Re: [RFCv2 03/10] x86: Introduce userspace API to handle per-thread features

Edgecombe, Rick P
2022-05-14T03:00:42Z

On Sat, 2022-05-14 at 02:09 +0300, Kirill A. Shutemov wrote:
> On Fri, May 13, 2022 at 05:34:12PM +0000, Edgecombe, Rick P wrote:
> > On Fri, 2022-05-13 at 16:09 +0200, Alexander Potapenko wrote:
> > > > +
> > > > + /* Handle ARCH_THREAD_FEATURE_ENABLE */
> > > > +
> > > > + task->thread.features |= features;
> > > > +out:
> > > > + return task->thread.features;
> > >
> > > Isn't arch_prctl() supposed to return 0 on success?
> >
> > Hmm, good point. Maybe we'll need a struct to pass info in and out.
>
> But values >0 are unused. I don't see why can't we use them.

Hmm, I don't know what it would break since it is a new "code"
argument. But the man page says:
"On success, arch_prctl() returns 0; on error, -1 is returned, and
errno is set to indicate the error."

So just change the man pages?
"On success, arch_prctl() returns positive values; on error, -1 is
returned, and errno is set to indicate the error."