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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Fri, 21 Jun 2019 18:41:04 +0100 Received: from b01ledav003.gho.pok.ibm.com (b01ledav003.gho.pok.ibm.com [9.57.199.108]) by b01cxnp22033.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x5LHf36E48169386 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 21 Jun 2019 17:41:03 GMT Received: from b01ledav003.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 24A4EB206A; Fri, 21 Jun 2019 17:41:03 +0000 (GMT) Received: from b01ledav003.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 083C5B2068; Fri, 21 Jun 2019 17:41:03 +0000 (GMT) Received: from paulmck-ThinkPad-W541 (unknown [9.70.82.26]) by b01ledav003.gho.pok.ibm.com (Postfix) with ESMTP; Fri, 21 Jun 2019 17:41:02 +0000 (GMT) Received: by paulmck-ThinkPad-W541 (Postfix, from userid 1000) id 22A7D16C1D2E; Fri, 21 Jun 2019 10:41:04 -0700 (PDT) Date: Fri, 21 Jun 2019 10:41:04 -0700 From: "Paul E. McKenney" To: Peter Zijlstra Cc: linux-kernel@vger.kernel.org, mingo@redhat.com, frederic@kernel.org, tglx@linutronix.de Subject: Re: [PATCH] time/tick-broadcast: Fix tick_broadcast_offline() lockdep complaint Reply-To: paulmck@linux.ibm.com References: <20190619181903.GA14233@linux.ibm.com> <20190620121032.GU3436@hirez.programming.kicks-ass.net> <20190620160118.GQ26519@linux.ibm.com> <20190620211019.GA3436@hirez.programming.kicks-ass.net> <20190620221336.GZ26519@linux.ibm.com> <20190621105503.GI3436@hirez.programming.kicks-ass.net> <20190621121630.GE26519@linux.ibm.com> <20190621122927.GV3402@hirez.programming.kicks-ass.net> <20190621133414.GF26519@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190621133414.GF26519@linux.ibm.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-GCONF: 00 x-cbid: 19062117-0072-0000-0000-0000043F461C X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00011304; HX=3.00000242; KW=3.00000007; PH=3.00000004; SC=3.00000286; SDB=6.01221277; UDB=6.00642520; IPR=6.01002415; MB=3.00027409; MTD=3.00000008; XFM=3.00000015; UTC=2019-06-21 17:41:05 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19062117-0073-0000-0000-00004CAF5966 Message-Id: <20190621174104.GA7519@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-06-21_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=965 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1906210137 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jun 21, 2019 at 06:34:14AM -0700, Paul E. McKenney wrote: > On Fri, Jun 21, 2019 at 02:29:27PM +0200, Peter Zijlstra wrote: > > On Fri, Jun 21, 2019 at 05:16:30AM -0700, Paul E. McKenney wrote: > > > A pair of full hangs at boot (TASKS03 and TREE04), no console output > > > whatsoever. Not sure how these changes could cause that, but suspicion > > > falls on sched_tick_offload_init(). Though even that is a bit strange > > > because if so, why didn't TREE01 and TREE07 also hang? Again, looking > > > into it. > > > > Pesky details ;-) > > And backing out to the earlier patch removes the hangs, though statistical > insignificance and all that. And purists might argue that four failures out of four attempts does not constitute true statistical significance, but too bad. If I interpose a twork pointer in sched_tick_offload_init()'s initialization, it seems to work fine, give or take lack of statistical significance. This is surprising, so I am rerunning with added parentheses in the atomic_set() expression. Thanx, Paul "I hate initialization" McKenney > Ah, in answer to your earlier question, if you want it in v5.3, you > will need to take it (but I do humbly request that you wait until it > actually works). If you don't take it, I won't be submitting it earlier > than v5.4. Either way, your choice! > > Thanx, Paul