From mboxrd@z Thu Jan  1 00:00:00 1970
From: Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH v3 00/13] Virtually mapped stacks with guard pages (x86,
 core)
Date: Thu, 23 Jun 2016 20:55:56 +0200
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To: Oleg Nesterov <oleg@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>, Andy Lutomirski <luto@amacapital.net>, Andy Lutomirski <luto@kernel.org>, the arch/x86 maintainers <x86@kernel.org>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, "linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>, Borislav Petkov <bp@alien8.de>, Nadav Amit <nadav.amit@gmail.com>, Kees Cook <keescook@chromium.org>, Brian Gerst <brgerst@gmail.com>, "kernel-hardening@lists.openwall.com" <kernel-hardening@lists.openwall.com>, Josh Poimboeuf <jpoimboe@redhat.com>, Jann Horn <jann@thejh.net>, Heiko Carstens <heiko.carstens@de.ibm.com>

On Thu, Jun 23, 2016 at 08:12:16PM +0200, Oleg Nesterov wrote:
> 
> And probably kill task_struct->blocked_on? I do not see the point of
> this task->blocked_on != waiter check.

I think that came about because of PI and or deadlock detection. Of
course, the current mutex code doesn't have anything like that these
days, and rt_mutex has task_struct::pi_blocked_on.