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SubjectRe: [patch/rfc] eventfd semaphore-like behavior
On Thu, 5 Feb 2009 12:59:07 +1300
Michael Kerrisk <mtk.manpages@googlemail.com> 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.


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