Linus Torvalds writes: (Summary) wrote:
writing the same value to them (zero) anyway.
So who cares if the write ends up being two instructions, because the write to the upper bits doesn't actually *do* anything. write to the upper bits doesn't actually *do* anything.
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the padding with 0, and only update the low bits with single-copy atomicity. It's actually still single-copy atomicity as a 64-bit value. It's actually still single-copy atomicity as a 64-bit value. Because it doesn't matter how you write the upper bits. You'll be writing the same value to them (zero) anyway.writing the same value to them (zero) anyway.
So who cares if the write ends up being two instructions, because the write to the upper bits doesn't actually *do* anything. write to the upper bits doesn't actually *do* anything.