Re: [Xen-devel] [PATCHv3 4/6] evtchn: use a per-event channel lock for sending events

[David Vrabel <david.vrabel@xxxxxxxxxx>]

On 18/06/15 12:20, Jan Beulich wrote:
>>>> On 17.06.15 at 14:03, <david.vrabel@xxxxxxxxxx> wrote:
>> When sending an event, use a new per-event channel lock to safely
>> validate the event channel state.
>>
>> This new lock must be held when changing event channel state.  Note
>> that the event channel lock must also be held when changing state from
>> ECS_FREE or it will race with a concurrent get_free_port() call.
>>
>> To avoid having to take the remote event channel locks when sending to
>> an interdomain event channel, the local and remote channel locks are
>> both held when binding or closing an interdomain event channel.
>>
>> This significantly  increases the  number of events  that can  be sent
>> from multiple  VCPUs.  But struct  evtchn increases in  size, reducing
>> the number that fit into a single page to 64 (instead of 128).
>>
>> Signed-off-by: David Vrabel <david.vrabel@xxxxxxxxxx>
> 
> Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
> 
> But iiuc this functionally depends on the earlier patches, and
> hence can't go in without the issues there addressed.

Yes, this depends on #1, #2 and #3.

David

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