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ERROR_INTERRUPT_VECTOR_ALREADY_CONNECTED
the requested interrupt vector already has an active connection.
ERROR_INTERRUPT_VECTOR_ALREADY_CONNECTED identifies the condition that this condition A driver attempted to connect an interrupt vector that is already connected under the applicable sharing and affinity rules. The cause can be duplicate initialization, stale teardown state, or incorrect resource descriptors.
Where the result appears
- driver start or restart.
- MSI/MSI-X vector setup.
- legacy line-based interrupt registration.
- recovery after partial device initialization.
How to interpret the result
Interpret the numeric value in the Win32/LRESULT domain and in the context of the API that returned it. Preserve this result before wrappers convert it to an HRESULT, exception, Boolean failure, or provider-specific message. When recording it, note whether the operation produced usable output; this determines whether the value is completion information, control flow, or a terminal failure.
Diagnostic evidence to collect
- translated interrupt resource and vector.
- interrupt mode, polarity, sharing, and affinity.
- number of prior successful connect calls.
- driver start/stop trace and cleanup status.
A diagnostic record for it should contain the API name, input flags, relevant handles or object identifiers, thread and process identity, timestamp, and the immediately preceding state transition. Those fields are more useful than a generic screenshot because they show which contract and lifecycle phase produced the value.
Handling and recovery
Prevent the second connection or disconnect the original one through the documented lifecycle before reconnecting. Validate that each successful IoConnectInterruptEx-style operation has exactly one matching disconnect and that restart paths reset ownership state.
Retry after this result only when an external state relevant to this operation can actually change. When it is rooted in object state, unsupported capability, ownership, or invalid sequencing, an unchanged retry repeats the defect and can obscure the first useful diagnostic record.
Common misinterpretation
Do not assume a hardware IRQ conflict solely from this status. Duplicate software registration in the same driver is often the more direct explanation.
Guidance for developers
Keep the original this result value and its Win32 domain in structured telemetry. If it crosses COM or another HRESULT-based boundary, store both the source Win32 value and the converted result. If it crosses JSON, RPC, or a database boundary, include error_domain, error_code, operation, and object_state so the receiver does not apply a second conversion.
An automated test should construct the specific state that leads to this result, assert the exact returned value, and verify cleanup on both the normal and exceptional path. The result test should additionally prove that the caller does not collapse this status into an unrelated generic error and does not retry forever.
References
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