[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCHv2 3/5] evtchn: use a per-event channel lock for sending events
On 16/06/15 10:51, Jan Beulich wrote: >>>> On 16.06.15 at 11:34, <david.vrabel@xxxxxxxxxx> wrote: >> On 16/06/15 10:18, Jan Beulich wrote: >>>>>> On 15.06.15 at 17:48, <david.vrabel@xxxxxxxxxx> wrote: >>>> @@ -609,21 +662,18 @@ int evtchn_send(struct domain *ld, unsigned int >>>> lport) >>>> struct domain *rd; >>>> int rport, ret = 0; >>>> >>>> - spin_lock(&ld->event_lock); >>>> - >>>> - if ( unlikely(!port_is_valid(ld, lport)) ) >>>> - { >>>> - spin_unlock(&ld->event_lock); >>>> + if ( unlikely(lport >= read_atomic(&ld->valid_evtchns)) ) >>>> return -EINVAL; >>>> - } >>> >>> I don't think you really want to open code part of port_is_valid() >>> (and avoid other parts of it) here? Or if really so, I think a comment >>> should be added to explain it. >> >> The ld->valid_evtchns is the only field we can safely check without >> ld->event_lock. >> >> We do check the channel state and the code that set this state uses the >> full port_is_valid() call. I'll add a comment. > > Hmm, port_is_valid() also checks d->max_evtchns and d->evtchn. > The latter is involved in evtchn_from_port(), so I can't see how > you checking the channel's state _afterwards_ can leverage that > whoever set this state did a full check. > > Another question is whether with the ->valid_evtchns check the > ->evtchn check is necessary at all anymore. (The check against > ->max_evtchns isn't wrong with the lock not held, i.e. could only > end up being too strict, and hence the open coding would then > still be questionable.) Ok. I'll remove the d->evtchn check from port_is_valid() and use it. David _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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