On Tue, 2024-09-03 at 18:14 +0300, Andy Shevchenko wrote:
> 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.
>
This is intended to be an inner block scope within the function, it
does not expand the critical section.
> > ...
> > 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.
>
