> -----Original Message----- > From: Xen-devel <[email protected]> On Behalf Of Jan > Beulich > Sent: 28 September 2020 11:58 > To: [email protected] > Cc: Andrew Cooper <[email protected]>; George Dunlap > <[email protected]>; Ian > Jackson <[email protected]>; Julien Grall <[email protected]>; Wei Liu > <[email protected]>; Stefano Stabellini > <[email protected]> > 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 <[email protected]> > > --- 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); > >
