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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Thu, 27 Jun 2019 19:00:06 +0100 Received: from b01ledav003.gho.pok.ibm.com (b01ledav003.gho.pok.ibm.com [9.57.199.108]) by b01cxnp22035.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x5RI05xC54067698 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 27 Jun 2019 18:00:05 GMT Received: from b01ledav003.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 377F8B2064; Thu, 27 Jun 2019 18:00:05 +0000 (GMT) Received: from b01ledav003.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 242E4B206B; Thu, 27 Jun 2019 18:00:05 +0000 (GMT) Received: from paulmck-ThinkPad-W541 (unknown [9.70.82.26]) by b01ledav003.gho.pok.ibm.com (Postfix) with ESMTP; Thu, 27 Jun 2019 18:00:05 +0000 (GMT) Received: by paulmck-ThinkPad-W541 (Postfix, from userid 1000) id 252A116C0E68; Thu, 27 Jun 2019 11:00:07 -0700 (PDT) Date: Thu, 27 Jun 2019 11:00:07 -0700 From: "Paul E. McKenney" To: Scott Wood Cc: Steven Rostedt , Sebastian Andrzej Siewior , Peter Zijlstra , Thomas Gleixner , Juri Lelli , Clark Williams , linux-rt-users@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH RT 4/4] rcutorture: Avoid problematic critical section nesting Reply-To: paulmck@linux.ibm.com References: <20190619011908.25026-1-swood@redhat.com> <20190619011908.25026-5-swood@redhat.com> <20190620211826.GX26519@linux.ibm.com> <20190621163821.rm2rhsnvfo5tnjul@linutronix.de> <20190621235955.GK26519@linux.ibm.com> <20190626110847.2dfdf72c@gandalf.local.home> <8462f30720637ec0da377aa737d26d2cad424d36.camel@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <8462f30720637ec0da377aa737d26d2cad424d36.camel@redhat.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-GCONF: 00 x-cbid: 19062718-2213-0000-0000-000003A5D520 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00011342; HX=3.00000242; KW=3.00000007; PH=3.00000004; SC=3.00000286; SDB=6.01224104; UDB=6.00644247; IPR=6.01005293; MB=3.00027492; MTD=3.00000008; XFM=3.00000015; UTC=2019-06-27 18:00:09 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19062718-2214-0000-0000-00005F04DBB5 Message-Id: <20190627180007.GA27126@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-06-27_12:,, 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 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1906270205 Sender: linux-rt-users-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-rt-users@vger.kernel.org On Wed, Jun 26, 2019 at 11:49:16AM -0500, Scott Wood wrote: > On Wed, 2019-06-26 at 11:08 -0400, Steven Rostedt wrote: > > On Fri, 21 Jun 2019 16:59:55 -0700 > > "Paul E. McKenney" wrote: > > > > > I have no objection to the outlawing of a number of these sequences in > > > mainline, but am rather pointing out that until they really are outlawed > > > and eliminated, rcutorture must continue to test them in mainline. > > > Of course, an rcutorture running in -rt should avoid testing things that > > > break -rt, including these sequences. > > > > We should update lockdep to complain about these sequences. That would > > "outlaw" them in mainline. That is, after we clean up all the current > > sequences in the code. And we also need to get Linus's approval of this > > as I believe he was against enforcing this in the past. > > Was the opposition to prohibiting some specific sequence? It's only certain > misnesting scenarios that are problematic. The rcu_read_lock/ > local_irq_disable restriction can be dropped with the IPI-to-self added in > Paul's tree. Are there any known instances of the other two (besides > rcutorture)? Given the failure scenario Sebastian Siewior reported today, there apparently are some, at least when running threaded interrupt handlers. Thanx, Paul