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_ 27 #define _EVENT2_THREAD_H_ 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 #ifdef __cplusplus 50 extern "C" { 51 #endif 52 53 #include <event2/event-config.h> 54 55 /** 56 @name Flags passed to lock functions 57 58 @{ 59 */ 60 /** A flag passed to a locking callback when the lock was allocated as a 61 * read-write lock, and we want to acquire or release the lock for writing. */ 62 #define EVTHREAD_WRITE 0x04 63 /** A flag passed to a locking callback when the lock was allocated as a 64 * read-write lock, and we want to acquire or release the lock for reading. */ 65 #define EVTHREAD_READ 0x08 66 /** A flag passed to a locking callback when we don't want to block waiting 67 * for the lock; if we can't get the lock immediately, we will instead 68 * return nonzero from the locking callback. */ 69 #define EVTHREAD_TRY 0x10 70 /**@}*/ 71 72 #if !defined(_EVENT_DISABLE_THREAD_SUPPORT) || defined(_EVENT_IN_DOXYGEN) 73 74 #define EVTHREAD_LOCK_API_VERSION 1 75 76 /** 77 @name Types of locks 78 79 @{*/ 80 /** A recursive lock is one that can be acquired multiple times at once by the 81 * same thread. No other process can allocate the lock until the thread that 82 * has been holding it has unlocked it as many times as it locked it. */ 83 #define EVTHREAD_LOCKTYPE_RECURSIVE 1 84 /* A read-write lock is one that allows multiple simultaneous readers, but 85 * where any one writer excludes all other writers and readers. */ 86 #define EVTHREAD_LOCKTYPE_READWRITE 2 87 /**@}*/ 88 89 /** This structure describes the interface a threading library uses for 90 * locking. It's used to tell evthread_set_lock_callbacks() how to use 91 * locking on this platform. 92 */ 93 struct evthread_lock_callbacks { 94 /** The current version of the locking API. Set this to 95 * EVTHREAD_LOCK_API_VERSION */ 96 int lock_api_version; 97 /** Which kinds of locks does this version of the locking API 98 * support? A bitfield of EVTHREAD_LOCKTYPE_RECURSIVE and 99 * EVTHREAD_LOCKTYPE_READWRITE. 100 * 101 * (Note that RECURSIVE locks are currently mandatory, and 102 * READWRITE locks are not currently used.) 103 **/ 104 unsigned supported_locktypes; 105 /** Function to allocate and initialize new lock of type 'locktype'. 106 * Returns NULL on failure. */ 107 void *(*alloc)(unsigned locktype); 108 /** Funtion to release all storage held in 'lock', which was created 109 * with type 'locktype'. */ 110 void (*free)(void *lock, unsigned locktype); 111 /** Acquire an already-allocated lock at 'lock' with mode 'mode'. 112 * Returns 0 on success, and nonzero on failure. */ 113 int (*lock)(unsigned mode, void *lock); 114 /** Release a lock at 'lock' using mode 'mode'. Returns 0 on success, 115 * and nonzero on failure. */ 116 int (*unlock)(unsigned mode, void *lock); 117 }; 118 119 /** Sets a group of functions that Libevent should use for locking. 120 * For full information on the required callback API, see the 121 * documentation for the individual members of evthread_lock_callbacks. 122 * 123 * Note that if you're using Windows or the Pthreads threading library, you 124 * probably shouldn't call this function; instead, use 125 * evthread_use_windows_threads() or evthread_use_posix_threads() if you can. 126 */ 127 int evthread_set_lock_callbacks(const struct evthread_lock_callbacks *); 128 129 #define EVTHREAD_CONDITION_API_VERSION 1 130 131 struct timeval; 132 133 /** This structure describes the interface a threading library uses for 134 * condition variables. It's used to tell evthread_set_condition_callbacks 135 * how to use locking on this platform. 136 */ 137 struct evthread_condition_callbacks { 138 /** The current version of the conditions API. Set this to 139 * EVTHREAD_CONDITION_API_VERSION */ 140 int condition_api_version; 141 /** Function to allocate and initialize a new condition variable. 142 * Returns the condition variable on success, and NULL on failure. 143 * The 'condtype' argument will be 0 with this API version. 144 */ 145 void *(*alloc_condition)(unsigned condtype); 146 /** Function to free a condition variable. */ 147 void (*free_condition)(void *cond); 148 /** Function to signal a condition variable. If 'broadcast' is 1, all 149 * threads waiting on 'cond' should be woken; otherwise, only on one 150 * thread is worken. Should return 0 on success, -1 on failure. 151 * This function will only be called while holding the associated 152 * lock for the condition. 153 */ 154 int (*signal_condition)(void *cond, int broadcast); 155 /** Function to wait for a condition variable. The lock 'lock' 156 * will be held when this function is called; should be released 157 * while waiting for the condition to be come signalled, and 158 * should be held again when this function returns. 159 * If timeout is provided, it is interval of seconds to wait for 160 * the event to become signalled; if it is NULL, the function 161 * should wait indefinitely. 162 * 163 * The function should return -1 on error; 0 if the condition 164 * was signalled, or 1 on a timeout. */ 165 int (*wait_condition)(void *cond, void *lock, 166 const struct timeval *timeout); 167 }; 168 169 /** Sets a group of functions that Libevent should use for condition variables. 170 * For full information on the required callback API, see the 171 * documentation for the individual members of evthread_condition_callbacks. 172 * 173 * Note that if you're using Windows or the Pthreads threading library, you 174 * probably shouldn't call this function; instead, use 175 * evthread_use_windows_threads() or evthread_use_pthreads() if you can. 176 */ 177 int evthread_set_condition_callbacks( 178 const struct evthread_condition_callbacks *); 179 180 /** 181 Sets the function for determining the thread id. 182 183 @param base the event base for which to set the id function 184 @param id_fn the identify function Libevent should invoke to 185 determine the identity of a thread. 186 */ 187 void evthread_set_id_callback( 188 unsigned long (*id_fn)(void)); 189 190 #if (defined(WIN32) && !defined(_EVENT_DISABLE_THREAD_SUPPORT)) || defined(_EVENT_IN_DOXYGEN) 191 /** Sets up Libevent for use with Windows builtin locking and thread ID 192 functions. Unavailable if Libevent is not built for Windows. 193 194 @return 0 on success, -1 on failure. */ 195 int evthread_use_windows_threads(void); 196 /** 197 Defined if Libevent was built with support for evthread_use_windows_threads() 198 */ 199 #define EVTHREAD_USE_WINDOWS_THREADS_IMPLEMENTED 1 200 #endif 201 202 #if defined(_EVENT_HAVE_PTHREADS) || defined(_EVENT_IN_DOXYGEN) 203 /** Sets up Libevent for use with Pthreads locking and thread ID functions. 204 Unavailable if Libevent is not build for use with pthreads. Requires 205 libraries to link against Libevent_pthreads as well as Libevent. 206 207 @return 0 on success, -1 on failure. */ 208 int evthread_use_pthreads(void); 209 /** Defined if Libevent was built with support for evthread_use_pthreads() */ 210 #define EVTHREAD_USE_PTHREADS_IMPLEMENTED 1 211 212 #endif 213 214 /** Enable debugging wrappers around the current lock callbacks. If Libevent 215 * makes one of several common locking errors, exit with an assertion failure. 216 * 217 * If you're going to call this function, you must do so before any locks are 218 * allocated. 219 **/ 220 void evthread_enable_lock_debuging(void); 221 222 #endif /* _EVENT_DISABLE_THREAD_SUPPORT */ 223 224 struct event_base; 225 /** Make sure it's safe to tell an event base to wake up from another thread 226 or a signal handler. 227 228 @return 0 on success, -1 on failure. 229 */ 230 int evthread_make_base_notifiable(struct event_base *base); 231 232 #ifdef __cplusplus 233 } 234 #endif 235 236 #endif /* _EVENT2_THREAD_H_ */ 237