1 /* 2 * Copyright (c) 2008-2012 Niels Provos and Nick Mathewson 3 * 4 * Redistribution and use in source and binary forms, with or without 5 * modification, are permitted provided that the following conditions 6 * are met: 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 10 * notice, this list of conditions and the following disclaimer in the 11 * documentation and/or other materials provided with the distribution. 12 * 3. The name of the author may not be used to endorse or promote products 13 * derived from this software without specific prior written permission. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 25 */ 26 #ifndef EVENT2_THREAD_H_INCLUDED_ 27 #define EVENT2_THREAD_H_INCLUDED_ 28 29 /** @file event2/thread.h 30 31 Functions for multi-threaded applications using Libevent. 32 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. 36 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 39 use them. 40 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(). 46 47 */ 48 49 #include <event2/visibility.h> 50 51 #ifdef __cplusplus 52 extern "C" { 53 #endif 54 55 #include <event2/event-config.h> 56 57 /** 58 @name Flags passed to lock functions 59 60 @{ 61 */ 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 72 /**@}*/ 73 74 #if !defined(EVENT__DISABLE_THREAD_SUPPORT) || defined(EVENT_IN_DOXYGEN_) 75 76 #define EVTHREAD_LOCK_API_VERSION 1 77 78 /** 79 @name Types of locks 80 81 @{*/ 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 89 /**@}*/ 90 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. 94 */ 95 struct evthread_lock_callbacks { 96 /** The current version of the locking API. Set this to 97 * EVTHREAD_LOCK_API_VERSION */ 98 int 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. 102 * 103 * (Note that RECURSIVE locks are currently mandatory, and 104 * READWRITE locks are not currently used.) 105 **/ 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); 119 }; 120 121 /** 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. 124 * 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. 128 */ 129 EVENT2_EXPORT_SYMBOL 130 int evthread_set_lock_callbacks(const struct evthread_lock_callbacks *); 131 132 #define EVTHREAD_CONDITION_API_VERSION 1 133 134 struct timeval; 135 136 /** 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. 139 */ 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. 147 */ 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. 156 */ 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. 165 * 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); 170 }; 171 172 /** 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. 175 * 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. 179 */ 180 EVENT2_EXPORT_SYMBOL 181 int evthread_set_condition_callbacks( 182 const struct evthread_condition_callbacks *); 183 184 /** 185 Sets the function for determining the thread id. 186 187 @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. 190 */ 191 EVENT2_EXPORT_SYMBOL 192 void evthread_set_id_callback( 193 unsigned long (*id_fn)(void)); 194 195 #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. 198 199 @return 0 on success, -1 on failure. */ 200 EVENT2_EXPORT_SYMBOL 201 int evthread_use_windows_threads(void); 202 /** 203 Defined if Libevent was built with support for evthread_use_windows_threads() 204 */ 205 #define EVTHREAD_USE_WINDOWS_THREADS_IMPLEMENTED 1 206 #endif 207 208 #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. 212 213 @return 0 on success, -1 on failure. */ 214 EVENT2_EXPORT_SYMBOL 215 int evthread_use_pthreads(void); 216 /** Defined if Libevent was built with support for evthread_use_pthreads() */ 217 #define EVTHREAD_USE_PTHREADS_IMPLEMENTED 1 218 219 #endif 220 221 /** Enable debugging wrappers around the current lock callbacks. If Libevent 222 * makes one of several common locking errors, exit with an assertion failure. 223 * 224 * If you're going to call this function, you must do so before any locks are 225 * allocated. 226 **/ 227 EVENT2_EXPORT_SYMBOL 228 void evthread_enable_lock_debugging(void); 229 230 /* Old (misspelled) version: This is deprecated; use 231 * evthread_enable_log_debugging instead. */ 232 EVENT2_EXPORT_SYMBOL 233 void evthread_enable_lock_debuging(void); 234 235 #endif /* EVENT__DISABLE_THREAD_SUPPORT */ 236 237 struct event_base; 238 /** Make sure it's safe to tell an event base to wake up from another thread 239 or a signal handler. 240 241 You shouldn't need to call this by hand; configuring the base with thread 242 support should be necessary and sufficient. 243 244 @return 0 on success, -1 on failure. 245 */ 246 EVENT2_EXPORT_SYMBOL 247 int evthread_make_base_notifiable(struct event_base *base); 248 249 #ifdef __cplusplus 250 } 251 #endif 252 253 #endif /* EVENT2_THREAD_H_INCLUDED_ */ 254
