> -----Original Message-----
> From: Xen-devel <xen-devel-boun...@lists.xenproject.org> On Behalf Of Jan
> Beulich
> Sent: 28 September 2020 11:58
> To: xen-devel@lists.xenproject.org
> Cc: Andrew Cooper <andrew.coop...@citrix.com>; George Dunlap
> <george.dun...@eu.citrix.com>; Ian
> Jackson <i...@xenproject.org>; Julien Grall <jul...@xen.org>; Wei Liu
> <w...@xen.org>; Stefano Stabellini
> <sstabell...@kernel.org>
> Subject: [PATCH 04/12] evtchn: evtchn_set_priority() needs to acquire the
> per-channel lock
>
> evtchn_fifo_set_pending() (invoked with the per-channel lock held) has
> two uses of the channel's priority field.
AFAICT it is invoked with only the sending end's lock held...
> The field gets updated by
> evtchn_fifo_set_priority() with only the per-domain event_lock held,
> i.e. the two reads may observe two different values. While the 2nd use
> could - afaict - in principle be replaced by q->priority, I think
> evtchn_set_priority() should acquire the per-channel lock in any event.
>
... so how is this going to help?
Paul
> Signed-off-by: Jan Beulich <jbeul...@suse.com>
>
> --- a/xen/common/event_channel.c
> +++ b/xen/common/event_channel.c
> @@ -1132,7 +1132,9 @@ static long evtchn_set_priority(const st
> {
> struct domain *d = current->domain;
> unsigned int port = set_priority->port;
> + struct evtchn *chn;
> long ret;
> + unsigned long flags;
>
> spin_lock(&d->event_lock);
>
> @@ -1142,8 +1144,10 @@ static long evtchn_set_priority(const st
> return -EINVAL;
> }
>
> - ret = evtchn_port_set_priority(d, evtchn_from_port(d, port),
> - set_priority->priority);
> + chn = evtchn_from_port(d, port);
> + spin_lock_irqsave(&chn->lock, flags);
> + ret = evtchn_port_set_priority(d, chn, set_priority->priority);
> + spin_unlock_irqrestore(&chn->lock, flags);
>
> spin_unlock(&d->event_lock);
>
>
