Fix UI-thread hang when resuming the target during launch#1596
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Fix UI-thread hang when resuming the target during launch#1596WardenGnaw wants to merge 1 commit into
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AD7Engine.ContinueFromSynchronousEvent (the AD7ProgramCreateEvent path) dispatched ResumeFromLaunch through the blocking WorkerThread.RunOperation, coupling the VS UI/SDM thread to debugger I/O. Over a slow or remote (SSH) transport, AD7Engine.ContinueFromSynchronousEvent + ResumeFromLaunch could stall for a long time or indefinitely, producing a Watson hang. - Add WorkerThread.PostAsyncOperation, a non-blocking dispatch that claims the running-op slot (so later AD7 operations still serialize behind it) but returns without waiting for completion. Faults from the operation are routed to an onError callback from both the synchronous and async completion paths. - ContinueFromSynchronousEvent now posts ResumeFromLaunch via PostAsyncOperation and returns S_OK immediately, so the UI thread is no longer blocked. Resume faults report through SendStartDebuggingError + Terminate via onError, and synchronous failures (OnLoadComplete or the dispatch itself) are still handled locally, since the SDM drops errors returned from this method. - [x] Built and tested locally - [x] Debugged through WSL Linux gdb and the async resume completed.
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Pull request overview
This PR addresses a Visual Studio UI/SDM-thread hang during launch by decoupling AD7Engine.ContinueFromSynchronousEvent (ProgramCreate path) from blocking debugger I/O, while still preserving operation serialization behind the worker thread’s “running-op” slot.
Changes:
- Added
WorkerThread.PostAsyncOperationto dispatch anAsyncOperationwithout blocking the caller while still claiming the running-op slot. - Routed
AD7Engine.ContinueFromSynchronousEventlaunch-resume (ResumeFromLaunch) through the new non-blocking dispatch so it can returnS_OKimmediately. - Added an error-handler pathway for
PostAsyncOperationfaults and surfaced them via an engine callback.
Show a summary per file
| File | Description |
|---|---|
| src/MIDebugEngine/Engine.Impl/OperationThread.cs | Introduces PostAsyncOperation and error-handler plumbing for async operations. |
| src/MIDebugEngine/AD7.Impl/AD7Engine.cs | Stops blocking the UI thread on ResumeFromLaunch by posting it asynchronously and handling failures via callback. |
Review details
- Files reviewed: 2/2 changed files
- Comments generated: 2
- Review effort level: Low
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| /// <summary> | ||
| /// Handler invoked on the worker thread if the operation faults. Only set for PostAsyncOperation. | ||
| /// </summary> | ||
| public Action<Exception> ErrorHandler; |
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| if (errorHandler != null && exceptionDispatchInfo != null) | ||
| { | ||
| InvokeErrorHandler(errorHandler, exceptionDispatchInfo.SourceException); | ||
| } |
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AD7Engine.ContinueFromSynchronousEvent (the AD7ProgramCreateEvent path) dispatched ResumeFromLaunch through the blocking WorkerThread.RunOperation, coupling the VS UI/SDM thread to debugger I/O. Over a slow or remote (SSH) transport, AD7Engine.ContinueFromSynchronousEvent + ResumeFromLaunch could stall for a long time or indefinitely, producing a Watson hang.
Add WorkerThread.PostAsyncOperation, a non-blocking dispatch that claims the running-op slot (so later AD7 operations still serialize behind it) but returns without waiting for completion. Faults from the operation are routed to an onError callback from both the synchronous and async completion paths.
ContinueFromSynchronousEvent now posts ResumeFromLaunch via PostAsyncOperation and returns S_OK immediately, so the UI thread is no longer blocked. Resume faults report through SendStartDebuggingError + Terminate via onError, and synchronous failures (OnLoadComplete or the dispatch itself) are still handled locally, since the SDM drops errors returned from this method.
Built and tested locally