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    SubjectRe: [RFC] New locking primitive for 2.5


    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

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