parameter passing, this macro will still work correctly even
00046  * if the id of the task to delete changes. This holds as long as 
00047  * the name of the id which could change is passed to the macro 
00048  * and not a copy of the value of the id.
00049  */
00050 #define AST_SCHED_DEL(sched, id) \
00051    ({ \
00052       int _count = 0; \
00053       int _sched_res = -1; \
00054       while (id > -1 && (_sched_res = ast_sched_del(sched, id)) && ++_count < 10) \
00055          usleep(1); \
00056       if (_count == 10 && option_debug > 2) { \
00057          ast_log(LOG_DEBUG, "Unable to cancel schedule ID %d.\n", id); \
00058       } \
00059       id = -1; \
00060       (_sched_res); \
00061    })
00062 
00063 #define AST_SCHED_DEL_SPINLOCK(sched, id, lock) \
00064    ({ \
00065       int _count = 0; \
00066       int _sched_res = -1; \
00067       while (id > -1 && (_sched_res = ast_sched_del(sched, id)) && ++_count < 10) { \
00068          ast_mutex_unlock(lock); \
00069          usleep(1); \
00070          ast_mutex_lock(lock); \
00071       } \
00072       if (_count == 10 && option_debug > 2) { \
00073          ast_log(LOG_DEBUG, "Unable to cancel schedule ID %d.\n", id); \
00074       } \
00075       id = -1; \
00076       (_sched_res); \
00077    })
00078 
00079 struct sched_context;
00080 
00081 /*! \brief New schedule context
00082  * \note Create a scheduling context
00083  * \return Returns a malloc'd sched_context structure, NULL on failure
00084  */
00085 struct sched_context *sched_context_create(void);
00086 
00087 /*! \brief destroys a schedule context
00088  * Destroys (free's) the given sched_context structure
00089  * \param c Context to free
00090  * \return Returns 0 on success, -1 on failure
00091  */
00092 void sched_context_destroy(struct sched_context *c);
00093 
00094 /*! \brief callback for a cheops scheduler
00095  * A cheops scheduler callback takes a pointer with callback data and
00096  * \return returns a 0 if it should not be run again, or non-zero if it should be
00097  * rescheduled to run again
00098  */
00099 typedef int (*ast_sched_cb)(const void *data);
00100 #define AST_SCHED_CB(a) ((ast_sched_cb)(a))
00101 
00102 /*! \brief Adds a scheduled event
00103  * Schedule an event to take place at some point in the future.  callback
00104  * will be called with data as the argument, when milliseconds into the
00105  * future (approximately)
00106  * If callback returns 0, no further events will be re-scheduled
00107  * \param con Scheduler context to add
00108  * \param when how many milliseconds to wait for event to occur
00109  * \param callback function to call when the amount of time expires
00110  * \param data data to pass to the callback
00111  * \return Returns a schedule item ID on success, -1 on failure
00112  */
00113 int ast_sched_add(struct sched_context *con, int when, ast_sched_cb callback, const void *data);
00114 
00115 /*!Adds a scheduled event with rescheduling support
00116  * \param con Scheduler context to add
00117  * \param when how many milliseconds to wait for event to occur
00118  * \param callback function to call when the amount of time expires
00119  * \param data data to pass to the callback
00120  * \param variable If true, the result value of callback function will be
00121  *       used for rescheduling
00122  * Schedule an event to take place at some point in the future.  Callback
00123  * will be called with data as the argument, when milliseconds into the
00124  * future (approximately)
00125  * If callback returns 0, no further events will be re-scheduled
00126  * \return Returns a schedule item ID on success, -1 on failure
00127  */
00128 int ast_sched_add_variable(struct sched_context *con, int when, ast_sched_cb callback, const void *data, int variable);
00129 
00130 /*! \brief Deletes a scheduled event
00131  * Remove this event from being run.  A procedure should not remove its
00132  * own event, but return 0 instead.
00133  * \param con scheduling context to delete item from
00134  * \param id ID of the scheduled item to delete
00135  * \return Returns 0 on success, -1 on failure
00136  */
00137 #ifndef AST_DEVMODE
00138 int ast_sched_del(struct sched_context *con, int id);
00139 #else
00140 int _ast_sched_del(struct sched_context *con, int id, const char *file, int line, const char *function);
00141 #define  ast_sched_del(a, b)  _ast_sched_del(a, b, __FILE__, __LINE__, __PRETTY_FUNCTION__)
00142 #endif
00143 
00144 /*! \brief Determines number of seconds until the next outstanding event to take place
00145  * Determine the number of seconds until the next outstanding event
00146  * should take place, and return the number of milliseconds until
00147  * it needs to be run.  This value is perfect for passing to the poll
00148  * call.
00149  * \param con context to act upon
00150  * \return Returns "-1" if there is nothing there are no scheduled events
00151  * (and thus the poll should not timeout)
00152  */
00153 int ast_sched_wait(struct sched_context *con);
00154 
00155 /*! \brief Runs the queue
00156  * \param con Scheduling context to run
00157  * Run the queue, executing all callbacks which need to be performed
00158  * at this time.
00159  * \param con context to act upon
00160  * \return Returns the number of events processed.
00161  */
00162 int ast_sched_runq(struct sched_context *con);
00163 
00164 /*! \brief Dumps the scheduler contents
00165  * Debugging: Dump the contents of the scheduler to stderr
00166  * \param con Context to dump
00167  */
00168 void ast_sched_dump(const struct sched_context *con);
00169 
00170 /*! \brief Returns the number of seconds before an event takes place
00171  * \param con Context to use
00172  * \param id Id to dump
00173  */
00174 long ast_sched_when(struct sched_context *con,int id);
00175 
00176 /*!
00177  * \brief Convenience macro for objects and reference (add)
00178  *
00179  */
00180 #define ast_sched_add_object(obj,con,when,callback) ast_sched_add((con),(when),(callback), ASTOBJ_REF((obj)))
00181 
00182 /*!
00183  * \brief Convenience macro for objects and reference (del)
00184  *
00185  */
00186 #define ast_sched_del_object(obj,destructor,con,id) do { \
00187    if ((id) > -1) { \
00188       ast_sched_del((con),(id)); \
00189       (id) = -1; \
00190       ASTOBJ_UNREF((obj),(destructor)); \
00191    } \
00192 } while(0)
00193 
00194 #if defined(__cplusplus) || defined(c_plusplus)
00195 }
00196 #endif
00197 
00198 #endif /* _ASTERISK_SCHED_H */

Generated on Sat Aug 6 00:39:32 2011 for Asterisk - the Open Source PBX by  doxygen 1.4.7