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    SubjectRe: [PATCH v2 1/3] locking: Document the semantics of spin_is_locked()
    Date
    Andrea Parri <andrea.parri@amarulasolutions.com> wrote:

    > +/**
    > + * spin_is_locked() - Check whether a spinlock is locked.
    > + * @lock: Pointer to the spinlock.
    > + *
    > + * This function is NOT required to provide any memory ordering
    > + * guarantees; it could be used for debugging purposes or, when
    > + * additional synchronization is needed, accompanied with other
    > + * constructs (memory barriers) enforcing the synchronization.
    > + *
    > + * Return: 1, if @lock is (found to be) locked; 0, otherwise.

    It's more complicated than that. This function is dangerous and should be
    used with extreme care. In the case where CONFIG_SMP=n the value is locked
    one way or the other and it might be the wrong way.

    David

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