From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751398AbeEKR0M (ORCPT ); Fri, 11 May 2018 13:26:12 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:37032 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750711AbeEKR0L (ORCPT ); Fri, 11 May 2018 13:26:11 -0400 Date: Fri, 11 May 2018 10:27:35 -0700 From: "Paul E. McKenney" To: Steven Rostedt Cc: Byungchul Park , jiangshanlai@gmail.com, josh@joshtriplett.org, mathieu.desnoyers@efficios.com, linux-kernel@vger.kernel.org, kernel-team@lge.com, peterz@infradead.org Subject: Re: [PATCH] rcu: Report a quiescent state when it's exactly in the state Reply-To: paulmck@linux.vnet.ibm.com References: <1526027434-21237-1-git-send-email-byungchul.park@lge.com> <3af4cec0-4019-e3ac-77f9-8631252fb6da@lge.com> <20180511161746.GX26088@linux.vnet.ibm.com> <20180511122321.722a12cc@gandalf.local.home> <20180511122528.2a398d24@gandalf.local.home> <20180511122712.2d67992b@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180511122712.2d67992b@gandalf.local.home> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-GCONF: 00 x-cbid: 18051117-0056-0000-0000-0000044D0351 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00009007; HX=3.00000241; KW=3.00000007; PH=3.00000004; SC=3.00000260; SDB=6.01030821; UDB=6.00526848; IPR=6.00809952; MB=3.00021051; MTD=3.00000008; XFM=3.00000015; UTC=2018-05-11 17:26:09 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18051117-0057-0000-0000-00000891140E Message-Id: <20180511172735.GB26088@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-05-11_08:,, 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-1805110162 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, May 11, 2018 at 12:27:12PM -0400, Steven Rostedt wrote: > On Fri, 11 May 2018 12:25:28 -0400 > Steven Rostedt wrote: > > > I would also say that one should never call schedule() directly without > > changing its state to something other than TASK_RUNNING. Hence, calling > > schedule directly is saying you are ready to sleep. But that is not the > > case with cond_resched() which should always be called with the state > > as TASK_RUNNING. > > To continue this, with tracing, when a task is scheduled out in the > RUNNING state, it is considered preempted, otherwise it is not. I suppose another option would be for cond_resched_tasks_rcu_qs() to set (and later clear) a per-CPU variable that causes rcu_note_context_switch() to ignore its "preempt" parameter. Byungchul's approach seems more straightforward, though. Thanx, Paul