[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH v2 net] xen: netback: read hotplug script once at start of day.
From: Ian Campbell <ian.campbell@xxxxxxxxxx> Date: Mon, 1 Jun 2015 11:30:24 +0100 > When we come to tear things down in netback_remove() and generate the > uevent it is possible that the xenstore directory has already been > removed (details below). > > In such cases netback_uevent() won't be able to read the hotplug > script and will write a xenstore error node. > > A recent change to the hypervisor exposed this race such that we now > sometimes lose it (where apparently we didn't ever before). > > Instead read the hotplug script configuration during setup and use it > for the lifetime of the backend device. > > The apparently more obvious fix of moving the transition to > state=Closed in netback_remove() to after the uevent does not work > because it is possible that we are already in state=Closed (in > reaction to the guest having disconnected as it shutdown). Being > already in Closed means the toolstack is at liberty to start tearing > down the xenstore directories. In principal it might be possible to > arrange to unregister the device sooner (e.g on transition to Closing) > such that xenstore would still be there but this state machine is > fragile and prone to anger... > > A modern Xen system only relies on the hotplug uevent for driver > domains, when the backend is in the same domain as the toolstack it > will run the necessary setup/teardown directly in the correct sequence > wrt xenstore changes. > > Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx> Applied and queued up for -stable, thanks. _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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