带回调到python VM的pthread [英] pthread with callback to python VM

问题描述

假设我有一个python脚本，可通过ctypes加载共享库(SL).

Let's say I have a python script which loads a shared library (SL) through ctypes.

• SL设置了pthread T1
• python脚本通过SL配置回调，即python脚本从SL中调用对python可调用对象的引用的函数

• The SL sets up a pthread T1
• The python script configures callbacks through the SL i.e. python script calls functions from the SL with references to python callables

替代文本http://www.gliffy.com/pubdoc/1993061/L .jpg

现在，假设T1调用了回调"功能，那么以下假设是正确的:

Now, let's say T1 calls a "callback" function, are the following assumptions true:

• Python端的回调函数在T1的上下文中执行
• 我可以使用 队列 T1和Python VM
• 我需要在Python VM端轮询所说的queue

• the callback function on the Python side is executed within the context of T1
• I can use a queue to communicate between T1 and the Python VM
• I would need to poll the said queue on the Python VM side

我了解线程，共享状态等的所有概念，但是我对Python的多线程方面还没有深入研究.由于目前还没有足够的适应层(ctypes)，我恐怕会缺少该过程的一些关键方面.

I understand all the concepts of threading, shared state etc. but I haven't dug very deep on the multi-threading side with Python. Since there is an adaptation layer which I do not know enough at the moment (ctypes), I am afraid I'll be missing some key aspects of the process.

推荐答案

通常不需要轮询队列(您可以在Python端投入另一个线程来阻塞其上的.get调用)，但这不是必需的.大不了的.问题是，通过这样的安排，您可能会被 GIL 抓到–参见三个Wikipedia页面上的链接可对其进行充分的处理.

Polling the queue isn't normally necessary (you can devote another thread on the Python side to doing blocking .get calls on it), but that's not a big deal. Problem is, with such an arrangement, you might get caught by the GIL -- see the three links from this wikipedia page for ample treatments thereof.

使用Python C API使用C(或 Cython )代码与C进行交互时，您至少可以相当简单地释放和获取GIL，希望避免死锁等问题；使用ctypes时，GIL操作会在C情境的回调中自动执行，因此，如果有其他任何发挥作用，则死锁是有风险的(由于事情不在您的控制范围之内，因此您无法轻易确保Djikstra的 应用了Banker算法 .

When you interface to/from C with C (or Cython) code using the Python C API, you can release and acquire the GIL pretty simply, at least, hopefully avoiding deadlocks and the like; with ctypes, GIL operations are automated in callback to/from C situations, so if there's any other lock in play a deadlock is a risk (since things are not within your control you can't easily ensure Djikstra's Banker Algorithm is applied).

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