Re: [Xen-devel] [PATCHv2 3/5] evtchn: use a per-event channel lock for sending events

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 16.06.15 at 17:58, <david.vrabel@xxxxxxxxxx> wrote:
> On 16/06/15 16:19, David Vrabel wrote:
>>>> @@ -1221,6 +1277,8 @@ void notify_via_xen_event_channel(struct domain *ld, 
> int lport)
>>>>          evtchn_port_set_pending(rd, rchn->notify_vcpu_id, rchn);
>>>>      }
>>>>  
>>>> +    spin_unlock(&lchn->lock);
>>>> +
>>>>      spin_unlock(&ld->event_lock);
>>>>  }
>>>
>>> Again I think the event lock can be dropped earlier now.
>> 
>> Ditto.
> 
> Uh, no. This is notify.  I've kept the locking like this because of the
> ld->is_dying check.  I think we need the ld->event_lock in case
> d->is_dying is set and evtchn_destroy(ld) is called.

Right, but if evtchn_destroy() was a concern, then this wouldn't
apply just here, but also in the sending path you are relaxing.
Afaict due to the channel lock being taken in __evtchn_close()
you can drop the even lock here as the latest after you acquired
the channel one (I haven't been able to convince myself yet that
dropping it even before that would be okay).

Jan


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel