Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751297AbbEYUVB (ORCPT ); Mon, 25 May 2015 16:21:01 -0400 Received: from mail.efficios.com ([78.47.125.74]:60983 "EHLO mail.efficios.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750837AbbEYUU6 (ORCPT ); Mon, 25 May 2015 16:20:58 -0400 Date: Mon, 25 May 2015 20:21:02 +0000 (UTC) From: Mathieu Desnoyers To: Linus Torvalds Cc: Paul Turner , Andrew Hunter , Ben Maurer , Linux Kernel Mailing List , Peter Zijlstra , Ingo Molnar , Steven Rostedt , "Paul E. McKenney" , Josh Triplett , Lai Jiangshan , Andrew Morton Message-ID: <1331844166.7646.1432585262356.JavaMail.zimbra@efficios.com> In-Reply-To: References: <1432219487-13364-1-git-send-email-mathieu.desnoyers@efficios.com> Subject: Re: [RFC PATCH] percpu system call: fast userspace percpu critical sections MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-Originating-IP: [192.222.194.238] X-Mailer: Zimbra 8.0.7_GA_6021 (ZimbraWebClient - FF38 (Linux)/8.0.7_GA_6021) Thread-Topic: percpu system call: fast userspace percpu critical sections Thread-Index: ZN96vP6ddpf1kokQNuxf8qPAvDl2jA== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1323 Lines: 39 ----- Original Message ----- > On Thu, May 21, 2015 at 7:44 AM, Mathieu Desnoyers wrote: > > Expose a new system call allowing userspace threads to register > > a TLS area used as an ABI between the kernel and userspace to > > share information required to create efficient per-cpu critical > > sections in user-space. > > Not a way in hell. > > You do user accesses from preempt notifiers. > > That's so ludicrously broken that it's not even funny. > > This patch needs to die, and never *ever* be resurrected. Put a stake > in it, and bury it 6ft deep. There is no need to fetch your vampire hunting kit just yet. ;-) As an RFC patch, this should be considered as a prototype, nothing more. I was mainly expecting feedback on the general approach, and trying to put some pressure on Paul Turner, so he would post the patches he talked about back in 2013. Peter Zijlstra already pointed out that I should move those user accesses before return to userspace. Thanks, Mathieu -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/