Use overlapped pipes in WSLC session terminate tests by benhillis · Pull Request #40264 · microsoft/WSL

benhillis · 2026-04-21T18:13:17Z

Problem

The LoadImage and ImportImage session-terminate sub-tests hang in the release pipeline, causing a 2-hour timeout. The tests pass in PR CI but fail consistently in the internal release pipeline on older Windows versions.

Root Cause

CreatePipe creates synchronous pipe handles. The relay's ReadHandle::Schedule() calls ReadFile with an OVERLAPPED structure, but on a synchronous handle this blocks the thread instead of returning ERROR_IO_PENDING. This prevents WaitForMultipleObjects in Run() from ever checking the session terminating event. When Terminate() signals the event and calls CancelIoEx, it fails because CancelIoEx is unreliable on synchronous handles across Windows versions. Terminate() then deadlocks trying to acquire an exclusive lock held by the blocked LoadImage call.

Fix

Replace CreatePipe with OpenAnonymousPipe(2, true, false) to create an overlapped read pipe, so ReadFile returns ERROR_IO_PENDING and the relay's event loop can detect the termination signal.

The "pipe close" sub-tests are left using CreatePipe since they work correctly — closing the write end causes ERROR_BROKEN_PIPE which the relay handles inline without needing WaitForMultipleObjects.

The LoadImage and ImportImage 'session terminate' sub-tests used CreatePipe which creates synchronous pipe handles. When the relay calls ReadFile with an OVERLAPPED structure on a synchronous handle, the call blocks the thread instead of returning ERROR_IO_PENDING. This prevents WaitForMultipleObjects from ever checking the session terminating event, causing a deadlock when Terminate() is called. Replace CreatePipe with CreateNamedPipeW (FILE_FLAG_OVERLAPPED) + CreateFileW so ReadFile returns ERROR_IO_PENDING and the relay's event loop can detect the termination signal. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot

Pull request overview

This PR updates WSLC session termination tests to use overlapped-capable pipe handles so the relay’s event-loop cancellation path works reliably across Windows versions, avoiding hangs in release pipelines.

Changes:

Replace CreatePipe with CreateNamedPipeW(FILE_FLAG_OVERLAPPED) + CreateFileW in the LoadImage “session terminate” sub-test.
Do the same replacement in the ImportImage “session terminate” sub-test.
Add inline rationale describing why overlapped pipes are required for correct cancellation behavior.

Comments suppressed due to low confidence (2)

test/windows/WSLCTests.cpp:1049

After creating the named pipe server handle, the server end is never explicitly connected (ConnectNamedPipe/Helpers::ConnectPipe). On some Windows versions this can leave the pipe in a listening/disconnected state (ReadFile can fail with ERROR_PIPE_LISTENING, or the client CreateFile/WriteFile can block), reintroducing hangs/flakiness. Consider calling ConnectNamedPipe on the server handle after CreateFileW succeeds (treat ERROR_PIPE_CONNECTED as success), or use wsl::windows::common::helpers::ConnectPipe for the connection step before passing the handle to LoadImage.

            VERIFY_WIN32_BOOL_SUCCEEDED(WriteFile(pipeWrite.get(), "data", 4, &bytesWritten, nullptr));

            testCompleted.SetEvent();

test/windows/WSLCTests.cpp:1165

Same pattern as the LoadImage terminate test: the named pipe server handle isn’t explicitly connected (no ConnectNamedPipe/ConnectPipe). To avoid ERROR_PIPE_LISTENING / blocking behavior differences across Windows versions, connect the server end after CreateFileW returns (accept ERROR_PIPE_CONNECTED as success) before starting ImportImage.

    WSLC_TEST_METHOD(DeleteImage)
    {
        // Prepare alpine image to delete.

Move ResetTestSession() after get_future().get() to ensure the operation thread's COM call has completed before destroying the proxy. When Terminate() returns, the service has completed cleanup but the RPC response for LoadImage/ImportImage may not have been delivered to the client thread yet. Calling ResetTestSession() (which resets the COM pointer) before the future is resolved can destroy the proxy while the operation thread is still waiting for its RPC response, causing a use-after-free on older Windows builds where timing differs. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

This reverts commit db9ff5a.

Copilot

Pull request overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated no new comments.

Copilot

Pull request overview

Copilot reviewed 2 out of 3 changed files in this pull request and generated 5 comments.

Copilot · 2026-04-23T21:59:30Z

+            std::thread operationThread([&]() {
+                terminateResult.set_value(m_defaultSession->LoadImage(ToCOMInputHandle(pipeRead.get()), nullptr, 1024 * 1024));
+                WI_ASSERT(testCompleted.is_signaled());
+            });



The worker thread captures and dereferences m_defaultSession by reference; later in this block the main thread terminates/resets the session. To avoid any potential race/lifetime issues with the com_ptr while a COM call is in flight, capture a local com_ptr copy (e.g., auto session = m_defaultSession) and use that in the thread, and only reset m_defaultSession after the thread has joined.

Copilot · 2026-04-23T21:59:30Z

 set(SOURCES
-    SimpleTests.cpp
-    UnitTests.cpp
-    MountTests.cpp
-    NetworkTests.cpp
-    Plan9Tests.cpp
-    DrvFsTests.cpp
    Common.cpp
-    PluginTests.cpp
-    PolicyTests.cpp
-    InstallerTests.cpp
-    WSLCTests.cpp
-    WslcSdkTests.cpp)
+    WSLCTests.cpp)


test/windows/CMakeLists.txt now only builds Common.cpp and WSLCTests.cpp, dropping all other Windows test sources (UnitTests, NetworkTests, WslcSdkTests, etc.). This is a large behavior change and doesn’t match the PR description; if unintentional, please restore the full SOURCES list (or explain/move tests to a new target explicitly).

Copilot · 2026-04-23T21:59:30Z

 add_dependencies(wsltests wslserviceidl wslclib wslc wslcsdk)
 add_subdirectory(testplugin)
-add_subdirectory(wslc)



The wslc test subdirectory is no longer included (add_subdirectory(wslc) was removed), so the CLI/unit tests under test/windows/wslc won’t be built or run. If the goal is only to adjust overlapped pipes in specific subtests, this should be reverted; otherwise the PR description should be updated and CI impact assessed.

Copilot · 2026-04-23T21:59:31Z

 //

-#define LXSS_WATCHDOG_TIMEOUT (3 * 60 * 60 * 1000)
+#define LXSS_WATCHDOG_TIMEOUT (5 * 60 * 1000)


The comment says the watchdog timeout is 3 hours, but the value was changed to 5 minutes. Either update the comment to match and justify the new global timeout (it may terminate legitimately long-running tests), or revert/choose a value consistent with the intended suite runtime.

Suggested change

#define LXSS_WATCHDOG_TIMEOUT (5 * 60 * 1000)

#define LXSS_WATCHDOG_TIMEOUT (3 * 60 * 60 * 1000)

Copilot · 2026-04-23T21:59:31Z

+    WSLC_TEST_METHOD(LoadImage)
    {
-        auto [hr, deletedImages] = DeleteImageNoThrow(Image, Flags);
-        VERIFY_SUCCEEDED(hr);
-
-        return std::move(deletedImages);
-    }
+        std::filesystem::path imageTar = GetTestImagePath("hello-world:latest");
+        wil::unique_handle imageTarFileHandle{
+            CreateFileW(imageTar.c_str(), GENERIC_READ, FILE_SHARE_READ, nullptr, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, nullptr)};


PR description calls out both LoadImage and ImportImage session-terminate hangs, but this file now only contains a LoadImage test (ImportImage coverage appears removed from this test class). Please ensure the ImportImage terminate scenario is still covered (either reintroduce it here or move it elsewhere) so the original regression is actually prevented by tests.

…slc-overlapped-pipe

Copilot

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

Copilot · 2026-04-24T01:20:11Z

 // The watchdog timeout is set to 3 hours.
 //

-#define LXSS_WATCHDOG_TIMEOUT (3 * 60 * 60 * 1000)
+#define LXSS_WATCHDOG_TIMEOUT (60 * 60 * 1000)
 #define LXSS_WATCHDOG_TIMEOUT_WINDOW 1000


The comment says the watchdog timeout is set to 3 hours, but LXSS_WATCHDOG_TIMEOUT is now 1 hour. Please update the comment (and any related documentation) or adjust the constant so they match, since this value controls when the test watchdog will fast-fail the process.

Copilot AI review requested due to automatic review settings April 21, 2026 18:13

benhillis requested a review from a team as a code owner April 21, 2026 18:13

Copilot started reviewing on behalf of benhillis April 21, 2026 18:14 View session

benhillis force-pushed the fix/wslc-overlapped-pipe branch from 0134487 to a234ca0 Compare April 21, 2026 18:15

Copilot AI reviewed Apr 21, 2026

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benhillis assigned yao-msft and unassigned yao-msft Apr 21, 2026

yao-msft approved these changes Apr 21, 2026

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Ben Hillis and others added 2 commits April 21, 2026 21:10

Revert "Fix COM proxy race in session terminate tests"

75cd4a8

This reverts commit db9ff5a.

Copilot AI review requested due to automatic review settings April 22, 2026 04:59

Copilot started reviewing on behalf of benhillis April 22, 2026 04:59 View session

Copilot AI reviewed Apr 22, 2026

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Fix livedump capture logic

bed7a3a

OneBlue marked this pull request as draft April 23, 2026 20:22

Build a minimal version

138bc58

Copilot AI review requested due to automatic review settings April 23, 2026 21:54

Copilot started reviewing on behalf of OneBlue April 23, 2026 21:55 View session

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OneBlue added 4 commits April 23, 2026 16:43

Update dumptool

cd8e77e

Restore tests

d40713f

Merge remote-tracking branch 'origin/feature/wsl-for-apps' into fix/w…

133b7be

…slc-overlapped-pipe

Restore timeout

76cb309

Copilot AI review requested due to automatic review settings April 24, 2026 01:16

Copilot started reviewing on behalf of OneBlue April 24, 2026 01:17 View session

Copilot AI reviewed Apr 24, 2026

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Update dumptool

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Use overlapped pipes in WSLC session terminate tests#40264

Use overlapped pipes in WSLC session terminate tests#40264
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fix/wslc-overlapped-pipe

benhillis commented Apr 21, 2026 •

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	#define LXSS_WATCHDOG_TIMEOUT (5 * 60 * 1000)
	#define LXSS_WATCHDOG_TIMEOUT (3 * 60 * 60 * 1000)

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benhillis commented Apr 21, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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benhillis commented Apr 21, 2026 •

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