Function

OSBitAndAtomic

32-bit logical and operation, performed atomically with respect to all devices that participate in the coherency architecture of the platform.

Declaration

UInt32 OSBitAndAtomic(UInt32 mask, volatile UInt32 *address);

Parameters

mask

The mask to logically and with the value.

address

The 4-byte aligned address of the value to update atomically.

Return Value

The value before the bitwise operation

Discussion

The OSBitAndAtomic function logically ands the bits of the specified mask into the value at the specified address and returns the original value.

This function guarantees atomicity only with main system memory. It is specifically unsuitable for use on noncacheable memory such as that in devices; this function cannot guarantee atomicity, for example, on memory mapped from a PCI device. Previous incarnations of this function incorporated a memory barrier on systems with weakly-ordered memory architectures, but current versions contain no barriers..