Merge branch 'ethtool-allow-nesting-of-begin-and-complete-callbacks'
Michal Kubecek says:
====================
ethtool: allow nesting of begin() and complete() callbacks
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@netronome.com>
Signed-off-by: 
David S. Miller <davem@davemloft.net>
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