From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtprelay0148.hostedemail.com ([216.40.44.148]:52551 "EHLO smtprelay.hostedemail.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1757192AbbESPmJ (ORCPT ); Tue, 19 May 2015 11:42:09 -0400 Date: Tue, 19 May 2015 11:42:01 -0400 From: Steven Rostedt To: Christoph Lameter Cc: Linus Torvalds , LKML , Ingo Molnar , Andrew Morton , stable , Uwe Kleine-Koenig Subject: Re: [GIT PULL] ring-buffer: Replace this_cpu_*() with __this_cpu_*() Message-ID: <20150519114201.39c19d61@gandalf.local.home> In-Reply-To: References: <20150319180216.62c9fa4a@gandalf.local.home> <20150319183444.3d26f078@grimm.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: stable-owner@vger.kernel.org List-ID: On Tue, 19 May 2015 10:35:32 -0500 (CDT) Christoph Lameter wrote: > On Thu, 19 Mar 2015, Steven Rostedt wrote: > > > On Thu, 19 Mar 2015 15:16:25 -0700 > > Linus Torvalds wrote: > > > > > So I don't think the ring-buffer change is necessarily _wrong_, but if > > > this is a performance issue, why don't we just fix it up for the > > > generic case rather than for just one user? > > > > I totally agree with your analysis, but it's up to Christoph to come up > > with an answer to your questions. > > Something beyond: Do not use this_cpu_* when preemption is already > off but use __this_cpu_*? I think the question was, why exactly does the generic this_cpu_read() require disabling preemption? What breaks if it is not disabled? -- Steve