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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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