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    SubjectRe: [PATCH] jump_label: jump_label for boot options.
    On Thu, Dec 01, 2011 at 05:28:18PM +0100, Peter Zijlstra wrote:
    > On Thu, 2011-12-01 at 10:40 -0500, Jason Baron wrote:
    > > I should probably rename
    > > static_branch() -> 'static_branch_default_false()' to make that clear.
    >
    > The rename doesn't really make sense until you can also provide
    > static_branch_true() also:

    I think its just a matter of reversing the true and false returns.
    That is, instead of:

    static __always_inline bool arch_static_branch_default_false(struct jump_label_key
    *key)
    {
    asm goto("1:"
    JUMP_LABEL_INITIAL_NOP
    ".pushsection __jump_table, \"aw\" \n\t"
    _ASM_ALIGN "\n\t"
    _ASM_PTR "1b, %l[l_yes], %c0 \n\t"
    ".popsection \n\t"
    : : "i" (key) : : l_yes);
    return false;
    l_yes:
    return true;
    }

    We just have (untested):

    static __always_inline bool arch_static_branch_default_true(struct jump_label_key
    *key)
    {
    asm goto("1:"
    JUMP_LABEL_INITIAL_NOP
    ".pushsection __jump_table, \"aw\" \n\t"
    _ASM_ALIGN "\n\t"
    _ASM_PTR "1b, %l[l_no], %c0 \n\t"
    ".popsection \n\t"
    : : "i" (key) : : l_no);
    return true;
    l_no:
    return false;
    }

    jump_label_inc/dec(), don't need to be changed, they just mean reverse
    the branch on 0, 1 transitions. Although using the same key in both
    static_branch_true, and static_branch_false, might be confusing. Maybe
    we rename jump_label_inc/dec to static_branch_reverse_inc()/dec()?

    >
    > > Maybe we need an unbiased static_branch() too, but I'm not sure excatly
    > > how to implement it...
    >
    > I'd think the same way we got in this situation in the first place, go
    > kick some GCC people ;-)

    If you think this is a useful case, I'll try and see how to implement it.
    Then we can add static_branch_default_true/false_unbiased() :)

    -Jason


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