ARM: add support for kernel mode NEON

In order to safely support the use of NEON instructions in
kernel mode, some precautions need to be taken:
- the userland context that may be present in the registers (even
  if the NEON/VFP is currently disabled) must be stored under the
  correct task (which may not be 'current' in the UP case),
- to avoid having to keep track of additional vfpstates for the
  kernel side, disallow the use of NEON in interrupt context
  and run with preemption disabled,
- after use, re-enable preemption and re-enable the lazy restore
  machinery by disabling the NEON/VFP unit.

This patch adds the functions kernel_neon_begin() and
kernel_neon_end() which take care of the above. It also adds
the Kconfig symbol KERNEL_MODE_NEON to enable it.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Acked-by: Nicolas Pitre <nico@linaro.org>

Signed-off-by: Paul Reioux <reioux@gmail.com>
scheduler: compute time-average nr_running per run-queue

Compute the time-average number of running tasks per run-queue for a
trailing window of a fixed time period. The detla add/sub to the
average value is weighted by the amount of time per nr_running value
relative to the total measurement period.

Change-Id: I076e24ff4ed65bed3b8dd8d2b279a503318071ff
Signed-off-by: Diwakar Tundlam <dtundlam@nvidia.com>
(cherry picked from commit 3a12d7499cee352e8a46eaf700259ba3c733f0e3)
Reviewed-on: http://git-master/r/111635
Reviewed-by: Automatic_Commit_Validation_User
Reviewed-by: Sai Gurrappadi <sgurrappadi@nvidia.com>
Tested-by: Sai Gurrappadi <sgurrappadi@nvidia.com>
Reviewed-by: Peter Boonstoppel <pboonstoppel@nvidia.com>
Reviewed-by: Yu-Huan Hsu <yhsu@nvidia.com>

forward ported to Linux 3.4 for use on Mako

Signed-off-by: Paul Reioux <reioux@gmail.com>
scheduler: Re-compute time-average nr_running on read

Re-compute time-average nr_running when it is read. This would
prevent reading stalled average value if there were no run-queue
changes for a long time. New average value is returned to the reader,
but not stored to avoid concurrent writes. Light-weight sequential
counter synchronization is used to assure data consistency for
re-computing average.

Change-Id: I8e4ea1b28ea00b3ddaf6ef7cdcd27866f87d360b
Signed-off-by: Alex Frid <afrid@nvidia.com>
(cherry picked from commit 527a759d9b40bf57958eb002edd2bb82014dab99)
Reviewed-on: http://git-master/r/111637
Reviewed-by: Sai Gurrappadi <sgurrappadi@nvidia.com>
Tested-by: Sai Gurrappadi <sgurrappadi@nvidia.com>
Reviewed-by: Automatic_Commit_Validation_User
Reviewed-by: Peter Boonstoppel <pboonstoppel@nvidia.com>
Reviewed-by: Yu-Huan Hsu <yhsu@nvidia.com>

forward ported to Linux 3.4 for use on Mako

Signed-off-by: faux123 <reioux@gmail.com>