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Current implementation of Bakery Lock does tight-loop waiting upon lock
contention.

This commit reworks the implementation to use WFE instruction for
waiting, and SEV to signal lock availability. It also adds the rationale
for choosing Bakery Locks instead of exclusion primitives, and more
comments for the lock algorithm.

Fixes ARM-software/tf-issue#67

Change-Id: Ie351d3dbb27ec8e64dbc9507c84af07bd385a7df
Co-authored-by: Vikram Kanigiri <vikram.kanigiri@arm.com>

bakery_lock_release() expects an mpidr as the first argument however
bakery_lock_release() is calling it with the 'entry' argument it has
calculated. Rather than fixing this to pass the mpidr value it would be
much more efficient to just replace the call with

   assert(bakery->owner == entry)

As this leaves no remaining users of bakery_lock_held(), we might as
well delete it.

Fixes ARM-software/tf-issues#27
Signed-off-by: Jon Medhurst <tixy@linaro.org>

Ctags seem to have a problem with generating tags for assembler symbols
when a comment immediately follows an assembly label.

This patch inserts a single space character between the label
definition and the following comments to help ctags.

The patch is generated by the command:

  git ls-files -- \*.S | xargs sed -i 's/^\([^:]\+\):;/\1: ;/1'

Change-Id: If7a3c9d0f51207ea033cc8b8e1b34acaa0926475

Change-Id: Ic7fb61aabae1d515b9e6baf3dd003807ff42da60

- Add instructions for contributing to ARM Trusted Firmware.

- Update copyright text in all files to acknowledge contributors.

Change-Id: I9311aac81b00c6c167d2f8c889aea403b84450e5