ADDITIONAL SYSTEM INFORMATION :
Linux

A DESCRIPTION OF THE PROBLEM :
Occassionally, calls to com.sun.management.OperatingSystemMXBean.getSystemCpuLoad() throw an NPE:

java.lang.NullPointerException: Cannot read the array length because the return value of "jdk.internal.platform.Metrics.getCpuSetCpus()" is null
at jdk.management/com.sun.management.internal.OperatingSystemImpl.isCpuSetSameAsHostCpuSet(Unknown Source)
at jdk.management/com.sun.management.internal.OperatingSystemImpl$ContainerCpuTicks.getContainerCpuLoad(Unknown Source)
at jdk.management/com.sun.management.internal.OperatingSystemImpl.getCpuLoad(Unknown Source)
at jdk.management/com.sun.management.OperatingSystemMXBean.getSystemCpuLoad(Unknown Source)
        ...

This appears to be caused by a TOCTOU (time of check, time of use) issue with a null check at https://github.com/openjdk/jdk/blob/16ef6e2a187181f49b7b2d601c660bbd25ab3845/src/jdk.management/unix/classes/com/sun/management/internal/OperatingSystemImpl.java#L277-L278.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
This issue is flaky and there is no clear reproducer. The exception has been observed running the build system Bazel in a container setup in CI (https://github.com/bazelbuild/bazel/issues/24519).

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
Method does not throw any exceptions.
ACTUAL -
Method throws:

java.lang.NullPointerException: Cannot read the array length because the return value of "jdk.internal.platform.Metrics.getCpuSetCpus()" is null
at jdk.management/com.sun.management.internal.OperatingSystemImpl.isCpuSetSameAsHostCpuSet(Unknown Source)
at jdk.management/com.sun.management.internal.OperatingSystemImpl$ContainerCpuTicks.getContainerCpuLoad(Unknown Source)
at jdk.management/com.sun.management.internal.OperatingSystemImpl.getCpuLoad(Unknown Source)
at jdk.management/com.sun.management.OperatingSystemMXBean.getSystemCpuLoad(Unknown Source)
        ...

This appears to be

CUSTOMER SUBMITTED WORKAROUND :
Catching any NPEs thrown by the method.

FREQUENCY : occasionally