Problem with spawning an external process
I want to execute a command (in this case, and it seems to be significant, a Java program) in a thread in Python. When I execute the java binary in the main python thread, everything runs correctly. But when I try and execute java in a thread, java segfaults. I am using Python 2.3.3 and trying to run the java binary from the 1.4.2 SDK from Sun. I have tried executing some arbitrary C program that I wrote, and it works fine in the main thread and the started thread. The problem seems to be specific to the Java binary. Here is the example code: --- START CODE --- import os import popen2 import time import select import threading # Change these to suit your system PATH = '/home/nico/j2sdk1.4.2/bin/java' #PATH = '/home/nico/j2sdk1.4.2/bin/java -invalid_arg' def get_ret(status): signal = status 0xff if signal == 0: retcode = status 8 else: retcode = 0 return signal,retcode print In main thread # Using spawn pid = os.spawnl(os.P_NOWAIT,PATH,PATH) ret = os.waitpid(pid,0) print PID: %i signal: %i return code: %i % (ret[0],get_ret(ret[1])[0],get_ret(ret[1])[1]) class TestThread(threading.Thread): def run(self): # Using spawn pid = os.spawnl(os.P_NOWAIT,PATH,PATH) ret = os.waitpid(pid,0) print PID: %i signal: %i return code: %i % (ret[0],get_ret(ret[1])[0],get_ret(ret[1])[1]) print In Thread TestThread().start() print Waiting... time.sleep(2) print ...Finished END CODE Here is the output that I get on my machine: [nico@ script]$ python testcrash2.py In main thread JAVA USAGE INFO STRIPPED PID: 32107 signal: 0 return code: 1 In Thread PID: 32116 signal: 11 return code: 0 You will notice that in the main thread, the program executes correctly (return code 1, signal 0). When the command is executed in the thread, it segfaults (signal 11). The second PATH= line calls Java with an invalid argument. In this case, it does not crash in the thread. I have tried a fork() and then os.execv in the thread as well, and get the same behaviour. I would appreciate it if someone with both Java and Python could try and run this sample and report back. Any suggestions would be welcome, as this is quite the showstopper for me at the moment. I am sure I am missing something totally obvious... Thanks in advance, Nico. -- NetSys International (Pty) Ltd. Tel : +27 12 349 2056 Fax : +27 12 349 2757 Web : http://www.netsys.co.za P.O. Box 35798, Menlo Park, 0102, South Africa The information contained in this communication is confidential and may be legally privileged. It is solely for use of the individual or entity to whom is addressed and others authorised to receive it. If you are not the intended recipient you are hereby notified that any disclosure, copying, distribution or taking of any action in reliance on the contents of this information is strictly prohibited and may be unlawful. This Message has been scanned for viruses and dangerous content by the NetSys International Mail Scanner and is believed to be clean. -- http://mail.python.org/mailman/listinfo/python-list
Re: Problem with spawning an external process
Apologies, this is on a Fedora Core 2 system. On Wed, 2006-04-12 at 11:27, Nico Kruger wrote: I want to execute a command (in this case, and it seems to be significant, a Java program) in a thread in Python. When I execute the java binary in the main python thread, everything runs correctly. But when I try and execute java in a thread, java segfaults. I am using Python 2.3.3 and trying to run the java binary from the 1.4.2 SDK from Sun. I have tried executing some arbitrary C program that I wrote, and it works fine in the main thread and the started thread. The problem seems to be specific to the Java binary. Here is the example code: --- START CODE --- import os import popen2 import time import select import threading # Change these to suit your system PATH = '/home/nico/j2sdk1.4.2/bin/java' #PATH = '/home/nico/j2sdk1.4.2/bin/java -invalid_arg' def get_ret(status): signal = status 0xff if signal == 0: retcode = status 8 else: retcode = 0 return signal,retcode print In main thread # Using spawn pid = os.spawnl(os.P_NOWAIT,PATH,PATH) ret = os.waitpid(pid,0) print PID: %i signal: %i return code: %i % (ret[0],get_ret(ret[1])[0],get_ret(ret[1])[1]) class TestThread(threading.Thread): def run(self): # Using spawn pid = os.spawnl(os.P_NOWAIT,PATH,PATH) ret = os.waitpid(pid,0) print PID: %i signal: %i return code: %i % (ret[0],get_ret(ret[1])[0],get_ret(ret[1])[1]) print In Thread TestThread().start() print Waiting... time.sleep(2) print ...Finished END CODE Here is the output that I get on my machine: [nico@ script]$ python testcrash2.py In main thread JAVA USAGE INFO STRIPPED PID: 32107 signal: 0 return code: 1 In Thread PID: 32116 signal: 11 return code: 0 You will notice that in the main thread, the program executes correctly (return code 1, signal 0). When the command is executed in the thread, it segfaults (signal 11). The second PATH= line calls Java with an invalid argument. In this case, it does not crash in the thread. I have tried a fork() and then os.execv in the thread as well, and get the same behaviour. I would appreciate it if someone with both Java and Python could try and run this sample and report back. Any suggestions would be welcome, as this is quite the showstopper for me at the moment. I am sure I am missing something totally obvious... Thanks in advance, Nico. -- NetSys International (Pty) Ltd. Tel : +27 12 349 2056 Fax : +27 12 349 2757 Web : http://www.netsys.co.za P.O. Box 35798, Menlo Park, 0102, South Africa The information contained in this communication is confidential and may be legally privileged. It is solely for use of the individual or entity to whom is addressed and others authorised to receive it. If you are not the intended recipient you are hereby notified that any disclosure, copying, distribution or taking of any action in reliance on the contents of this information is strictly prohibited and may be unlawful. This Message has been scanned for viruses and dangerous content by the NetSys International Mail Scanner and is believed to be clean. -- http://mail.python.org/mailman/listinfo/python-list
Re: Problem with spawning an external process
Daniel, you are correct, it is not that good news for me :) But anyway, thanks to your responses, I installed Python 2.4.3 and it is working on my machine now as well. We were overdue for an upgrade to our Python environment anyways, so I think this is the final incentive to upgrade. Although, I will download 2.3.5 now and get back to you with the status. Would be interesting to know when exactly this problem was fixed, maybe it would help to know what is causing the problem? It really is a strange one. Again, thanks for your effort! On Wed, 2006-04-12 at 12:41, Daniel Nogradi wrote: Daniel, thanks for your input. What version of the JDK/JRE and Python are you using? So the previous test was on python 2.4, java 1.4.2, suse 9.3 but now I ran it on python 2.3.5, java 1.4.2, gentoo 1.4.16 and your code still does what it supposed to do. I'm not sure if that is good new for you though :) -- NetSys International (Pty) Ltd. Tel : +27 12 349 2056 Fax : +27 12 349 2757 Web : http://www.netsys.co.za P.O. Box 35798, Menlo Park, 0102, South Africa The information contained in this communication is confidential and may be legally privileged. It is solely for use of the individual or entity to whom is addressed and others authorised to receive it. If you are not the intended recipient you are hereby notified that any disclosure, copying, distribution or taking of any action in reliance on the contents of this information is strictly prohibited and may be unlawful. This Message has been scanned for viruses and dangerous content by the NetSys International Mail Scanner and is believed to be clean. -- http://mail.python.org/mailman/listinfo/python-list
Re: Problem with spawning an external process
Not working with Python 2.3.5 here on Fedora Core 2 :(. Oh well, at least it's working on 2.4. Must be specific to something in the combination of Fedora Core 2 and Python 2.3.x, that is all I can think of. On Wed, 2006-04-12 at 12:55, Nico Kruger wrote: Daniel, you are correct, it is not that good news for me :) But anyway, thanks to your responses, I installed Python 2.4.3 and it is working on my machine now as well. We were overdue for an upgrade to our Python environment anyways, so I think this is the final incentive to upgrade. Although, I will download 2.3.5 now and get back to you with the status. Would be interesting to know when exactly this problem was fixed, maybe it would help to know what is causing the problem? It really is a strange one. Again, thanks for your effort! -- NetSys International (Pty) Ltd. Tel : +27 12 349 2056 Fax : +27 12 349 2757 Web : http://www.netsys.co.za P.O. Box 35798, Menlo Park, 0102, South Africa The information contained in this communication is confidential and may be legally privileged. It is solely for use of the individual or entity to whom is addressed and others authorised to receive it. If you are not the intended recipient you are hereby notified that any disclosure, copying, distribution or taking of any action in reliance on the contents of this information is strictly prohibited and may be unlawful. This Message has been scanned for viruses and dangerous content by the NetSys International Mail Scanner and is believed to be clean. -- http://mail.python.org/mailman/listinfo/python-list
