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

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Message-ID: <5d477777-28c2-af84-9b92-1a89d3f51067@oracle.com>
Date:   Fri, 6 Oct 2017 16:31:11 -0400
From:   Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:     Stefano Stabellini <sstabellini@...nel.org>
Cc:     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 10/06/2017 04:29 PM, Stefano Stabellini wrote:
> 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.

Oh, yes, of course. I think you also might be accessing it after the
struct is freed. Nevermind then.

-boris