Expand Minimize

KeMemoryBarrier routine

The KeMemoryBarrier routine creates a barrier at its position in the code—across which the compiler and the processor cannot move any operations.

Syntax


VOID KeMemoryBarrier(void);

Parameters

This routine has no parameters.

Return value

None

Remarks

The KeMemoryBarrier routine inserts a memory barrier into your code. This barrier guarantees that every operation that appears in the source code before the call to KeMemoryBarrier will complete before any operation that appears after the call.

The implementation of the KeMemoryBarrier routine depends on the processor architecture. For example, for an x86 processor, the Wdm.h header file defines KeMemoryBarrier to be the following inline function:


FORCEINLINE
VOID
KeMemoryBarrier (
    VOID
    )
{
    LONG Barrier;

    __asm {
        xchg Barrier, eax
    }
}

In this definition, the braces that follow the __asm keyword contain inline assembly code. The compiler optimizer cannot move an instruction from a position before the inline assembly code to a position after the inline assembly code, and vice versa. In addition, the xchg instruction implicitly includes the lock prefix, which forces the processor hardware to complete the memory operations for all instructions that precede the xchg instruction before it initiates memory operations for instructions that follow the xchg instruction.

KeMemoryBarrier prevents both the compiler and the processor from moving operations across the barrier. To prevent only the compiler from moving operations, call KeMemoryBarrierWithoutFence.

Requirements

Header

Wdm.h (include Wdm.h, Ntddk.h, or Ntifs.h)

IRQL

Any level

See also

KeMemoryBarrierWithoutFence

 

 

Send comments about this topic to Microsoft

Show:
© 2014 Microsoft