[jdk11u-dev] RFR: 8283199: Linux os::cpu_microcode_revision() stalls cold startup

Mon Oct 24 09:41:28 UTC 2022

Unclean backport to fix the startup time regression.

The backport is not clean, because [JDK-8238161](https://bugs.openjdk.org/browse/JDK-8238161) is not present in JDK 11, and thus we have `fopen` instead of `os::fopen` in these hunks. I changed the code back to `fopen` to be consistent with the rest of JDK 11.

Verified the startup time improves, using the scripts from the issue.

# Before
real	0m0.081s
real	0m0.081s
real	0m0.081s

# After
real	0m0.062s
real	0m0.062s
real	0m0.062s

Additional testing:
 - [ ] Linux x86_64 fastdebug `tier1`

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

Commit messages:
 - Backport 1443f6b9191c127abdae38cadb1a44af3c652f1d

Changes: https://git.openjdk.org/jdk11u-dev/pull/1471/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=1471&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8283199
  Stats: 19 lines in 1 file changed: 16 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk11u-dev/pull/1471.diff
  Fetch: git fetch https://git.openjdk.org/jdk11u-dev pull/1471/head:pull/1471

PR: https://git.openjdk.org/jdk11u-dev/pull/1471