RFR: 8358680: AOT cache creation fails: no strings should have been added

[Aleksey Shipilev]

On Mon, 16 Jun 2025 03:30:40 GMT, Ioi Lam <iklam at openjdk.org> wrote:

> Background: when writing the string table in the AOT cache, we do this:
> 
> 1. Find out the number of strings in the interned string table
> 2. Allocate Java object arrays that are large enough to store these strings. These arrays are used by `StringTable::lookup_shared()` in the production run.
> 3. Enter safepoint
> 4. Copy the strings into the arrays
> 
> This bug happened because:
> 
> - Step 1 is not thread safe, so it may be reading a stale version of `_items_count`
> - JIT compiler threads may create more interned strings after step 1
> 
> This PR attempts to fix both issues.

I still dislike hooking up to compiler infrastructure to figure out if something is adding interned strings. I really, really dislike the divergence we would introduce with JDK 25 -> JDK 26 once a variant of [JDK-8357473](https://bugs.openjdk.org/browse/JDK-8357473) lands in mainline. I cannot yet think of better solution though, let me think about it some more. At very least we need to get the sequencing of patches right...

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PR Comment: https://git.openjdk.org/jdk/pull/25816#issuecomment-2985136083