[Python-Dev] Making python C-API thread safe (try 2)
shane at zope.com
Thu Sep 11 20:50:02 CEST 2003
[Moved to python-list at python.org, where this thread belongs]
Harri Pesonen wrote:
> But my basic message is this: Python needs to be made thread safe.
> Making the individual interpreters thread safe is trivial, and benefits
> many people, and is a necessary first step; making threads within
> interpreter thread safe is possible as well, at least if you leave
> something for the developer, as you should, as you do in every other
> programming language as well.
Lately, I've been considering an alternative to this line of thinking.
I've been wondering whether threads are truly the right direction to
pursue. This would be heresy in the Java world, but maybe Pythonistas
are more open to this thought.
The concept of a thread is composed of two concepts: multiple processes
and shared memory. Supporting multiple simultaneous processes is
relatively simple and has proven value. Shared memory, on the other
hand, results in a great number of complications. Some of the
complications have remained difficult problems for a long time:
preventing deadlocks, knowing exactly what needs to be locked, finding
race conditions, etc. I don't believe we should force the burden of
thread safety on every software engineer. Engineers have better things
At the same time, shared memory is quite valuable when you're ready to
take on the burden of thread safety. Therefore, I'm looking for a good
way to split a process into multiple processes and share only certain
parts of a program with other processes. I'd like some form of
*explicit* sharing with a Pythonic API.
Imagine the following Python module:
data = pseudothreads.shared()
s = get_some_data()
for n in range(4):
In this made-up example, nothing is shared between threads except for
the "data" global. The shared() function copies the list to shared
memory and returns a wrapper around the list that prevents access by
multiple threads simultaneously. start_new_thread() is a thin wrapper
around os.fork(). Each pseudothread has its own global interpreter lock.
I wonder whether others would consider such a thing valuable, or even
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