[v5,0/7] riscv: Add qspinlock/qrwlock

From: Guo Ren <guoren@linux.alibaba.com>

Current riscv is still using baby spinlock implementation. It'll cause
fairness and cache line bouncing problems. Many people are involved
and pay the efforts to improve it:

 - The first version of patch was made in 2019.1:
   https://lore.kernel.org/linux-riscv/20190211043829.30096-1-michaeljclark@mac.com/#r

 - The second version was made in 2020.11:
   https://lore.kernel.org/linux-riscv/1606225437-22948-2-git-send-email-guoren@kernel.org/

 - A good discussion at Platform HSC.2021-03-08:
   https://drive.google.com/drive/folders/1ooqdnIsYx7XKor5O1XTtM6D1CHp4hc0p

Hope your comments and Tested-by or Co-developed-by or Reviewed-by ...

Let's kick the qspinlock into riscv right now (Also for the
architecture which hasn't xchg16 atomic instruction.)

Change V5:
 - Fixup #endif comment typo by Waiman
 - Remove cmpxchg coding convention patches which will get into a
   separate patchset later by Arnd's advice
 - Try to involve more architectures in the discussion

Change V4:
 - Remove custom sub-word xchg implementation
 - Add ARCH_USE_QUEUED_SPINLOCKS_XCHG32 in locking/qspinlock

Change V3:
 - Coding convention by Peter Zijlstra's advices

Change V2:
 - Coding convention in cmpxchg.h
 - Re-implement short xchg
 - Remove char & cmpxchg implementations

Guo Ren (6):
  locking/qspinlock: Add ARCH_USE_QUEUED_SPINLOCKS_XCHG32
  csky: Convert custom spinlock/rwlock to generic qspinlock/qrwlock
  powerpc/qspinlock: Add ARCH_USE_QUEUED_SPINLOCKS_XCHG32
  openrisc: qspinlock: Add ARCH_USE_QUEUED_SPINLOCKS_XCHG32
  sparc: qspinlock: Add ARCH_USE_QUEUED_SPINLOCKS_XCHG32
  xtensa: qspinlock: Add ARCH_USE_QUEUED_SPINLOCKS_XCHG32

Michael Clark (1):
  riscv: Convert custom spinlock/rwlock to generic qspinlock/qrwlock

 arch/csky/Kconfig                       |   2 +
 arch/csky/include/asm/Kbuild            |   2 +
 arch/csky/include/asm/spinlock.h        |  82 +--------------
 arch/csky/include/asm/spinlock_types.h  |  16 +--
 arch/openrisc/Kconfig                   |   1 +
 arch/powerpc/Kconfig                    |   1 +
 arch/riscv/Kconfig                      |   3 +
 arch/riscv/include/asm/Kbuild           |   3 +
 arch/riscv/include/asm/spinlock.h       | 126 +-----------------------
 arch/riscv/include/asm/spinlock_types.h |  15 +--
 arch/sparc/Kconfig                      |   1 +
 arch/xtensa/Kconfig                     |   1 +
 kernel/Kconfig.locks                    |   3 +
 kernel/locking/qspinlock.c              |  46 +++++----
 14 files changed, 49 insertions(+), 253 deletions(-)