RFR: 8255799: AArch64: CPU_A53MAC feature may be set incorrectly

Tue Nov 3 17:08:03 UTC 2020

JDK-8255716 (#983) uncovered that os::processor_count on Linux can be not equal to number of cores reported in /proc/cpuinfo. The latter historically was used to decide CPU_A53MAC feature. This patch restores feature detection based on /proc/cpuinfo.

Testing: linux -version
Unfortunately I cannot test windows/aarch64, CC: @lewurm @luhenry

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Commit messages:
 - Set CPU_A53MAC after /proc/cpuinfo

Changes: https://git.openjdk.java.net/jdk/pull/1039/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=1039&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8255799
  Stats: 15 lines in 4 files changed: 13 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1039.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1039/head:pull/1039

PR: https://git.openjdk.java.net/jdk/pull/1039