backports: backport ww_mutex support

backports: backport ww_mutex support

This backports the kernel's wound/wait style locks 040a0a371,
using the linux-stable v3.11-rc2 as a base for development.
Given the complexity to support debugging mutexes this backport
implementation is simplified by only making this feature availabe
if you to have DEBUG_MUTEXES and DEBUG_LOCK_ALLOC disabled.

Given that ww mutex is required for DRM this also means we must
update the kconfig for DRM and require you to also not be able to build
DRM if you have either of these options enabled. Support for
DEBUG_MUTEXES and DEBUG_LOCK_ALLOC can be added later by anyone
daring. This uses the new dependencies file kconfig language
extension to specify the backport feature build restrictions
for DRM.

Part of the ww mutex addition to the kernel required modifying
the fast path mutex locking scheme by requiring you to deal
with the slow path alternatives on your own (refer to a41b56ef).
The reason for this change was that the mutex fastpath implementation
assumed your slowpath alternative can only be passed one argument
and the addition of ww mutexes requires dealing with the slow
path with a context passed.

It'd be painful to backport all asm for an optimized fastpath
implementation so we penalize the backport ww mutex fast path
by using the generic atomic_dec_return().

To backport a clean our own mutex_lock_common() with the least
amount of changes against upstream commits 2bd2c92c and 41fcb9f2
also needed to be backported. Commit 2bd2c92c dealt with adding
support for queue mutex spinners with an MCS lock, since this
cannot be backported for older kernels we provide empty inlines.
Commit 41fcb9f2 just removed SCHED_FEAT_OWNER_SPIN as it was an
early hack, the only thing required to backport this commit was
to provide an alternative declaration for mutex_spin_on_owner()
as it was declared non-inline for older kernels.

Finally c5491ea7 required backporting schedule_preempt_disabled()
as well but that just consisted of carrying over the original
implementation. Since its not exported we need to reimplement
it to make it available to our internal core ww mutex port.

mcgrof@frijol ~/linux-stable (git::master)$ git describe --contains 040a0a371
v3.11-rc1~147^2~5

mcgrof@frijol ~/linux-stable (git::master)$ git describe --contains a41b56ef
v3.11-rc1~147^2~6

mcgrof@frijol ~/linux-stable (git::master)$ git describe --contains 2bd2c92c
v3.10-rc1~200^2~3

mcgrof@frijol ~/linux-stable (git::master)$ git describe --contains 41fcb9f2
v3.10-rc1~200^2~5

mcgrof@frijol ~/linux-stable (git::master)$ git describe --contains c5491ea7
v3.4-rc1~3^2~27

commit 040a0a37100563754bb1fee6ff6427420bcfa609
Author: Maarten Lankhorst <maarten.lankhorst@canonical.com>
Date:   Mon Jun 24 10:30:04 2013 +0200

    mutex: Add support for wound/wait style locks

    Wound/wait mutexes are used when other multiple lock
    acquisitions of a similar type can be done in an arbitrary
    order. The deadlock handling used here is called wait/wound in
    the RDBMS literature: The older tasks waits until it can acquire
    the contended lock. The younger tasks needs to back off and drop
    all the locks it is currently holding, i.e. the younger task is
    wounded.

    For full documentation please read Documentation/ww-mutex-design.txt.

    References: https://lwn.net/Articles/548909/
    Signed-off-by: Maarten Lankhorst <maarten.lankhorst@canonical.com>
    Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
    Acked-by: Rob Clark <robdclark@gmail.com>
    Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
    Cc: dri-devel@lists.freedesktop.org
    Cc: linaro-mm-sig@lists.linaro.org
    Cc: rostedt@goodmis.org
    Cc: daniel@ffwll.ch
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Andrew Morton <akpm@linux-foundation.org>
    Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/51C8038C.9000106@canonical.com
    Signed-off-by: Ingo Molnar <mingo@kernel.org>
commit a41b56efa70e060f650aeb54740aaf52044a1ead
Author: Maarten Lankhorst <maarten.lankhorst@canonical.com>
Date:   Thu Jun 20 13:31:05 2013 +0200

    arch: Make __mutex_fastpath_lock_retval return whether fastpath succeeded or not

    This will allow me to call functions that have multiple
    arguments if fastpath fails. This is required to support ticket
    mutexes, because they need to be able to pass an extra argument
    to the fail function.

    Originally I duplicated the functions, by adding
    __mutex_fastpath_lock_retval_arg. This ended up being just a
    duplication of the existing function, so a way to test if
    fastpath was called ended up being better.

    This also cleaned up the reservation mutex patch some by being
    able to call an atomic_set instead of atomic_xchg, and making it
    easier to detect if the wrong unlock function was previously
    used.

    Signed-off-by: Maarten Lankhorst <maarten.lankhorst@canonical.com>
    Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
    Cc: dri-devel@lists.freedesktop.org
    Cc: linaro-mm-sig@lists.linaro.org
    Cc: robclark@gmail.com
    Cc: rostedt@goodmis.org
    Cc: daniel@ffwll.ch
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Andrew Morton <akpm@linux-foundation.org>
    Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20130620113105.4001.83929.stgit@patser
    Signed-off-by: Ingo Molnar <mingo@kernel.org>
commit 2bd2c92cf07cc4a373bf316c75b78ac465fefd35
Author: Waiman Long <Waiman.Long@hp.com>
Date:   Wed Apr 17 15:23:13 2013 -0400

    mutex: Queue mutex spinners with MCS lock to reduce cacheline contention

    <-- snip -->

commit 41fcb9f230bf773656d1768b73000ef720bf00c3
Author: Waiman Long <Waiman.Long@hp.com>
Date:   Wed Apr 17 15:23:11 2013 -0400

    mutex: Move mutex spinning code from sched/core.c back to mutex.c

    <-- snip -->

commit c5491ea779793f977d282754db478157cc409d82
Author: Thomas Gleixner <tglx@linutronix.de>
Date:   Mon Mar 21 12:09:35 2011 +0100

    sched/rt: Add schedule_preempt_disabled()

    <-- snip -->

Cc: maarten.lankhorst@canonical.com
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Rob Clark <robdclark@gmail.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: dri-devel@lists.freedesktop.org
Cc: linaro-mm-sig@lists.linaro.org
Cc: rostedt@goodmis.org
Cc: daniel@ffwll.ch
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Luis R. Rodriguez <mcgrof@do-not-panic.com>