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McKenney" To: Joel Fernandes Cc: LKML , Josh Triplett , Lai Jiangshan , linux-kselftest , Mathieu Desnoyers , Shuah Khan , Steven Rostedt Subject: Re: [PATCH] rcutorture: Select from only online CPUs Reply-To: paulmck@linux.ibm.com References: <20190323034619.15792-1-joel@joelfernandes.org> <20190325150133.GA4102@linux.ibm.com> <20190325164253.GE4102@linux.ibm.com> <20190326160140.GP4102@linux.ibm.com> <20190326183549.GA162738@google.com> <20190326184013.GA114492@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20190326184013.GA114492@google.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-GCONF: 00 x-cbid: 19032620-0072-0000-0000-00000410AF93 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00010819; HX=3.00000242; KW=3.00000007; PH=3.00000004; SC=3.00000282; SDB=6.01180084; UDB=6.00617543; IPR=6.00960799; MB=3.00026167; MTD=3.00000008; XFM=3.00000015; UTC=2019-03-26 20:46:16 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19032620-0073-0000-0000-00004B9D10CA Message-Id: <20190326204613.GS4102@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-03-26_14:,, 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-1903260141 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Mar 26, 2019 at 02:40:13PM -0400, Joel Fernandes wrote: > On Tue, Mar 26, 2019 at 02:35:49PM -0400, Joel Fernandes wrote: > > On Tue, Mar 26, 2019 at 09:01:40AM -0700, Paul E. McKenney wrote: > > > On Mon, Mar 25, 2019 at 06:40:17PM -0400, Joel Fernandes wrote: > > > > On Mon, Mar 25, 2019 at 12:42 PM Paul E. McKenney wrote: > > > > > > > > > > On Mon, Mar 25, 2019 at 12:33:37PM -0400, Joel Fernandes wrote: > > > > > > On Mon, Mar 25, 2019 at 11:02 AM Paul E. McKenney wrote: > > > > > > > > > > > > > > On Fri, Mar 22, 2019 at 11:46:19PM -0400, Joel Fernandes (Google) wrote: > > > > > > > > The rcutorture jitter.sh script selects a random CPU but does not check > > > > > > > > if it is offline or online. This leads to taskset errors many times. On > > > > > > > > my machine, hyper threading is disabled so half the cores are offline > > > > > > > > causing taskset errors a lot of times. Let us fix this by checking from > > > > > > > > only the online CPUs on the system. > > > > > > > > > > > > > > > > Signed-off-by: Joel Fernandes (Google) > > > > > > > > > > > > > > Good catch! > > > > > > > > > > > > > > Please see below for one suggestion for simplification. > > > > > > > > > > > > > > Thanx, Paul > > > > > > > > > > > > > > > --- > > > > > > > > tools/testing/selftests/rcutorture/bin/jitter.sh | 11 ++++++++++- > > > > > > > > 1 file changed, 10 insertions(+), 1 deletion(-) > > > > > > > > > > > > > > > > diff --git a/tools/testing/selftests/rcutorture/bin/jitter.sh b/tools/testing/selftests/rcutorture/bin/jitter.sh > > > > > > > > index 3633828375e3..53bf9d99b5cd 100755 > > > > > > > > --- a/tools/testing/selftests/rcutorture/bin/jitter.sh > > > > > > > > +++ b/tools/testing/selftests/rcutorture/bin/jitter.sh > > > > > > > > @@ -47,10 +47,19 @@ do > > > > > > > > exit 0; > > > > > > > > fi > > > > > > > > > > > > > > > > - # Set affinity to randomly selected CPU > > > > > > > > + # Set affinity to randomly selected online CPU > > > > > > > > cpus=`ls /sys/devices/system/cpu/*/online | > > > > > > > > > > > > > > cpus=`grep 1 /sys/devices/system/cpu/*/online | > > > > > > > > > > > > Yes, this is better. Lets do it this way :) > > > > > > > > > > > > > > sed -e 's,/[^/]*$,,' -e 's/^[^0-9]*//' | > > > > > > > > grep -v '^0*$'` > > > > > > > > > > > > > > Of course, now I have no idea why I excluded CPU 0... :-/ > > > > > > > > > > > > Yes, I was wondering as well about that :-) > > > > > > > > > > Please feel free to try including CPU 0 and running the set of single-CPU > > > > > rcutorture scenarios. ;-) > > > > > > > > Will do and then will update the patch by adding the CPU back, if all > > > > is well. Thanks. > > > > > > And rcutorture doesn't like the rcu_is_cpu_rrupt_from_idle() patch on > > > scenarios SRCU-P, TASKS01, and TREE05, which are the Tree RCU scenarios > > > that enable CONFIG_PROVE_RCU. The compiler error is: > > > > > > kernel/rcu/tree.c:391:2: error: implicit declaration of function ‘_this_cpu_read’ [-Werror=implicit-function-declaration] > > > > > > My guess is that the initial underscore needs to go. I will drop > > > these two patches in favor of an update from you. ;-) > > > > Sorry, I fixed that up and running tests now. Very good. ;-) > > By the way, may be you decided to not run the jitter on CPU0 just because on > > some systems, CPU0 does not have an 'online' file? In this case, the grep may > > throw errors I guess which troubles the script. > > > > From the old cpu hotplug docs, I found that if CONFIG_BOOTPARAM_HOTPLUG_CPU0 > > or cpu0_hotplug boot command line option is not passed, then cpu0 cannot be > > offlined in which case, presumably the 'online' file will be missing, like > > some systems I am testing on. > > Never mind, the "*" in your path search would take care of not erroring out :-) > > The other reason you may have done it is for making the jitter be > consistent across systems that can offline CPU0, and the others that can't :-). > I am just guessing. Or maybe I was just being stupid. If I wasn't being stupid, it might have been that in the uniprocessor case the jitter caused some failure. But the kernel is a lot better about handling preemption these days, so that might well be an obsolete concern. Who knows? ;-) > Any way, I will just add back CPU0 forcefully to the cpus list in my testing, > without checking for the online file existence, and see what happens :-) If > there's no smoke, then I'll roll that into a patch and send it out. Sounds good, especially if you include a few of the uniprocessor tests. ;-) Thanx, Paul