From: Nathan Lynch <nathanl@linux.ibm.com>
To: linuxppc-dev@lists.ozlabs.org
Cc: Gautham R Shenoy <ego.lkml@gmail.com>,
Nicholas Piggin <npiggin@gmail.com>
Subject: Re: missing doorbell interrupt when onlining cpu
Date: Wed, 04 Sep 2019 18:18:46 -0500 [thread overview]
Message-ID: <87woenr6p5.fsf@linux.ibm.com> (raw)
In-Reply-To: <87zhjjr7yw.fsf@linux.ibm.com>
Nathan Lynch <nathanl@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.
next prev parent reply other threads:[~2019-09-04 23:21 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-04 22:51 missing doorbell interrupt when onlining cpu Nathan Lynch
2019-09-04 23:18 ` Nathan Lynch [this message]
2019-09-10 23:04 ` Nathan Lynch
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