Re: xl dev-detach hangs with missing frontends

[Wei Liu <wei.liu2@citrix.com>]

CC'ing other tools maintainer.

On Thu, Feb 11, 2016 at 11:37:49AM +0100, Olaf Hering wrote:
> How should libxl__initiate_device_generic_remove deal with devices which

I think you meant libxl__initiate_device_remove. There is no function
called libxl__initiate_device_generic _remove.

> have no frontend driver? Right now it moves "state" from either
> XenbusStateInitialising or XenbusStateInitWait to XenbusStateClosing.
> Then it expects the backend to move "state" to XenbusStateClosed. This
> will never happen, at least for netback and scsiback. The result is a 10
> second delay.
> 

I don't think there is a way to tell whether there is no frontend driver
or the frontend driver is just too slow.

Do you think the timeout is too long?

Wei.

> 
> # xl -vvvv network-detach $domU $mac
> 2016-02-11 11:33:19 CET [20318] libxl: debug: libxl.c:4614:libxl_device_nic_remove: ao 0x19b3870: create: how=(nil) callback=(nil) poller=0x19b0200
> 2016-02-11 11:33:19 CET [20318] libxl: debug: libxl_event.c:636:libxl__ev_xswatch_register: watch w=0x19b2c40 wpath=/local/domain/0/backend/vif/10/1/state token=3/0: register slotnum=3
> 2016-02-11 11:33:19 CET [20318] libxl: debug: libxl.c:4614:libxl_device_nic_remove: ao 0x19b3870: inprogress: poller=0x19b0200, flags=i
> 2016-02-11 11:33:19 CET [20318] libxl: debug: libxl_event.c:573:watchfd_callback: watch w=0x19b2c40 wpath=/local/domain/0/backend/vif/10/1/state token=3/0: event epath=/local/domain/0/backend/vif/10/1/state
> 2016-02-11 11:33:19 CET [20318] libxl: debug: libxl_event.c:878:devstate_callback: backend /local/domain/0/backend/vif/10/1/state wanted state 6 still waiting state 5
> 2016-02-11 11:33:29 CET [20318] libxl: debug: libxl_aoutils.c:88:xswait_timeout_callback: backend /local/domain/0/backend/vif/10/1/state (hoping for state change to 6): xswait timeout (path=/local/domain/0/backend/vif/10/1/state)
> 2016-02-11 11:33:29 CET [20318] libxl: debug: libxl_event.c:673:libxl__ev_xswatch_deregister: watch w=0x19b2c40 wpath=/local/domain/0/backend/vif/10/1/state token=3/0: deregister slotnum=3
> 2016-02-11 11:33:29 CET [20318] libxl: debug: libxl_event.c:862:devstate_callback: backend /local/domain/0/backend/vif/10/1/state wanted state 6  timed out
> 2016-02-11 11:33:29 CET [20318] libxl: debug: libxl_event.c:686:libxl__ev_xswatch_deregister: watch w=0x19b2c40: deregister unregistered
> 2016-02-11 11:33:29 CET [20318] libxl: debug: libxl_device.c:939:device_backend_callback: calling device_backend_cleanup
> 2016-02-11 11:33:29 CET [20318] libxl: debug: libxl_event.c:686:libxl__ev_xswatch_deregister: watch w=0x19b2c40: deregister unregistered
> 2016-02-11 11:33:29 CET [20318] libxl: debug: libxl_device.c:945:device_backend_callback: Timeout reached, initiating forced remove
> 2016-02-11 11:33:29 CET [20318] libxl: debug: libxl_event.c:636:libxl__ev_xswatch_register: watch w=0x19b2c40 wpath=/local/domain/0/backend/vif/10/1/state token=3/1: register slotnum=3
> 2016-02-11 11:33:29 CET [20318] libxl: debug: libxl_event.c:573:watchfd_callback: watch w=0x19b2c40 wpath=/local/domain/0/backend/vif/10/1/state token=3/1: event epath=/local/domain/0/backend/vif/10/1/state
> 2016-02-11 11:33:29 CET [20318] libxl: debug: libxl_event.c:874:devstate_callback: backend /local/domain/0/backend/vif/10/1/state wanted state 6 ok
> 2016-02-11 11:33:29 CET [20318] libxl: debug: libxl_event.c:673:libxl__ev_xswatch_deregister: watch w=0x19b2c40 wpath=/local/domain/0/backend/vif/10/1/state token=3/1: deregister slotnum=3
> 2016-02-11 11:33:29 CET [20318] libxl: debug: libxl_device.c:939:device_backend_callback: calling device_backend_cleanup
> 2016-02-11 11:33:29 CET [20318] libxl: debug: libxl_event.c:686:libxl__ev_xswatch_deregister: watch w=0x19b2c40: deregister unregistered
> 2016-02-11 11:33:29 CET [20318] libxl: debug: libxl_device.c:1036:device_hotplug: calling hotplug script: /opt/xen/staging-wip/etc/xen/scripts/vif-bridge offline
> 2016-02-11 11:33:29 CET [20318] libxl: debug: libxl_aoutils.c:593:libxl__async_exec_start: forking to execute: /opt/xen/staging-wip/etc/xen/scripts/vif-bridge offline
> 2016-02-11 11:33:29 CET [20318] libxl: debug: libxl_event.c:542:watchfd_callback: watch epath=/local/domain/0/backend/vif/10/1/state token=3/1: empty slot
> 2016-02-11 11:33:29 CET [20318] libxl: debug: libxl_event.c:686:libxl__ev_xswatch_deregister: watch w=0x19b2d40: deregister unregistered
> 2016-02-11 11:33:29 CET [20318] libxl: debug: libxl_device.c:1023:device_hotplug: No hotplug script to execute
> 2016-02-11 11:33:29 CET [20318] libxl: debug: libxl_event.c:686:libxl__ev_xswatch_deregister: watch w=0x19b2d40: deregister unregistered
> 2016-02-11 11:33:29 CET [20318] libxl: debug: libxl_event.c:1869:libxl__ao_complete: ao 0x19b3870: complete, rc=0
> 2016-02-11 11:33:29 CET [20318] libxl: debug: libxl_event.c:1838:libxl__ao__destroy: ao 0x19b3870: destroy
> 2016-02-11 11:33:29 CET [20318] xencall:buffer: debug: total allocations:22 total releases:22
> 2016-02-11 11:33:29 CET [20318] xencall:buffer: debug: current allocations:0 maximum allocations:2
> 2016-02-11 11:33:29 CET [20318] xencall:buffer: debug: cache current size:2
> 2016-02-11 11:33:29 CET [20318] xencall:buffer: debug: cache hits:14 misses:2 toobig:6
> # echo $?
> 0
> 
> At least ${dev}-detach reports no error in this case.
> 
> Olaf
> 
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