Regression in JDK15/16: CGroup v2 support

[Bob Vandette]

Thanks David.

The problem seems to be caused by improper scanning of /proc/mountinfo.

Failing System

439 434 0:33 /docker/0a67832faae434cc8fa0a942e04a308bb8b120b5099018f1ee09f1d7a52746b7 /sys/fs/cgroup/memory ro,nosuid,nodev,noexec,relatime master:22 - cgroup memory rw,memory

Working System

36 31 0:31 / /sys/fs/cgroup/memory rw,nosuid,nodev,noexec,relatime shared:15 - cgroup cgroup rw,memory

When the cgroupv2 support was added we started scanning the second “cgroup” entry in /proc/mountinfo as the file system type. According to the man pages, the first “cgroup” is the file system type. Entry position 10 in [1]mountinfo is “mount source: filesystem-specific information”. All systems we’ve tested on thus far have had two cgroup strings so this regression was not caught. 

I’ll work on a fix.

[1] https://man7.org/linux/man-pages/man5/proc.5.htm

Bob.


> On Sep 1, 2020, at 9:23 AM, David Holmes <david.holmes at oracle.com> wrote:
> 
> On 1/09/2020 10:51 pm, Bob Vandette wrote:
>> Bruno,
>> I can take a look.  Is there a bugs.openjdk.java.net bug filed yet?
>> Please send me information on this issue.  I can’t locate bug 9066610 in the bug database (bugreport.java.com).
> 
> That was the JI number. It is now:
> 
> https://bugs.openjdk.java.net/browse/JDK-8252359
> 
> David
> 
>> Bob.
>>> On Aug 30, 2020, at 6:59 PM, Bruno Borges <Bruno.Borges at microsoft.com> wrote:
>>> 
>>> Hi all,
>>> 
>>> Just wanted to check if anyone at Oracle had a chance to review bug 9066610 that was submitted last week.
>>> 
>>> We would like to continue our discussion and a proposed fix for evaluation.
>>> 
>>> On 2020-08-26, 12:06 AM, "David Holmes" <david.holmes at oracle.com> wrote:
>>> 
>>>    Please note that the discuss at openjdk.java.net mailing list is not the
>>>    appropriate place to discuss this kind of issue. hotspot-runtime-dev
>>>    would be the correct place to discuss this.
>>> 
>>>    Thanks,
>>>    David
>>> 
>>>    On 25/08/2020 7:29 pm, Bruno Borges wrote:
>>>> No worries.
>>>> 
>>>> I am not aware of any other way for non-OpenJDK Authors to submit a bug to OpenJDK except through bugreport.java.com. If there is, happy to follow that for any future issue.
>>>> 
>>>> bb.
>>>> 
>>>> On 2020-08-25, 1:38 AM, "Severin Gehwolf" <sgehwolf at redhat.com> wrote:
>>>> 
>>>>     Hi Bruno,
>>>> 
>>>>     On Tue, 2020-08-25 at 08:05 +0000, Bruno Borges wrote:
>>>>> Hi Severin,
>>>>> 
>>>>> Issue created: 9066610.
>>>> 
>>>>     Thanks. We might need somebody from Oracle to push this one through to
>>>>     https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fbugs.openjdk.java.net%2F&data=02%7C01%7CBruno.Borges%40microsoft.com%7C60dffad37c904298679408d8498e85f3%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637340223777936292&sdata=upvvC%2BHc49Il6L%2B6koJYhVj2hwJhPxDBlApIwKH6pN0%3D&reserved=0. 9XXXX bugs are AFAIK created by the web-
>>>>     interface and need active triage to show up as JDK-8XXXX bugs.
>>>> 
>>>>> Charlie has a fix to propose.
>>>> 
>>>>     Great! Looking forward to it.
>>>> 
>>>>     Thanks,
>>>>     Severin
>>>> 
>>>> 
>>>