From mboxrd@z Thu Jan  1 00:00:00 1970
From: Florian Weimer <fweimer-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Subject: Re: [RFC PATCH v6 1/5] Thread-local ABI system call: cache CPU number
 of running thread
Date: Thu, 7 Apr 2016 18:50:20 +0200
Message-ID: <57068FCC.8000701@redhat.com>
References: <1459789313-4917-1-git-send-email-mathieu.desnoyers@efficios.com>
 <1459789313-4917-2-git-send-email-mathieu.desnoyers@efficios.com>
 <5702A037.60200@zytor.com>
 <492303698.44994.1459799188052.JavaMail.zimbra@efficios.com>
 <856357054.45028.1459802903401.JavaMail.zimbra@efficios.com>
 <5703E191.2040707@redhat.com>
 <20160405164722.GB3430@twins.programming.kicks-ass.net>
 <570621E5.7060306@redhat.com>
 <20160407103158.GP3430@twins.programming.kicks-ass.net>
 <570638D9.7010108@redhat.com>
 <20160407111938.GR3430@twins.programming.kicks-ass.net>
 <CA+55aFxrWx5pFN3LseaKpUHtB6nqXtkgP84seU3pjys-kq7utQ@mail.gmail.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 7bit
Return-path: <linux-api-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>
In-Reply-To: <CA+55aFxrWx5pFN3LseaKpUHtB6nqXtkgP84seU3pjys-kq7utQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
Sender: linux-api-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
To: Linus Torvalds <torvalds-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>, Peter Zijlstra <peterz-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers-vg+e7yoeK/dWk0Htik3J/w@public.gmane.org>, "H. Peter Anvin" <hpa-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org>, Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>, Russell King <linux-lFZ/pmaqli7XmaaqVzeoHQ@public.gmane.org>, Thomas Gleixner <tglx-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org>, Ingo Molnar <mingo-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, Linux Kernel Mailing List <linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, linux-api <linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, Paul Turner <pjt-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>, Andrew Hunter <ahh-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>, Andy Lutomirski <luto-kltTT9wpgjJwATOyAt5JVQ@public.gmane.org>, Andi Kleen <andi-Vw/NltI1exuRpAAqCnN02g@public.gmane.org>, Dave Watson <davejwatson-b10kYP2dOMg@public.gmane.org>, Chris Lameter <cl-vYTEC60ixJUAvxtiuMwx3w@public.gmane.org>, Ben Maurer <bmaurer-b10kYP2dOMg@public.gmane.org>, rostedt <rostedt-nx8X9YLhiw1AfugRpC6u6w@public.gmane.org>, "Paul E. McKenney" <paulmck-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>, Josh Triplett <josh-iaAMLnmF4UmaiuxdJuQwMA@public.gmane.org>, Catalin Marinas <catalin.marinas-5wv7dgnIgG8@public.gmane.org>, Will Deacon <will.deacon-5wv7dgnIgG8@public.gmane.org>, Michael Kerrisk <mtk.manpages-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>, Boqun Feng <boqun.feng-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
List-Id: linux-api@vger.kernel.org

On 04/07/2016 06:39 PM, Linus Torvalds wrote:

> Can anybody give a *coherent* and actual *real* reason why the kernel
> would ever care about anything else?

We already have a similar per-thread data structure, the robust mutex
list.  The CPU ID is another one.  So it's conceivable we might get
further such fields in the future.

(AFAICS set_robust_list was designed with such extensions in mind.)

Florian