RFR: 8255716: AArch64: Regression: JVM crashes if manually offline a core

[Andrew Dinn]

On Sun, 1 Nov 2020 12:26:15 GMT, Patrick Zhang <qpzhang at openjdk.org> wrote:

> This assertion is practically not needed. While a test system with some cores intentionally turned off, e.g. via echo 0 > /sys/devices/system/cpu/cpu1/online, java -version would crash, building openjdk on this system would fail too.

I don't follow this comment. I am not saying the check is redundant but the rationale provided above does not really cut it. Sure, a build might also fail. But that misses several possibilities. The image could be built on a different machine which didn't have the cpu switched off. The cpu switch off could happen on the same machine between building and running. If there is a good reason for not including this check the one cited above is not it.

Can you just state in simple terms why it is ok to continue when the info retrieved from /proc/cpuinfo and os::processor_count() do not match up?

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PR: https://git.openjdk.java.net/jdk/pull/983