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The PsQueryProcessAvailableCpus function queries the set of CPUs that are available for a given process to run on.
Syntax
NTSTATUS PsQueryProcessAvailableCpus(
[in] PEPROCESS Process,
[in, out] PKAFFINITY_EX Affinity,
[in, optional] PULONG64 ObservedSequenceNumber,
[out] PULONG64 SequenceNumber
);
Parameters
[in] Process
Pointer to a process (PEPROCESS).
[in, out] Affinity
Pointer to an extended affinity object (PKAFFINITY_EX) that will receive the set of available CPUs for the process.
[in, optional] ObservedSequenceNumber
Optionally supplies a pointer to the most recent sequence number observed by the caller through a previous call to this routine. If this sequence number matches the current sequence number, the routine returns STATUS_NO_WORK_DONE and doesn't write to the affinity buffer.
[out] SequenceNumber
Pointer to a buffer that will receive the current sequence number for the available CPUs to the given process.
Return value
PsQueryProcessAvailableCpus returns one of the following NTSTATUS values:
| Return code | Description |
|---|---|
| STATUS_SUCCESS | The query was completed successfully. |
| STATUS_INVALID_PARAMETER | Any of the required buffers is NULL. |
| STATUS_NO_WORK_DONE | The given sequence number matches the current sequence number and no query was performed. |
| STATUS_BUFFER_TOO_SMALL | The given affinity buffer is too small. |
Remarks
This routine can be called at IRQL from PASSIVE_LEVEL to DISPATCH_LEVEL.
The affinity buffer must be large enough to accommodate the active processor group count. Use KeQueryActiveGroupCount to determine the required size.
The sequence number allows callers to optimize repeated queries by checking if the CPU availability has changed since the last call.
Requirements
| Requirement | Value |
|---|---|
| Header | wdm.h |
| IRQL | PASSIVE_LEVEL to DISPATCH_LEVEL |