Nick Coghlan added the comment: Proposed wording for a warning pointing that threads and imports can get you in trouble. It might be better to squirrel off into a new subsection on threaded imports, rather than giving it too much prominence (since the recommended approach to creating subthreads should 'just work' - it's only daemon threads and using the thread module directly that can get you in trouble):
"""While the import machinery is thread safe, there are two key restrictions on threaded imports due to inherent limitations in the way that thread safety is provided. Firstly, other than in the main module, an import should not have the side effect of spawning a new thread and then waiting for that thread in any way. Failing to abide by this restriction can lead to a deadlock if the spawned thread directly or indirectly attempts to import a module. Secondly, all import attempts must be completed before the interpreter starts shutting itself down. This can be most easily achieved by only performing imports from non-daemon threads created through the threading module. Daemon threads and threads created directly with the thread module will require some other form of synchronization to ensure they do not attempt imports after system shutdown has commenced. Failure to abide by this restriction will lead to intermittent exceptions and crashes during interpreter shutdown (as the late imports attempt to access machinery which is no longer in a valid state).""" (If we were going to actually change anything in the code, it would be to ensure that breaking the second restriction could only lead to exceptions rather than crashes - I suspect that would be pretty messy though, as there are a bunch of PyImport_* calls that currently can't fail that would start having to be checked for error returns) _____________________________________ Tracker <[EMAIL PROTECTED]> <http://bugs.python.org/issue1720705> _____________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
