Re: [PATCH v4 14/17] net: do not delete nics in net_cleanup()

[David Woodhouse <dwmw2@infradead.org>]

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On Mon, 2023-11-06 at 14:35 +0000, David Woodhouse wrote:
> From: David Woodhouse <dwmw@amazon.co.uk>
> 
> In net_cleanup() we only need to delete the netdevs, as those may have
> state which outlives Qemu when it exits, and thus may actually need to
> be cleaned up on exit.
> 
> The nics, on the other hand, are owned by the device which created them.
> Most devices don't bother to clean up on exit because they don't have
> any state which will outlive Qemu... but XenBus devices do need to clean
> up their nodes in XenStore, and do have an exit handler to delete them.
> 
> When the XenBus exit handler destroys the xen-net-device, it attempts
> to delete its nic after net_cleanup() had already done so. And crashes.
> 
> Fix this by only deleting netdevs as we walk the list. As the comment
> notes, we can't use QTAILQ_FOREACH_SAFE() as each deletion may remove
> *multiple* entries, including the "safely" saved 'next' pointer. But
> we can store the *previous* entry, since nics are safe.
> 
> Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
> Reviewed-by: Paul Durrant <paul@xen.org>

I've left this out of the pull request I've just sent, pending Jason's
approval for it. As it's a bugfix, I don't think we strictly has to be
in by *today*, right? We still have a little time?

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