On Tue, Jan 17, 2023 at 12:34 PM Joel Fernandes <joel@xxxxxxxxxxxxxxxxx> wrote: > > > > > On Jan 16, 2023, at 10:15 PM, Zhouyi Zhou <zhouzhouyi@xxxxxxxxx> wrote: > > > > On Tue, Jan 17, 2023 at 9:45 AM Joel Fernandes <joel@xxxxxxxxxxxxxxxxx> wrote: > >> > >>> On Tue, Jan 17, 2023 at 08:37:16AM +0800, Zhouyi Zhou wrote: > >>> On Tue, Jan 17, 2023 at 8:15 AM Joel Fernandes <joel@xxxxxxxxxxxxxxxxx> wrote: > >>>> > >>>> On Mon, Jan 16, 2023 at 05:38:00PM -0500, Joel Fernandes wrote: > >>>>> Hi Zhouyi, > >>>>> > >>>>> On Mon, Jan 16, 2023 at 1:33 PM Zhouyi Zhou <zhouzhouyi@xxxxxxxxx> wrote: > >>>>>> > >>>>> [..] > >>>>>> On Tue, Jan 17, 2023 at 1:27 AM Joel Fernandes <joel@xxxxxxxxxxxxxxxxx> wrote: > >>>>>>> > >>>>>>> Hello, > >>>>>>> I am seeing -EBUSY returned a lot during torture_onoff() when running > >>>>>>> rcutorture on arm64. This causes hotplug failure 30% of the time. I am > >>>>>>> also seeing this in 6.1-rc kernels. I believe see this only for CPU0. > >>>>>>> > >>>>>>> This causes warnings in torture tests: > >>>>>>> [ 217.582290] rcu-torture:torture_onoff task: offline 0 failed: errno -16 > >>>>>>> [ 221.866362] rcu-torture:torture_onoff task: offline 0 failed: errno -16 > >>>>>>> > >>>>>>> Full kernel log here: > >>>>>>> http://box.joelfernandes.org:9080/job/rcutorture_stable_arm/job/linux-5.15.y/7/artifact/tools/testing/selftests/rcutorture/res/2023.01.15-14.51.11/TREE04/console.log > >>>>>>> > >>>>>>> Any ideas on why this is happening and only for CPU 0 (presumably the > >>>>>>> boot CPU)? I'd personally need these warnings to go away for my tests > >>>>>>> as this causes rcutorture's tests to not cleanly pass for me. It > >>>>>>> appears remove_cpu() -> device_offline() is what returns the error. > >>>>>>> > >>>>>> I guess this probably because CPU 0 is the tick_do_timer_cpu in > >>>>>> nohz_full mode, which prevent that cpu from > >>>>>> going offline [1]. We have discussed this topic, but there is no > >>>>>> agreement on how to solve it yet. > >>>>> > >>>>> But I am seeing the issue in TRACE02 config which is: > >>>>> CONFIG_NO_HZ_IDLE=y > >>>>> # CONFIG_NO_HZ_FULL is not set > >>>>> > >>>>> So that is not NO_HZ_FULL: > >>>>> http://box.joelfernandes.org:9080/job/rcutorture_stable_arm/job/linux-5.15.y/7/artifact/tools/testing/selftests/rcutorture/res/2023.01.15-14.51.11/TRACE02/console.log.diags/ > >>>>> However, I can't seem to find the full kernel logs for that. > >>>>> > >>>>> Also, other than the TRACE02 fail, I only see the issue with configs > >>>>> with CONFIG_NO_HZ_FULL=y > >>>>> > >>>>> Can you try TRACE02 specifically, and see if you can reproduce the > >>>>> same issue on your setup? Meanwhile, I'll try to trace what is > >>>>> returning the -EBUSY. > >>> I am trying TRACE02 on my X86_64 machine using cross compile and > >>> qemu-system-aarch64 now, my equipment is limited, but hope I can be of > >>> beneficial to the community ;-) > >> > >> Cool, I am assuming you are trying the patch you shared which you wrote in > >> November. I bet you will still see the issue. > > yes, I still see the issue with no hz full. > >> > >>>> > >>>> How about something simple like the following? (untested) > >>>> > >>>> ---8<----------------------- > >>>> > >>>> diff --git a/kernel/torture.c b/kernel/torture.c > >>>> index bc8fb361efc0..cd64110694c0 100644 > >>>> --- a/kernel/torture.c > >>>> +++ b/kernel/torture.c > >>>> @@ -220,6 +220,9 @@ bool torture_offline(int cpu, long *n_offl_attempts, long *n_offl_successes, > >>>> // PCI probe frequently disables hotplug during boot. > >>>> (*n_offl_attempts)--; > >>>> s = " (-EBUSY forgiven during boot)"; > >>>> + } else if (tick_nohz_full_running && ret == -EBUSY) { > >>>> + (*n_offl_attempts)--; > >>>> + s = " (-EBUSY forgiven if nohz_full is running)"; > >>> Fantastic fix!! thus we can fix the time keeper cpu torture problem > >>> without touch the time keeper code. > >> > >> Thanks. Unfortunately this does not fix the issue for TRACE02 and the patch > >> you shared does not fix it either -- because TRACE02 is not a no-hz-full > >> test. :-( > >> > >> We will need to do a bit of tracing to figure out where the -EBUSY is coming > >> from for TRACE02. > > agree TRACE02 is another issue, unfortunately I can't reproduce the > > bug neither with your original Image [1] > > nor with my cross compiled kernel using [2]. > > > > I guess there may be two reasons: > > 1) my testbed is X86_64 based. > > 2) the command that I invoke qemu is not right: > > 2-1) the newly compiled linux-5.15.89-rc1 > > qemu-system-aarch64 -machine virt -cpu cortex-a57 -nographic -smp 4 > > Does 8 CPUs make any difference? That is my setup. 8 CPUs make no difference ;-( > > Not sure what else is different. It could be a CPU model specific issue, or something. But why donot you just use the same setup you used in November and check TRACE02? That is actually what I was requesting you to rest, since you saw the same issue on that setup. I guess it may be a CPU model specific issue, while I can't invoke qemu-system-aarch64 with "-machine virt,gic-version=host -cpu host" because I didn't have an aarch64 bare metal host. OK, I am doing the same setup on linux-5.15.y as I did last November in the PPC VM of Open Source Lab of Oregon State University, this will take about 20 hours, and report what I found after the test finishes. Thanks Zhouyi > > Thanks, > > Joel > > > > > -serial file:/tmp/consoleJan1702.log -kernel arch/arm64/boot/Image > > -append "console=ttyAMA0 oops=panic panic_on_warn=1 panic=-1 > > ftrace_dump_on_oops=orig_cpu debug earlyprintk=serial slub_debug=UZ > > rcutorture.torture_type=tasks-tracing rcutorture.onoff_interval=1000 > > rcutorture.onoff_holdoff=1000 rcutorture.n_barrier_cbs=4 > > rcutorture.stat_interval=15 rcutorture.shutdown_secs=1200 > > test_no_idle_hz=1 verbose=1" -m 2048 -net user,hostfwd=tcp::10024-:22 > > -net nic > > 2-2) original Image [1] > > qemu-system-aarch64 -machine virt -cpu cortex-a57 -nographic -smp > > 4 -serial file:/tmp/consoleJan1701.log -kernel /home/zzy/Image > > -append "console=ttyAMA0 oops=panic panic_on_warn=1 panic=-1 > > ftrace_dump_on_oops=orig_cpu debug earlyprintk=serial slub_debug=UZ > > rcutorture.torture_type=tasks-tracing rcutorture.onoff_interval=1000 > > rcutorture.onoff_holdoff=30 n_barrier_cbs=4 > > rcutorture.stat_interval=15 rcutorture.shutdown_secs=1200 > > test_no_idle_hz=1 verbose=1" -m 2048 -net > > user,hostfwd=tcp::10023-:22 -net nic > > > > As Mark can reproduce the issue using [1], there must be something > > wrong with my x86_64 based environment. > > > > Sorry not to be of help this time. > > > > I am very happy and interested to perform further tests whenever there > > are further instructions ;-) > > > > [1] http://box.joelfernandes.org:9080/job/rcutorture_stable_arm/job/linux-5.15.y/7/artifact/tools/testing/selftests/rcutorture/res/2023.01.15-14.51.11/TRACE02/Image > > [2] http://box.joelfernandes.org:9080/job/rcutorture_stable_arm/job/linux-5.15.y/7/artifact/tools/testing/selftests/rcutorture/res/2023.01.15-14.51.11/TRACE02/.config > >> > >> I wonder if we should ignore -EBUSY altogether, since as Thomas mentioned, > >> hotplug failure is "normal". Thoughts? > > This decision is too important for a beginner like me, however may > > thanks for your trust in me ;-) What does Paul think about it ;-) > > > > Thanks > > Zhouyi > >> > >> thanks, > >> > >> - Joel > >>
