2 * Copyright (c) 2008-2012 Niels Provos and Nick Mathewson
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
7 * 1. Redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
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11 * documentation and/or other materials provided with the distribution.
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13 * derived from this software without specific prior written permission.
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26 #ifndef EVENT2_THREAD_H_INCLUDED_
27 #define EVENT2_THREAD_H_INCLUDED_
29 /** @file event2/thread.h
31 Functions for multi-threaded applications using Libevent.
33 When using a multi-threaded application in which multiple threads
34 add and delete events from a single event base, Libevent needs to
35 lock its data structures.
37 Like the memory-management function hooks, all of the threading functions
38 _must_ be set up before an event_base is created if you want the base to
41 Most programs will either be using Windows threads or Posix threads. You
42 can configure Libevent to use one of these event_use_windows_threads() or
43 event_use_pthreads() respectively. If you're using another threading
44 library, you'll need to configure threading functions manually using
45 evthread_set_lock_callbacks() and evthread_set_condition_callbacks().
49 #include <event2/visibility.h>
55 #include <event2/event-config.h>
58 @name Flags passed to lock functions
62 /** A flag passed to a locking callback when the lock was allocated as a
63 * read-write lock, and we want to acquire or release the lock for writing. */
64 #define EVTHREAD_WRITE 0x04
65 /** A flag passed to a locking callback when the lock was allocated as a
66 * read-write lock, and we want to acquire or release the lock for reading. */
67 #define EVTHREAD_READ 0x08
68 /** A flag passed to a locking callback when we don't want to block waiting
69 * for the lock; if we can't get the lock immediately, we will instead
70 * return nonzero from the locking callback. */
71 #define EVTHREAD_TRY 0x10
74 #if !defined(EVENT__DISABLE_THREAD_SUPPORT) || defined(EVENT_IN_DOXYGEN_)
76 #define EVTHREAD_LOCK_API_VERSION 1
82 /** A recursive lock is one that can be acquired multiple times at once by the
83 * same thread. No other process can allocate the lock until the thread that
84 * has been holding it has unlocked it as many times as it locked it. */
85 #define EVTHREAD_LOCKTYPE_RECURSIVE 1
86 /* A read-write lock is one that allows multiple simultaneous readers, but
87 * where any one writer excludes all other writers and readers. */
88 #define EVTHREAD_LOCKTYPE_READWRITE 2
91 /** This structure describes the interface a threading library uses for
92 * locking. It's used to tell evthread_set_lock_callbacks() how to use
93 * locking on this platform.
95 struct evthread_lock_callbacks {
96 /** The current version of the locking API. Set this to
97 * EVTHREAD_LOCK_API_VERSION */
99 /** Which kinds of locks does this version of the locking API
100 * support? A bitfield of EVTHREAD_LOCKTYPE_RECURSIVE and
101 * EVTHREAD_LOCKTYPE_READWRITE.
103 * (Note that RECURSIVE locks are currently mandatory, and
104 * READWRITE locks are not currently used.)
106 unsigned supported_locktypes;
107 /** Function to allocate and initialize new lock of type 'locktype'.
108 * Returns NULL on failure. */
109 void *(*alloc)(unsigned locktype);
110 /** Funtion to release all storage held in 'lock', which was created
111 * with type 'locktype'. */
112 void (*free)(void *lock, unsigned locktype);
113 /** Acquire an already-allocated lock at 'lock' with mode 'mode'.
114 * Returns 0 on success, and nonzero on failure. */
115 int (*lock)(unsigned mode, void *lock);
116 /** Release a lock at 'lock' using mode 'mode'. Returns 0 on success,
117 * and nonzero on failure. */
118 int (*unlock)(unsigned mode, void *lock);
121 /** Sets a group of functions that Libevent should use for locking.
122 * For full information on the required callback API, see the
123 * documentation for the individual members of evthread_lock_callbacks.
125 * Note that if you're using Windows or the Pthreads threading library, you
126 * probably shouldn't call this function; instead, use
127 * evthread_use_windows_threads() or evthread_use_posix_threads() if you can.
130 int evthread_set_lock_callbacks(const struct evthread_lock_callbacks *);
132 #define EVTHREAD_CONDITION_API_VERSION 1
136 /** This structure describes the interface a threading library uses for
137 * condition variables. It's used to tell evthread_set_condition_callbacks
138 * how to use locking on this platform.
140 struct evthread_condition_callbacks {
141 /** The current version of the conditions API. Set this to
142 * EVTHREAD_CONDITION_API_VERSION */
143 int condition_api_version;
144 /** Function to allocate and initialize a new condition variable.
145 * Returns the condition variable on success, and NULL on failure.
146 * The 'condtype' argument will be 0 with this API version.
148 void *(*alloc_condition)(unsigned condtype);
149 /** Function to free a condition variable. */
150 void (*free_condition)(void *cond);
151 /** Function to signal a condition variable. If 'broadcast' is 1, all
152 * threads waiting on 'cond' should be woken; otherwise, only on one
153 * thread is worken. Should return 0 on success, -1 on failure.
154 * This function will only be called while holding the associated
155 * lock for the condition.
157 int (*signal_condition)(void *cond, int broadcast);
158 /** Function to wait for a condition variable. The lock 'lock'
159 * will be held when this function is called; should be released
160 * while waiting for the condition to be come signalled, and
161 * should be held again when this function returns.
162 * If timeout is provided, it is interval of seconds to wait for
163 * the event to become signalled; if it is NULL, the function
164 * should wait indefinitely.
166 * The function should return -1 on error; 0 if the condition
167 * was signalled, or 1 on a timeout. */
168 int (*wait_condition)(void *cond, void *lock,
169 const struct timeval *timeout);
172 /** Sets a group of functions that Libevent should use for condition variables.
173 * For full information on the required callback API, see the
174 * documentation for the individual members of evthread_condition_callbacks.
176 * Note that if you're using Windows or the Pthreads threading library, you
177 * probably shouldn't call this function; instead, use
178 * evthread_use_windows_threads() or evthread_use_pthreads() if you can.
181 int evthread_set_condition_callbacks(
182 const struct evthread_condition_callbacks *);
185 Sets the function for determining the thread id.
187 @param base the event base for which to set the id function
188 @param id_fn the identify function Libevent should invoke to
189 determine the identity of a thread.
192 void evthread_set_id_callback(
193 unsigned long (*id_fn)(void));
195 #if (defined(_WIN32) && !defined(EVENT__DISABLE_THREAD_SUPPORT)) || defined(EVENT_IN_DOXYGEN_)
196 /** Sets up Libevent for use with Windows builtin locking and thread ID
197 functions. Unavailable if Libevent is not built for Windows.
199 @return 0 on success, -1 on failure. */
201 int evthread_use_windows_threads(void);
203 Defined if Libevent was built with support for evthread_use_windows_threads()
205 #define EVTHREAD_USE_WINDOWS_THREADS_IMPLEMENTED 1
208 #if defined(EVENT__HAVE_PTHREADS) || defined(EVENT_IN_DOXYGEN_)
209 /** Sets up Libevent for use with Pthreads locking and thread ID functions.
210 Unavailable if Libevent is not build for use with pthreads. Requires
211 libraries to link against Libevent_pthreads as well as Libevent.
213 @return 0 on success, -1 on failure. */
215 int evthread_use_pthreads(void);
216 /** Defined if Libevent was built with support for evthread_use_pthreads() */
217 #define EVTHREAD_USE_PTHREADS_IMPLEMENTED 1
221 /** Enable debugging wrappers around the current lock callbacks. If Libevent
222 * makes one of several common locking errors, exit with an assertion failure.
224 * If you're going to call this function, you must do so before any locks are
228 void evthread_enable_lock_debugging(void);
230 /* Old (misspelled) version: This is deprecated; use
231 * evthread_enable_log_debugging instead. */
233 void evthread_enable_lock_debuging(void);
235 #endif /* EVENT__DISABLE_THREAD_SUPPORT */
238 /** Make sure it's safe to tell an event base to wake up from another thread
241 You shouldn't need to call this by hand; configuring the base with thread
242 support should be necessary and sufficient.
244 @return 0 on success, -1 on failure.
247 int evthread_make_base_notifiable(struct event_base *base);
253 #endif /* EVENT2_THREAD_H_INCLUDED_ */