[jdk11u-dev] RFR: 8229147: Linux os::create_thread() overcounts guardpage size with newer glibc (>=2.27)

[Goetz Lindenmaier]

On Mon, 10 Jul 2023 19:47:08 GMT, Lutz Schmidt <lucy at openjdk.org> wrote:

> This backport is for parity with 11.0.21-oracle. 
> Fix didn't apply at all, os/linux/os_linux.cpp was too different in particular. 
> I managed to create a working version by massaging and applying the changes manually. 
> 
> There is some risk involved. It is not caused by the intentional change of behavior but by potential collateral damage. 
> 
> Tests (SAP nightly test suite) do not indicate any issues.
> Reviews pending.

It is a bummer "8225035: Thread stack size issue caused by large TLS size"
is not in 11. But that was a quite unstable change and has a CSR,
so no good candidate to backport.

This backport contains parts of 8225035, though, but they are blocked
by setting the corresponding flag statically to false.
I think this makes sense as this keeps the code similar
and thus easier to maintai

src/hotspot/os/linux/os_linux.cpp line 912:

> 910: 
> 911: #if defined(__GLIBC__) // TLS not in jdk11
> 912: static bool AdjustStackSizeForTLS = false; // Dumy decl as substitute for cmdline parameter

AdjustStackSizeForTLS is declared under ifdef GLIBC, but
the usage is not. Is this correct?
I think the comment " // TLS not in jdk11" should go into a new line.
Also, maybe we should make this "const" so it can be optimized?

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PR Review: https://git.openjdk.org/jdk11u-dev/pull/2035#pullrequestreview-1536650743
PR Review Comment: https://git.openjdk.org/jdk11u-dev/pull/2035#discussion_r1267794180