RFR: 8278951: containers/cgroup/PlainRead.java fails on Ubuntu 21.10

[Ioi Lam]

On Wed, 12 Jan 2022 21:37:50 GMT, Harold Seigel <hseigel at openjdk.org> wrote:

>> When running on Ubuntu 21.10 (which has cgroupv2 enabled by default) but outside of a container, the VM was printing only this:
>> 
>> 
>> [0.114s][debug][os,container] 
>>    Open of file /sys/fs/cgroup/user.slice/user-529964.slice/session-1168.scope/cpu.weight failed,
>>    No such file or directory
>> 
>> 
>> After my fix, this is also printed to make the PlainRead.java test happy:
>> 
>> 
>> [0.114s][trace][os,container] Raw value for CPU Shares is: -2
>> 
>> 
>> Note that the `GET_CONTAINER_INFO_CPTR` and `GET_CONTAINER_INFO_LINE` macros still don't print the trace log when the requested file doesn't exist. I don't know whether I should change them or not. Since no tests seem to look for such a such a log message, I'll leave the code as-is for now.
>
> Changes look good.
> Thanks! Harold

Hi @hseigel and @jerboaa thanks for the review.

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PR: https://git.openjdk.java.net/jdk/pull/7043