[Python-Dev] Issue #10348: concurrent.futures doesn't work on BSD (original) (raw)

Philip Semanchuk philip at semanchuk.com
Wed Dec 29 15:24:07 CET 2010

On Dec 29, 2010, at 8:17 AM, Victor Stinner wrote:

Hi,

FreeBSD 7.2 3.x buildbot is red since some weeks (or months?) because of a concurrent.futures failure. The problem is that testconcurrentfutures uses many (multiprocessing) POSIX semaphores, whereas POSIX semaphores support in FreeBSD is recent and limited. We have to use SysV semaphores (ftok, semget, semop, semctl, ...) instead of POSIX semaphores (semopen, semgetvalue, semunlink, ...). See: * http://bugs.python.org/issue10348 * "Too many open files" errors on "x86 FreeBSD 7.2 3.x" buildbot ^-- thread in python-dev opened last month I would like to know if it should be considered as a release blocker. Georg Brandl said yes on IRC. Does anyone know SysV API? I tried to write a patch, but I never used semaphores (POSIX or SysV). There is a third party module which looks complete and stable: http://semanchuk.com/philip/sysvipc/ It is released under the BSD license. It supports semaphores, but also shared memory and message queues. We don't need all of those, semaphores would be enough. I added its author (Philip Semanchuk) to this thread.

Hi all, What Victor says above is correct, although I wasn't aware that POSIX IPC under FreeBSD 7.2 was still having problems. Prior to 7.2 it was broken but 7.2 worked OK in my limited testing. In any case, the sysv_ipc module is mine and it's mature and you're welcome to pillage it in whole or in part.

I don't know how we should decide to use POSIX or SysV semaphores. It looks like SysV is preferred on FreeBSD and Darwin (and maybe all BSD based OSes), and POSIX is preferred on Linux.

Hmmm, "preferred" is a tricky word here. I would phrase it slightly differently: POSIX IPC is preferred everywhere (by me, at least) because it's a more modern API. However, SysV IPC is fully supported everywhere while the same can't be said about POSIX IPC.

Speaking of POSIX IPC, I also have a posix_ipc module that's quite similar to sysv_ipc and the platform notes in the documentation tell one what support to expect for POSIX IPC under various platforms: http://semanchuk.com/philip/posix_ipc/#platforms

Cheers Philip

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