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 -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 >
