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Subject: Re: [PATCH 4/9] drm/xen-front: Implement Xen event channel handling
To:     Boris Ostrovsky <boris.ostrovsky@oracle.com>,
        xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org,
        dri-devel@lists.freedesktop.org, airlied@linux.ie,
        daniel.vetter@intel.com, seanpaul@chromium.org,
        gustavo@padovan.org, jgross@suse.com, konrad.wilk@oracle.com
Cc:     Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
References: <1519200222-20623-1-git-send-email-andr2000@gmail.com>
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 <5145287f-40b0-c8e2-1b37-36d7e8cac908@gmail.com>
 <7d8ab151-e90d-baef-93b6-8ca1c7e42908@oracle.com>
From:   Oleksandr Andrushchenko <andr2000@gmail.com>
Message-ID: <63c64a2f-211e-2f62-21e7-289f0cc69df0@gmail.com>
Date:   Fri, 23 Feb 2018 16:49:46 +0200
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On 02/23/2018 04:44 PM, Boris Ostrovsky wrote:
> On 02/23/2018 02:00 AM, Oleksandr Andrushchenko wrote:
>> On 02/23/2018 01:50 AM, Boris Ostrovsky wrote:
>>> On 02/21/2018 03:03 AM, Oleksandr Andrushchenko wrote:
>>>> +
>>>> +static irqreturn_t evtchnl_interrupt_ctrl(int irq, void *dev_id)
>>>> +{
>>>> +    struct xen_drm_front_evtchnl *evtchnl = dev_id;
>>>> +    struct xen_drm_front_info *front_info = evtchnl->front_info;
>>>> +    struct xendispl_resp *resp;
>>>> +    RING_IDX i, rp;
>>>> +    unsigned long flags;
>>>> +
>>>> +    spin_lock_irqsave(&front_info->io_lock, flags);
>>>> +
>>>> +    if (unlikely(evtchnl->state != EVTCHNL_STATE_CONNECTED))
>>>> +        goto out;
>>> Do you need to check the state under lock? (in other routines too).
>> not really, will move out of the lock in interrupt handlers
>> other places (I assume you refer to be_stream_do_io)
>
> I was mostly referring to evtchnl_interrupt_evt().
ah, then we are on the same page: I will move the check
in interrupt handlers
> -boris
>
>
>> it is set under lock as a part of atomic operation, e.g.
>> we get a new request pointer from the ring and reset completion
>> So, those places still seem to be ok