From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758574AbeD0P5h (ORCPT ); Fri, 27 Apr 2018 11:57:37 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:36724 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1758290AbeD0P5f (ORCPT ); Fri, 27 Apr 2018 11:57:35 -0400 Date: Fri, 27 Apr 2018 08:58:46 -0700 From: "Paul E. McKenney" To: Steven Rostedt Cc: Mathieu Desnoyers , Joel Fernandes , linux-kernel , Peter Zijlstra , Ingo Molnar , Tom Zanussi , Namhyung Kim , Thomas Gleixner , Boqun Feng , fweisbec , Randy Dunlap , Masami Hiramatsu , kbuild test robot , baohong liu , vedang patel , kernel-team@android.com Subject: Re: [PATCH RFC] tracepoint: Introduce tracepoint callbacks executing with preempt on Reply-To: paulmck@linux.vnet.ibm.com References: <20180427042656.190746-1-joelaf@google.com> <1169911546.5820.1524839189395.JavaMail.zimbra@efficios.com> <20180427104747.2d965925@gandalf.local.home> <20180427153826.GK26088@linux.vnet.ibm.com> <20180427114005.31d1e8ab@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180427114005.31d1e8ab@gandalf.local.home> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-GCONF: 00 x-cbid: 18042715-0040-0000-0000-000004233B0D X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00008932; HX=3.00000241; KW=3.00000007; PH=3.00000004; SC=3.00000257; SDB=6.01024075; UDB=6.00522844; IPR=6.00803306; MB=3.00020808; MTD=3.00000008; XFM=3.00000015; UTC=2018-04-27 15:57:33 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18042715-0041-0000-0000-000008293D14 Message-Id: <20180427155846.GM26088@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-04-27_04:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 impostorscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1709140000 definitions=main-1804270153 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Apr 27, 2018 at 11:40:05AM -0400, Steven Rostedt wrote: > On Fri, 27 Apr 2018 08:38:26 -0700 > "Paul E. McKenney" wrote: > > > On Fri, Apr 27, 2018 at 10:47:47AM -0400, Steven Rostedt wrote: > > > On Fri, 27 Apr 2018 10:26:29 -0400 (EDT) > > > Mathieu Desnoyers wrote: > > > > > > > The general approach and the implementation look fine, except for > > > > one small detail: I would be tempted to explicitly disable preemption > > > > around the call to the tracepoint callback for the rcuidle variant, > > > > unless we plan to audit every tracer right away to remove any assumption > > > > that preemption is disabled in the callback implementation. > > > > > > I'm thinking that we do that audit. There shouldn't be many instances > > > of it. I like the idea that a tracepoint callback gets called with > > > preemption enabled. > > > > Are you really sure you want to increase your state space that much? > > Why not? The code I have in callbacks already deals with all sorts of > context - normal, softirq, irq, NMI, preemption disabled, irq > disabled. But why? Do people really expect good real-time response on systems instrumented with lots of tracing? Thanx, Paul