[patch 0/9] mutex subsystem, -V4

[Ingo Molnar <mingo@elte.hu>]

this is the -V4 of the mutex subsystem patch-queue. It consists of the 
following patches:

  add-atomic-xchg.patch
  add-atomic-call-func-i386.patch
  add-atomic-call-func-x86_64.patch
  add-atomic-call-wrappers-rest.patch
  mutex-core.patch
  mutex-switch-arm-to-xchg.patch
  mutex-debug.patch
  mutex-debug-more.patch
  xfs-mutex-namespace-collision-fix.patch

the patches are against Linus' latest GIT tree, and they should work 
fine on every Linux architecture.

Changes since -V3:

- imlemented an atomic_xchg() based mutex implementation. It integrated
  pretty nicely into the generic code, and most of the code is still
  shared.

- added __ARCH_WANT_XCHG_BASED_ATOMICS: if an architecture defines 
  this then the generic mutex code will switch to the atomic_xchg() 
  implementation.

  This should be conceptually equivalent to the variant Nicolas Pitre 
  posted - Nicolas, could you check out this one? It's much easier to 
  provide this in the generic implementation, and the code ends up 
  looking cleaner.

- eliminated ARCH_IMPLEMENTS_MUTEX_FASTPATH: there's no need for 
  architectures to override the generic code anymore, with the 
  introduction of __ARCH_WANT_XCHG_BASED_ATOMICS.

- ARM: enable __ARCH_WANT_XCHG_BASED_ATOMICS.

- ARM buildfix: move the new atomic primitives to the correct place.
  (Nicolas Pitre)

- optimization: unlock the mutex outside of the spinlock (suggested by 
  Nicolas Pitre)

- removed leftover arch_semaphore reference from the XFS patch. (noticed
  by Arjan van de Ven)

- better document the fact that mutex_trylock() follows spin_trylock() 
  semantics, not sem_trylock() semantics.

- cleanup: got rid of the MUTEX_LOCKLESS_FASTPATH define. (in -V3 this
  became equivalent to DEBUG_MUTEXES, via the elimination of the
  __HAVE_ARCH_CMPXCHG dependency on the fastpath.)

- further simplified and unified mutex_trylock().

- DocBook entries, and more documentation of internals.

- dropped the spinlock-debug fix, Linus merged it.

	Ingo