linux-kernel - Re: [PATCH v4 02/13] xen/pvcalls: implement frontend disconnect

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Date:   Fri, 6 Oct 2017 13:29:12 -0700 (PDT)
From:   Stefano Stabellini <sstabellini@...nel.org>
To:     Boris Ostrovsky <boris.ostrovsky@...cle.com>
cc:     Stefano Stabellini <sstabellini@...nel.org>,
        xen-devel@...ts.xen.org, linux-kernel@...r.kernel.org,
        jgross@...e.com, Stefano Stabellini <stefano@...reto.com>
Subject: Re: [PATCH v4 02/13] xen/pvcalls: implement frontend disconnect

On Fri, 6 Oct 2017, Boris Ostrovsky wrote:
> On 10/06/2017 01:51 PM, Stefano Stabellini wrote:
> > On Wed, 20 Sep 2017, Boris Ostrovsky wrote:
> >>> +
> >>> +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?
> > Yes it is, but only one back/frontend connection is supported by the
> > frontend. I can add a comment.
> 
> Since it's per backend connection --- shouldn't it be part of struct
> pvcalls_bedata?

struct pvcalls_bedata is allocated with kzalloc. To protect accesses to
it, pvcalls_refcount needs to be outside of it.