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Marek Marczykowski-Górecki
9eaaedfcde
Backend domain may be independently destroyed - there is no synchronization of libxl structures (including /libxl tree) elsewhere. Backend might also remove the device info from its backend xenstore subtree on its own. We have various cases (not comprehensive list): - both frontend and backend operational: after setting be/state=XenbusStateClosing backend wait for frontend confirmation and respond with be/state=XenbusStateClosed; then libxl in dom0 remove frontend entries and libxl in backend domain (which may be the same) remove backend entries - unresponsive backend/frontend: after a timeout, force=1 is used to remove frontend entries, instead of just setting be/state=XenbusStateClosing; then wait for be/state=XenbusStateClosed. If that timeout too, remove both frontend and backend entries - backend gone, with this patch: no place for setting/waiting on be/state - go directly to removing frontend entries, without waiting for be/state=XenbusStateClosed (this is the difference vs force=1) Without this patch the end result is similar, both frontend and backend entries are removed, but in case of backend gone: - libxl waits for be/state=XenbusStateClosed (and obviously timeout) - return value from the function signal an error, which for example confuse libvirt - it thinks the device remove failed, so is still there If such situation is detected, do not fail the removal, but finish the cleanup of the frontend side and return 0. This is just workaround, the real fix should watch when the device backend is removed (including backend domain destruction) and remove frontend at that time. And report such event to higher layer code, so for example libvirt could synchronize its state. Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com> Reviewed-by: Roger Pau Monné <roger.pau@citrix.com> Acked-by: Wei Liu <wei.liu2@citrix.com>