* ebpf trace doesn't work during cpu hotplug
@ 2019-05-29 3:28 Ming Lei
2019-07-08 9:43 ` Ming Lei
0 siblings, 1 reply; 2+ messages in thread
From: Ming Lei @ 2019-05-29 3:28 UTC (permalink / raw)
To: Linux Kernel Mailing List, Alexei Starovoitov, bpf
Hi,
Looks ebpf trace doesn't work during cpu hotplug, see the following trace:
1) trace two functions called during CPU unplug via bcc/trace
/usr/share/bcc/tools/trace -T 'takedown_cpu "%d", arg1' 'take_cpu_down'
2) put cpu7 offline via:
echo 0 > /sys/devices/system/cpu/cpu7/online
3) only trace on 'takedown_cpu' is dumped via bcc/trace:
TIME PID TID COMM FUNC -
03:23:17 733 733 bash takedown_cpu 7
The lost trace on 'take_cpu_down' can never be shown, even though
CPU7 is switched ON again.
take_cpu_down is called via stop_machine_cpuslocked.
Thanks,
Ming Lei
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: ebpf trace doesn't work during cpu hotplug
2019-05-29 3:28 ebpf trace doesn't work during cpu hotplug Ming Lei
@ 2019-07-08 9:43 ` Ming Lei
0 siblings, 0 replies; 2+ messages in thread
From: Ming Lei @ 2019-07-08 9:43 UTC (permalink / raw)
To: Linux Kernel Mailing List, Alexei Starovoitov, bpf
On Wed, May 29, 2019 at 11:28 AM Ming Lei <tom.leiming@gmail.com> wrote:
>
> Hi,
>
> Looks ebpf trace doesn't work during cpu hotplug, see the following trace:
>
> 1) trace two functions called during CPU unplug via bcc/trace
>
> /usr/share/bcc/tools/trace -T 'takedown_cpu "%d", arg1' 'take_cpu_down'
>
> 2) put cpu7 offline via:
>
> echo 0 > /sys/devices/system/cpu/cpu7/online
>
> 3) only trace on 'takedown_cpu' is dumped via bcc/trace:
>
> TIME PID TID COMM FUNC -
> 03:23:17 733 733 bash takedown_cpu 7
>
> The lost trace on 'take_cpu_down' can never be shown, even though
> CPU7 is switched ON again.
>
> take_cpu_down is called via stop_machine_cpuslocked.
From a user view, I think the tool should be reliable to collect
traces any time.
So ping on this issue...
Thanks,
Ming Lei
^ permalink raw reply [flat|nested] 2+ messages in thread
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