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

Message

Michal Kubecek Jan. 5, 2020, 9:16 p.m. UTC

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.


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(-)