[issue8865] select.poll is not thread safe
Changes by Serhiy Storchaka storch...@gmail.com: -- assignee: gregory.p.smith - serhiy.storchaka versions: -Python 3.2 ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue8865 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue8865] select.poll is not thread safe
Roundup Robot added the comment: New changeset 072ba5df77e4 by Serhiy Storchaka in branch '3.3': Issue #8865: Concurrent invocation of select.poll.poll() now raises a http://hg.python.org/cpython/rev/072ba5df77e4 New changeset 4543408e2ba6 by Serhiy Storchaka in branch 'default': Issue #8865: Concurrent invocation of select.poll.poll() now raises a http://hg.python.org/cpython/rev/4543408e2ba6 New changeset a4091c1de27a by Serhiy Storchaka in branch '2.7': Issue #8865: Concurrent invocation of select.poll.poll() now raises a http://hg.python.org/cpython/rev/a4091c1de27a -- nosy: +python-dev ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue8865 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue8865] select.poll is not thread safe
Serhiy Storchaka added the comment: Thank you for the report and the patch Christian. -- resolution: - fixed stage: commit review - committed/rejected status: open - closed ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue8865 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue8865] select.poll is not thread safe
Serhiy Storchaka added the comment: Gregory, could you commit the patch or allow me to do this? -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue8865 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue8865] select.poll is not thread safe
Changes by STINNER Victor victor.stin...@gmail.com: -- nosy: +haypo ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue8865 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue8865] select.poll is not thread safe
Serhiy Storchaka added the comment: Gregory? -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue8865 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue8865] select.poll is not thread safe
Serhiy Storchaka added the comment: Ping. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue8865 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue8865] select.poll is not thread safe
Antoine Pitrou added the comment: Patches look good to me. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue8865 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue8865] select.poll is not thread safe
Serhiy Storchaka added the comment: Here is a test made from Charles-François's crasher. Let's go. -- Added file: http://bugs.python.org/file28855/issue8865_test.patch ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue8865 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue8865] select.poll is not thread safe
Changes by Serhiy Storchaka storch...@gmail.com: -- stage: test needed - commit review ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue8865 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue8865] select.poll is not thread safe
Charles-François Natali added the comment: This patch should be updated to also fix epoll(). Also, is it right to raise an exception in case of concurrent invocation? Here's a simple script that crashes systematically on my Linux box. -- nosy: +neologix Added file: http://bugs.python.org/file28687/test.py ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue8865 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue8865] select.poll is not thread safe
Serhiy Storchaka added the comment: Also, is it right to raise an exception in case of concurrent invocation? It is right for poll() because it was not concurrently usable in previous versions in any case. For epoll() it is an another issue. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue8865 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue8865] select.poll is not thread safe
Changes by Andrew Svetlov andrew.svet...@gmail.com: -- nosy: +asvetlov ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue8865 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue8865] select.poll is not thread safe
Serhiy Storchaka added the comment: Test should check changed behavior. I.e. it should test that calling poll concurrently raises an exception. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue8865 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue8865] select.poll is not thread safe
Serhiy Storchaka added the comment: As I see, Christian's contributor agreement already confirmed. Let's go ahead. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue8865 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue8865] select.poll is not thread safe
Serhiy Storchaka added the comment: Christian, it would be nice if you write the tests. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue8865 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue8865] select.poll is not thread safe
Christian Schubert added the comment: What's a proper test for this? Testing, that the (now expected) exception occurs when invoking poll concurrently? Or rather, that the race condition does not occur? Last time I checked, pypy handled the concurrent poll invocation well, so it would fail both tests. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue8865 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue8865] select.poll is not thread safe
Christian Schubert added the comment: Would you please submit a PSF contributor agreement form? FYI: did that yesterday 9:43 UTC, no reaction (yet) -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue8865 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue8865] select.poll is not thread safe
Antoine Pitrou added the comment: Would you please submit a PSF contributor agreement form? FYI: did that yesterday 9:43 UTC, no reaction (yet) Don't worry, it can take some time to process. We can still apply your patch, though, since you said you sent a contributor agreement. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue8865 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue8865] select.poll is not thread safe
Christian Schubert added the comment: new proposed fix: forbid concurrent poll() invocation -- Added file: http://bugs.python.org/file27967/issue8865_v2.diff ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue8865 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue8865] select.poll is not thread safe
Serhiy Storchaka added the comment: The patch LGTM. I doubt about the exception type. May be RuntimeError is more appropriate? -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue8865 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue8865] select.poll is not thread safe
Christian Schubert added the comment: I doubt about the exception type. May be RuntimeError is more appropriate? mea culpa, just copypasted without actually looking; fixed in v3 -- Added file: http://bugs.python.org/file27968/issue8865_v3.diff ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue8865 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue8865] select.poll is not thread safe
Changes by Antoine Pitrou pit...@free.fr: -- nosy: +serhiy.storchaka ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue8865 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue8865] select.poll is not thread safe
Serhiy Storchaka added the comment: I was unable to apply the patch automatically, so I had to do it manually. Here is an updated patch for review. I did not consider it in detail yet, but it seems to correct these errors. -- type: behavior - crash versions: +Python 3.3, Python 3.4 -Python 2.6, Python 3.1 Added file: http://bugs.python.org/file27961/select_concurrent_poll.patch ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue8865 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue8865] select.poll is not thread safe
Gregory P. Smith added the comment: i'm looking at getting this in. -- assignee: - gregory.p.smith ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue8865 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue8865] select.poll is not thread safe
Gregory P. Smith added the comment: Christian Schubert (apexo) - Would you please submit a PSF contributor agreement form? http://www.python.org/psf/contrib/ http://www.python.org/psf/contrib/contrib-form-python/ thanks! -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue8865 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue8865] select.poll is not thread safe
Serhiy Storchaka added the comment: In general the patch looks good to me. I only get rid of non-needed macros. -- stage: - test needed Added file: http://bugs.python.org/file27963/select_concurrent_poll.patch ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue8865 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue8865] select.poll is not thread safe
Gregory P. Smith added the comment: here's an updated patch. it strikes me that this should not be a very common problem. how many applications are going to share the same poll object _across_ multiple threads? if they do and the file descriptor they'll be spending a lot of time mallocing and freeing new pollfd ufds arrays in each thread as a result as they all fight for ownership of the pollObject's ufds. -- Added file: http://bugs.python.org/file27964/issue8865-poll-multithread-gps01.diff ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue8865 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue8865] select.poll is not thread safe
Gregory P. Smith added the comment: our patches are similar. i updated it to use long long and Py_ssize_t and Py_CLEAR and Py_RETURN_NONE in a few places and added comments. getting rid of the CLEAR_UFDS macro as you did is a good idea. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue8865 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue8865] select.poll is not thread safe
Antoine Pitrou added the comment: it strikes me that this should not be a very common problem. how many applications are going to share the same poll object _across_ multiple threads? Indeed that doesn't sound very likely. How about raising an error on concurrent modification, instead of trying to make it thread-safe? -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue8865 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue8865] select.poll is not thread safe
Christian Schubert added the comment: How about raising an error on concurrent modification, instead of trying to make it thread-safe? That's totally fine with me. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue8865 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue8865] select.poll is not thread safe
Changes by Gregory P. Smith g...@krypto.org: -- assignee: gregory.p.smith - ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue8865 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue8865] select.poll is not thread safe
Changes by Gregory P. Smith g...@krypto.org: -- assignee: - gregory.p.smith nosy: +gregory.p.smith ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue8865 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue8865] select.poll is not thread safe
Christian Schubert b...@apexo.de added the comment: added a patch which fixes both issues before releasing the GIL we take a copy of the ufds pointer and its len, erasing the ufds pointer in the poll object (to make sure nobody else fiddles with it); when we're done we either but it back into the object (when it's still NULL) or we free it the update logic is modified as well, since the uptodate flag is not sufficient anymore, we now count up a tag for each modification of the poll dictionary and remember that tag together with the ufds pointer the result is: - for the single-threaded case we do little extra work (moving ufds from/to poll object) - correct for the multi-threaded case, with slightly higher overhead (one additional call to each of malloc, update_ufd_array, free), probably worse than having one poll object per thread, but not worse than allocating a new poll object each time we want to poll there still is potential for incorrect poll results (but not for memory corruption): when poll_register/poll_unregister are called exactly 2**32 times (or multiples thereof) while poll_poll is running, it will happily put back its outdated ufds pointer into the poll object when its done, this could be alleviated by changing tag to long long ... which is unlikely to wrap around anytime soon. -- keywords: +patch Added file: http://bugs.python.org/file17675/select.patch ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue8865 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue8865] select.poll is not thread safe
Changes by Antoine Pitrou pit...@free.fr: -- nosy: +exarkun ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue8865 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue8865] select.poll is not thread safe
Changes by Éric Araujo mer...@netwok.org: -- nosy: -d...@python ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue8865 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue8865] select.poll is not thread safe
Christian Schubert b...@apexo.de added the comment: okay, I've managed to put together a script that fairly consistently reproduces the problem on my (core2 duo 2,something GHz) machine some parameters (sleep times) are randomized in each iteration, the script runs for 30 iterations, each for 1 second, and counts the number of events where the fd looks bogus (max 1 per iteration); some other events (fd correct, revents bogus are also reported, but not counted) example output: poll returned [(-3, 65535)], we were looking for fd 3 poll returned [(-3, 65535)], we were looking for fd 3 poll returned [(-3, 65535)], we were looking for fd 3 poll returned [(-3, 65535)], we were looking for fd 3 poll returned [(-3, 65535)], we were looking for fd 3 poll returned [(-1, 65535)], we were looking for fd 3 poll returned [(-1, 65535)], we were looking for fd 3 poll returned [(-1627358347, 60497)], we were looking for fd 3 should not get here; poll returned [(3, 0)] poll returned [(-3, 65535)], we were looking for fd 3 9 events in 30 iterations -- Added file: http://bugs.python.org/file17510/select_threads.py ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue8865 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue8865] select.poll is not thread safe
Christian Schubert b...@apexo.de added the comment: the other issue (poll_register freeing data structures that poll_poll currently uses) can be reproduced by the attached script (at least I can) depending on the parameters/circumstances it either segfaults or prints garbage results from poll, e.g. [(1684955474, 28192)]; the expected result would be [(3, 1)] -- Added file: http://bugs.python.org/file17511/concurrent_poll_and_register.py ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue8865 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue8865] select.poll is not thread safe
New submission from Christian Schubert b...@apexo.de: invoking select.poll.poll() concurrently from multiple threads frequently yields garbage in one thread: while poll_poll in thread 1 is parsing its result, another thread 2 calling poll may overwrite revents; assuming poll_result was 1 in thread 1 and thread 2 managed to clear all revents before thread 1 started scanning ufds, thread 1 would iterate straight through all ufds, past its bounds (no bound checks there), and return the first out-of-bounds entry that happens to have revents != 0 this issue needs at least documentation (although bounds-checking to prevent garbage in the result wouldn't hurt) also, since there doesn't seem to be any locking w/ regards to ufds, it might be possible to corrupt python's heap, by concurrently invoking poll_register and poll_poll. poll_register could move the ufds array to another location while resizing it and poll_poll would subsequently overwrite memory that is not allocated anymore or allocated by someone else (did not test that) python 2.5.5 -- assignee: d...@python components: Documentation, Library (Lib) messages: 106815 nosy: apexo, d...@python priority: normal severity: normal status: open title: select.poll is not thread safe type: behavior versions: Python 2.5 ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue8865 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue8865] select.poll is not thread safe
Antoine Pitrou pit...@free.fr added the comment: Do you have a script that reproduces it? -- assignee: d...@python - components: -Documentation nosy: +pitrou versions: +Python 2.6, Python 2.7, Python 3.1, Python 3.2 -Python 2.5 ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue8865 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
