I think there is a bug in pvusb when the DomU does not respond to the XenbusStateReconfiguring state change and is then rebooted. This caused the following Dom0 (after a long freeze): BUG: soft lockup detected on CPU#0! Call Trace: <IRQ> [<ffffffff802a938c>] softlockup_tick+0xe1/0xef [<ffffffff80268f82>] timer_interrupt+0x408/0x466 [<ffffffff8020fb41>] handle_IRQ_event+0x4d/0x95 [<ffffffff802a9870>] __do_IRQ+0xb4/0x127 [<ffffffff8026729c>] do_IRQ+0x44/0x4d [<ffffffff80375f6b>] evtchn_do_upcall+0x1b3/0x26e [<ffffffff8025c8d2>] do_hypervisor_callback+0x1e/0x2c <EOI> [<ffffffff88355b7e>] :usbbk:usbbk_schedule+0x1e0/0xa3f [<ffffffff8029482f>] autoremove_wake_function+0x0/0x2e [<ffffffff802947ba>] keventd_create_kthread+0x0/0x62 [<ffffffff8835599e>] :usbbk:usbbk_schedule+0x0/0xa3f [<ffffffff802947ba>] keventd_create_kthread+0x0/0x62 [<ffffffff802325e4>] kthread+0xd4/0x108 [<ffffffff8025cb24>] child_rip+0xa/0x12 [<ffffffff802947ba>] keventd_create_kthread+0x0/0x62 [<ffffffff8025c827>] error_exit+0x0/0x71 [<ffffffff80232510>] kthread+0x0/0x108 [<ffffffff8025cb1a>] child_rip+0x0/0x12 FYI, I am trying to get pvusb working under GPLPV and I had never seen the Reconfiguring/Reconfigured states before and so I wasn''t doing anything with them... James _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Cc''ing the author... K. On 25/07/2009 11:01, "James Harper" <james.harper@bendigoit.com.au> wrote:> I think there is a bug in pvusb when the DomU does not respond to the > XenbusStateReconfiguring state change and is then rebooted. This caused > the following Dom0 (after a long freeze): > > BUG: soft lockup detected on CPU#0! > > Call Trace: > <IRQ> [<ffffffff802a938c>] softlockup_tick+0xe1/0xef > [<ffffffff80268f82>] timer_interrupt+0x408/0x466 > [<ffffffff8020fb41>] handle_IRQ_event+0x4d/0x95 > [<ffffffff802a9870>] __do_IRQ+0xb4/0x127 > [<ffffffff8026729c>] do_IRQ+0x44/0x4d > [<ffffffff80375f6b>] evtchn_do_upcall+0x1b3/0x26e > [<ffffffff8025c8d2>] do_hypervisor_callback+0x1e/0x2c > <EOI> [<ffffffff88355b7e>] :usbbk:usbbk_schedule+0x1e0/0xa3f > [<ffffffff8029482f>] autoremove_wake_function+0x0/0x2e > [<ffffffff802947ba>] keventd_create_kthread+0x0/0x62 > [<ffffffff8835599e>] :usbbk:usbbk_schedule+0x0/0xa3f > [<ffffffff802947ba>] keventd_create_kthread+0x0/0x62 > [<ffffffff802325e4>] kthread+0xd4/0x108 > [<ffffffff8025cb24>] child_rip+0xa/0x12 > [<ffffffff802947ba>] keventd_create_kthread+0x0/0x62 > [<ffffffff8025c827>] error_exit+0x0/0x71 > [<ffffffff80232510>] kthread+0x0/0x108 > [<ffffffff8025cb1a>] child_rip+0x0/0x12 > > FYI, I am trying to get pvusb working under GPLPV and I had never seen > the Reconfiguring/Reconfigured states before and so I wasn''t doing > anything with them... > > James > > > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xensource.com > http://lists.xensource.com/xen-devel_______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Also, a question on behaviour: When we receive a reconfigure event, I assume that we should then read ''num-ports'' and scan through each of the port-n values in xenstore. Is there any guarantee that a device hasn''t been unplugged and replugged from the same port during the reconfiguration window? How should I detect such a thing if the value of port-n hasn''t changed? Should I then probe each device? I''m doing this under Windows which is a bit more picky and much less flexible... Thanks James> -----Original Message----- > From: Keir Fraser [mailto:keir.fraser@eu.citrix.com] > Sent: Saturday, 25 July 2009 20:13 > To: James Harper; xen-devel@lists.xensource.com > Cc: n_iwamatsu@jp.fujitsu.com > Subject: Re: [Xen-devel] bug in usbback > > Cc''ing the author... > > K. > > On 25/07/2009 11:01, "James Harper" <james.harper@bendigoit.com.au>wrote:> > > I think there is a bug in pvusb when the DomU does not respond tothe> > XenbusStateReconfiguring state change and is then rebooted. Thiscaused> > the following Dom0 (after a long freeze): > > > > BUG: soft lockup detected on CPU#0! > > > > Call Trace: > > <IRQ> [<ffffffff802a938c>] softlockup_tick+0xe1/0xef > > [<ffffffff80268f82>] timer_interrupt+0x408/0x466 > > [<ffffffff8020fb41>] handle_IRQ_event+0x4d/0x95 > > [<ffffffff802a9870>] __do_IRQ+0xb4/0x127 > > [<ffffffff8026729c>] do_IRQ+0x44/0x4d > > [<ffffffff80375f6b>] evtchn_do_upcall+0x1b3/0x26e > > [<ffffffff8025c8d2>] do_hypervisor_callback+0x1e/0x2c > > <EOI> [<ffffffff88355b7e>] :usbbk:usbbk_schedule+0x1e0/0xa3f > > [<ffffffff8029482f>] autoremove_wake_function+0x0/0x2e > > [<ffffffff802947ba>] keventd_create_kthread+0x0/0x62 > > [<ffffffff8835599e>] :usbbk:usbbk_schedule+0x0/0xa3f > > [<ffffffff802947ba>] keventd_create_kthread+0x0/0x62 > > [<ffffffff802325e4>] kthread+0xd4/0x108 > > [<ffffffff8025cb24>] child_rip+0xa/0x12 > > [<ffffffff802947ba>] keventd_create_kthread+0x0/0x62 > > [<ffffffff8025c827>] error_exit+0x0/0x71 > > [<ffffffff80232510>] kthread+0x0/0x108 > > [<ffffffff8025cb1a>] child_rip+0x0/0x12 > > > > FYI, I am trying to get pvusb working under GPLPV and I had neverseen> > the Reconfiguring/Reconfigured states before and so I wasn''t doing > > anything with them... > > > > James > > > > > > _______________________________________________ > > Xen-devel mailing list > > Xen-devel@lists.xensource.com > > http://lists.xensource.com/xen-devel >_______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Hi James, Reconfiguring/Resconfigured states are used to notify the hotplug event, as follows. usb device usbback usbfront --------- ------- -------- Connected Connected | | ---plug&probe--->| | | | Reconfiguring-------------------->| | | | <---------------------Reconfiguring | | | | usbback_do_hotplug() | | | | | Reconfigured-------------------->| | | | | | usbfront_do_hotplug() | | | | |<----------------------Connected | | Connected | | | You mean: - Your version of usbfront NOT respond to Reconfiguring state. It''s not bug of original usbfront. - When usbback is in Reconfiguring state and usbfront NOT respond to that, rebooting domU causes the BUG. Is my understanding right? Regards, Noboru James Harper wrote:> I think there is a bug in pvusb when the DomU does not respond to the > XenbusStateReconfiguring state change and is then rebooted. This caused > the following Dom0 (after a long freeze): > > BUG: soft lockup detected on CPU#0! > > Call Trace: > <IRQ> [<ffffffff802a938c>] softlockup_tick+0xe1/0xef > [<ffffffff80268f82>] timer_interrupt+0x408/0x466 > [<ffffffff8020fb41>] handle_IRQ_event+0x4d/0x95 > [<ffffffff802a9870>] __do_IRQ+0xb4/0x127 > [<ffffffff8026729c>] do_IRQ+0x44/0x4d > [<ffffffff80375f6b>] evtchn_do_upcall+0x1b3/0x26e > [<ffffffff8025c8d2>] do_hypervisor_callback+0x1e/0x2c > <EOI> [<ffffffff88355b7e>] :usbbk:usbbk_schedule+0x1e0/0xa3f > [<ffffffff8029482f>] autoremove_wake_function+0x0/0x2e > [<ffffffff802947ba>] keventd_create_kthread+0x0/0x62 > [<ffffffff8835599e>] :usbbk:usbbk_schedule+0x0/0xa3f > [<ffffffff802947ba>] keventd_create_kthread+0x0/0x62 > [<ffffffff802325e4>] kthread+0xd4/0x108 > [<ffffffff8025cb24>] child_rip+0xa/0x12 > [<ffffffff802947ba>] keventd_create_kthread+0x0/0x62 > [<ffffffff8025c827>] error_exit+0x0/0x71 > [<ffffffff80232510>] kthread+0x0/0x108 > [<ffffffff8025cb1a>] child_rip+0x0/0x12 > > FYI, I am trying to get pvusb working under GPLPV and I had never seen > the Reconfiguring/Reconfigured states before and so I wasn''t doing > anything with them... > > James > > > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xensource.com > http://lists.xensource.com/xen-devel_______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
> You mean: > - Your version of usbfront NOT respond to Reconfiguring state. > It''s not bug of original usbfront.Correct. I was not responding at all to ''Reconfiguring'' (I didn''t even know they existed at the time - I was just plugging my generic xenbus routines into a skeleton usb driver).> - When usbback is in Reconfiguring state and usbfront NOT respond to > that, rebooting domU causes the BUG.Yes. Actually just stopping DomU is enough to cause the bug. It doesn''t appear to matter if it restarts or not. I was able to work around the problem by writing ''Reconfiguring'' and then ''Connected'' into the frontend xenstore to complete my testing.> > Is my understanding right? >Yes. Obviously with a correctly functioning frontend (mine works properly now) the bug in the backend should not become apparent, but if the DomU ever crashed during the transition from backend Reconfiguring to frontend Reconfiguring, then Dom0 would be affected so I think it is worth fixing this bug. Also a malicious DomU could exploit this. Thanks James _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Hi, James Harper wrote:> Also, a question on behaviour: > > When we receive a reconfigure event, I assume that we should then read > ''num-ports'' and scan through each of the port-n values in xenstore. Is > there any guarantee that a device hasn''t been unplugged and replugged > from the same port during the reconfiguration window? How should I > detect such a thing if the value of port-n hasn''t changed? Should I then > probe each device? I''m doing this under Windows which is a bit more > picky and much less flexible..."num-ports" is only read in creating the hcd. This value is unchanged during reconfiguring state. Reconfiguring is called from usb probe and disconnect callbacks. So, reconfiguring is called every time unplugging and plugging are detected. However, connecting and disconnecting the devices at the same time or frequent operations were not tested enough. Do you think it''s good idea that the method for the notification of hotplug is switched from xenbus to RING (like pv network''s rx_ring)? Regards, Noboru _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
> James Harper wrote: > > Also, a question on behaviour: > > > > When we receive a reconfigure event, I assume that we should thenread> > ''num-ports'' and scan through each of the port-n values in xenstore.Is> > there any guarantee that a device hasn''t been unplugged andreplugged> > from the same port during the reconfiguration window? How should I > > detect such a thing if the value of port-n hasn''t changed? Should Ithen> > probe each device? I''m doing this under Windows which is a bit more > > picky and much less flexible... > > "num-ports" is only read in creating the hcd. This value is unchanged > during reconfiguring state. > > Reconfiguring is called from usb probe and disconnect callbacks. > So, reconfiguring is called every time unplugging and plugging are > detected. > > However, connecting and disconnecting the devices at the same time > or frequent operations were not tested enough. > > Do you think it''s good idea that the method for the notification > of hotplug is switched from xenbus to RING (like pv network''srx_ring)?>I like the idea of having the port states in the xenstore. It is a low speed and (mostly) relatively infrequently changing thing so I think keeping it in xenstore is appropriate. I think the problem could be solved by simply including a port change counter for each port, either as part of the existing port-N value or as an additional ''port-N-generation'' field. The backend would just increment that every time there is a plug or unplug event, and the frontend could compare the value to what it was last time to see if the port had changed. So maybe "port-N=S" would become "port-N=GGS", where S is the current ''speed'' value, and "GG" is a change counter. As an example: 1. port-1=000 2. <hot plug> 3. port-1=013 4. <hot unplug> 5. port-1=020 6. <hot plug> 7. port-1=033 It would unfortunately break backwards compatibility, but it''s still in the staging area, for exactly this reason right? Thanks James _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Hi,>> Do you think it''s good idea that the method for the notification >> of hotplug is switched from xenbus to RING (like pv network''s > rx_ring)? > > I like the idea of having the port states in the xenstore. It is a low > speed and (mostly) relatively infrequently changing thing so I think > keeping it in xenstore is appropriate. > > I think the problem could be solved by simply including a port change > counter for each port, either as part of the existing port-N value or as > an additional ''port-N-generation'' field. The backend would just > increment that every time there is a plug or unplug event, and the > frontend could compare the value to what it was last time to see if the > port had changed. > > > So maybe "port-N=S" would become "port-N=GGS", where S is the current > ''speed'' value, and "GG" is a change counter. As an example: > > 1. port-1=000 > 2. <hot plug> > 3. port-1=013 > 4. <hot unplug> > 5. port-1=020 > 6. <hot plug> > 7. port-1=033I don''t think it''s a good idea. If disconnection happened, the urb transfer is sure to make an error, and usbfront can detect this error without counter. Furthermore, usbfront only emulates the roothub ports'' virtual status by the value of port-N''s speed, and, even if the counter value is wrong, this value cannot be associated to the rootport''s status. As I mentioned, if notifications by xenbus has the problem, I prefer using RING. Regards, Noboru _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
> > > > So maybe "port-N=S" would become "port-N=GGS", where S is thecurrent> > ''speed'' value, and "GG" is a change counter. As an example: > > > > 1. port-1=000 > > 2. <hot plug> > > 3. port-1=013 > > 4. <hot unplug> > > 5. port-1=020 > > 6. <hot plug> > > 7. port-1=033 > > I don''t think it''s a good idea. > > If disconnection happened, the urb transfer is sure to make an error, > and usbfront can detect this error without counter.Is it a good idea for the usb device driver running in the frontend to detect an unplug->replug event by getting error codes? It could report a device failure in that case rather than figuring out that the device has been unplugged and replugged.> > Furthermore, usbfront only emulates the roothub ports'' virtual status > by the value of port-N''s speed, and, even if the counter value iswrong,> this value cannot be associated to the rootport''s status.The last digit of the counter still represents the port virtual status. Only the first two digits increment. As per my previous email, the format of the port-N xenstore entry would become ''GGS'' where GG is the counter value and ''S'' is the status, as it is now.> > As I mentioned, if notifications by xenbus has the problem, I prefer > using RING. >The problem with the ring method is that there has to be an outstanding ring request sent by the frontend in order for the backend to be able to notify the frontend. I think that would add unnecessary overhead. James _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Hi, James Harper wrote:>>> So maybe "port-N=S" would become "port-N=GGS", where S is the > current >>> ''speed'' value, and "GG" is a change counter. As an example: >>> >>> 1. port-1=000 >>> 2. <hot plug> >>> 3. port-1=013 >>> 4. <hot unplug> >>> 5. port-1=020 >>> 6. <hot plug> >>> 7. port-1=033 >> I don''t think it''s a good idea. >> >> If disconnection happened, the urb transfer is sure to make an error, >> and usbfront can detect this error without counter. > > Is it a good idea for the usb device driver running in the frontend to > detect an unplug->replug event by getting error codes? It could report a > device failure in that case rather than figuring out that the device has > been unplugged and replugged.USB device driver (aka function driver) detects plug/unplug event by probe/disconnect callbacks. These callbacks and URB transfer error callback are different. Disconnection causes the transfer error, or disconnection is detected and the transfer is canceled. Normally, after canceling the transfer, the device is re-initialized (if the device is still present). In any case, it might be another problem that reports the disconnection event as an error.>> Furthermore, usbfront only emulates the roothub ports'' virtual status >> by the value of port-N''s speed, and, even if the counter value is > wrong, >> this value cannot be associated to the rootport''s status. > > The last digit of the counter still represents the port virtual status. > Only the first two digits increment. As per my previous email, the > format of the port-N xenstore entry would become ''GGS'' where GG is the > counter value and ''S'' is the status, as it is now.I mean "roothub ports'' virtual status" as port status that is emulated in usbfront roothub part. How do you associate the error of the counter to wPortChange bit field? (See struct rhport_status in usbfront.h and usbfront_hub.c)>> As I mentioned, if notifications by xenbus has the problem, I prefer >> using RING. >> > > The problem with the ring method is that there has to be an outstanding > ring request sent by the frontend in order for the backend to be able to > notify the frontend. I think that would add unnecessary overhead. >I believe the method of no "reconfiguring mismatch" happening is better than correcting the mismatch. It''s necessary overhead. Regards, Noboru _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel