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    SubjectRe: [PATCH v4 02/13] xen/pvcalls: implement frontend disconnect
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    > +
    > +struct pvcalls_bedata {
    > + struct xen_pvcalls_front_ring ring;
    > + grant_ref_t ref;
    > + int irq;
    > +
    > + struct list_head socket_mappings;
    > + struct list_head socketpass_mappings;
    > + spinlock_t socket_lock;
    > +
    > + wait_queue_head_t inflight_req;
    > + struct xen_pvcalls_response rsp[PVCALLS_NR_REQ_PER_RING];
    > +};
    > +static struct xenbus_device *pvcalls_front_dev;
    > +static atomic_t pvcalls_refcount;

    Should the refcount be per back/frontend?

    > +
    > +/* first increment refcount, then proceed */
    > +#define pvcalls_enter { \
    > + atomic_inc(&pvcalls_refcount); \
    > + smp_mb(); \
    > +}
    > +
    > +/* first complete other operations, then decrement refcount */
    > +#define pvcalls_exit { \
    > + smp_mb(); \
    > + atomic_dec(&pvcalls_refcount); \
    > +}

    I think atomic increment/decrement imply a barrier.


    -boris

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