Fix Wasm async continuation stack walk by lewing · Pull Request #133995 · dotnet/runtime

lewing · 2026-09-15T22:14:33Z

Summary

use the caller shadow stack's virtual IP as the return address for the Wasm ResumeInterpreterContinuation transition frame
enable the full runtime-async runner on Wasm while filtering only tests that require multithreading
use class-level capability conditions where every test in a class requires multithreading and method-level conditions for mixed classes
quarantine only the exact unsupported cases: Async2PInvoke.TestEntryPoint under [wasm][coreclr] GetUnmanagedCallersOnlyThunk: unknown thunk for unmanaged callers only method #124219 and Async2CollectibleAlc under Browser WASM collectible ALC test has no loadable assembly path #134001
run the diagnostic stack-trace scenario twice to cover cold and warm FCall paths
make reflection method ordering deterministic with StringComparer.Ordinal

Root cause

The Wasm FCall supplied the managed caller's R2R shadow stack pointer but used the native ResumeInterpreterContinuation entrypoint as the transition block return address. On the warm path, stack walking paired those unrelated values and failed the GetWasmVirtualIPFromStackPointer(sp) == controlPC invariant.

#133768 also enabled the full src/tests/async runner on Wasm. Many tests intentionally block on incomplete tasks and therefore require multithreading; those tests now use PlatformDetection.IsMultithreadingSupported rather than disabling the whole runner.

Validation

browser-Wasm Checked CoreCLR build
browser-Wasm interpreter runner: 142 discovered, 42 passed, 0 failed, 100 capability/issue filtered
browser-Wasm R2R-CG2 runner: 142 discovered, 42 passed, 0 failed, 100 capability/issue filtered
WASI runner: 142 discovered, 44 passed, 0 failed, 98 capability/issue filtered
native macOS arm64 runner: 142 passed, 0 failed
the diagnostic test fails on the old runtime's warm path and passes after the fix

Resolves #133931

Note

This pull request description was generated with GitHub Copilot assistance.

Use the caller shadow stack virtual IP for the interpreter continuation transition frame and exercise both cold and warm FCall paths. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: 8a57fff8-6c30-4d3c-ac72-a80975122a96

azure-pipelines · 2026-09-15T22:15:15Z

Azure Pipelines: Successfully started running 3 pipeline(s). 13 pipeline(s) were filtered out due to trigger conditions. There may be pipelines that require an authorized user to comment /azp run to run.

dotnet-policy-service · 2026-09-15T22:15:40Z

Tagging subscribers to this area: @steveisok, @tommcdon, @dotnet/dotnet-diag
See info in area-owners.md if you want to be subscribed.

Add the active re-enable tracker beside the project-level WebAssembly exclusion. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: 8a57fff8-6c30-4d3c-ac72-a80975122a96

lewing · 2026-09-15T22:20:28Z

This got opened too early, fixing

Copilot

Copilot review overview

🔵 Needs a closer look

The transition-frame virtual IP should be derived lazily during stack inspection.

Review tier: Lite
Findings: None

What changed in this PR

Fixes Wasm async continuation stack walking and adds focused regression coverage.

Changes:

Updates Wasm continuation transition-frame metadata.
Adds a Wasm-specific async test runner.
Runs cold and warm diagnostic stack-trace scenarios.

File	Description
`src/tests/async/diagnostic-ip-stacktrace/diagnostic-ip-stacktrace.cs`	Runs the diagnostic scenario twice.
`src/tests/async/async.csproj`	Keeps the general async runner disabled on Wasm.
`src/tests/async/async-wasm.csproj`	Adds the focused Wasm runner.
`src/coreclr/vm/interpexec.cpp`	Updates the Wasm continuation transition frame return address.

This reverts commit b3b2ec9.

Guard synchronous-wait tests with the multithreading capability, quarantine the two exact unsupported Wasm cases, and preserve all native coverage. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: 8a57fff8-6c30-4d3c-ac72-a80975122a96

azure-pipelines · 2026-09-15T23:20:25Z

Azure Pipelines: Successfully started running 3 pipeline(s). 13 pipeline(s) were filtered out due to trigger conditions. There may be pipelines that require an authorized user to comment /azp run to run.

dotnet-policy-service · 2026-09-15T23:20:40Z

Tagging subscribers to 'arch-wasm': @lewing, @pavelsavara
See info in area-owners.md if you want to be subscribed.

Copilot

Copilot review overview

🟡 Changes recommended

Critical findings remain in async test dependency ordering and reflection test capability gating.

Get a fresh assessment by requesting another Copilot review.

Review tier: Lite
Findings: 2

Open (2)

Import the parent targets before adding the TestLibrary reference · New
Gate the remaining reflection suspension theories on Wasm · New

davidwrighton

This will do for now.

Enable the full runner, gate multithreading-dependent tests by capability, and quarantine only exact unsupported Wasm scenarios. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: 8a57fff8-6c30-4d3c-ac72-a80975122a96

Keep the shared TestLibrary reference on standalone async children while relying on the parent test targets for the merged runner. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: 8a57fff8-6c30-4d3c-ac72-a80975122a96

Copilot

Copilot review overview

🟡 Changes recommended

Unresolved critical and moderate test-gating issues remain in pinvoke.cs and simple-eh.cs.

Get a fresh assessment by requesting another Copilot review.

Review tier: Lite
Findings: 1

Open (1)

Gate the P/Invoke test on multithreading support · New

Resolved since last review (2)

Gate the remaining reflection suspension theories on Wasm
Import the parent targets before adding the TestLibrary reference

jakobbotsch · 2026-09-16T05:08:56Z

 public class AwaitNotAsync
 {
-    [Fact]
+    [ConditionalFact(typeof(TestLibrary.PlatformDetection), nameof(TestLibrary.PlatformDetection.IsMultithreadingSupported))]


Is this really how we want to deal with this for wasm? I do not think it is very reasonable to have to mark all async tests this way if they don't finish synchronously....

Browser has single thread.

.Wait() is or should be PNSE.

The better way is to make the whole unit test method async and await instead of .Wait().

I'm not sure if some of the tests actually validate .Wait() specifically, those should stay ConditionalFact ... IsMultithreadingSupported

The better way is to make the whole unit test method async and await instead of .Wait().

Yes, I agree. I think this requires work in the test generator to support Task-returning tests and to hook that up in the way WASM expects.

I'm not sure if some of the tests actually validate .Wait() specifically, those should stay ConditionalFact ... IsMultithreadingSupported

We may start and run async tasks in parallel, but I do not think any runtime async test should be validating Task.Wait() specifically. It is all about waiting for the tasks to finish.

@lewing could you please ask your copilot to do that as follow up?

I am working on it in #134042

## Summary - use the caller shadow stack's virtual IP as the return address for the Wasm `ResumeInterpreterContinuation` transition frame - enable the full runtime-async runner on Wasm while filtering only tests that require multithreading - use class-level capability conditions where every test in a class requires multithreading and method-level conditions for mixed classes - quarantine only the exact unsupported cases: `Async2PInvoke.TestEntryPoint` under dotnet#124219 and `Async2CollectibleAlc` under dotnet#134001 - run the diagnostic stack-trace scenario twice to cover cold and warm FCall paths - make reflection method ordering deterministic with `StringComparer.Ordinal` ## Root cause The Wasm FCall supplied the managed caller's R2R shadow stack pointer but used the native `ResumeInterpreterContinuation` entrypoint as the transition block return address. On the warm path, stack walking paired those unrelated values and failed the `GetWasmVirtualIPFromStackPointer(sp) == controlPC` invariant. dotnet#133768 also enabled the full `src/tests/async` runner on Wasm. Many tests intentionally block on incomplete tasks and therefore require multithreading; those tests now use `PlatformDetection.IsMultithreadingSupported` rather than disabling the whole runner. ## Validation - browser-Wasm Checked CoreCLR build - browser-Wasm interpreter runner: 142 discovered, 42 passed, 0 failed, 100 capability/issue filtered - browser-Wasm R2R-CG2 runner: 142 discovered, 42 passed, 0 failed, 100 capability/issue filtered - WASI runner: 142 discovered, 44 passed, 0 failed, 98 capability/issue filtered - native macOS arm64 runner: 142 passed, 0 failed - the diagnostic test fails on the old runtime's warm path and passes after the fix Resolves dotnet#133931 > [!NOTE] > This pull request description was generated with GitHub Copilot assistance. --------- Copilot-Session: 8a57fff8-6c30-4d3c-ac72-a80975122a96

lewing requested review from BrzVlad and janvorli as code owners September 15, 2026 22:14

Copilot AI lite review requested due to automatic review settings September 15, 2026 22:14

github-actions Bot added the area-Diagnostics-coreclr label Sep 15, 2026

dotnet-policy-service Bot assigned lewing Sep 15, 2026

Copilot started reviewing on behalf of lewing September 15, 2026 22:15 View session

Link Wasm async test quarantine

b3b2ec9

Add the active re-enable tracker beside the project-level WebAssembly exclusion. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: 8a57fff8-6c30-4d3c-ac72-a80975122a96

lewing marked this pull request as draft September 15, 2026 22:19

Copilot AI reviewed Sep 15, 2026

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lewing added 2 commits September 15, 2026 17:27

Revert "Link Wasm async test quarantine"

f4d626b

This reverts commit b3b2ec9.

lewing marked this pull request as ready for review September 15, 2026 23:20

Copilot AI review requested due to automatic review settings September 15, 2026 23:20

lewing added the arch-wasm WebAssembly architecture label Sep 15, 2026

Copilot started reviewing on behalf of lewing September 15, 2026 23:20 View session

lewing mentioned this pull request Sep 15, 2026

AF: GetWasmVirtualIPFromStackPointer(sp) == controlPC in diagnostic-ip-stacktrace test #133931

Closed

lewing requested a review from davidwrighton September 15, 2026 23:22

Copilot AI reviewed Sep 15, 2026

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Comment thread src/tests/async/Directory.Build.targets Outdated

Comment thread src/tests/async/reflection/reflection.cs

lewing requested a review from jkotas September 15, 2026 23:31

davidwrighton approved these changes Sep 15, 2026

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Comment thread src/coreclr/vm/interpexec.cpp

lewing added 2 commits September 15, 2026 18:47

Copilot AI review requested due to automatic review settings September 15, 2026 23:48

Copilot started reviewing on behalf of lewing September 15, 2026 23:49 View session

davidwrighton approved these changes Sep 15, 2026

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lewing enabled auto-merge (squash) September 15, 2026 23:56

Copilot AI reviewed Sep 15, 2026

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Comment thread src/tests/async/pinvoke/pinvoke.cs

lewing merged commit 76e6281 into dotnet:main Sep 16, 2026
113 of 116 checks passed

build-analysis Bot mentioned this pull request Sep 16, 2026

[ci-scan] Test failure: Runtime_133715.TestEntryPoint on Mono interpreter #133992

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jakobbotsch reviewed Sep 16, 2026

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dotnet-maestro Bot mentioned this pull request Sep 17, 2026

[main] Source code updates from dotnet/runtime dotnet/dotnet#9438

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dotnet-milestone-bot Bot added this to the 12.0-preview1 milestone Sep 17, 2026

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Summary

Root cause

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