[PATCH 0/6] Switch arm64 over to qrwlock

[Will Deacon]

Hi all,

This patch series reworks bits of the qrwlock code that it can be used
to replace the asm rwlocks currently implemented for arm64. The structure
of the series is:

  Patches 1-3	: Work WFE into qrwlock using atomic_cond_read_acquire so
		  we can avoid busy-waiting.

  Patch 4	: Enable qrwlocks for arm64

  Patch 5-6	: Ensure writer slowpath fairness. This has a potential
		  performance impact on the writer unlock path, so I've
		  kept them at the end.

The patches apply on top of my other locking cleanups:

  http://lkml.kernel.org/r/1507055129-12300-1-git-send-email-will.deacon@xxxxxxx

although the conflict with mainline is trivial to resolve without those.
The full stack is also pushed here:

  git://git.kernel.org/pub/scm/linux/kernel/git/will/linux.git qrwlock

All comments (particularly related to testing and performance) welcome!

Cheers,

Will

--->8

Will Deacon (6):
  kernel/locking: Use struct qrwlock instead of struct __qrwlock
  locking/atomic: Add atomic_cond_read_acquire
  kernel/locking: Use atomic_cond_read_acquire when spinning in qrwlock
  arm64: locking: Move rwlock implementation over to qrwlocks
  kernel/locking: Prevent slowpath writers getting held up by fastpath
  kernel/locking: Remove unused union members from struct qrwlock

 arch/arm64/Kconfig                      |  17 ++++
 arch/arm64/include/asm/Kbuild           |   1 +
 arch/arm64/include/asm/spinlock.h       | 164 +-------------------------------
 arch/arm64/include/asm/spinlock_types.h |   6 +-
 include/asm-generic/atomic-long.h       |   3 +
 include/asm-generic/qrwlock.h           |  14 +--
 include/asm-generic/qrwlock_types.h     |   2 +-
 include/linux/atomic.h                  |   4 +
 kernel/locking/qrwlock.c                |  83 +++-------------
 9 files changed, 43 insertions(+), 251 deletions(-)

-- 
2.1.4