Developers Manual > Cocos2d-x > Modules > Threading > How to use pthread

How to use pthread

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

  1. Don’t call any functions which invokes Ref::retain(), Ref::release() or Ref::autorelease(), because AutoreleasePool are not thread-safe. Please refer to Reference Count and AutoReleasePool in Cocos2d-x for more details. Cocos2d-x use AutoreleasePool 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 TextureCache::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:

pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;

struct SimpleStructure
{
    int data;
    float otherData;
};

void* ThreadFunction(void* arg)
{
    pthread_mutex_lock(&mutex);
    SimpleStructure* args = (SimpleStructure*)arg;
    // do something with args->data and args->otherData
    delete args;
    pthread_mutex_unlock(&mutex);
    return NULL;
}

void CreateThread()
{
    pthread_t thread;
    SimpleStructure* args = new SimpleStructure();
    args->data = 1;
    args->otherData = 2.0f;
    pthread_create(&thread, NULL, &ThreadFunction, args);
}

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