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    SubjectRe: [patch] Re: using long instead of atomic_t when only set/read is required
    On Mon, 3 Mar 2008, Alan Cox wrote:

    > > Atomicity of reads of write for pointers and integral types (other than
    > > long long) should be documented.
    > NAK.
    > Atomicity of reads or writes for pointers and integral types is NOT
    > guaranteed. Gcc doesn't believe in your guarantee.

    Miscommunication and lack of clarity. CPU reads and writes _are_
    guaranteed to be atomic. What is not guaranteed is that the compiler
    will generate a single read or write instruction corresponding to a
    particular expression in C.

    Consider a routine like the following:

    static task_struct *the_task;

    void store_task(void)
    the_task = current;

    Is it possible to say whether readers examining "the_task" are
    guaranteed to see a coherent value?

    Alan Stern

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