Nathan Lynch <nath...@linux.ibm.com> writes:
> I'm hoping for some help investigating a behavior I see when doing cpu
> hotplug under load on P9 and P8 LPARs. Occasionally, while coming online
> a cpu will seem to get "stuck" in idle, with a pending doorbell
> interrupt unserviced (cpu 12 here):
>
> cpuhp/12-70 [012] 46133.602202: cpuhp_enter: cpu: 0012 target:
> 205 step: 174 (0xc000000000028920s)
> load.sh-8201 [014] 46133.602248: sched_waking: comm=cpuhp/12 pid=70
> prio=120 target_cpu=012
> load.sh-8201 [014] 46133.602251: smp_send_reschedule: (c000000000052868)
> cpu=12
> <idle>-0 [012] 46133.602252: do_idle: (c000000000162e08)
> load.sh-8201 [014] 46133.602252: smp_muxed_ipi_message_pass:
> (c0000000000527e8) cpu=12 msg=1
> load.sh-8201 [014] 46133.602253: doorbell_core_ipi: (c00000000004d3e8)
> cpu=12
> <idle>-0 [012] 46133.602257: arch_cpu_idle: (c000000000022d08)
> <idle>-0 [012] 46133.602259: pseries_lpar_idle: (c0000000000d43c8)
I should be more explicit that given my tracing configuration I would
expect to see doorbell events etc here e.g.
<idle>-0 [012] 46133.602086: doorbell_entry:
pt_regs=0xc000000200e7fb50
<idle>-0 [012] 46133.602087: smp_ipi_demux_relaxed:
(c0000000000530f8)
<idle>-0 [012] 46133.602088: scheduler_ipi:
(c00000000015e4f8)
<idle>-0 [012] 46133.602091: sched_wakeup: cpuhp/12:70
[120] success=1 CPU:012
<idle>-0 [012] 46133.602092: sched_wakeup: migration/12:71
[0] success=1 CPU:012
<idle>-0 [012] 46133.602093: doorbell_exit:
pt_regs=0xc000000200e7fb50
but instead cpu 12 goes to idle.
