Re: Callback from c thread with ctypes
Victor Lin wrote: On 3月8日, 下午9時56分, "Diez B. Roggisch" wrote: Victor Lin schrieb: Hi, I am going to develop a c library binding with ctypes. That c library will call callback from worker threads it created. Here comes the problem : Will the GIL be acquired before it goes into Python function? I got a little try.. DSPPROC = WINFUNCTYPE(None, DWORD, DWORD, c_void_p, DWORD, c_void_p) def test(handle, channel, buffer, length, user): print handle, channel, buffer, length, user dsp = BASS_ChannelSetDSP(stream, DSPPROC(test), None, 123) I got "access violation" when I run it... It seems that the ctypes did't acquire GIL before it call the python callback. As the document says. WINFUNCTYPE will release GIL during the call But it does not mention callback about Python function? How about a call from another thread? Could somebody help me? The releasing takes only place when entering a c-function. A python-callback acquires the GIL, see callbacks.c in the python source. The access violation has nothing to do with that I presume, that's just a general programming error as it happens with ctypes during development. Diez Hi, Thanks your replying, I try it again, found that my program only crash when I call it from python's IDLE. If I click it, namely execute it with python directly, it works fine. Why the program will crash within IDLE? Usually because IDLE is written in python and Tkinter. IDLE doesn't give a completely isolated environment for your program to run in, this causes python program that uses Tkinter often causes various undescribable oddities. -- http://mail.python.org/mailman/listinfo/python-list
Re: Callback from c thread with ctypes
Victor Lin wrote > I know I have to call PyEval_InitThreads if my module create threads > that will contact python stuff, for example, call a python callback > function from threads. But however, it is ctypes. I have no idea > should I do that for the imported dll? If it is, how? You have to initialize the thread state for the current thread, too. See Python/pystate.c:PyThreadState_New() -- http://mail.python.org/mailman/listinfo/python-list
Re: Callback from c thread with ctypes
On 3月8日, 下午10時20分, Christian Heimes wrote: > Victor Lin wrote: > > Hi, > > > I am going to develop a c library binding with ctypes. That c library > > will call callback from worker threads it created. Here comes the > > problem : Will the GIL be acquired before it goes into Python > > function? > > > I got a little try.. > > > DSPPROC = WINFUNCTYPE(None, DWORD, DWORD, c_void_p, DWORD, c_void_p) > > > def test(handle, channel, buffer, length, user): > > print handle, channel, buffer, length, user > > > dsp = BASS_ChannelSetDSP(stream, DSPPROC(test), None, 123) > > > I got "access violation" when I run it... It seems that the ctypes > > did't acquire GIL before it call the python callback. As the document > > says. > > > WINFUNCTYPE will release GIL during the call > > > But it does not mention callback about Python function? How about a > > call from another thread? Could somebody help me? > > You can't call Python code from an arbitrary thread. Before you are > allowed to call a Python function from a thread, you must enable > Python's threading subsystem and register the thread. Python need to > store information (like the exception information) in a thread local > variable (TLS). > > I can't tell you how to register your thread with Python, though. > > Christian I know I have to call PyEval_InitThreads if my module create threads that will contact python stuff, for example, call a python callback function from threads. But however, it is ctypes. I have no idea should I do that for the imported dll? If it is, how? Thanks. -- http://mail.python.org/mailman/listinfo/python-list
Re: Callback from c thread with ctypes
On 3月8日, 下午9時56分, "Diez B. Roggisch" wrote: > Victor Lin schrieb: > > > > > Hi, > > > I am going to develop a c library binding with ctypes. That c library > > will call callback from worker threads it created. Here comes the > > problem : Will the GIL be acquired before it goes into Python > > function? > > > I got a little try.. > > > DSPPROC = WINFUNCTYPE(None, DWORD, DWORD, c_void_p, DWORD, c_void_p) > > > def test(handle, channel, buffer, length, user): > > print handle, channel, buffer, length, user > > > dsp = BASS_ChannelSetDSP(stream, DSPPROC(test), None, 123) > > > I got "access violation" when I run it... It seems that the ctypes > > did't acquire GIL before it call the python callback. As the document > > says. > > > WINFUNCTYPE will release GIL during the call > > > But it does not mention callback about Python function? How about a > > call from another thread? Could somebody help me? > > The releasing takes only place when entering a c-function. A > python-callback acquires the GIL, see callbacks.c in the python source. > > The access violation has nothing to do with that I presume, that's just > a general programming error as it happens with ctypes during development. > > Diez Hi, Thanks your replying, I try it again, found that my program only crash when I call it from python's IDLE. If I click it, namely execute it with python directly, it works fine. Why the program will crash within IDLE? -- http://mail.python.org/mailman/listinfo/python-list
Re: Callback from c thread with ctypes
Victor Lin wrote: > Hi, > > I am going to develop a c library binding with ctypes. That c library > will call callback from worker threads it created. Here comes the > problem : Will the GIL be acquired before it goes into Python > function? > > I got a little try.. > > DSPPROC = WINFUNCTYPE(None, DWORD, DWORD, c_void_p, DWORD, c_void_p) > > def test(handle, channel, buffer, length, user): > print handle, channel, buffer, length, user > > dsp = BASS_ChannelSetDSP(stream, DSPPROC(test), None, 123) > > I got "access violation" when I run it... It seems that the ctypes > did't acquire GIL before it call the python callback. As the document > says. > > WINFUNCTYPE will release GIL during the call > > But it does not mention callback about Python function? How about a > call from another thread? Could somebody help me? You can't call Python code from an arbitrary thread. Before you are allowed to call a Python function from a thread, you must enable Python's threading subsystem and register the thread. Python need to store information (like the exception information) in a thread local variable (TLS). I can't tell you how to register your thread with Python, though. Christian -- http://mail.python.org/mailman/listinfo/python-list
Re: Callback from c thread with ctypes
Victor Lin schrieb: Hi, I am going to develop a c library binding with ctypes. That c library will call callback from worker threads it created. Here comes the problem : Will the GIL be acquired before it goes into Python function? I got a little try.. DSPPROC = WINFUNCTYPE(None, DWORD, DWORD, c_void_p, DWORD, c_void_p) def test(handle, channel, buffer, length, user): print handle, channel, buffer, length, user dsp = BASS_ChannelSetDSP(stream, DSPPROC(test), None, 123) I got "access violation" when I run it... It seems that the ctypes did't acquire GIL before it call the python callback. As the document says. WINFUNCTYPE will release GIL during the call But it does not mention callback about Python function? How about a call from another thread? Could somebody help me? The releasing takes only place when entering a c-function. A python-callback acquires the GIL, see callbacks.c in the python source. The access violation has nothing to do with that I presume, that's just a general programming error as it happens with ctypes during development. Diez -- http://mail.python.org/mailman/listinfo/python-list
