Merge branch 'mptcp-avoid-workqueue-usage-for-data'

Paolo Abeni says:

====================
mptcp: avoid workqueue usage for data

The current locking schema used to protect the MPTCP data-path
requires the usage of the MPTCP workqueue to process the incoming
data, depending on trylock result.

The above poses scalability limits and introduces random delays
in MPTCP-level acks.

With this series we use a single spinlock to protect the MPTCP
data-path, removing the need for workqueue and delayed ack usage.

This additionally reduces the number of atomic operations required
per packet and cleans-up considerably the poll/wake-up code.
====================

Link: https://lore.kernel.org/r/cover.1606413118.git.pabeni@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>