On Wed, 4 Feb 2009 16:25:52 -0800 (PST) Davide Libenzi <[email protected]> wrote:
> On Wed, 4 Feb 2009, Andrew Morton wrote: > > > On Thu, 5 Feb 2009 12:59:07 +1300 > > Michael Kerrisk <[email protected]> wrote: > > > > > >> > > > What should be userspace's fallback strategy if that support is > > > >> > > > not > > > >> > > > present? > > > >> > > > > > >> > > #ifdef EFD_SEMAPHORE, maybe? > > > >> > > > > >> > That's compile-time. People who ship binaries will probably want > > > >> > to find a runtime thing for back-compatibility. > > > >> > > > >> I dunno. How do they actually do when we add new flags, like the O_ > > > >> ones? > > > >> > > > > > > > > Dunno. Probably try the syscall and see if it returned -EINVAL. Does > > > > that work in this case? > > > > > > As youll have seen by now, Ulrich and I noted that it works. > > > > I think you means "should work" ;) > > > > We're talking about this, yes? > > > > SYSCALL_DEFINE2(eventfd2, unsigned int, count, int, flags) > > { > > int fd; > > struct eventfd_ctx *ctx; > > > > /* Check the EFD_* constants for consistency. */ > > BUILD_BUG_ON(EFD_CLOEXEC != O_CLOEXEC); > > BUILD_BUG_ON(EFD_NONBLOCK != O_NONBLOCK); > > > > if (flags & ~(EFD_CLOEXEC | EFD_NONBLOCK)) > > return -EINVAL; > > > > That looks like it should work to me. > > I lost you guys. On old kernels you'd get -EINVAL when using the new flag. > Wasn't it clear? Or is there some side-band traffic in this conversation > that I missed? :) > Well yes, that. What I was trying to establish here is that we have thought about (and preferably tested) userspace's back-compatibility arrangements. We have now done that. -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
