[PATCH net-next 0/3] ethtool: allow nesting of begin() and complete() callbacks

From: Michal Kubecek
Date: Sun Jan 05 2020 - 16:17:07 EST

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:

/* other ethtool_ops calls */

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

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.

Michal Kubecek (3):
wil6210: get rid of begin() and complete() ethtool_ops
via-velocity: allow nesting of ethtool_ops begin() and complete()
epic100: allow nesting of ethtool_ops begin() and complete()

drivers/net/ethernet/smsc/epic100.c | 7 +++-
drivers/net/ethernet/via/via-velocity.c | 14 +++++--
drivers/net/ethernet/via/via-velocity.h | 1 +
drivers/net/wireless/ath/wil6210/ethtool.c | 43 ++++++++--------------
4 files changed, 32 insertions(+), 33 deletions(-)