ZwSetInformationThread routine

The ZwSetInformationThread routine sets the priority of a thread.

Syntax


NTSTATUS ZwSetInformationThread(
  _In_ HANDLE          ThreadHandle,
  _In_ THREADINFOCLASS ThreadInformationClass,
  _In_ PVOID           ThreadInformation,
  _In_ ULONG           ThreadInformationLength
);

Parameters

ThreadHandle [in]

Handle to the thread object. To create a new thread and get a handle to it, call PsCreateSystemThread. To specify the current thread, use the ZwCurrentThread macro.

ThreadInformationClass [in]

One of the system-defined values in the THREADINFOCLASS enumeration (see ntddk.h), ThreadPriority, ThreadBasePriority, or ThreadPagePriority.

ThreadInformation [in]

Pointer to a variable that specifies the information to set.

If ThreadInformationClass is ThreadPriority, this value must be > LOW_PRIORITY and <= HIGH_PRIORITY.

If ThreadInformationClass is ThreadBasePriority, this value must fall within the system's valid base-priority range and the original priority class for the given thread. That is, if a thread's priority class is variable, that thread's base priority cannot be reset to a real-time priority value, and vice versa.

If ThreadInformationClass is ThreadPagePriority, this value is a pointer to a PAGE_PRIORITY_INFORMATION structure, see ntddk.h. The PagePriority member value must be one of these values.

ValueMeaning
MEMORY_PRIORITY_VERY_LOW
1

Very low memory priority.

MEMORY_PRIORITY_LOW
2

Low memory priority.

MEMORY_PRIORITY_MEDIUM
3

Medium memory priority.

MEMORY_PRIORITY_BELOW_NORMAL
4

Below normal memory priority.

MEMORY_PRIORITY_NORMAL
5

Normal memory priority. This is the default priority for all threads and processes on the system.

 

ThreadInformationLength [in]

The size, in bytes, of ThreadInformation.

Return value

ZwSetInformationThread returns STATUS_SUCCESS on success, or the appropriate NTSTATUS error code on failure. Possible error codes include STATUS_INFO_LENGTH_MISMATCH or STATUS_INVALID_PARAMETER.

Remarks

ZwSetInformationThread can be called by higher-level drivers to set the priority of a thread for which they have a handle.

The caller must have THREAD_SET_INFORMATION access rights for the given thread in order to call this routine.

Usually, device and intermediate drivers that set up driver-created threads call KeSetBasePriorityThread or KeSetPriorityThread from their driver-created threads, rather than calling ZwSetInformationThread. However, a driver can call ZwSetInformationThread to raise the priority of a driver-created thread before that thread runs.

Kernel mode drivers can call the ZwSetInformationThread function with ThreadPagePriority to specify a thread's page priority.

To help improve system performance, drivers should use the function with ThreadPagePriority to lower the page priority of threads that perform background operations or access files and data that are not expected to be accessed again soon. For example, an anti-malware application might lower the priority of threads involved in scanning files.

To determine the page priority for a thread, call ZwQueryInformationThread.

Note  If the call to this function occurs in user mode, you should use the name NtSetInformationThread instead of ZwSetInformationThread.
 

Requirements

Target platform

Universal

Version

Available starting with Windows 2000.

Header

Ntddk.h (include Ntddk.h)

Library

NtosKrnl.lib

DLL

NtosKrnl.exe

IRQL

PASSIVE_LEVEL

DDI compliance rules

PowerIrpDDis, HwStorPortProhibitedDDIs

See also

KeSetBasePriorityThread
KeSetPriorityThread
PsCreateSystemThread

 

 

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