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Subject: Re: [PATCH v3 08/13] xen/pvcalls: implement accept command
From: Boris Ostrovsky <boris.ostrovsky@oracle.com>
To: Stefano Stabellini <sstabellini@kernel.org>, xen-devel@lists.xen.org
Cc: linux-kernel@vger.kernel.org, jgross@suse.com,
        Stefano Stabellini <stefano@aporeto.com>
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Date: Mon, 14 Aug 2017 22:04:59 -0400
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>> +
>> +    ret = bedata->rsp[req_id].ret;
> 
> You can just return bedata->rsp[req_id].ret;

Or maybe not. The slot may get reused by the time you get to the end.

-boris

> 
> -boris
> 
>> +    /* read ret, then set this rsp slot to be reused */
>> +    smp_mb();
>> +    WRITE_ONCE(bedata->rsp[req_id].req_id, PVCALLS_INVALID_ID);
>> +    WRITE_ONCE(map->passive.inflight_req_id, PVCALLS_INVALID_ID);
>> +    return ret;
>> +}