New submission from David Decotigny <[EMAIL PROTECTED]>: With the attached script, then demo() called with for example datasize=40*1024*1024 and timeout=1 will deadlock: the program never terminates.
The bug appears on Linux (RHEL4) / intel x86 with "multiprocessing" coming with python 2.6b3 and I think it can be easily reproduced on other Unices. It also appears with python 2.5 and the standalone processing package 0.52 (https://developer.berlios.de/bugs/?func=detailbug&bug_id=14453&group_id=9001). After a quick investigation, it seems to be a deadlock between waitpid in the parent process, and a pipe::send in the "_feed" thread of the child process. Indeed, the problem seems to be that "_feed" is still sending data (the data is laaarge) to the pipe while the parent process already called waitpid (because of the "short" timeout): the pipe fills up because no consumer is eating the data (consumer already in waitpid) and hence the "_feed" thread in the child blocks forever. Since the child process does a _feed.join() before exiting (after function f), it never exits. And hence the waitpid in the parent process never returns because the child never exits. This doesn't happen anymore if I use timeout=None or a larger timeout (eg. 10 seconds). Because in both cases, waitpid is called /after/ the "_feed" thread in the child process could send all of its data through the pipe. ---------- components: Library (Lib) files: c.py messages: 72640 nosy: DavidDecotigny severity: normal status: open title: multiprocessing deadlocks when sending large data through Queue with timeout versions: Python 2.6 Added file: http://bugs.python.org/file11401/c.py _______________________________________ Python tracker <[EMAIL PROTECTED]> <http://bugs.python.org/issue3789> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
