On Thu, Jun 23, 2016 at 10:44 AM, Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> The thread_info->tsk pointer, that was one of the most critical issues
> and the main raison d'être of the thread_info, has been replaced on
> x86 by just using the per-cpu "current_task". Yes,.there are probably
> more than a few "ti->task" users left for legacy reasons, harking back
> to when the thread-info was cheaper to access, but it shouldn't be a
> big deal.

Ugh. Looking around at this, it turns out that a great example of this
kind of legacy issue is the debug_mutex stuff.

It uses "struct thread_info *" as the owner pointer, and there is _no_
existing reason for it. In fact, in every single place it actually
wants the task_struct, and it does task_thread_info(task) just to
convert it to the thread-info, and then converts it back with
"ti->task".

So the attached patch seems to be the right thing to do regardless of
this whole discussion.

                   Linus