Re: Embedding Python in a C extension
Thanks for the reply. I'm looking into the Global Interpreter Lock today. On Thu, 03 Jun 2010 01:07:39 +0100, MRAB pyt...@mrabarnett.plus.com wrote: p...@mail.python.org wrote: I have a problem with embedding Python into a C extension in Windows Vista. I have implemented a timer routine in C as an extension, which I can import into Python 2.6.5 and run. Each timer interval, the extension calls a C CALLBACK function. I want to be able to have this CALLBACK function call a Python function, so that I can write the timer handler in Python. I can write Python functions and call them from a C extension function with no trouble in all cases EXCEPT when the function that calls the Python code is the timer's CALLBACK function. That is, if I call PyRun_SimpleString or PyRun_SimpleFile, or PyImport_ImportModule, or basically any Python-y function in the CALLBACK function, Python crashes and I get a window saying Python has stopped working. Windows is searching for a solution to the problem. The Python code runs fine if I call it from a function in the extension that is not the CALLBACK function. And regular C code runs in the CALLBACK function properly. It only crashes if I try to run the Python code from the timer CALLBACK function (or any C function I call from the CALLBACK function). Does anybody know how to fix this? Is there a workaround of some sort? Here's a quote from the Python docs at: http://docs.python.org/c-api/init.html The Python interpreter is not fully thread safe. In order to support multi-threaded Python programs, there's a global lock, called the global interpreter lock or GIL, that must be held by the current thread before it can safely access Python objects. Without the lock, even the simplest operations could cause problems in a multi-threaded program: for example, when two threads simultaneously increment the reference count of the same object, the reference count could end up being incremented only once instead of twice. That's probably what's happening to you. -- http://mail.python.org/mailman/listinfo/python-list
Re: Embedding Python in a C extension
Thanks for the reply. I'm checking this out today. On Wed, 2 Jun 2010 22:30:37 -0700 (PDT), Carl Banks pavlovevide...@gmail.com wrote: On Jun 2, 1:46 pm, Paul Grunau wrote: I have a problem with embedding Python into a C extension in Windows Vista. I have implemented a timer routine in C as an extension, which I can import into Python 2.6.5 and run. Each timer interval, the extension calls a C CALLBACK function. I want to be able to have this CALLBACK function call a Python function, so that I can write the timer handler in Python. I can write Python functions and call them from a C extension function with no trouble in all cases EXCEPT when the function that calls the Python code is the timer's CALLBACK function. That is, if I call PyRun_SimpleString or PyRun_SimpleFile, or PyImport_ImportModule, or basically any Python-y function in the CALLBACK function, Python crashes and I get a window saying Python has stopped working. Windows is searching for a solution to the problem. The Python code runs fine if I call it from a function in the extension that is not the CALLBACK function. And regular C code runs in the CALLBACK function properly. It only crashes if I try to run the Python code from the timer CALLBACK function (or any C function I call from the CALLBACK function). Does anybody know how to fix this? Is there a workaround of some sort? See PEP 311. When an external/uncertain thread calls into Python, it has to be sure a Python thread state exists for that thread, and that the thread holds the global interpreter lock. This is done by surrounding all Python code with the following calls: PyGILState_STATE state = PyGILState_Ensure(); and PyGILState_Release(state); Normally, code in extension modules can rely on the current thread having the global lock at all entry points, so it doesn't have worry about the thread state. But a callback from a timer can't assume that. Carl Banks -- http://mail.python.org/mailman/listinfo/python-list
Embedding Python in a C extension
I have a problem with embedding Python into a C extension in Windows Vista. I have implemented a timer routine in C as an extension, which I can import into Python 2.6.5 and run. Each timer interval, the extension calls a C CALLBACK function. I want to be able to have this CALLBACK function call a Python function, so that I can write the timer handler in Python. I can write Python functions and call them from a C extension function with no trouble in all cases EXCEPT when the function that calls the Python code is the timer's CALLBACK function. That is, if I call PyRun_SimpleString or PyRun_SimpleFile, or PyImport_ImportModule, or basically any Python-y function in the CALLBACK function, Python crashes and I get a window saying Python has stopped working. Windows is searching for a solution to the problem. The Python code runs fine if I call it from a function in the extension that is not the CALLBACK function. And regular C code runs in the CALLBACK function properly. It only crashes if I try to run the Python code from the timer CALLBACK function (or any C function I call from the CALLBACK function). Does anybody know how to fix this? Is there a workaround of some sort? -- http://mail.python.org/mailman/listinfo/python-list
Re: Embedding Python in a C extension
p...@mail.python.org wrote: I have a problem with embedding Python into a C extension in Windows Vista. I have implemented a timer routine in C as an extension, which I can import into Python 2.6.5 and run. Each timer interval, the extension calls a C CALLBACK function. I want to be able to have this CALLBACK function call a Python function, so that I can write the timer handler in Python. I can write Python functions and call them from a C extension function with no trouble in all cases EXCEPT when the function that calls the Python code is the timer's CALLBACK function. That is, if I call PyRun_SimpleString or PyRun_SimpleFile, or PyImport_ImportModule, or basically any Python-y function in the CALLBACK function, Python crashes and I get a window saying Python has stopped working. Windows is searching for a solution to the problem. The Python code runs fine if I call it from a function in the extension that is not the CALLBACK function. And regular C code runs in the CALLBACK function properly. It only crashes if I try to run the Python code from the timer CALLBACK function (or any C function I call from the CALLBACK function). Does anybody know how to fix this? Is there a workaround of some sort? Here's a quote from the Python docs at: http://docs.python.org/c-api/init.html The Python interpreter is not fully thread safe. In order to support multi-threaded Python programs, there's a global lock, called the global interpreter lock or GIL, that must be held by the current thread before it can safely access Python objects. Without the lock, even the simplest operations could cause problems in a multi-threaded program: for example, when two threads simultaneously increment the reference count of the same object, the reference count could end up being incremented only once instead of twice. That's probably what's happening to you. -- http://mail.python.org/mailman/listinfo/python-list
Re: Embedding Python in a C extension
On Jun 2, 1:46 pm, Paul Grunau wrote: I have a problem with embedding Python into a C extension in Windows Vista. I have implemented a timer routine in C as an extension, which I can import into Python 2.6.5 and run. Each timer interval, the extension calls a C CALLBACK function. I want to be able to have this CALLBACK function call a Python function, so that I can write the timer handler in Python. I can write Python functions and call them from a C extension function with no trouble in all cases EXCEPT when the function that calls the Python code is the timer's CALLBACK function. That is, if I call PyRun_SimpleString or PyRun_SimpleFile, or PyImport_ImportModule, or basically any Python-y function in the CALLBACK function, Python crashes and I get a window saying Python has stopped working. Windows is searching for a solution to the problem. The Python code runs fine if I call it from a function in the extension that is not the CALLBACK function. And regular C code runs in the CALLBACK function properly. It only crashes if I try to run the Python code from the timer CALLBACK function (or any C function I call from the CALLBACK function). Does anybody know how to fix this? Is there a workaround of some sort? See PEP 311. When an external/uncertain thread calls into Python, it has to be sure a Python thread state exists for that thread, and that the thread holds the global interpreter lock. This is done by surrounding all Python code with the following calls: PyGILState_STATE state = PyGILState_Ensure(); and PyGILState_Release(state); Normally, code in extension modules can rely on the current thread having the global lock at all entry points, so it doesn't have worry about the thread state. But a callback from a timer can't assume that. Carl Banks -- http://mail.python.org/mailman/listinfo/python-list
