From: "Jan Beulich" <JBeulich@suse.com>
To: David Vrabel <david.vrabel@citrix.com>
Cc: xen-devel@lists.xenproject.org, Keir Fraser <keir@xen.org>,
Ian Campbell <ian.campbell@citrix.com>, Tim Deegan <tim@xen.org>
Subject: Re: [PATCHv2 3/5] evtchn: use a per-event channel lock for sending events
Date: Tue, 16 Jun 2015 17:06:45 +0100 [thread overview]
Message-ID: <558065B50200007800085AE9@mail.emea.novell.com> (raw)
In-Reply-To: <55803E73.2010603@citrix.com>
>>> On 16.06.15 at 17:19, <david.vrabel@citrix.com> wrote:
> On 16/06/15 10:18, Jan Beulich wrote:
>>>>> On 15.06.15 at 17:48, <david.vrabel@citrix.com> wrote:
>>> @@ -1163,11 +1213,15 @@ int alloc_unbound_xen_event_channel(
>>> if ( rc )
>>> goto out;
>>>
>>> + spin_lock(&chn->lock);
>>> +
>>> chn->state = ECS_UNBOUND;
>>> chn->xen_consumer = get_xen_consumer(notification_fn);
>>> chn->notify_vcpu_id = lvcpu;
>>> chn->u.unbound.remote_domid = remote_domid;
>>>
>>> + spin_unlock(&chn->lock);
>>> +
>>> out:
>>> spin_unlock(&ld->event_lock);
>>
>> I don't see why you shouldn't be able to move up this unlock.
>
> Because we need to (also) hold ld->event_lock while changing the state
> from ECS_FREE or a concurrent get_free_port() will find this port again.
I buy this one (and moving the unlock up after the state adjustment
is unlikely to be worth it), but ...
>>> @@ -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.
... there's no state change involved here.
Jan
next prev parent reply other threads:[~2015-06-16 16:06 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-15 15:48 [PATCHv2 0/5] evtchn: Improve scalebility David Vrabel
2015-06-15 15:48 ` [PATCHv2 1/5] evtchn: factor out freeing an event channel David Vrabel
2015-06-15 15:48 ` [PATCHv2 2/5] evtchn: simplify port_is_valid() David Vrabel
2015-06-15 15:57 ` Ian Campbell
2015-06-15 15:59 ` David Vrabel
2015-06-15 16:09 ` Ian Campbell
2015-06-15 15:48 ` [PATCHv2 3/5] evtchn: use a per-event channel lock for sending events David Vrabel
2015-06-16 9:18 ` Jan Beulich
2015-06-16 9:34 ` David Vrabel
2015-06-16 9:51 ` Jan Beulich
2015-06-16 9:57 ` David Vrabel
2015-06-16 15:19 ` David Vrabel
2015-06-16 15:58 ` David Vrabel
2015-06-16 16:19 ` Jan Beulich
2015-06-16 16:39 ` David Vrabel
2015-06-17 7:05 ` Jan Beulich
2015-06-16 16:06 ` Jan Beulich [this message]
2015-06-15 15:48 ` [PATCHv2 4/5] evtchn: remove the locking when unmasking an event channel David Vrabel
2015-06-16 9:19 ` Jan Beulich
2015-06-16 9:40 ` David Vrabel
2015-06-15 15:48 ` [PATCHv2 5/5] evtchn: pad struct evtchn to 64 bytes David Vrabel
2015-06-16 9:22 ` Jan Beulich
2015-06-16 11:14 ` Julien Grall
2015-06-16 11:59 ` Jan Beulich
2015-06-16 12:57 ` Julien Grall
2015-06-16 13:13 ` David Vrabel
2015-06-16 13:27 ` Julien Grall
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