Re: [RFC] New locking primitive for 2.5

[Linus Torvalds]

On Fri, 8 Feb 2002, Ingo Molnar wrote:
>
> and regarding the reintroduction of BKL, *please* do not just use a global
> locks around such pieces of code, lock bouncing sucks on SMP, even if
> there is no overhead.

I'd suggest not having a lock at all, but instead add two functions: one
to read a 64-bit value atomically, the other to write it atomically (and
they'd be atomic only wrt each other, no memory barriers etc implied).

On 64-bit architectures that's just a direct dereference, and even on x86
it's just a "cmpxchg8b".

		Linus