On Tue, Sep 03, 2024 at 05:00:51PM +0200, Gergo Koteles wrote:
> On Thu, 2024-08-29 at 19:50 +0300, Andy Shevchenko wrote:
> > First of all, it's a bit counterintuitive to have something like
> >
> > int err;
> > ...
> > scoped_guard(...)
> > err = foo(...);
> > if (err)
> > return err;
> >
> > Second, with a particular kernel configuration and compiler version in
> > one of such cases the objtool is not happy:
> >
> > ideapad-laptop.o: warning: objtool: .text.fan_mode_show: unexpected end of section
> >
> > I'm not an expert on all this, but the theory is that compiler and
> > linker in this case can't understand that 'result' variable will be
> > always initialized as long as no error has been returned. Assigning
> > 'result' to a dummy value helps with this. Note, that fixing the
> > scoped_guard() scope (as per above) does not make issue gone.
> >
> > That said, assign dummy value and make the scope_guard() clear of its scope.
> > For the sake of consistency do it in the entire file.
> >
>
> Interestingly, if I open a scope manually and use the plain guard, the
> warning disappears.
Yes, that's what I also have, but I avoid that approach because in that case
the printing will be done inside the lock, widening the critical section for
no benefits.
> ...
> unsigned long result;
> int err;
>
> {
> guard(mutex)(&priv->vpc_mutex);
> err = read_ec_data(priv->adev->handle, VPCCMD_R_FAN,
> &result);
> if (err)
> return err;
> }
> ...
>
> This looks a bit strange, but is probably easier for the compiler than
> the for loop of scoped_guard.
>
> But I don't know how well this style fits into the kernel.
--
With Best Regards,
Andy Shevchenko
