Re: [RFC 09/10] x86/mm: Rework lazy TLB to track the actual loaded mm

[Ingo Molnar]

* Thomas Gleixner <t...@linutronix.de> wrote:

> On Wed, 10 May 2017, Ingo Molnar wrote:
> > 
> > * Thomas Gleixner <t...@linutronix.de> wrote:
> > 
> > > On Sun, 7 May 2017, Andy Lutomirski wrote:
> > > >  /* context.lock is held for us, so we don't need any locking. */
> > > >  static void flush_ldt(void *current_mm)
> > > >  {
> > > > +       struct mm_struct *mm = current_mm;
> > > >         mm_context_t *pc;
> > > >  
> > > > -       if (current->active_mm != current_mm)
> > > > +       if (this_cpu_read(cpu_tlbstate.loaded_mm) != current_mm)
> > > 
> > > While functional correct, this really should compare against 'mm'.
> > > 
> > > >                 return;
> > > >  
> > > > -       pc = &current->active_mm->context;
> > > > +       pc = &mm->context;
> > 
> > So this appears to be the function:
> > 
> >  static void flush_ldt(void *current_mm)
> >  {
> >         struct mm_struct *mm = current_mm;
> >         mm_context_t *pc;
> > 
> >         if (this_cpu_read(cpu_tlbstate.loaded_mm) != current_mm)
> >                 return;
> > 
> >         pc = &mm->context;
> >         set_ldt(pc->ldt->entries, pc->ldt->size);
> >  }
> > 
> > why not rename 'current_mm' to 'mm' and remove the 'mm' local variable?
> 
> Because you cannot dereference a void pointer, i.e. &mm->context ....

Indeed, doh! The naming totally confused me. The way I'd write it is the 
canonical 
form for such callbacks:

        static void flush_ldt(void *data)
        {
                struct mm_struct *mm = data;

... which beyond unconfusing me would probably also have prevented any 
accidental 
use of the 'current_mm' callback argument.

Thanks,

        Ingo