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ERROR_GRAPHICS_UNASSIGNED_MODESET_ALREADY_EXISTS
Why this is not a generic GPU failure: graphics unassigned modeset already exists
ERROR_GRAPHICS_UNASSIGNED_MODESET_ALREADY_EXISTS, value 0xC0262350, is produced by vidpn when a second unassigned mode set was created for an endpoint that already has one pending. The investigation should stay attached to unassigned source or target mode set and to the exact generation in which it was obtained.
VidPN handles and subobjects are generation-bound. A monitor hot-plug, docking action, session switch or mode commit can invalidate an otherwise well-formed cached object.
The smallest evidence set
| Capture item | Why it matters |
|---|---|
| Rejected condition | a second unassigned mode set was created for an endpoint that already has one pending |
| What to capture | endpoint ID, existing unassigned handle, transaction state and assignment attempt order |
| Current graph state | VidPN, topology, source and target mode sets, and the present path connecting them |
| Supporting trace | source and target IDs, topology generation, path descriptors, pinned modes, mode-set handles and monitor timing data |
| Object identity | unassigned source or target mode set |
A/B test for the exact condition
- Capture the failing state. Record endpoint ID, existing unassigned handle, transaction state and assignment attempt order.
- Assign or release the first mode set before creating another.
The comparison with ERROR_GRAPHICS_MODE_ALREADY_IN_MODESET is especially useful: ERROR_GRAPHICS_MODE_ALREADY_IN_MODESET concerns duplicate mode membership inside a set.
Safe remediation
Enforce one in-flight unassigned set per source or target.
- debug-layer, ETW or driver diagnostics no longer report the rejected unassigned source or target mode set contract during the same scenario.
Implementation notes
Log source and target IDs, topology generation, path descriptors, pinned modes, mode-set handles and monitor timing data.
Technical references
- Microsoft: Introduction to Video Present Networks — background for the unassigned source or target mode set.
- Microsoft: VidPN objects and interfaces
- Microsoft: Enumerating cofunctional VidPN modes
- Microsoft: Determining VidPN support
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