On Tue, 8 Dec 2009, Linus Torvalds wrote: > > No, that's not needed. Unlike reads, writes can't move in front of > > data or control dependencies. Or so I've been lead to believe... > > Sure they can. Control dependencies are trivial - it's called "branch > prediction", and everybody does it, and data dependencies don't exist on > many CPU architectures (even to the point of reading through a pointer > that you loaded). Wait a second. Are you saying that with code like this: if (x == 1) y = 5; the CPU may write to y before it has finished reading the value of x? And this write is visible to other CPUs, so that if x was initially 0 and a second CPU sets x to 1, the second CPU may see y == 5 before it executes the write to x (whatever that may mean)? Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
