linux-kernel - Re: [PATCH v3 08/13] xen/pvcalls: implement accept command

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Message-ID: <37d72529-c8d4-96e1-422c-342a19af9055@oracle.com>
Date:   Mon, 14 Aug 2017 22:04:59 -0400
From:   Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:     Stefano Stabellini <sstabellini@...nel.org>,
        xen-devel@...ts.xen.org
Cc:     linux-kernel@...r.kernel.org, jgross@...e.com,
        Stefano Stabellini <stefano@...reto.com>
Subject: Re: [PATCH v3 08/13] xen/pvcalls: implement accept command


>> +
>> +    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;
>> +}