ExInterlockedInsertHeadList

The ExInterlockedInsertHeadList routine inserts an entry at the head of a doubly linked list so that access to the list is synchronized in a multiprocessor-safe way.

PLIST_ENTRY 
  ExInterlockedInsertHeadList(
    IN PLIST_ENTRY  ListHead,
    IN PLIST_ENTRY  ListEntry,
    IN PKSPIN_LOCK  Lock
    );

Parameters

ListHead

Pointer to the head of the doubly linked list into which an entry is to be inserted.

ListEntry

Pointer to the entry to be inserted at the head of the list.

Lock

Pointer to a caller-supplied spin lock used to synchronize access to the list.

Return Value

ExInterlockedInsertHeadList returns a pointer to the entry that was at the head of the interlocked queue before this entry was inserted. If the queue was empty, it returns NULL.

Headers

Declared in wdm.h and ntddk.h. Include wdm.h or ntddk.h.

Comments

Support routines that do interlocked operations are assumed to be incapable of causing a page fault. That is, neither their code nor any of the data they touch can cause a page fault without bringing down the system. They use spin locks to achieve atomicity in SMP machines. The caller must provide resident storage for the Lock, which must be initialized with KeInitializeSpinLock before the initial call to an ExInterlockedXxx. A caller must not be holding this spin lock when it calls ExInterlockedInsertHeadList.

The caller also must supply resident storage for the interlocked queue. The ListHead must be initialized with InitializedListHead before the initial call to an ExInterlocked..List.

If the caller uses only ExInterlocked..List routines to manipulate the list, these routines can be called from a single IRQL that is <= DIRQL. If other driver routines access the list using any other routines, such as the noninterlocked InsertHeadList, callers of ExInterlocked..List must be at <= DISPATCH_LEVEL.

Usually, drivers call ExInterlockedInsertTailList to insert an IRP into a driver-managed interlocked queue. They call ExInterlockedInsertHeadList only to requeue an IRP for a retry.

See Also

ExInterlockedInsertTailList, ExInterlockedRemoveHeadList, InitializeListHead, KeInitializeSpinLock