From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1752979AbbCQSAV (ORCPT <rfc822;w@1wt.eu>);
	Tue, 17 Mar 2015 14:00:21 -0400
Received: from relay4-d.mail.gandi.net ([217.70.183.196]:50745 "EHLO
	relay4-d.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1752529AbbCQSAT (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Tue, 17 Mar 2015 14:00:19 -0400
Date: Tue, 17 Mar 2015 11:00:14 -0700
From: josh@joshtriplett.org
To: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: linux-kernel@vger.kernel.org,
        "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
        KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Nicholas Miell <nmiell@comcast.net>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Ingo Molnar <mingo@redhat.com>, Alan Cox <gnomes@lxorguk.ukuu.org.uk>,
        Lai Jiangshan <laijs@cn.fujitsu.com>,
        Stephen Hemminger <stephen@networkplumber.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Peter Zijlstra <peterz@infradead.org>,
        David Howells <dhowells@redhat.com>
Subject: Re: [RFC PATCH v13] sys_membarrier(): system/process-wide memory
 barrier (x86)
Message-ID: <20150317180014.GC4141@cloud>
References: <1426612922-3308-1-git-send-email-mathieu.desnoyers@efficios.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <1426612922-3308-1-git-send-email-mathieu.desnoyers@efficios.com>
User-Agent: Mutt/1.5.20 (2009-06-14)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Tue, Mar 17, 2015 at 01:22:02PM -0400, Mathieu Desnoyers wrote:
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -1568,6 +1568,15 @@ config PCI_QUIRKS
>  	  bugs/quirks. Disable this only if your target machine is
>  	  unaffected by PCI quirks.
>  
> +config MEMBARRIER
> +	bool "Enable membarrier() system call" if EXPERT
> +	default y
> +	help
> +	  Enable the membarrier() system call that allows issuing
> +	  memory barriers across cores.

Nit: CPUs, not cores.  Nothing here is specific to
packages/cores/threads.

> --- a/kernel/rcu/update.c
> +++ b/kernel/rcu/update.c
> @@ -49,6 +49,8 @@
>  #include <linux/module.h>
>  #include <linux/kthread.h>
>  #include <linux/tick.h>
> +#include <linux/syscalls.h>
> +#include <linux/membarrier.h>
>  
>  #define CREATE_TRACE_POINTS
>  
> @@ -775,3 +777,73 @@ late_initcall(rcu_verify_early_boot_tests);
>  #else
>  void rcu_early_boot_tests(void) {}
>  #endif /* CONFIG_PROVE_RCU */
> +
> +#ifdef CONFIG_MEMBARRIER

As mentioned in my previous mail, please consider moving this to its own
file, if it doesn't use any of the internals of kernel/rcu/update.c
(which I don't think it does).  That then means you can enable/disable
the entire file in the Makefile rather than using an #ifdef in the .c
file.

- Josh Triplett