[PATCH v5 0/4] MCS Lock: MCS lock code cleanup and optimizations

[PATCH v5 0/4] MCS Lock: MCS lock code cleanup and optimizations

[Tim Chen]

In this patch series, we separated out the MCS lock code which was
previously embedded in the mutex.c.  This allows for easier reuse of
MCS lock in other places like rwsem and qrwlock.  We also did some micro
optimizations and barrier cleanup.  

The original code has potential leaks between critical sections, which
was not a problem when MCS was embedded within the mutex but needs
to be corrected when allowing the MCS lock to be used by itself for
other locking purposes. 

Proper barriers are now embedded with the usage of smp_load_acquire() in
mcs_spin_lock() and smp_store_release() in mcs_spin_unlock.  See
http://marc.info/?l=linux-arch&m=138386254111507 for info on the
new smp_load_acquire() and smp_store_release() functions. 

One thing to note is the use of smp_load_acquire in a spin loop
to check for lock acquisition.  If there are concerns about 
a potential barrier being in the spin loop for some architectures, please let
us know.  

This patches were previously part of the rwsem optimization patch series
but now we spearate them out.

Tim Chen

Jason Law (1):
  MCS Lock: optimizations and extra comments

Tim Chen (1):
  MCS Lock: Restructure the MCS lock defines and locking code into its
    own file

Waiman Long (2):
  MCS Lock: Move mcs_lock/unlock function into its own file
  MCS Lock: Barrier corrections

 include/linux/mcs_spinlock.h  |   25 +++++++++
 include/linux/mutex.h         |    5 +-
 kernel/locking/Makefile       |    6 +-
 kernel/locking/mcs_spinlock.c |  108 +++++++++++++++++++++++++++++++++++++++++
 kernel/locking/mutex.c        |   60 +++--------------------
 5 files changed, 146 insertions(+), 58 deletions(-)
 create mode 100644 include/linux/mcs_spinlock.h
 create mode 100644 kernel/locking/mcs_spinlock.c

-- 
1.7.4.4


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