RFR: 8283199: Linux os::cpu_microcode_revision() stalls cold startup [v2]

[Aleksey Shipilev]

On Mon, 21 Mar 2022 10:26:02 GMT, Claes Redestad <redestad at openjdk.org> wrote:

>> No, because AFAICS, `fgets` reads until buffer is full or the EOL is read. We are looking for a rather short "microcode: 0x..." line in procfs, so there is no need to allocate the entire 2K for this. This was my first attempt to improve this code, and it is not directly relevant to issue at hand, so I can revert it, if that's a questionable change.
>
> Ok, makes sense. If it's safe and works I don't mind if you keep it. I guess JDK-8283200 will make such micro-optimizations moot, though.

Did it anyway, see new commit.

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PR: https://git.openjdk.java.net/jdk/pull/7825