ExInterlockedRemoveHeadList

PLIST_ENTRY
ExInterlockedRemoveHeadList(
IN PLIST_ENTRY ListHead,
IN PKSPIN_LOCK Lock
);

ExInterlockedRemoveHeadList removes an entry from the head of a doubly linked list so access to the list is synchronized in a multiprocessor-safe way.

Parameters

ListHead: Points to the head of the doubly linked list from which an entry is to be removed.
Lock: Points to a caller-supplied spin lock.

Return Value

If the list is empty, a NULL pointer is returned. Otherwise, a pointer to the dequeued entry is returned.

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.

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

If the caller uses only ExInterlocked..List routines to manipulate the list, then 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, then callers of ExInterlocked..List must be at <= DISPATCH_LEVEL.