From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.4 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6C920C04AB1 for ; Thu, 9 May 2019 17:37:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4104E217D8 for ; Thu, 9 May 2019 17:37:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726839AbfEIRhB (ORCPT ); Thu, 9 May 2019 13:37:01 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:39260 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726576AbfEIRhA (ORCPT ); Thu, 9 May 2019 13:37:00 -0400 Received: from pps.filterd (m0098421.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x49HakTa067240 for ; Thu, 9 May 2019 13:36:59 -0400 Received: from e14.ny.us.ibm.com (e14.ny.us.ibm.com [129.33.205.204]) by mx0a-001b2d01.pphosted.com with ESMTP id 2scpwq51hr-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Thu, 09 May 2019 13:36:58 -0400 Received: from localhost by e14.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Thu, 9 May 2019 18:36:58 +0100 Received: from b01cxnp22035.gho.pok.ibm.com (9.57.198.25) by e14.ny.us.ibm.com (146.89.104.201) with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Thu, 9 May 2019 18:36:55 +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 x49Hasn830015696 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 9 May 2019 17:36:54 GMT Received: from b01ledav003.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id A2041B205F; Thu, 9 May 2019 17:36:54 +0000 (GMT) Received: from b01ledav003.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 75041B2066; Thu, 9 May 2019 17:36:54 +0000 (GMT) Received: from paulmck-ThinkPad-W541 (unknown [9.70.82.216]) by b01ledav003.gho.pok.ibm.com (Postfix) with ESMTP; Thu, 9 May 2019 17:36:54 +0000 (GMT) Received: by paulmck-ThinkPad-W541 (Postfix, from userid 1000) id A602616C3968; Thu, 9 May 2019 10:36:54 -0700 (PDT) Date: Thu, 9 May 2019 10:36:54 -0700 From: "Paul E. McKenney" To: Steven Rostedt Cc: Peter Zijlstra , linux-kernel@vger.kernel.org, andrea.parri@amarulasolutions.com Subject: Re: Question about sched_setaffinity() Reply-To: paulmck@linux.ibm.com References: <20190427180246.GA15502@linux.ibm.com> <20190430100318.GP2623@hirez.programming.kicks-ass.net> <20190430105129.GA3923@linux.ibm.com> <20190430115551.GT2623@hirez.programming.kicks-ass.net> <20190501191213.GX3923@linux.ibm.com> <20190501151655.51469a4c@gandalf.local.home> <20190501202713.GY3923@linux.ibm.com> <20190507221613.GA11057@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190507221613.GA11057@linux.ibm.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-GCONF: 00 x-cbid: 19050917-0052-0000-0000-000003BD00E0 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00011077; HX=3.00000242; KW=3.00000007; PH=3.00000004; SC=3.00000285; SDB=6.01200919; UDB=6.00630155; IPR=6.00981810; MB=3.00026815; MTD=3.00000008; XFM=3.00000015; UTC=2019-05-09 17:36:57 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19050917-0053-0000-0000-000060D554E4 Message-Id: <20190509173654.GA23530@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-05-09_02:,, 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-1905090101 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, May 07, 2019 at 03:16:13PM -0700, Paul E. McKenney wrote: > On Wed, May 01, 2019 at 01:27:13PM -0700, Paul E. McKenney wrote: > > On Wed, May 01, 2019 at 03:16:55PM -0400, Steven Rostedt wrote: > > > On Wed, 1 May 2019 12:12:13 -0700 > > > "Paul E. McKenney" wrote: > > > > > > > > > > OK, what I did was to apply the patch at the end of this email to -rcu > > > > branch dev, then run rcutorture as follows: > > > > > > > > nohup tools/testing/selftests/rcutorture/bin/kvm.sh --cpus 8 --duration 2 --configs "TRIVIAL" --bootargs "trace_event=sched:sched_switch,sched:sched_wakeup ftrace=function_graph ftrace_graph_filter=sched_setaffinity,migration_cpu_stop" > > > > > > > > This resulted in the console output that I placed here: > > > > > > > > http://www2.rdrop.com/~paulmck/submission/console.log.gz > > > > > > > > But I don't see calls to sched_setaffinity() or migration_cpu_stop(). > > > > Steve, is something else needed on the kernel command line in addition to > > > > the following? > > > > > > > > ftrace=function_graph ftrace_graph_filter=sched_setaffinity,migration_cpu_stop > > > > > > Do you have function graph enabled in the config? > > > > > > [ 2.098303] ftrace bootup tracer 'function_graph' not registered. > > > > I guess I don't! Thank you, will fix. > > > > Let's see... > > > > My .config has CONFIG_HAVE_FUNCTION_GRAPH_TRACER=y. It looks like I > > need CONFIG_FUNCTION_GRAPH_TRACER=y, which I don't have. And it looks > > like that needs CONFIG_FUNCTION_TRACER=y, which I also don't have. > > But I do have CONFIG_HAVE_FUNCTION_TRACER=y. So I should add this > > to my rcutorture command line: > > > > --kconfig "CONFIG_FUNCTION_TRACER=y CONFIG_FUNCTION_GRAPH_TRACER=y". > > > > I fired this up. Here is hoping! ;-) > > > > And it does have sched_setaffinity(), woo-hoo!!! I overwrote the old file: > > > > http://www2.rdrop.com/~paulmck/submission/console.log.gz > > And I reran after adding a trace_printk(), which shows up as follows: > > [ 211.409565] 6) | /* On unexpected CPU 6, expected 4!!! */ > > I placed the console log here: > > http://www2.rdrop.com/~paulmck/submission/console.tpk.log.gz > > Just in case the earlier log proves useful. > > And it is acting as if the destination CPU proved to be offline. Except > that this rcutorture scenario doesn't offline anything, and I don't see > any CPU-hotplug removal messages. So I added another trace_printk() to > print out cpu_online_mask. This gets me the following: > > [ 31.565605] 0) | /* On unexpected CPU 0, expected 1!!! */ > [ 31.565605] 0) | /* Online CPUs: 0-7 */ > > So we didn't make it to CPU 1 despite its being online. I placed the > console log here: > > http://www2.rdrop.com/~paulmck/submission/console.tpkol.log.gz > > Thoughts? > > Updated patch against -rcu below in case it is useful. I added more debug and got this: [ 215.097318] 4) | /* On unexpected CPU 4, expected 5!!! */ [ 215.098285] 4) | /* Online CPUs: 0-7 Active CPUs: 0-7 */ [ 215.099283] 4) | /* ret = 0, ->cpus_allowed 0-4,6-7 */ http://www.rdrop.com/~paulmck/submission/console.tpkm.log.gz The task's ->cpus_allowed got set to the bitwise not of the requested mask. I took a quick scan through the code but don't see how this happens. Very strange. Any suggestions for further debugging? Left to myself, I would copy the requested cpumask to a per-task location and insert checks in the sched_setaffinity() code path, crude and ugly though that might seem. (Ugly enough that I will wait until tomorrow to try it out.) Thanx, Paul ------------------------------------------------------------------------ diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c index da04b5073dc3..51db19543012 100644 --- a/kernel/rcu/rcutorture.c +++ b/kernel/rcu/rcutorture.c @@ -680,12 +680,31 @@ static struct rcu_torture_ops tasks_ops = { static void synchronize_rcu_trivial(void) { int cpu; + int destcpu; + static int dont_trace; + static cpumask_t my_cpumask; + static DEFINE_SPINLOCK(my_cpumask_lock); + int ret; for_each_online_cpu(cpu) { - while (raw_smp_processor_id() != cpu) - rcutorture_sched_setaffinity(current->pid, - cpumask_of(cpu)); - WARN_ON_ONCE(raw_smp_processor_id() != cpu); + if (!READ_ONCE(dont_trace)) + tracing_on(); + rcutorture_sched_setaffinity(current->pid, cpumask_of(cpu)); + destcpu = raw_smp_processor_id(); + if (destcpu == cpu) { + tracing_off(); + } else { + trace_printk("On unexpected CPU %d, expected %d!!!\n", destcpu, cpu); + trace_printk("Online CPUs: %*pbl Active CPUs: %*pbl\n", cpumask_pr_args(cpu_online_mask), cpumask_pr_args(cpu_active_mask)); + spin_lock(&my_cpumask_lock); + ret = sched_getaffinity(current->pid, &my_cpumask); + trace_printk("ret = %d, ->cpus_allowed %*pbl\n", ret, cpumask_pr_args(&my_cpumask)); + spin_unlock(&my_cpumask_lock); + tracing_stop(); + WRITE_ONCE(dont_trace, 1); + WARN_ON_ONCE(1); + rcu_ftrace_dump(DUMP_ALL); + } } } diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index caffee644932..edaf0ca22ff7 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -3495,6 +3495,7 @@ void __init rcu_init(void) rcu_par_gp_wq = alloc_workqueue("rcu_par_gp", WQ_MEM_RECLAIM, 0); WARN_ON(!rcu_par_gp_wq); srcu_init(); + tracing_off(); } #include "tree_stall.h"