> > 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)? No, the write really depends on x being 1 at any time before the comparison. On the other hand x being != 0 during the comparison does not prevent the write without proper locking or barriers. Have a look at http://www.linuxjournal.com/article/8211 http://www.linuxjournal.com/article/8212 especially at the alpha part what can happen when dealing with pointer accesses. Christian -- 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
