Thanks for the fixups!
These are now merged.
Bruce
In message: [linux-yocto][v4.19/standard/preempt-rt/base][PATCH] sched/core:
Fix CPU offline/online process
on 16/11/2020 Daniel Dragomir wrote:
> From: Daniel Dragomir
>
> This error was introduced in commit d02636e8d3 ("Merge branch
> 'v4.19/standard/base' into v4.19/standard/preempt-rt/base")
> when a merge conflict has overwrited the changes from commit
> 373491f1f4 ("sched/core: Fix illegal RCU from offline CPUs").
>
> This BUG occurs when running cpu_hotplug_stress testcase from
> KTS or when stressing one CPU by switching it online/offline
> (echo 0 and 1 in /sys/devices/system/cpu/cpu0/online).
>
> kernel BUG at kernel/fork.c:633!
> Internal error: Oops - BUG: 0 [#1] PREEMPT SMP
> Modules linked in:
> Process sh (pid: 2016, stack limit = 0xca5ad524)
> CPU: 10 PID: 2016 Comm: sh Not tainted 4.19.131-rt30 axxia_gen2
> Hardware name: AXM56xx Victoria (DT)
> pstate: 6005 (nZCv daif -PAN -UAO)
> pc : __mmdrop+0x120/0x138
> lr : finish_cpu+0x68/0x70
> sp : ff8012153a40
> x29: ff8012153a40 x28: ffc07b389e00
> x27: x26: 00407610f000
> x25: ffc07ee62ee0 x24:
> x23: ff80080dfc20 x22: ff8008d9a9d8
> x21: ff8008d53ee0 x20: 0055
> x19: ff8008dc1b58 x18: 0001
> x17: x16:
> x15: x14: ff8008d89688
> x13: ff8088d918d7 x12: ff8008d918e0
> x11: ff8008da4000 x10: ff8012153a00
> x9 : ffd0 x8 : ff80121539d0
> x7 : x6 : 0001
> x5 : fffb x4 : 0030
> x3 : 0030 x2 : ff8008dc1b58
> x1 : ff8008dc1ba4 x0 : ff8008dc1b58
> Call trace:
> __mmdrop+0x120/0x138
> finish_cpu+0x68/0x70
> cpuhp_invoke_callback+0xa8/0x800
> _cpu_down+0x100/0x220
> do_cpu_down+0x48/0x70
> cpu_down+0x24/0x30
> cpu_subsys_offline+0x20/0x30
> device_offline+0xa4/0xd0
> online_store+0x60/0xc0
> dev_attr_store+0x44/0x60
> sysfs_kf_write+0x5c/0x78
> kernfs_fop_write+0xd8/0x1d0
> __vfs_write+0x60/0x178
> vfs_write+0xac/0x1b0
> ksys_write+0x74/0xe8
> __arm64_sys_write+0x24/0x30
> el0_svc_common+0xa4/0x1a0
> el0_svc_compat_handler+0x30/0x40
> el0_svc_compat+0x8/0x18
> Code: a94153f3 a9425bf5 a8c37bfd d65f03c0 (d421)
> ---[ end trace 0002 ]---
> BUG: Bad rss-counter state mm:1136ddcb idx:0 val:1012
> BUG: Bad rss-counter state mm:1136ddcb idx:1 val:5902
> BUG: non-zero pgtables_bytes on freeing mm: 180224
>
> Signed-off-by: Daniel Dragomir
> ---
> kernel/sched/core.c | 7 ++-
> 1 file changed, 2 insertions(+), 5 deletions(-)
>
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 218b93a..c62dbf9 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -5702,11 +5702,8 @@ void idle_task_exit(void)
> switch_mm(mm, _mm, current);
> finish_arch_post_lock_switch();
> }
> - /*
> - * Defer the cleanup to an alive cpu. On RT we can neither
> - * call mmdrop() nor mmdrop_delayed() from here.
> - */
> - per_cpu(idle_last_mm, smp_processor_id()) = mm;
> +
> + /* finish_cpu(), as ran on the BP, will clean up the active_mm state */
> }
>
> /*
> --
> 2.7.4
>
>
>
>
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