From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753731AbdDKXr3 (ORCPT ); Tue, 11 Apr 2017 19:47:29 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:34984 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752515AbdDKXr1 (ORCPT ); Tue, 11 Apr 2017 19:47:27 -0400 Date: Tue, 11 Apr 2017 16:47:20 -0700 From: "Paul E. McKenney" To: Steven Rostedt Cc: LKML Subject: Re: [PATCH] tracing: Have the trace_event benchmark thread call cond_resched_rcu_qs() Reply-To: paulmck@linux.vnet.ibm.com References: <20170411185435.313ce179@gandalf.local.home> <20170411185601.01b32a0e@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170411185601.01b32a0e@gandalf.local.home> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-GCONF: 00 x-cbid: 17041123-0036-0000-0000-000001DA965D X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00006919; HX=3.00000240; KW=3.00000007; PH=3.00000004; SC=3.00000208; SDB=6.00846250; UDB=6.00417393; IPR=6.00624683; BA=6.00005284; NDR=6.00000001; ZLA=6.00000005; ZF=6.00000009; ZB=6.00000000; ZP=6.00000000; ZH=6.00000000; ZU=6.00000002; MB=3.00015011; XFM=3.00000013; UTC=2017-04-11 23:47:23 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17041123-0037-0000-0000-00003FA21153 Message-Id: <20170411234720.GB3956@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-04-11_18:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=0 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1702020001 definitions=main-1704110184 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Apr 11, 2017 at 06:56:01PM -0400, Steven Rostedt wrote: > On Tue, 11 Apr 2017 18:54:35 -0400 > Steven Rostedt wrote: > > > From: "Steven Rostedt (VMware)" > > > > The trace_event benchmark thread runs in kernel space in an infinite loop > > while also calling cond_resched() in case anything else wants to schedule > > in. Unfortunately, on a PREEMPT kernel, that makes it a nop, in which case, > > this will never voluntarily schedule. That will cause synchronize_rcu_tasks() > > to forever block on this thread, while it is running. > > > > This is exactly what cond_resched_rcu_qs() is for. Use that instead. > > > > Cc: "Paul E. McKenney" > > This actually should be: > > Recommended-by: "Paul E. McKenney" And: Acked-by: "Paul E. McKenney" > -- Steve > > > Signed-off-by: Steven Rostedt (VMware) > > --- >