[PATCH v4 0/5] [PATCH v3 0/4] locking/rwsem: Add reader-owned state to the owner field

[Waiman Long <Waiman.Long@hpe.com>]

 v3->v4:
  - Add a new patch 2 to use WRITE_ONCE() for all rwsem->owner stores
    to prevent store tearing.

 v2->v3:
  - Make minor code changes as suggested by PeterZ & Peter Hurley.
  - Add 2 minor patches (#2 & #3) to improve the rwsem code
  - Add a 4th patch to streamline the rwsem_optimistic_spin() code.

 v1->v2:
  - Add rwsem_is_reader_owned() helper & rename rwsem_reader_owned()
    to rwsem_set_reader_owned().
  - Add more comments to clarify the purpose of some of the code
    changes.

Patch 1 is the main patch of this series.

Patch 2 protects against store tearing of rwsem->owner field which 
can cause problem when a reader tries to dereference it.

Patch 3 eliminates redundant wakeup caused by a reader waking itself.

Patch 4 improves the efficiency of the reader wakeup code.

Patch 5 streamlines the rwsem_optimistic_spin() to make it simpler.

Waiman Long (5):
  locking/rwsem: Add reader-owned state to the owner field
  locking/rwsem: Protect all writes to owner by WRITE_ONCE()
  locking/rwsem: Don't wake up one's own task
  locking/rwsem: Improve reader wakeup code
  locking/rwsem: Streamline the rwsem_optimistic_spin() code

 kernel/locking/rwsem-xadd.c |   75 ++++++++++++++++++++++++------------------
 kernel/locking/rwsem.c      |    8 +++-
 kernel/locking/rwsem.h      |   52 ++++++++++++++++++++++++++++-
 3 files changed, 99 insertions(+), 36 deletions(-)