> -----Original Message----- > From: Jason Wang [mailto:jasowang@xxxxxxxxxx] > Sent: Thursday, January 29, 2015 18:09 PM > To: Dexuan Cui > Cc: Vitaly Kuznetsov; KY Srinivasan; devel@xxxxxxxxxxxxxxxxxxxxxx; Haiyang Zhang; > linux-kernel@xxxxxxxxxxxxxxx; Radim Krčmář; Dan Carpenter > Subject: RE: [PATCH v3 3/3] Drivers: hv: vmbus: serialize Offer and Rescind offer > > > > On Wed, Jan 28, 2015 at 8:51 PM, Dexuan Cui <decui@xxxxxxxxxxxxx> wrote: > >> -----Original Message----- > >> From: Vitaly Kuznetsov [mailto:vkuznets@xxxxxxxxxx] > >> Sent: Wednesday, January 28, 2015 20:09 PM > >> To: Dexuan Cui > >> Cc: KY Srinivasan; devel@xxxxxxxxxxxxxxxxxxxxxx; Haiyang Zhang; > >> linux- > >> kernel@xxxxxxxxxxxxxxx; Jason Wang; Radim Krčmář; Dan Carpenter > >> Subject: Re: [PATCH v3 3/3] Drivers: hv: vmbus: serialize Offer and > >> Rescind > >> offer > >> > >> Dexuan Cui <decui@xxxxxxxxxxxxx> writes: > >> > >> >> -----Original Message----- > >> >> From: Vitaly Kuznetsov [mailto:vkuznets@xxxxxxxxxx] > >> >> Sent: Tuesday, January 20, 2015 23:45 PM > >> >> To: KY Srinivasan; devel@xxxxxxxxxxxxxxxxxxxxxx > >> >> Cc: Haiyang Zhang; linux-kernel@xxxxxxxxxxxxxxx; Dexuan Cui; > >> Jason Wang; > >> >> Radim Krčmář; Dan Carpenter > >> >> Subject: [PATCH v3 3/3] Drivers: hv: vmbus: serialize Offer and > >> Rescind > >> offer > >> ... > >> > > >> > Hi Vitaly and all, > >> > I have 2 questions: > >> > In vmbus_process_offer(), in the cases of "goto err_free_chan", > >> > should we consider the possibility a rescind message could be > >> pending for > >> > the new channel? > >> > In the cases, because we don't run > >> > "INIT_WORK(&newchannel->work, vmbus_process_rescind_offer); ", > >> > vmbus_onoffer_rescind() will do nothing and as a result, > >> > vmbus_process_rescind_offer() won't be invoked. > >> > >> Yes, but processing the rescind offer results in freeing the channel > >> (and this processing supposes the channel wasn't freed before) so > >> there is no difference... or is it? > >> > >> > > >> > Question 2: in vmbus_process_offer(), in the case > >> > vmbus_device_register() fails, we'll run > >> > "list_del(&newchannel->listentry);" -- just after this line, > >> > what will happen at this time if relid2channel() returns NULL > >> > in vmbus_onoffer_rescind()? > >> > > >> > I think we'll lose the rescind message. > >> > > >> > >> Yes, but same logic applies - we already freed the channes so no > >> rescind > >> proccessing required. > > free_channel() and vmbus_process_rescind_offer() are different, > > because > > the latter does more work, e.g., sending the host a message > > CHANNELMSG_RELID_RELEASED. > > > > In the cases of "goto err_free_chan" + "a pending rescind message", > > the host may expect the message CHANNELMSG_RELID_RELEASED and > > could reoffer the channel once the message is received. > > > > It would be better if the VM doesn't lose the rescind message here. > > :-) > > It's interesting that rescind needs a ack from guest. But looks like > the offer does not need it? Is there a spec for this for us for > reference? My understanding is: The host may reuse the same relid after the VM acks the rescind message. I don't have a VMBus spec either. > > > > > >> If we still need to do something we need to > >> add support for already freed channel to the rescind offer > >> processing path. > >> This sounds reasonable to me. Error handling is always full of various corner cases... Thanks, -- Dexuan _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
