How to use pthread in cocos2d-x

Now, you can use pthread in cocos2d-x, but there are some limitations.

1. Don't call any functions which invokes CCObject::retain(), CCObject::release() or CCObject::autorelease(), because CCAutoreleasePool are not thread-safe. Please refer to Reference Count and AutoReleasePool in Cocos2d-x for more details. Cocos2d-x use CCAutoreleasePool every where in its framework, so my suggestion is that, don't invoke any cocos2d-x API in a new thread except Data Structures.

2. If you want to load resources in a new thread, you can use CCTextureCache::addImageAsync()

3. pthread_cond_wait() seems have a bug, it can not wait at the first time, but works properly in subsequence.

If we make retain(), release() and autorealese() thread-safe, then mutex would be required. For the reason that cocos2d-x framework releases the autorelease pool at each end of message loop, using mutex may cause performance issue.

By the way, OpenGL context is not thread-safe, which you should always keep in mind.

cocos2d-x/extensions/network/HttpClient.cpp uses pthread_t and pthread_mutex_t to create network thread. You can look into it as a sample.

Simple pthread example that shows how to run a function in a separate thread, pass a structure to it and set a mutex:

 1pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
 2
 3struct SimpleStructure
 4{
 5    int data;
 6    float otherData;
 7};
 8
 9void* ThreadFunction(void* arg)
10{
11    pthread_mutex_lock(&mutex);
12    SimpleStructure* args = (SimpleStructure*)arg;
13    // do something with args->data and args->otherData
14    delete args;
15    pthread_mutex_unlock(&mutex);
16    return NULL;
17}
18
19void CreateThread()
20{
21    pthread_t thread;
22    SimpleStructure* args = new SimpleStructure();
23    args->data = 1;
24    args->otherData = 2.0f;
25    pthread_create(&thread, NULL, &ThreadFunction, args);
26}