Bugs item #1404925, was opened at 2006-01-13 16:05 Message generated for change (Comment added) made by ragnark You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=105470&aid=1404925&group_id=5470
Please note that this message will contain a full copy of the comment thread, including the initial issue submission, for this request, not just the latest update. Category: Threads Group: Python 2.4 Status: Open Resolution: None Priority: 5 Submitted By: Toon Verstraelen (tovrstra) Assigned to: Peter à strand (astrand) Summary: subprocess.Popen inside thread locks the thread in some case Initial Comment: The bug can be verified with the example program attached to this bugs. Two files are attached: my_thread.py and main.py When main.py is executed the thread hangs on subprocess.Popen, while my_thread.py, which is imported by main.py runs without problems. In fact both should do exactly the same since main.py doesn nothing but importing my_thread. My python version: Python 2.4.2 (#1, Oct 17 2005, 09:05:20) [GCC 3.3.6 (Gentoo 3.3.6, ssp-3.3.6-1.0, pie-8.7.8)] on linux2 If any more info is required, ---------------------------------------------------------------------- Comment By: Ragnar Kjørstad (ragnark) Date: 2006-05-19 10:37 Message: Logged In: YES user_id=10550 I too have verified that the testprograms (with an additional sleep) cause a deadlock, and that moving the import statement out of os._execvp solves the problem. However, there is a more generic problem. If fork() is executed while any locks are held by other threads than the one executing fork, it will deadlock the new process. E.g, if you have a process with 2 threads. The first one is doing work that requires locking. This could be imports, but also anything else that uses other locks. The second thread does a fork. If this is accidently done while thread 1 held the lock, it will deadlock if the new process needs the same lock. Now, the most common use of fork is of course to do exec right afterwards, in which case it doesn't really matter, but it's not the only use of fork. See the rationalie in the manpage of pthread_atfork for details. (http://www.opengroup.org/onlinepubs/009695399/functions/pthread_atfork.html) ---------------------------------------------------------------------- Comment By: Yair Chuchem (bigorilla) Date: 2006-05-09 12:30 Message: Logged In: YES user_id=232571 this thread explains why this happens and how to solve it: http://groups.google.com/group/comp.lang.python/browse_thread/thread/5fae8a453c95ae89/42f5c9f9215dbb1e#42f5c9f9215dbb1e I implemented the fix locally at mine: at os.py, _execvpe, first line: remove the "from errno import ...", add a global "import errno" at the start and change stuff imported from errno from "X" to "errno.X" ---------------------------------------------------------------------- Comment By: Ralf Schmitt (titty) Date: 2006-01-13 17:41 Message: Logged In: YES user_id=17929 glibc version 2.3.5. If I add a time.sleep(1) at the end of my_thread.py I can also reproduce this error reliably on ubuntu. ---------------------------------------------------------------------- Comment By: Toon Verstraelen (tovrstra) Date: 2006-01-13 16:58 Message: Logged In: YES user_id=970944 What version of glibc do you have on your ubuntu system? I have glibc-2.3.5-r2, where r2 stands for second patch revision from the gentoo distribution. In my case I can not interrupt 'python main.py'. I have to use ctrl-z and then 'kill %1'. ---------------------------------------------------------------------- Comment By: Ralf Schmitt (titty) Date: 2006-01-13 16:30 Message: Logged In: YES user_id=17929 I cannot reproduce this error on ubuntu linux using python 2.4.2. However, I am able to reproduce it using python 2.4.2 running on FreeBSD 4.11. Stopping the program with ctrl-c results in the following output: [EMAIL PROTECTED]:~/tmp$ python main.py before Popen ^CException in thread Thread-1: Traceback (most recent call last): File "/usr/local/lib/python2.4/threading.py", line 442, in __bootstrap self.run() File "/home/ralf/tmp/my_thread.py", line 7, in run sp = Popen(["ls", "-al"], stdout=PIPE, stderr=STDOUT) File "/usr/local/lib/python2.4/subprocess.py", line 542, in __init__ errread, errwrite) File "/usr/local/lib/python2.4/subprocess.py", line 970, in _execute_child data = os.read(errpipe_read, 1048576) # Exceptions limited to 1 MB OSError: [Errno 4] Interrupted system call Error in atexit._run_exitfuncs: Traceback (most recent call last): File "/usr/local/lib/python2.4/atexit.py", line 24, in _run_exitfuncs func(*targs, **kargs) File "/usr/local/lib/python2.4/threading.py", line 632, in __exitfunc t.join() File "/usr/local/lib/python2.4/threading.py", line 539, in join self.__block.wait() File "/usr/local/lib/python2.4/threading.py", line 203, in wait waiter.acquire() KeyboardInterrupt Error in sys.exitfunc: Traceback (most recent call last): File "/usr/local/lib/python2.4/atexit.py", line 24, in _run_exitfuncs func(*targs, **kargs) File "/usr/local/lib/python2.4/threading.py", line 632, in __exitfunc t.join() File "/usr/local/lib/python2.4/threading.py", line 539, in join self.__block.wait() File "/usr/local/lib/python2.4/threading.py", line 203, in wait waiter.acquire() KeyboardInterrupt [EMAIL PROTECTED]:~/tmp$ ---------------------------------------------------------------------- You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=105470&aid=1404925&group_id=5470 _______________________________________________ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
