On Thu, Dec 13, 2012 at 09:49:43PM -0800, Andy Lutomirski wrote: > This is a serious cause of mmap_sem contention. MAP_POPULATE > and MCL_FUTURE, in particular, are disastrous in multithreaded programs. > > Signed-off-by: Andy Lutomirski <l...@amacapital.net> > --- > > Sensible people use anonymous mappings. I write kernel patches :) > > I'm not entirely thrilled by the aesthetics of this patch. The MAP_POPULATE > case > could also be improved by doing it without any lock at all. This is still a > big > improvement, though.
Wait a minute. get_user_pages() relies on ->mmap_sem being held. Unless I'm seriously misreading your patch it removes that protection. And yes, I'm aware of execve-related exception; it's in special circumstances - bprm->mm is guaranteed to be not shared (and we need to rearchitect that area anyway, but that's a separate story). -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
