Re: [RFC PATCH v3 4/7] powerpc: regain entire stack space

[Christophe LEROY]

Le 03/10/2018 Ã 08:30, Nicholas Piggin a ÃcritÂ:
> On Wed, 3 Oct 2018 07:52:59 +0200
> Christophe LEROY <christophe.leroy@xxxxxx> wrote:
>
> > Le 03/10/2018 Ã 07:34, Nicholas Piggin a ÃcritÂ:
> > > On Mon,  1 Oct 2018 12:30:25 +0000 (UTC)
> > > Christophe Leroy <christophe.leroy@xxxxxx> wrote:
> > >    
> > > > thread_info is not anymore in the stack, so the entire stack
> > > > can now be used.
> > >
> > > Nice.
> > >    
> > > > In the meantime, all pointers to the stacks are not anymore
> > > > pointers to thread_info so this patch changes them to void*
> > >
> > > Wasn't this previously effectively already the case with patch
> > > 3/7? You had thread_info sized space left there, but it was not
> > > used or initialized right? Does it make sense to move this part
> > > of it to the previous patch?
> >
> > Not really.
> >
> > In 3/7 I changed the prototypes of two functions that really used the
> > pointer as a task pointer only.

I meant 2/7 here sorry.

> > Here it change things that before 4/7 were really used as both stack
> > pointers and thread_info pointers.

And here I meant 3/7

> What uses it as a thread_info pointer? It seems more like a stack
> with some amount of unused space in it but that's all.

Before 3/7, we have

void do_softirq_own_stack(void)
{
	struct thread_info *curtp, *irqtp;

	curtp = current_thread_info();
	irqtp = softirq_ctx[smp_processor_id()];
	irqtp->task = curtp->task;
	irqtp->flags = 0;
	call_do_softirq(irqtp);
	irqtp->task = NULL;

	/* Set any flag that may have been set on the
	 * alternate stack
	 */
	if (irqtp->flags)
		set_bits(irqtp->flags, &curtp->flags);
}

After 3/7, we have

 void do_softirq_own_stack(void)
 {
	struct thread_info *irqtp;

 	irqtp = softirq_ctx[smp_processor_id()];
 	call_do_softirq(irqtp);
 }


So now only we can change irqtp to void* can't we ?

> That said I don't care to nitpick too much where things go exactly
> if you like it better here that's fine.

No worry, I may have missed something, your comments are always welcome.

Thanks
Christophe

> Thanks,
> Nick