[Xen-devel] RING_HAS_UNCONSUMED_REQUESTS oddness

[Zoltan Kiss <zoltan.kiss@xxxxxxxxxx>]

Hi,

I was wondering for a while why this macro looks like this:

#define RING_HAS_UNCONSUMED_REQUESTS(_r)                                \
    ({                                                                  \
        unsigned int req = (_r)->sring->req_prod - (_r)->req_cons;      \
        unsigned int rsp = RING_SIZE(_r) -                              \
                           ((_r)->req_cons - (_r)->rsp_prod_pvt);       \
        req < rsp ? req : rsp;                                          \
    })

I would expect to check prod - cons, like RING_HAS_UNCONSUMED_RESPONSES does:

#define RING_HAS_UNCONSUMED_RESPONSES(_r)                               \
    ((_r)->sring->rsp_prod - (_r)->rsp_cons)

By my understanding, there is no way rsp could be smaller than req, so
there is no point having this. Am I missing something?

Regards,

Zoli

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