[PATCH v3 0/3] locking/spinlock_debug: Change it to a mostly fair lock

[Waiman Long <longman@redhat.com>]

 v2->v3:
  - Keep the original v1 patches but move patch 3 of v2 in front so
    as to disable GENERIC_LOCKBREAK when DEBUG_LOCK_ALLOC is on.

 v1->v2:
  - Pack lockup and break_lock into a single 4-byte slot so as not
    to in increase spinlock size when GENERIC_LOCKBREAK is
    on. Hopefully that will be enough to fix a frame size too large
    warning in 0-day build.
  - Add a new patch to disable GENERIC_LOCKBREAK when DEBUG_LOCK_ALLOC
    is on.

The current debug spinlock implementation is a TATAS unfair lock. This
can occasionally lead to system lockup with a debug kernel because
of the unfairness of the lock rather than inherent locking problem.

This patch set changes the debug spinlock implementation to a
mostly fair spinlock based on the MCS lock similar to what is done
in qspinlock. It also includes a patch that disable GENERIC_LOCKBREAK
when DEBUG_LOCK_ALLOC is on.

Waiman Long (3):
  locking/spinlock: Disable GENERIC_LOCKBREAK when DEBUG_LOCK_ALLOC is
    on
  locking/spinlock_debug: Reduce lockup suspected message clutter
  locking/spinlock_debug: Reduce lock cacheline contention

 arch/m32r/Kconfig               |  2 +-
 arch/parisc/Kconfig             |  2 +-
 arch/powerpc/Kconfig            |  2 +-
 arch/s390/Kconfig               |  2 +-
 arch/sh/Kconfig                 |  2 +-
 arch/sparc/Kconfig              |  2 +-
 include/linux/spinlock_types.h  |  8 +++--
 kernel/locking/spinlock_debug.c | 73 ++++++++++++++++++++++++++++++-----------
 8 files changed, 64 insertions(+), 29 deletions(-)

-- 
1.8.3.1