RFR: 8257746: Regression introduced with JDK-8250984 - memory might be null in some machines

[Severin Gehwolf]

On Thu, 28 Jan 2021 15:01:11 GMT, Poonam Bajaj <poonam at openjdk.org> wrote:

>> I'm curious: What config is this to actually trigger the NPE? How does `/proc/self/mountinfo`, `/proc/self/cgroup` and `/proc/cgroups` look like?
>
>> I'm curious: What config is this to actually trigger the NPE? How does `/proc/self/mountinfo`, `/proc/self/cgroup` and `/proc/cgroups` look like?
> 
> I don't have access to the config. The issue was reported by a customer.

> I'm curious: What config is this to actually trigger the NPE? How does `/proc/self/mountinfo`, `/proc/self/cgroup` and `/proc/cgroups` look like?



> > I'm curious: What config is this to actually trigger the NPE? How does `/proc/self/mountinfo`, `/proc/self/cgroup` and `/proc/cgroups` look like?
> 
> I don't have access to the config. The issue was reported by a customer.

This isn't very satisfying, though. How can we be sure this issue isn't also present in the cgroup v2 code? Has this been tested? Surely, there was some stack trace reported by the customer or some sort of reproducer got provided. What was the reasoning that established this issue is present in JDK head and **only** in cgroups v1 code? My guess is that the issue got triggered via the OperatingSystemMXBean, but nothing to that effect has been noted here or in the bug.

If I were to propose such a point fix, clearly, I'd have to provide some details what the actual problem is and explain why the fix is sufficient and covers all branches. All that got provided is: "But memory could be Null on some machines that have cgroup entries for CPU but not for memory."

-------------

PR: https://git.openjdk.java.net/jdk/pull/2269