> -----Original Message----- > From: Dexuan Cui > Sent: Monday, July 20, 2015 2:39 AM > To: KY Srinivasan; davem@xxxxxxxxxxxxx; netdev@xxxxxxxxxxxxxxx; linux- > kernel@xxxxxxxxxxxxxxx; devel@xxxxxxxxxxxxxxxxxxxxxx; olaf@xxxxxxxxx; > apw@xxxxxxxxxxxxx; jasowang@xxxxxxxxxx; vkuznets@xxxxxxxxxx > Subject: RE: [PATCH net-next 1/1] hv_netvsc: Wait for sub-channels to be > processed during probe > > > From: KY Srinivasan > > Sent: Friday, July 17, 2015 23:33 > > > From: Dexuan Cui > > > Sent: Friday, July 17, 2015 3:01 AM > > > > From: K. Y. Srinivasan > > > > Sent: Friday, July 17, 2015 3:17 > > > > Subject: [PATCH net-next 1/1] hv_netvsc: Wait for sub-channels to be > > > processed > > > > during probe > > > > diff --git a/drivers/net/hyperv/hyperv_net.h > > > b/drivers/net/hyperv/hyperv_net.h > > > > ... > > > > @@ -1116,6 +1127,9 @@ int rndis_filter_device_add(struct hv_device > > > *dev, > > > > num_possible_rss_qs = cpumask_weight(node_cpu_mask); > > > > net_device->num_chn = min(num_possible_rss_qs, num_rss_qs); > > > > > > > > +num_rss_qs = net_device->num_chn - 1; > > > > +net_device->num_sc_offered = num_rss_qs; > > > > + > > > > if (net_device->num_chn == 1) > > > > goto out; > > > > > > > > @@ -1157,11 +1171,22 @@ int rndis_filter_device_add(struct > hv_device > > > *dev, > > > > > > > > ret = rndis_filter_set_rss_param(rndis_device, net_device- > > > >num_chn); > > > > > > > > +/* > > > > + * Wait for the host to send us the sub-channel offers. > > > > + */ > > > > +spin_lock_irqsave(&net_device->sc_lock, flags); > > > > +sc_delta = net_device->num_chn - 1 - num_rss_qs; > > > > +net_device->num_sc_offered -= sc_delta; > > > > > > Hi KY, > > > IMO here the "-= " should be "+="? > > > > > > I think sc_delta is usually <= 0, meaning the host may allocate less > > > subchannels than > > > we expect. > > > With "-=", net_device->num_sc_offered can become bigger -- this > doesn't > > > seem correct. > > We control how many sub-channels we want the host to offer (say > > sc_requested). Based on this > > number we begin to track how many have actually been processed - we > > decrement sc_requested > > each time a sub-channel offer is processed. If the host were to actually > offer all > > that we have requested, > > then checking for sc_requested to be zero is sufficient to ensure that we > have > > processed all the > > potentially in-flight sub-channels. However, the host may choose to offer > less > > than what we had asked for > > and the variable "delta" is tracking this difference. Since we are counting > down > > from what we had asked for > > we have to subtract "delta" for proper accounting. > > Yes, I understand the rationale. > Let me show the issue by example: > > Let's assume sc_requested is 7 and the host actually only offers 3 sub- > channels: > 1. Just before sending the NVSP_MSG5_TYPE_SUBCHANNEL message, we > have > net_device->num_chn == 8, > num_rss_qs == 7 > net_device->num_sc_offered == 7 > > 2. Just after we get the reply of the message, > net_device->num_chn == 4 > sc_delta = net_device->num_chn - 1 - num_rss_qs, so sc_delta == 4 - 1 - 7 = - > 4 > net_device->num_sc_offered -= sc_delta, so > net_device->num_sc_offered == 7 - (-4) = 11. It's not zero, so we sleep on > the > wait_for_completion(). > > 3. Now we process the 3 sub-channel and net_device->num_sc_offered will > become 11 -1 -1 -1 == 8 and no complete() will be invoked! > > That's why I think the "-=" in the line > net_device->num_sc_offered -= sc_delta > should be "+=". Thanks Dexuan; I will fix the issue and resend. Regards, K. Y _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
