John Baldwin wrote: > On Monday 01 June 2009 5:17:48 pm Bruce Simpson wrote: >> Jilles Tjoelker wrote: >>> If process-shared semaphores really work, then the above structure is >>> not a pathological case. Effectively, sem_t is carved in stone. So >>> process-private semaphores should continue to have most of their stuff >>> in a separately allocated structure, to preserve flexibility. >>> >> There was an inadvertent race in FreeBSD's POSIX semaphores which I >> fixed in HEAD and STABLE about 6 weeks before 7.2 was released. >> >> I believe process-shared POSIX semaphores now work -- the Python >> 'multiprocessing' regression test now runs to completion with no errors >> on both HEAD and STABLE. > > The semaphores in recent 7 and 8 are definitely not process-shared (at least > not intentionally). They may work across a fork accidentally, but you can't > store it in an mmap() region and share it with an arbitrary process. >
On a completely unrelated subject I was reading about PHP APC cache where they have the same need - cross-process locking with locks embedded in data structures and they have adopted userland spinlock code from PostgreSQL: http://www.scribd.com/doc/3288293/brian-shireapc-facebook (spin)locks are not the same as sempahores but maybe it will help the OP or anyone else trying to implement this feature: http://cvs.php.net/viewvc.cgi/pecl/apc/pgsql_s_lock.h?revision=3.4&view=markup http://cvs.php.net/viewvc.cgi/pecl/apc/pgsql_s_lock.c?revision=3.3&view=markup _______________________________________________ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to "freebsd-stable-unsubscr...@freebsd.org"
