On Thu, Feb 5, 2009 at 1:18 PM, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote:
> On Thu, 5 Feb 2009 12:59:07 +1300
> Michael Kerrisk <mtk.manpages@xxxxxxxxxxxxxx> 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.
Yes, that's what we're talking about, plus a similar check that Ulrih
added in the case that glibc's eventfd() falls back to sy_event().
Cheers,
Michael
--
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
git://git.kernel.org/pub/scm/docs/man-pages/man-pages.git
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