What does Windows error code 1791 (RPC_S_CALL_IN_PROGRESS) mean?

 
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ERROR_TRUST_FAILURE ERROR_NETLOGON_NOT_STARTED

RPC_S_CALL_IN_PROGRESS

A second operation overlaps an RPC call that has not completed

RPC_S_CALL_IN_PROGRESS indicates an RPC call-state conflict. The same thread, handle, or call context is being used for an operation that requires the previous call to finish. It differs from server-wide load limits: another independent thread or properly initialized asynchronous state may still be able to issue work.

Trace call begin, completion, exception, cancellation, and cleanup on the same thread and binding. Look for reentrant callbacks, nested use of an implicit handle, or code that reuses an async state before final completion. Waiting is appropriate only when the ownership design guarantees progress; otherwise serialize access or allocate a separate call state.

What to inspect

  • Correlate calls by thread, binding handle, and async-state address.
  • Ensure every call reaches a single final completion or failure path.
  • Avoid reusing implicit or automatic call state from nested callbacks.

References


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