[release/10.0] [mono][interp] Add missing intrinsic for Volatile.ReadBarrier/WriteBarrier

[github-actions]

Backport of #124538 to release/10.0

/cc @BrzVlad

Customer Impact

• Customer reported
• Found internally

Applications calling Volatile.ReadBarrier/WriteBarrier will crash when running under mono interpreter. This can impact ios, android debug and wasm. A customer upgrading to Microsoft.CodeAnalysis.CSharp 5.6.0 encountered this error.

Regression

• Yes
• No

This new api was added in .NET10. As more libraries will use this new API, this problem will become more frequent.

Testing

Tested on simple app calling this API.

Risk

Low. This just adds an intrisic for this API which conservatively emits a full memory barrier.

[dotnet-policy-service]

Tagging subscribers to this area: @vitek-karas, @BrzVlad, @kotlarmilos
See info in area-owners.md if you want to be subscribed.

[github-actions]

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[github-actions]

Holistic Review

Motivation: This is a backport of #124538 to release/10.0. The Volatile.ReadBarrier/Volatile.WriteBarrier APIs are new in .NET 10. Under the Mono interpreter these methods had no intrinsic handling, so calls crash. This impacts iOS, Android debug, and WASM scenarios, and a customer hit it after upgrading Microsoft.CodeAnalysis.CSharp.

Approach: Adds an intrinsic case in interp_handle_intrinsics that maps parameterless System.Threading.Volatile.ReadBarrier/WriteBarrier to MINT_MONO_MEMORY_BARRIER, mirroring the existing Thread.MemoryBarrier handling. A new VolatileTests set exercises the barriers directly, via reflection, and interleaved with Volatile.Read/Write, and is wired into the test csproj.

Summary: The change is minimal, self-contained, and faithfully matches the original PR. Emitting a full memory barrier is conservatively correct for both the acquire-style read barrier and the release-style write barrier, and the param_count == 0 guard keeps the intrinsic scoped to the intended overloads. The test asserts only that the calls do not throw (the equality assertions on single-threaded, non-shared locals are trivially true), which aligns with the crash-fix intent. No correctness, security, or performance concerns. Verdict: LGTM.

Note

This review was generated by this repository's Holistic Review agentic workflow to complement the built-in Copilot review.

Generated by Holistic Review · 40.7 AIC · ⌖ 10.2 AIC · ⊞ 10K

[snakefoot]

@rbhanda + @JulieLeeMSFT Have the merge been forgotten? Maybe update the milestone?

[svick]

Hi,

the code complete date for 10.0.12 (the September 2026 release) is Monday 10 August. Make sure to merge this PR on that date at the latest, or it won't make it into that release.

As a reminder, if this is a product change, you also need Tactics approval before merging this PR (test-only or infra-only changes don't require Tactics approval).

[svick]

/ba-g timeouts on wasm

[snakefoot]

@rbhanda + @JulieLeeMSFT Maybe update the milestone?