Merge tag 'mlx5-updates-2019-07-29' of git://git.kernel.org/pub/scm/linux/kernel/git/saeed/linux

Saeed Mahameed says:

====================
mlx5-updates-2019-07-29

This series includes updates to mlx5 driver,
1) Simplifications, cleanup and warning prints improvements

2) From Vlad Buslov:
Refactor mlx5 tc flow handling for unlocked execution (Part 1)

Currently, all cls API hardware offloads driver callbacks require caller
to hold rtnl lock when calling them. Cls API has already been updated to
update software filters in parallel (on classifiers that support
unlocked execution), however hardware offloads code still obtains rtnl
lock before calling driver tc callbacks. This set implements partial
support for unlocked execution that is leveraged by follow up
refactorings in specific mlx5 tc subsystems and patch to cls API that
implements API that allows drivers to register their callbacks as
rtnl-unlocked.

In mlx5 tc code mlx5e_tc_flow is the main structure that is used to
represent tc filter. Currently, code the structure itself and its
handlers in both tc and eswitch layers do not implement any kind of
synchronizations and assume external global synchronization provided by
rtnl lock instead. Implement following changes to remove dependency on
rtnl lock in flow handling code that are intended to be used a
groundwork for following changes to provide fully rtnl-independent mlx5
tc:

- Extend struct mlx5e_tc_flow with atomic reference counter and rcu to
  allow concurrent access from multiple tc and neigh update workqueue
  instances without introducing any additional locks specific to the
  structure. Its 'flags' field type is changed to atomic bitmask ops which
  is necessary for tc to interact with other concurrent tc instances or
  concurrent neigh update that need to skip flows that are not fully
  initialized (new INIT_DONE flow flag) and can change the flags
  according to neighbor state (flipping OFFLOADED flag).

- Protect unready flows list by new uplink_priv->unready_flows_lock
  mutex.

- Convert calls to netdev APIs that require rtnl lock in flow handling
  code to their rcu counterparts.

- Modify eswitch code that is called from tc layer and assume implicit
  external synchronization to be concurrency safe: change
  esw->offloads.num_flows type to atomic integer and re-arrange
  esw->state_lock usage to protect additional data.

Some of approaches to synchronizations presented in this patch set are
quite complicated (lockless concurrent usage of data structures with rcu
and reference counting, using fine-grained locking when necessary, retry
mechanisms to handle concurrent insertion of another instance of data
structure with same key, etc.). This is necessary to allow calling the
firmware in parallel in most cases, which is the main motivation of this
change since firmware calls are mach heavier operation than atomic
operations, multitude of locks and potential multiple retries during
concurrent accesses to same elements.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

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