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Implement out-of-process SetThreadContext support for debugger detach - #118849

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tommcdon merged 16 commits into
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tommcdon:dev/tommcdon/fix_cet_detach
Sep 19, 2025
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Implement out-of-process SetThreadContext support for debugger detach#118849
tommcdon merged 16 commits into
dotnet:mainfrom
tommcdon:dev/tommcdon/fix_cet_detach

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This change handles a race between debugger detach and Debugger::SendSetThreadContextNeeded notifications. When the debugger calls ICorDebugController::Detach, we either delete or mark in-flight controllers for deletion which allows for further processing of in-flight breakpoint/single-step exceptions. If out-of-process SetThreadContext is needed is enabled, we could cause the debuggee to crash with an unhandled breakpoint exception while sending SetThreadContextNeeded flares after we detached. This change causes the detach operation to track SetThreadContextNeeded operations before signaling completion. Note the change only takes affect if CET debugging is enabled, and it only tracks notification count and state if we are in the process of detaching. This change handles early process exit during attach as well.
Fixes#116870

@tommcdontommcdon added this to the 10.0.0 milestone Aug 18, 2025
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Pull Request Overview

This PR implements support for out-of-process SetThreadContext operations during debugger detach to handle a race condition between debugger detach and SetThreadContextNeeded notifications. The key issue addressed is preventing debuggee crashes from unhandled breakpoint exceptions when these notifications are sent after the debugger has already detached.

Key changes include:

  • Introduction of tracking mechanisms for SetThreadContext operations during detach
  • New IPC event type for detach completion with flare count information
  • Synchronization logic to ensure all pending SetThreadContext operations complete before detach finishes

Reviewed Changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 4 comments.

Show a summary per file
FileDescription
src/coreclr/debug/shared/dbgtransportsession.cppAdds size calculation for new DETACH_FROM_PROCESS_RESULT event type
src/coreclr/debug/inc/dbgipceventtypes.hDefines new DB_IPCE_DETACH_FROM_PROCESS_RESULT event type and updates RUNTIME_LAST marker
src/coreclr/debug/inc/dbgipcevents.hAdds DetachFromProcessResult structure with cDispatchedFlares field
src/coreclr/debug/ee/debugger.cppImplements tracking logic for SetThreadContext operations during detach
src/coreclr/debug/ee/controller.hAdds static variables and methods for tracking detach state and dispatched exceptions
src/coreclr/debug/ee/controller.cppImplements controller counting and detach cleanup logic
src/coreclr/debug/di/rspriv.hAdds DetachNotifications helper class and detach-related member variables
src/coreclr/debug/di/process.cppImplements detach synchronization logic and event handling

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Comment threadsrc/coreclr/debug/ee/controller.cpp Outdated
Comment threadsrc/coreclr/debug/ee/controller.h Outdated
Comment threadsrc/coreclr/debug/di/process.cpp Outdated
Comment threadsrc/coreclr/debug/ee/debugger.cpp Outdated
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LGTM

@tommcdon
Track active controller ref count for detach through DebuggerControll…
367c638
…er creation and desctruction and DispatchPatchOrSingleStep
@thaystg
thaystg self-requested a review August 23, 2025 02:57
This was referenced Aug 23, 2025
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Comment threadsrc/coreclr/debug/ee/controller.h Outdated
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3 tasks
@tommcdon
Revert "Continuously track active dispatched exceptions and flares sent"
4a1905f
This reverts commit dd6d28c.
@tommcdon
Revert "Track active controller ref count for detach through Debugger…
45878e0
…Controller creation and desctruction and DispatchPatchOrSingleStep"
This reverts commit 367c638.
@tommcdon
Revert "Fix build break"
aba7e35
This reverts commit 240b372.
@tommcdon
Revert "Implement out-of-process detach support"
c186a8d
This reverts commit d80b6c4.
@tommcdon
Out-of-process detach support for CET
c762a0d
Debugger events are tracked out of process to determine which threads have outstanding SetThreadContextNeeded flares
@tommcdon
Remove unused enum
1593263
@tommcdon
Break out of detach if timed out or process exited
50466bc
@tommcdontommcdon mentioned this pull request Sep 16, 2025
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Yeah, this is getting much easier to reason about. I put a few suggestions inline but overall looks good!

Comment threadsrc/coreclr/debug/ee/debugger.cpp Outdated
Comment threadsrc/coreclr/debug/di/process.cpp Outdated
@tommcdon
Add ClearSetIP to SetThreadContextNeeded event,
50869e4
Refactor HandleSetThreadContextNeeded for improved readability
@tommcdon
Handle case when out of process setthreadcontext is oped-out but avai…
e5310b1
…lable on the platform
noahfalk
noahfalk approved these changes Sep 19, 2025
View reviewed changes
Comment threadsrc/coreclr/debug/di/rspriv.h Outdated
@tommcdon
tommcdon enabled auto-merge (squash) September 19, 2025 16:49
@tommcdon
tommcdon merged commit 2db45f1 into dotnet:mainSep 19, 2025
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/backport to release/10.0

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Started backporting to release/10.0: https://github.com/dotnet/runtime/actions/runs/17866298253

@github-actionsgithub-actionsBot mentioned this pull request Sep 19, 2025
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xtqqczze pushed a commit to xtqqczze/dotnet-runtime that referenced this pull request Sep 20, 2025
@tommcdon@xtqqczze
Implement out-of-process SetThreadContext support for debugger detach (…
4ced7ef
…dotnet#118849)
* Implement out-of-process detach support
* Fix build break
* Handle early process termination during detach in out-of-process debugging
* Track active controller ref count for detach through DebuggerController creation and desctruction and DispatchPatchOrSingleStep
* Continuously track active dispatched exceptions and flares sent
* Revert "Continuously track active dispatched exceptions and flares sent"
This reverts commit dd6d28c.
* Revert "Track active controller ref count for detach through DebuggerController creation and desctruction and DispatchPatchOrSingleStep"
This reverts commit 367c638.
* Revert "Fix build break"
This reverts commit 240b372.
* Revert "Implement out-of-process detach support"
This reverts commit d80b6c4.
* Out-of-process detach support for CET
Debugger events are tracked out of process to determine which threads have outstanding SetThreadContextNeeded flares
* Remove unused enum
* Break out of detach if timed out or process exited
* Add ClearSetIP to SetThreadContextNeeded event,
Refactor HandleSetThreadContextNeeded for improved readability
* Handle case when out of process setthreadcontext is oped-out but available on the platform
* PR feedback on code comment
@github-actionsgithub-actionsBot locked and limited conversation to collaborators Oct 20, 2025
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@noahfalknoahfalknoahfalk approved these changes
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Detaching from a .Net9 debuggee can crash the application

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Implement out-of-process SetThreadContext support for debugger detach by tommcdon · Pull Request #118849 · dotnet/runtime · GitHub
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Implement out-of-process SetThreadContext support for debugger detach - #118849
Merged
tommcdon merged 16 commits into
dotnet:mainfrom 
tommcdon:dev/tommcdon/fix_cet_detach
Sep 19, 2025
Merged
Implement out-of-process SetThreadContext support for debugger detach#118849
tommcdon merged 16 commits into
dotnet:mainfrom 
tommcdon:dev/tommcdon/fix_cet_detach
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This change handles a race between debugger detach and Debugger::SendSetThreadContextNeeded notifications. When the debugger calls ICorDebugController::Detach, we either delete or mark in-flight controllers for deletion which allows for further processing of in-flight breakpoint/single-step exceptions. If out-of-process SetThreadContext is needed is enabled, we could cause the debuggee to crash with an unhandled breakpoint exception while sending SetThreadContextNeeded flares after we detached. This change causes the detach operation to track SetThreadContextNeeded operations before signaling completion. Note the change only takes affect if CET debugging is enabled, and it only tracks notification count and state if we are in the process of detaching. This change handles early process exit during attach as well.
Fixes#116870
@tommcdontommcdon
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Pull Request Overview
This PR implements support for out-of-process SetThreadContext operations during debugger detach to handle a race condition between debugger detach and SetThreadContextNeeded notifications. The key issue addressed is preventing debuggee crashes from unhandled breakpoint exceptions when these notifications are sent after the debugger has already detached.
Key changes include:
  • Introduction of tracking mechanisms for SetThreadContext operations during detach
  • New IPC event type for detach completion with flare count information
  • Synchronization logic to ensure all pending SetThreadContext operations complete before detach finishes
Reviewed Changes
Copilot reviewed 8 out of 8 changed files in this pull request and generated 4 comments.
Show a summary per file
FileDescription
src/coreclr/debug/shared/dbgtransportsession.cppAdds size calculation for new DETACH_FROM_PROCESS_RESULT event type
src/coreclr/debug/inc/dbgipceventtypes.hDefines new DB_IPCE_DETACH_FROM_PROCESS_RESULT event type and updates RUNTIME_LAST marker
src/coreclr/debug/inc/dbgipcevents.hAdds DetachFromProcessResult structure with cDispatchedFlares field
src/coreclr/debug/ee/debugger.cppImplements tracking logic for SetThreadContext operations during detach
src/coreclr/debug/ee/controller.hAdds static variables and methods for tracking detach state and dispatched exceptions
src/coreclr/debug/ee/controller.cppImplements controller counting and detach cleanup logic
src/coreclr/debug/di/rspriv.hAdds DetachNotifications helper class and detach-related member variables
src/coreclr/debug/di/process.cppImplements detach synchronization logic and event handling
You can also share your feedback on Copilot code review for a chance to win a $100 gift card. Take the survey.
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Comment threadsrc/coreclr/debug/ee/debugger.cpp
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LGTM
@tommcdon
Track active controller ref count for detach through DebuggerControll…
367c638
…er creation and desctruction and DispatchPatchOrSingleStep
@thaystg
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self-requested a review
August 23, 2025 02:57

This was referenced Aug 23, 2025

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3 tasks
@tommcdon
Revert "Continuously track active dispatched exceptions and flares sent"
4a1905f
This reverts commit dd6d28c.
@tommcdon
Revert "Track active controller ref count for detach through Debugger…
45878e0
…Controller creation and desctruction and DispatchPatchOrSingleStep"
This reverts commit 367c638.
@tommcdon
Revert "Fix build break"
aba7e35
This reverts commit 240b372.
@tommcdon
Revert "Implement out-of-process detach support"
c186a8d
This reverts commit d80b6c4.
@tommcdon
Out-of-process detach support for CET
c762a0d
Debugger events are tracked out of process to determine which threads have outstanding SetThreadContextNeeded flares
@tommcdon
Remove unused enum
1593263
@tommcdon
Break out of detach if timed out or process exited
50466bc
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Yeah, this is getting much easier to reason about. I put a few suggestions inline but overall looks good!
Comment threadsrc/coreclr/debug/ee/debugger.cpp
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Comment threadsrc/coreclr/debug/di/process.cpp
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@tommcdon
Add ClearSetIP to SetThreadContextNeeded event,
50869e4
Refactor HandleSetThreadContextNeeded for improved readability
@tommcdon
Handle case when out of process setthreadcontext is oped-out but avai…
e5310b1
…lable on the platform
noahfalk
noahfalk
approved these changes
Sep 19, 2025
View reviewed changes
Comment threadsrc/coreclr/debug/di/rspriv.h
Outdated

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tommcdon
enabled auto-merge (squash)
September 19, 2025 16:49
@tommcdon
tommcdon
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/backport to release/10.0
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Started backporting to release/10.0: https://github.com/dotnet/runtime/actions/runs/17866298253
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xtqqczze pushed a commit
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that referenced
this pull request
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@tommcdon@xtqqczze
Implement out-of-process SetThreadContext support for debugger detach (…
4ced7ef
…dotnet#118849)
* Implement out-of-process detach support
* Fix build break
* Handle early process termination during detach in out-of-process debugging
* Track active controller ref count for detach through DebuggerController creation and desctruction and DispatchPatchOrSingleStep
* Continuously track active dispatched exceptions and flares sent
* Revert "Continuously track active dispatched exceptions and flares sent"
This reverts commit dd6d28c.
* Revert "Track active controller ref count for detach through DebuggerController creation and desctruction and DispatchPatchOrSingleStep"
This reverts commit 367c638.
* Revert "Fix build break"
This reverts commit 240b372.
* Revert "Implement out-of-process detach support"
This reverts commit d80b6c4.
* Out-of-process detach support for CET
Debugger events are tracked out of process to determine which threads have outstanding SetThreadContextNeeded flares
* Remove unused enum
* Break out of detach if timed out or process exited
* Add ClearSetIP to SetThreadContextNeeded event,
Refactor HandleSetThreadContextNeeded for improved readability
* Handle case when out of process setthreadcontext is oped-out but available on the platform
* PR feedback on code comment
@github-actionsgithub-actionsBot
locked and limited conversation to collaborators
Oct 20, 2025
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Copilot left review comments
@noahfalknoahfalknoahfalk approved these changes
@lateralusXlateralusXAwaiting requested review from lateralusX
@hoyosjshoyosjsAwaiting requested review from hoyosjs
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Successfully merging this pull request may close these issues.

Detaching from a .Net9 debuggee can crash the application


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Implement out-of-process SetThreadContext support for debugger detach by tommcdon · Pull Request #118849 · dotnet/runtime · GitHub
Skip to content
Implement out-of-process SetThreadContext support for debugger detach - #118849
Merged
tommcdon merged 16 commits into
dotnet:mainfrom 
tommcdon:dev/tommcdon/fix_cet_detach
Sep 19, 2025
Merged
Implement out-of-process SetThreadContext support for debugger detach#118849
tommcdon merged 16 commits into
dotnet:mainfrom 
tommcdon:dev/tommcdon/fix_cet_detach
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@tommcdon
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This change handles a race between debugger detach and Debugger::SendSetThreadContextNeeded notifications. When the debugger calls ICorDebugController::Detach, we either delete or mark in-flight controllers for deletion which allows for further processing of in-flight breakpoint/single-step exceptions. If out-of-process SetThreadContext is needed is enabled, we could cause the debuggee to crash with an unhandled breakpoint exception while sending SetThreadContextNeeded flares after we detached. This change causes the detach operation to track SetThreadContextNeeded operations before signaling completion. Note the change only takes affect if CET debugging is enabled, and it only tracks notification count and state if we are in the process of detaching. This change handles early process exit during attach as well.
Fixes#116870
@tommcdontommcdon
added this to the 10.0.0 milestone
Aug 18, 2025
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Pull Request Overview
This PR implements support for out-of-process SetThreadContext operations during debugger detach to handle a race condition between debugger detach and SetThreadContextNeeded notifications. The key issue addressed is preventing debuggee crashes from unhandled breakpoint exceptions when these notifications are sent after the debugger has already detached.
Key changes include:
  • Introduction of tracking mechanisms for SetThreadContext operations during detach
  • New IPC event type for detach completion with flare count information
  • Synchronization logic to ensure all pending SetThreadContext operations complete before detach finishes
Reviewed Changes
Copilot reviewed 8 out of 8 changed files in this pull request and generated 4 comments.
Show a summary per file
FileDescription
src/coreclr/debug/shared/dbgtransportsession.cppAdds size calculation for new DETACH_FROM_PROCESS_RESULT event type
src/coreclr/debug/inc/dbgipceventtypes.hDefines new DB_IPCE_DETACH_FROM_PROCESS_RESULT event type and updates RUNTIME_LAST marker
src/coreclr/debug/inc/dbgipcevents.hAdds DetachFromProcessResult structure with cDispatchedFlares field
src/coreclr/debug/ee/debugger.cppImplements tracking logic for SetThreadContext operations during detach
src/coreclr/debug/ee/controller.hAdds static variables and methods for tracking detach state and dispatched exceptions
src/coreclr/debug/ee/controller.cppImplements controller counting and detach cleanup logic
src/coreclr/debug/di/rspriv.hAdds DetachNotifications helper class and detach-related member variables
src/coreclr/debug/di/process.cppImplements detach synchronization logic and event handling
You can also share your feedback on Copilot code review for a chance to win a $100 gift card. Take the survey.
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Comment threadsrc/coreclr/debug/ee/debugger.cpp
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LGTM
@tommcdon
Track active controller ref count for detach through DebuggerControll…
367c638
…er creation and desctruction and DispatchPatchOrSingleStep
@thaystg
thaystg
self-requested a review
August 23, 2025 02:57

This was referenced Aug 23, 2025

Closed


Closed

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Comment threadsrc/coreclr/debug/ee/controller.h
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3 tasks
@tommcdon
Revert "Continuously track active dispatched exceptions and flares sent"
4a1905f
This reverts commit dd6d28c.
@tommcdon
Revert "Track active controller ref count for detach through Debugger…
45878e0
…Controller creation and desctruction and DispatchPatchOrSingleStep"
This reverts commit 367c638.
@tommcdon
Revert "Fix build break"
aba7e35
This reverts commit 240b372.
@tommcdon
Revert "Implement out-of-process detach support"
c186a8d
This reverts commit d80b6c4.
@tommcdon
Out-of-process detach support for CET
c762a0d
Debugger events are tracked out of process to determine which threads have outstanding SetThreadContextNeeded flares
@tommcdon
Remove unused enum
1593263
@tommcdon
Break out of detach if timed out or process exited
50466bc
@tommcdontommcdon
mentioned this pull request
Sep 16, 2025
 Open

noahfalk
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Yeah, this is getting much easier to reason about. I put a few suggestions inline but overall looks good!
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Add ClearSetIP to SetThreadContextNeeded event,
50869e4
Refactor HandleSetThreadContextNeeded for improved readability
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Handle case when out of process setthreadcontext is oped-out but avai…
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Implement out-of-process SetThreadContext support for debugger detach (…
4ced7ef
…dotnet#118849)
* Implement out-of-process detach support
* Fix build break
* Handle early process termination during detach in out-of-process debugging
* Track active controller ref count for detach through DebuggerController creation and desctruction and DispatchPatchOrSingleStep
* Continuously track active dispatched exceptions and flares sent
* Revert "Continuously track active dispatched exceptions and flares sent"
This reverts commit dd6d28c.
* Revert "Track active controller ref count for detach through DebuggerController creation and desctruction and DispatchPatchOrSingleStep"
This reverts commit 367c638.
* Revert "Fix build break"
This reverts commit 240b372.
* Revert "Implement out-of-process detach support"
This reverts commit d80b6c4.
* Out-of-process detach support for CET
Debugger events are tracked out of process to determine which threads have outstanding SetThreadContextNeeded flares
* Remove unused enum
* Break out of detach if timed out or process exited
* Add ClearSetIP to SetThreadContextNeeded event,
Refactor HandleSetThreadContextNeeded for improved readability
* Handle case when out of process setthreadcontext is oped-out but available on the platform
* PR feedback on code comment
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Implement out-of-process SetThreadContext support for debugger detach by tommcdon · Pull Request #118849 · dotnet/runtime · GitHub
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Implement out-of-process SetThreadContext support for debugger detach - #118849
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Implement out-of-process SetThreadContext support for debugger detach#118849
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This change handles a race between debugger detach and Debugger::SendSetThreadContextNeeded notifications. When the debugger calls ICorDebugController::Detach, we either delete or mark in-flight controllers for deletion which allows for further processing of in-flight breakpoint/single-step exceptions. If out-of-process SetThreadContext is needed is enabled, we could cause the debuggee to crash with an unhandled breakpoint exception while sending SetThreadContextNeeded flares after we detached. This change causes the detach operation to track SetThreadContextNeeded operations before signaling completion. Note the change only takes affect if CET debugging is enabled, and it only tracks notification count and state if we are in the process of detaching. This change handles early process exit during attach as well.
Fixes#116870
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Pull Request Overview
This PR implements support for out-of-process SetThreadContext operations during debugger detach to handle a race condition between debugger detach and SetThreadContextNeeded notifications. The key issue addressed is preventing debuggee crashes from unhandled breakpoint exceptions when these notifications are sent after the debugger has already detached.
Key changes include:
  • Introduction of tracking mechanisms for SetThreadContext operations during detach
  • New IPC event type for detach completion with flare count information
  • Synchronization logic to ensure all pending SetThreadContext operations complete before detach finishes
Reviewed Changes
Copilot reviewed 8 out of 8 changed files in this pull request and generated 4 comments.
Show a summary per file
FileDescription
src/coreclr/debug/shared/dbgtransportsession.cppAdds size calculation for new DETACH_FROM_PROCESS_RESULT event type
src/coreclr/debug/inc/dbgipceventtypes.hDefines new DB_IPCE_DETACH_FROM_PROCESS_RESULT event type and updates RUNTIME_LAST marker
src/coreclr/debug/inc/dbgipcevents.hAdds DetachFromProcessResult structure with cDispatchedFlares field
src/coreclr/debug/ee/debugger.cppImplements tracking logic for SetThreadContext operations during detach
src/coreclr/debug/ee/controller.hAdds static variables and methods for tracking detach state and dispatched exceptions
src/coreclr/debug/ee/controller.cppImplements controller counting and detach cleanup logic
src/coreclr/debug/di/rspriv.hAdds DetachNotifications helper class and detach-related member variables
src/coreclr/debug/di/process.cppImplements detach synchronization logic and event handling
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LGTM
@tommcdon
Track active controller ref count for detach through DebuggerControll…
367c638
…er creation and desctruction and DispatchPatchOrSingleStep
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@tommcdon
Revert "Continuously track active dispatched exceptions and flares sent"
4a1905f
This reverts commit dd6d28c.
@tommcdon
Revert "Track active controller ref count for detach through Debugger…
45878e0
…Controller creation and desctruction and DispatchPatchOrSingleStep"
This reverts commit 367c638.
@tommcdon
Revert "Fix build break"
aba7e35
This reverts commit 240b372.
@tommcdon
Revert "Implement out-of-process detach support"
c186a8d
This reverts commit d80b6c4.
@tommcdon
Out-of-process detach support for CET
c762a0d
Debugger events are tracked out of process to determine which threads have outstanding SetThreadContextNeeded flares
@tommcdon
Remove unused enum
1593263
@tommcdon
Break out of detach if timed out or process exited
50466bc
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Yeah, this is getting much easier to reason about. I put a few suggestions inline but overall looks good!
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Comment threadsrc/coreclr/debug/di/process.cpp
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@tommcdon
Add ClearSetIP to SetThreadContextNeeded event,
50869e4
Refactor HandleSetThreadContextNeeded for improved readability
@tommcdon
Handle case when out of process setthreadcontext is oped-out but avai…
e5310b1
…lable on the platform
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@tommcdon@xtqqczze
Implement out-of-process SetThreadContext support for debugger detach (…
4ced7ef
…dotnet#118849)
* Implement out-of-process detach support
* Fix build break
* Handle early process termination during detach in out-of-process debugging
* Track active controller ref count for detach through DebuggerController creation and desctruction and DispatchPatchOrSingleStep
* Continuously track active dispatched exceptions and flares sent
* Revert "Continuously track active dispatched exceptions and flares sent"
This reverts commit dd6d28c.
* Revert "Track active controller ref count for detach through DebuggerController creation and desctruction and DispatchPatchOrSingleStep"
This reverts commit 367c638.
* Revert "Fix build break"
This reverts commit 240b372.
* Revert "Implement out-of-process detach support"
This reverts commit d80b6c4.
* Out-of-process detach support for CET
Debugger events are tracked out of process to determine which threads have outstanding SetThreadContextNeeded flares
* Remove unused enum
* Break out of detach if timed out or process exited
* Add ClearSetIP to SetThreadContextNeeded event,
Refactor HandleSetThreadContextNeeded for improved readability
* Handle case when out of process setthreadcontext is oped-out but available on the platform
* PR feedback on code comment
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Detaching from a .Net9 debuggee can crash the application


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Implement out-of-process SetThreadContext support for debugger detach by tommcdon · Pull Request #118849 · dotnet/runtime · GitHub
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Implement out-of-process SetThreadContext support for debugger detach - #118849
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tommcdon merged 16 commits into
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tommcdon:dev/tommcdon/fix_cet_detach
Sep 19, 2025
Merged
Implement out-of-process SetThreadContext support for debugger detach#118849
tommcdon merged 16 commits into
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tommcdon:dev/tommcdon/fix_cet_detach
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This change handles a race between debugger detach and Debugger::SendSetThreadContextNeeded notifications. When the debugger calls ICorDebugController::Detach, we either delete or mark in-flight controllers for deletion which allows for further processing of in-flight breakpoint/single-step exceptions. If out-of-process SetThreadContext is needed is enabled, we could cause the debuggee to crash with an unhandled breakpoint exception while sending SetThreadContextNeeded flares after we detached. This change causes the detach operation to track SetThreadContextNeeded operations before signaling completion. Note the change only takes affect if CET debugging is enabled, and it only tracks notification count and state if we are in the process of detaching. This change handles early process exit during attach as well.
Fixes#116870
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Pull Request Overview
This PR implements support for out-of-process SetThreadContext operations during debugger detach to handle a race condition between debugger detach and SetThreadContextNeeded notifications. The key issue addressed is preventing debuggee crashes from unhandled breakpoint exceptions when these notifications are sent after the debugger has already detached.
Key changes include:
  • Introduction of tracking mechanisms for SetThreadContext operations during detach
  • New IPC event type for detach completion with flare count information
  • Synchronization logic to ensure all pending SetThreadContext operations complete before detach finishes
Reviewed Changes
Copilot reviewed 8 out of 8 changed files in this pull request and generated 4 comments.
Show a summary per file
FileDescription
src/coreclr/debug/shared/dbgtransportsession.cppAdds size calculation for new DETACH_FROM_PROCESS_RESULT event type
src/coreclr/debug/inc/dbgipceventtypes.hDefines new DB_IPCE_DETACH_FROM_PROCESS_RESULT event type and updates RUNTIME_LAST marker
src/coreclr/debug/inc/dbgipcevents.hAdds DetachFromProcessResult structure with cDispatchedFlares field
src/coreclr/debug/ee/debugger.cppImplements tracking logic for SetThreadContext operations during detach
src/coreclr/debug/ee/controller.hAdds static variables and methods for tracking detach state and dispatched exceptions
src/coreclr/debug/ee/controller.cppImplements controller counting and detach cleanup logic
src/coreclr/debug/di/rspriv.hAdds DetachNotifications helper class and detach-related member variables
src/coreclr/debug/di/process.cppImplements detach synchronization logic and event handling
You can also share your feedback on Copilot code review for a chance to win a $100 gift card. Take the survey.
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LGTM
@tommcdon
Track active controller ref count for detach through DebuggerControll…
367c638
…er creation and desctruction and DispatchPatchOrSingleStep
@thaystg
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@tommcdon
Revert "Continuously track active dispatched exceptions and flares sent"
4a1905f
This reverts commit dd6d28c.
@tommcdon
Revert "Track active controller ref count for detach through Debugger…
45878e0
…Controller creation and desctruction and DispatchPatchOrSingleStep"
This reverts commit 367c638.
@tommcdon
Revert "Fix build break"
aba7e35
This reverts commit 240b372.
@tommcdon
Revert "Implement out-of-process detach support"
c186a8d
This reverts commit d80b6c4.
@tommcdon
Out-of-process detach support for CET
c762a0d
Debugger events are tracked out of process to determine which threads have outstanding SetThreadContextNeeded flares
@tommcdon
Remove unused enum
1593263
@tommcdon
Break out of detach if timed out or process exited
50466bc
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Yeah, this is getting much easier to reason about. I put a few suggestions inline but overall looks good!
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Comment threadsrc/coreclr/debug/di/process.cpp
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@tommcdon
Add ClearSetIP to SetThreadContextNeeded event,
50869e4
Refactor HandleSetThreadContextNeeded for improved readability
@tommcdon
Handle case when out of process setthreadcontext is oped-out but avai…
e5310b1
…lable on the platform
noahfalk
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Started backporting to release/10.0: https://github.com/dotnet/runtime/actions/runs/17866298253
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xtqqczze pushed a commit
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@tommcdon@xtqqczze
Implement out-of-process SetThreadContext support for debugger detach (…
4ced7ef
…dotnet#118849)
* Implement out-of-process detach support
* Fix build break
* Handle early process termination during detach in out-of-process debugging
* Track active controller ref count for detach through DebuggerController creation and desctruction and DispatchPatchOrSingleStep
* Continuously track active dispatched exceptions and flares sent
* Revert "Continuously track active dispatched exceptions and flares sent"
This reverts commit dd6d28c.
* Revert "Track active controller ref count for detach through DebuggerController creation and desctruction and DispatchPatchOrSingleStep"
This reverts commit 367c638.
* Revert "Fix build break"
This reverts commit 240b372.
* Revert "Implement out-of-process detach support"
This reverts commit d80b6c4.
* Out-of-process detach support for CET
Debugger events are tracked out of process to determine which threads have outstanding SetThreadContextNeeded flares
* Remove unused enum
* Break out of detach if timed out or process exited
* Add ClearSetIP to SetThreadContextNeeded event,
Refactor HandleSetThreadContextNeeded for improved readability
* Handle case when out of process setthreadcontext is oped-out but available on the platform
* PR feedback on code comment
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@noahfalknoahfalknoahfalk approved these changes
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if (__m === '*' || __re.test(location.href)) {
// Auto-enable theater mode on YouTube
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function tryTheater() {
var btn = document.querySelector('button[aria-label="Theater mode"], ytd-player #player button[title="Theater mode"]');
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Implement out-of-process SetThreadContext support for debugger detach by tommcdon · Pull Request #118849 · dotnet/runtime · GitHub
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Implement out-of-process SetThreadContext support for debugger detach - #118849
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tommcdon:dev/tommcdon/fix_cet_detach
Sep 19, 2025
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Implement out-of-process SetThreadContext support for debugger detach#118849
tommcdon merged 16 commits into
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tommcdon:dev/tommcdon/fix_cet_detach
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This change handles a race between debugger detach and Debugger::SendSetThreadContextNeeded notifications. When the debugger calls ICorDebugController::Detach, we either delete or mark in-flight controllers for deletion which allows for further processing of in-flight breakpoint/single-step exceptions. If out-of-process SetThreadContext is needed is enabled, we could cause the debuggee to crash with an unhandled breakpoint exception while sending SetThreadContextNeeded flares after we detached. This change causes the detach operation to track SetThreadContextNeeded operations before signaling completion. Note the change only takes affect if CET debugging is enabled, and it only tracks notification count and state if we are in the process of detaching. This change handles early process exit during attach as well.
Fixes#116870
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Pull Request Overview
This PR implements support for out-of-process SetThreadContext operations during debugger detach to handle a race condition between debugger detach and SetThreadContextNeeded notifications. The key issue addressed is preventing debuggee crashes from unhandled breakpoint exceptions when these notifications are sent after the debugger has already detached.
Key changes include:
  • Introduction of tracking mechanisms for SetThreadContext operations during detach
  • New IPC event type for detach completion with flare count information
  • Synchronization logic to ensure all pending SetThreadContext operations complete before detach finishes
Reviewed Changes
Copilot reviewed 8 out of 8 changed files in this pull request and generated 4 comments.
Show a summary per file
FileDescription
src/coreclr/debug/shared/dbgtransportsession.cppAdds size calculation for new DETACH_FROM_PROCESS_RESULT event type
src/coreclr/debug/inc/dbgipceventtypes.hDefines new DB_IPCE_DETACH_FROM_PROCESS_RESULT event type and updates RUNTIME_LAST marker
src/coreclr/debug/inc/dbgipcevents.hAdds DetachFromProcessResult structure with cDispatchedFlares field
src/coreclr/debug/ee/debugger.cppImplements tracking logic for SetThreadContext operations during detach
src/coreclr/debug/ee/controller.hAdds static variables and methods for tracking detach state and dispatched exceptions
src/coreclr/debug/ee/controller.cppImplements controller counting and detach cleanup logic
src/coreclr/debug/di/rspriv.hAdds DetachNotifications helper class and detach-related member variables
src/coreclr/debug/di/process.cppImplements detach synchronization logic and event handling
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LGTM
@tommcdon
Track active controller ref count for detach through DebuggerControll…
367c638
…er creation and desctruction and DispatchPatchOrSingleStep
@thaystg
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This was referenced Aug 23, 2025

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@tommcdon
Revert "Continuously track active dispatched exceptions and flares sent"
4a1905f
This reverts commit dd6d28c.
@tommcdon
Revert "Track active controller ref count for detach through Debugger…
45878e0
…Controller creation and desctruction and DispatchPatchOrSingleStep"
This reverts commit 367c638.
@tommcdon
Revert "Fix build break"
aba7e35
This reverts commit 240b372.
@tommcdon
Revert "Implement out-of-process detach support"
c186a8d
This reverts commit d80b6c4.
@tommcdon
Out-of-process detach support for CET
c762a0d
Debugger events are tracked out of process to determine which threads have outstanding SetThreadContextNeeded flares
@tommcdon
Remove unused enum
1593263
@tommcdon
Break out of detach if timed out or process exited
50466bc
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Yeah, this is getting much easier to reason about. I put a few suggestions inline but overall looks good!
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Comment threadsrc/coreclr/debug/di/process.cpp
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@tommcdon
Add ClearSetIP to SetThreadContextNeeded event,
50869e4
Refactor HandleSetThreadContextNeeded for improved readability
@tommcdon
Handle case when out of process setthreadcontext is oped-out but avai…
e5310b1
…lable on the platform
noahfalk
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Comment threadsrc/coreclr/debug/di/rspriv.h
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/backport to release/10.0
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Started backporting to release/10.0: https://github.com/dotnet/runtime/actions/runs/17866298253
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@tommcdon@xtqqczze
Implement out-of-process SetThreadContext support for debugger detach (…
4ced7ef
…dotnet#118849)
* Implement out-of-process detach support
* Fix build break
* Handle early process termination during detach in out-of-process debugging
* Track active controller ref count for detach through DebuggerController creation and desctruction and DispatchPatchOrSingleStep
* Continuously track active dispatched exceptions and flares sent
* Revert "Continuously track active dispatched exceptions and flares sent"
This reverts commit dd6d28c.
* Revert "Track active controller ref count for detach through DebuggerController creation and desctruction and DispatchPatchOrSingleStep"
This reverts commit 367c638.
* Revert "Fix build break"
This reverts commit 240b372.
* Revert "Implement out-of-process detach support"
This reverts commit d80b6c4.
* Out-of-process detach support for CET
Debugger events are tracked out of process to determine which threads have outstanding SetThreadContextNeeded flares
* Remove unused enum
* Break out of detach if timed out or process exited
* Add ClearSetIP to SetThreadContextNeeded event,
Refactor HandleSetThreadContextNeeded for improved readability
* Handle case when out of process setthreadcontext is oped-out but available on the platform
* PR feedback on code comment
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@noahfalknoahfalknoahfalk approved these changes
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Detaching from a .Net9 debuggee can crash the application


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})();
Implement out-of-process SetThreadContext support for debugger detach by tommcdon · Pull Request #118849 · dotnet/runtime · GitHub
Skip to content
Implement out-of-process SetThreadContext support for debugger detach - #118849
Merged
tommcdon merged 16 commits into
dotnet:mainfrom 
tommcdon:dev/tommcdon/fix_cet_detach
Sep 19, 2025
Merged
Implement out-of-process SetThreadContext support for debugger detach#118849
tommcdon merged 16 commits into
dotnet:mainfrom 
tommcdon:dev/tommcdon/fix_cet_detach
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@tommcdon
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This change handles a race between debugger detach and Debugger::SendSetThreadContextNeeded notifications. When the debugger calls ICorDebugController::Detach, we either delete or mark in-flight controllers for deletion which allows for further processing of in-flight breakpoint/single-step exceptions. If out-of-process SetThreadContext is needed is enabled, we could cause the debuggee to crash with an unhandled breakpoint exception while sending SetThreadContextNeeded flares after we detached. This change causes the detach operation to track SetThreadContextNeeded operations before signaling completion. Note the change only takes affect if CET debugging is enabled, and it only tracks notification count and state if we are in the process of detaching. This change handles early process exit during attach as well.
Fixes#116870
@tommcdontommcdon
added this to the 10.0.0 milestone
Aug 18, 2025
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Pull Request Overview
This PR implements support for out-of-process SetThreadContext operations during debugger detach to handle a race condition between debugger detach and SetThreadContextNeeded notifications. The key issue addressed is preventing debuggee crashes from unhandled breakpoint exceptions when these notifications are sent after the debugger has already detached.
Key changes include:
  • Introduction of tracking mechanisms for SetThreadContext operations during detach
  • New IPC event type for detach completion with flare count information
  • Synchronization logic to ensure all pending SetThreadContext operations complete before detach finishes
Reviewed Changes
Copilot reviewed 8 out of 8 changed files in this pull request and generated 4 comments.
Show a summary per file
FileDescription
src/coreclr/debug/shared/dbgtransportsession.cppAdds size calculation for new DETACH_FROM_PROCESS_RESULT event type
src/coreclr/debug/inc/dbgipceventtypes.hDefines new DB_IPCE_DETACH_FROM_PROCESS_RESULT event type and updates RUNTIME_LAST marker
src/coreclr/debug/inc/dbgipcevents.hAdds DetachFromProcessResult structure with cDispatchedFlares field
src/coreclr/debug/ee/debugger.cppImplements tracking logic for SetThreadContext operations during detach
src/coreclr/debug/ee/controller.hAdds static variables and methods for tracking detach state and dispatched exceptions
src/coreclr/debug/ee/controller.cppImplements controller counting and detach cleanup logic
src/coreclr/debug/di/rspriv.hAdds DetachNotifications helper class and detach-related member variables
src/coreclr/debug/di/process.cppImplements detach synchronization logic and event handling
You can also share your feedback on Copilot code review for a chance to win a $100 gift card. Take the survey.
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Comment threadsrc/coreclr/debug/ee/debugger.cpp
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LGTM
@tommcdon
Track active controller ref count for detach through DebuggerControll…
367c638
…er creation and desctruction and DispatchPatchOrSingleStep
@thaystg
thaystg
self-requested a review
August 23, 2025 02:57

This was referenced Aug 23, 2025

Closed


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Comment threadsrc/coreclr/debug/ee/controller.h
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3 tasks
@tommcdon
Revert "Continuously track active dispatched exceptions and flares sent"
4a1905f
This reverts commit dd6d28c.
@tommcdon
Revert "Track active controller ref count for detach through Debugger…
45878e0
…Controller creation and desctruction and DispatchPatchOrSingleStep"
This reverts commit 367c638.
@tommcdon
Revert "Fix build break"
aba7e35
This reverts commit 240b372.
@tommcdon
Revert "Implement out-of-process detach support"
c186a8d
This reverts commit d80b6c4.
@tommcdon
Out-of-process detach support for CET
c762a0d
Debugger events are tracked out of process to determine which threads have outstanding SetThreadContextNeeded flares
@tommcdon
Remove unused enum
1593263
@tommcdon
Break out of detach if timed out or process exited
50466bc
@tommcdontommcdon
mentioned this pull request
Sep 16, 2025
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noahfalk
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Yeah, this is getting much easier to reason about. I put a few suggestions inline but overall looks good!
Comment threadsrc/coreclr/debug/ee/debugger.cpp
Outdated

Comment threadsrc/coreclr/debug/di/process.cpp
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@tommcdon
Add ClearSetIP to SetThreadContextNeeded event,
50869e4
Refactor HandleSetThreadContextNeeded for improved readability
@tommcdon
Handle case when out of process setthreadcontext is oped-out but avai…
e5310b1
…lable on the platform
noahfalk
noahfalk
approved these changes
Sep 19, 2025
View reviewed changes
Comment threadsrc/coreclr/debug/di/rspriv.h
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@tommcdon
tommcdon
enabled auto-merge (squash)
September 19, 2025 16:49
@tommcdon
tommcdon
merged commit 2db45f1
into
dotnet:mainSep 19, 2025

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/backport to release/10.0
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Started backporting to release/10.0: https://github.com/dotnet/runtime/actions/runs/17866298253
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 Merged

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xtqqczze pushed a commit
to xtqqczze/dotnet-runtime
that referenced
this pull request
Sep 20, 2025
@tommcdon@xtqqczze
Implement out-of-process SetThreadContext support for debugger detach (…
4ced7ef
…dotnet#118849)
* Implement out-of-process detach support
* Fix build break
* Handle early process termination during detach in out-of-process debugging
* Track active controller ref count for detach through DebuggerController creation and desctruction and DispatchPatchOrSingleStep
* Continuously track active dispatched exceptions and flares sent
* Revert "Continuously track active dispatched exceptions and flares sent"
This reverts commit dd6d28c.
* Revert "Track active controller ref count for detach through DebuggerController creation and desctruction and DispatchPatchOrSingleStep"
This reverts commit 367c638.
* Revert "Fix build break"
This reverts commit 240b372.
* Revert "Implement out-of-process detach support"
This reverts commit d80b6c4.
* Out-of-process detach support for CET
Debugger events are tracked out of process to determine which threads have outstanding SetThreadContextNeeded flares
* Remove unused enum
* Break out of detach if timed out or process exited
* Add ClearSetIP to SetThreadContextNeeded event,
Refactor HandleSetThreadContextNeeded for improved readability
* Handle case when out of process setthreadcontext is oped-out but available on the platform
* PR feedback on code comment
@github-actionsgithub-actionsBot
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Oct 20, 2025
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@noahfalknoahfalknoahfalk approved these changes
@lateralusXlateralusXAwaiting requested review from lateralusX
@hoyosjshoyosjsAwaiting requested review from hoyosjs
@thaystgthaystgAwaiting requested review from thaystg

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Successfully merging this pull request may close these issues.

Detaching from a .Net9 debuggee can crash the application


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