On Mon, Jan 06, 2020 at 07:39:26AM +0100, Michal Kubecek wrote: > The ethtool ioctl interface used to guarantee that ethtool_ops callbacks > were always called in a block between calls to ->begin() and ->complete() > (if these are defined) and that this whole block was executed with RTNL > lock held: > > rtnl_lock(); > ops->begin(); > /* other ethtool_ops calls */ > ops->complete(); > rtnl_unlock(); > > This prevented any nesting or crossing of the begin-complete blocks. > However, this is no longer guaranteed even for ioctl interface as at least > ethtool_phys_id() releases RTNL lock while waiting for a timer. With the > introduction of netlink ethtool interface, the begin-complete pairs are > naturally nested e.g. when a request triggers a netlink notification. > > Fortunately, only minority of networking drivers implements begin() and > complete() callbacks and most of those that do, fall into three groups: > > - wrappers for pm_runtime_get_sync() and pm_runtime_put() > - wrappers for clk_prepare_enable() and clk_disable_unprepare() > - begin() checks netif_running() (fails if false), no complete() > > First two have their own refcounting, third is safe w.r.t. nesting of the > blocks. > > Only three in-tree networking drivers need an update to deal with nesting > of begin() and complete() calls: via-velocity and epic100 perform resume > and suspend on their own and wil6210 completely serializes the calls using > its own mutex (which would lead to a deadlock if a request request > triggered a netlink notification). The series addresses these problems. > > changes between v1 and v2: > - fix inverted condition in epic100 ethtool_begin() (thanks to Andrew > Lunn) Reviewed-by: Simon Horman <simon.horman@xxxxxxxxxxxxx>
