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Date: Thu, 23 Jun 2016 10:52:58 -0700
From: Linus Torvalds <>
To: Oleg Nesterov <>, Peter Zijlstra <>
Cc: Andy Lutomirski <>, Andy Lutomirski <>, 
	"the arch/x86 maintainers" <>, Linux Kernel Mailing List <>, 
	"" <>, Borislav Petkov <>, 
	Nadav Amit <>, Kees Cook <>, 
	Brian Gerst <>, 
	"" <>, Josh Poimboeuf <>, 
	Jann Horn <>, Heiko Carstens <>
Subject: Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86, core)

On Thu, Jun 23, 2016 at 10:44 AM, Linus Torvalds
<> wrote:
> The thread_info->tsk pointer, that was one of the most critical issues
> and the main raison d'ĂȘtre 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

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


View attachment "patch.diff" of type "text/plain" (3823 bytes)

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