ExEnterCriticalRegionAndAcquireResourceExclusive function (wdm.h)

Article
10/07/2022

The ExEnterCriticalRegionAndAcquireResourceExclusive routine first enters a critical region, and then acquires exclusive access to the specified resource.

Syntax

PVOID ExEnterCriticalRegionAndAcquireResourceExclusive(
  PERESOURCE Resource
);

Parameters

Resource

[in, out] A pointer to the resource to acquire for exclusive access. This parameter points to a caller-allocated ERESOURCE structure. The caller previously allocated this structure from nonpaged pool and initialized it by calling the ExInitializeResourceLite or ExReinitializeResourceLite routine.

Return value

A pointer to an opaque system structure. Drivers should ignore this return value.

Remarks

If this routine is called when the specified resource is not immediately available for exclusive access, the calling thread is blocked until the resource is available.

While a driver thread runs in the critical region, the driver's user APCs and normal kernel APCs are not executed. Special kernel APCs are still executed. For more information about these APC types, see Types of APCs.

By temporarily disabling normal kernel APCs, ExEnterCriticalRegionAndAcquireResourceExclusive prevents a passive-level calling thread from being preempted by an APC while the thread holds a shared resource that the APC might try to access.

The calling thread should stay in the critical region and hold the specified resource for no longer than is necessary. To release the specified resource and leave the critical region, call the ExReleaseResourceAndLeaveCriticalRegion routine.

For more information about using an ERESOURCE structure to synchronize exclusive access to a resource, see Introduction to ERESOURCE Routines. For more information about entering and leaving a critical region, see Critical Regions and Guarded Regions.

Requirements

Requirement	Value
Minimum supported client	Windows Vista
Minimum supported server	Windows Server 2003 SP1
Header	wdm.h
IRQL	<= APC_LEVEL
DDI compliance rules	CriticalRegions(wdm), HwStorPortProhibitedDDIs(storport)