rcu_sched self-detected stall on CPU

[Miguel Ojeda]

Hi PPC/RCU,

While merging v5.18-rc1 changes I noticed our CI PPC runs broke. I
reproduced the problem in v5.18-rc1 as well as next-20220405, under
both QEMU 4.2.1 and 6.1.0, with `-smp 2`; but I cannot reproduce it in
v5.17 from a few tries.

Sadly, the problem is not deterministic although it is not too hard to
reproduce (1 out of 5?). Please see attached config and QEMU output.

Cheers,
Miguel

qemu
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config
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