Re: [PATCH 2/2] lockdep: check that no locks held at freeze time

[Peter Zijlstra <a.p.zijlstra@chello.nl>]

On Mon, May 06, 2013 at 07:33:28AM -0700, Linus Torvalds wrote:
> On Mon, May 6, 2013 at 1:55 AM, Peter Zijlstra <a.p.zijlstra@chello.nl> wrote:
> >
> > Doesn't i386 have all the funny per-cpu stuff too? So the only reason it still
> > does the fugly stack based thing is because nobody could be arsed to do the
> > work of converting it.
> 
> Umm. That "fugly stack-based" thing is better than the per-cpu crap.
> 
> The percpu stuff implies a memory load. The stack based thing gets
> thread_info with pure register accesses. Much better.
> 
> For "current()" the per-cpu thing may be better, but if you actually
> need the thread-info (not the case here, but in other places), the
> stack masking is superior when it works (ie when you don't have
> multi-stack issues due to irq's etc)

But you can do both right? Use per-cpu for current and stack frobbery for
current_thread_info().

That said, ISTR some risky bits where the stack frobbery went awry due to
irq-stacks which is the source for my feelings towards the stack frobbery.

That and of course that i386 and x86-64 behave differently for no apparent
reason.