Re: [PATCH] arch_topology: Fix missing clear cluster_cpumask in remove_cpu_topology()

[Barry Song <21cnbao@gmail.com>]

On Thu, Nov 11, 2021 at 8:25 PM Wangshaobo (bobo)
<bobo.shaobowang@huawei.com> wrote:
>
>
> 在 2021/11/11 14:25, Barry Song 写道:
>
> On Wed, Nov 10, 2021 at 10:53 PM Wang ShaoBo <bobo.shaobowang@huawei.com> wrote:
>
> When testing cpu online and offline, warning happened like this:
>
> [  146.746743] WARNING: CPU: 92 PID: 974 at kernel/sched/topology.c:2215 build_sched_domains+0x81c/0x11b0
> [  146.749988] CPU: 92 PID: 974 Comm: kworker/92:2 Not tainted 5.15.0 #9
> [  146.750402] Hardware name: Huawei TaiShan 2280 V2/BC82AMDDA, BIOS 1.79 08/21/2021
> [  146.751213] Workqueue: events cpuset_hotplug_workfn
> [  146.751629] pstate: 00400009 (nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> [  146.752048] pc : build_sched_domains+0x81c/0x11b0
> [  146.752461] lr : build_sched_domains+0x414/0x11b0
> [  146.752860] sp : ffff800040a83a80
> [  146.753247] x29: ffff800040a83a80 x28: ffff20801f13a980 x27: ffff20800448ae00
> [  146.753644] x26: ffff800012a858e8 x25: ffff800012ea48c0 x24: 0000000000000000
> [  146.754039] x23: ffff800010ab7d60 x22: ffff800012f03758 x21: 000000000000005f
> [  146.754427] x20: 000000000000005c x19: ffff004080012840 x18: ffffffffffffffff
> [  146.754814] x17: 3661613030303230 x16: 30303078303a3239 x15: ffff800011f92b48
> [  146.755197] x14: ffff20be3f95cef6 x13: 2e6e69616d6f642d x12: 6465686373204c4c
> [  146.755578] x11: ffff20bf7fc83a00 x10: 0000000000000040 x9 : 0000000000000000
> [  146.755957] x8 : 0000000000000002 x7 : ffffffffe0000000 x6 : 0000000000000002
> [  146.756334] x5 : 0000000090000000 x4 : 00000000f0000000 x3 : 0000000000000001
> [  146.756705] x2 : 0000000000000080 x1 : ffff800012f03860 x0 : 0000000000000001
> [  146.757070] Call trace:
> [  146.757421]  build_sched_domains+0x81c/0x11b0
> [  146.757771]  partition_sched_domains_locked+0x57c/0x978
> [  146.758118]  rebuild_sched_domains_locked+0x44c/0x7f0
> [  146.758460]  rebuild_sched_domains+0x2c/0x48
> [  146.758791]  cpuset_hotplug_workfn+0x3fc/0x888
> [  146.759114]  process_one_work+0x1f4/0x480
> [  146.759429]  worker_thread+0x48/0x460
> [  146.759734]  kthread+0x158/0x168
> [  146.760030]  ret_from_fork+0x10/0x20
> [  146.760318] ---[ end trace 82c44aad6900e81a ]---
>
> For some architectures like risc-v and arm64 which use common code
> clear_cpu_topology() in shutting down CPUx, When CONFIG_SCHED_CLUSTER
> is set, cluster_sibling in cpu_topology of each sibling adjacent
> to CPUx is missed clearing, this causes checking failed in
> topology_span_sane() and rebuilding topology failure at end when CPU online.
>
> Different sibling's cluster_sibling in cpu_topology[] when CPU92 offline
> (CPU 92, 93, 94, 95 are in one cluster):
>
> Before revision:
> CPU                 [92]      [93]      [94]      [95]
> cluster_sibling     [92]     [92-95]   [92-95]   [92-95]
>
> After revision:
> CPU                 [92]      [93]      [94]      [95]
> cluster_sibling     [92]     [93-95]   [93-95]   [93-95]
>
> Signed-off-by: Wang ShaoBo <bobo.shaobowang@huawei.com>
>
> The patch looks correct. But how do you reproduce it?
>
> Hi Barry,
>
> you can try this test case in kunpeng 920:
>
>
echo 0 > cpu92/online
echo 0 > cpu93/online
echo 1 > cpu92/online

Yes. I was making the whole cluster offline. this warning can only be
reproduced when
we disable a part of CPUs in one cluster, then enable one of the disabled CPUs.

Acked-by: Barry Song <song.bao.hua@hisilicon.com>

Might need some refine to explain how to reproduce in commit log.

>
> - Wang ShaoBo

Thanks
Barry