thread.h File Reference

#include <event2/visibility.h>
#include <event2/event-config.h>

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Classes
struct	evthread_lock_callbacks
struct	evthread_condition_callbacks

Macros
#define	EVTHREAD_LOCK_API_VERSION   1
#define	EVTHREAD_CONDITION_API_VERSION   1
Flags passed to lock functions
#define	EVTHREAD_WRITE   0x04
#define	EVTHREAD_READ   0x08
#define	EVTHREAD_TRY   0x10
Types of locks
#define	EVTHREAD_LOCKTYPE_RECURSIVE   1
#define	EVTHREAD_LOCKTYPE_READWRITE   2

Functions
EVENT2_EXPORT_SYMBOL int	evthread_set_lock_callbacks (const struct evthread_lock_callbacks *)
EVENT2_EXPORT_SYMBOL int	evthread_set_condition_callbacks (const struct evthread_condition_callbacks *)
EVENT2_EXPORT_SYMBOL void	evthread_set_id_callback (unsigned long(*id_fn)(void))
EVENT2_EXPORT_SYMBOL void	evthread_enable_lock_debugging (void)
EVENT2_EXPORT_SYMBOL void	evthread_enable_lock_debuging (void)
EVENT2_EXPORT_SYMBOL int	evthread_make_base_notifiable (struct event_base *base)

Detailed Description

Functions for multi-threaded applications using Libevent.

When using a multi-threaded application in which multiple threads add and delete events from a single event base, Libevent needs to lock its data structures.

Like the memory-management function hooks, all of the threading functions must be set up before an event_base is created if you want the base to use them.

Most programs will either be using Windows threads or Posix threads. You can configure Libevent to use one of these event_use_windows_threads() or event_use_pthreads() respectively. If you're using another threading library, you'll need to configure threading functions manually using evthread_set_lock_callbacks() and evthread_set_condition_callbacks().

Macro Definition Documentation

EVTHREAD_LOCKTYPE_RECURSIVE

#define EVTHREAD_LOCKTYPE_RECURSIVE   1

A recursive lock is one that can be acquired multiple times at once by the same thread. No other process can allocate the lock until the thread that has been holding it has unlocked it as many times as it locked it.

EVTHREAD_READ

#define EVTHREAD_READ   0x08

A flag passed to a locking callback when the lock was allocated as a read-write lock, and we want to acquire or release the lock for reading.

EVTHREAD_TRY

#define EVTHREAD_TRY   0x10

A flag passed to a locking callback when we don't want to block waiting for the lock; if we can't get the lock immediately, we will instead return nonzero from the locking callback.

EVTHREAD_WRITE

#define EVTHREAD_WRITE   0x04

A flag passed to a locking callback when the lock was allocated as a read-write lock, and we want to acquire or release the lock for writing.

Function Documentation

evthread_enable_lock_debugging()

EVENT2_EXPORT_SYMBOL void evthread_enable_lock_debugging

(

void

)

Enable debugging wrappers around the current lock callbacks. If Libevent makes one of several common locking errors, exit with an assertion failure.

If you're going to call this function, you must do so before any locks are allocated.

evthread_make_base_notifiable()

EVENT2_EXPORT_SYMBOL int evthread_make_base_notifiable

(

struct event_base *

base

)

Make sure it's safe to tell an event base to wake up from another thread or a signal handler.

You shouldn't need to call this by hand; configuring the base with thread support should be necessary and sufficient.

Returns

0 on success, -1 on failure.

evthread_set_condition_callbacks()

EVENT2_EXPORT_SYMBOL int evthread_set_condition_callbacks

(

const struct evthread_condition_callbacks *

cbs

)

Sets a group of functions that Libevent should use for condition variables. For full information on the required callback API, see the documentation for the individual members of evthread_condition_callbacks.

Note that if you're using Windows or the Pthreads threading library, you probably shouldn't call this function; instead, use evthread_use_windows_threads() or evthread_use_pthreads() if you can.

evthread_set_id_callback()

EVENT2_EXPORT_SYMBOL void evthread_set_id_callback

(

unsigned long(*)(void)

id_fn

)

Sets the function for determining the thread id.

Parameters

base	the event base for which to set the id function
id_fn	the identify function Libevent should invoke to determine the identity of a thread.

evthread_set_lock_callbacks()

EVENT2_EXPORT_SYMBOL int evthread_set_lock_callbacks

(

const struct evthread_lock_callbacks *

cbs

)

Sets a group of functions that Libevent should use for locking. For full information on the required callback API, see the documentation for the individual members of evthread_lock_callbacks.

Note that if you're using Windows or the Pthreads threading library, you probably shouldn't call this function; instead, use evthread_use_windows_threads() or evthread_use_posix_threads() if you can.