Re: [Xen-devel] [PATCH 1/2] vm_event: sync domctl

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 23/12/2015 15:41, Razvan Cojocaru wrote:
> On 12/23/2015 04:53 PM, Tamas K Lengyel wrote:
>> Introduce new vm_event domctl option which allows an event subscriber
>> to request all vCPUs not currently pending a vm_event request to be paused,
>> thus allowing the subscriber to sync up on the state of the domain. This
>> is especially useful when the subscribed wants to disable certain events
>> from being delivered and wants to ensure no more requests are pending on the
>> ring before doing so.
>>
>> Cc: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
>> Cc: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
>> Cc: Ian Campbell <ian.campbell@xxxxxxxxxx>
>> Cc: Wei Liu <wei.liu2@xxxxxxxxxx>
>> Cc: Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>
>> Signed-off-by: Tamas K Lengyel <tamas@xxxxxxxxxxxxx>
> This certainly looks very interesting. Would xc_domain_pause() not be
> enough for your use case then?

I second this query.  I would have thought xc_domain_pause() does
exactly what you want in this case.

The code provided is racy, as it is liable to alter which pause
references it takes/releases depending on what other pause/unpause
actions are being made.

~Andrew

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