8371337: [CRaC] Fastdebug build fails when calling OperatingSystemMxBean.getProcessCpuLoad after restore

[rvansa]

A JVM that executed OperatingSystemImpl.getProcessCpuLoad() before checkpoint can fail with assertion failure after restore with:

java: /home/rvansa/work/zulu/src/jdk.management/linux/native/libmanagement_ext/UnixOperatingSystem.c:291: get_cpuload_internal: Assertion `pticks->usedKernel >= tmp.usedKernel' failed.

This is an assertion failure, therefore failing only in debug builds, and providing probably a non-sense value in release builds. We should remove the assertion and return a negative value (documented as value for ‘unavailable’) if this is detected.

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• JDK-8371337: [CRaC] Fastdebug build fails when calling OperatingSystemMxBean.getProcessCpuLoad after restore (Bug - P4)

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8371337: [CRaC] Fastdebug build fails when calling OperatingSystemMxBean.getProcessCpuLoad after restore

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[TimPushkin]

I haven't read the precise definitions of used, usedKernel, total, is checking only usedKernel enough to guarantee the comparison is also valid for the other two values? Shouldn't we check both used and usedKernel (assuming total is exactly their sum, which may not be the case) in case only one of them has gone backwards?