kernel: gtod: vsyscall

Introduce kernel user helper vsyscall to allow a higher performance
gettimeofday implementation in user-space.

Change-Id: I9b9971d217382129170ecd6a35461539dac9eebb
Signed-off-by: Brent DeGraaf <bdegraaf@codeaurora.org>
Signed-off-by: Joonwoo Park <joonwoop@codeaurora.org>
kernel: Add hooks for user-accessible timers in the kernel.

Hooks for user-accessible timers allow implementation of a
more efficient gettimeofday in user-space.

Change-Id: If2f63d010c1cf142eb84f3745617e756913e46f7
Signed-off-by: Brent DeGraaf <bdegraaf@codeaurora.org>
Signed-off-by: Joonwoo Park <joonwoop@codeaurora.org>
kernel: ARM-specific implementation of user-accessible timers

Expose a read-only timer page to user-space to allow for a more
efficient implementation of gettimeofday in user-space.

Change-Id: Ibd6ce41f5f4ff9435e4bf4582ef5de721283d56b
Signed-off-by: Brent DeGraaf <bdegraaf@codeaurora.org>
Signed-off-by: Joonwoo Park <joonwoop@codeaurora.org>
Revert "[ARM] msm: iommu_domains: replace vmalloc with kmalloc"

When overmapping is used, system can request higher order page allocaitons.
this can lead to page allocation failure if kmalloc is used

CRs-Fixed: 571753

This reverts commit 191a48ee7bda08bf88a61b48fd0433627c5918dc.

Change-Id: I4d44bf88d84d96d315f89a1304a2d25b75be79d8
Signed-off-by: Srinivasarao P <spathi@codeaurora.org>
kref: Implement kref_get_unless_zero v3

This function is intended to simplify locking around refcounting for
objects that can be looked up from a lookup structure, and which are
removed from that lookup structure in the object destructor.
Operations on such objects require at least a read lock around
lookup + kref_get, and a write lock around kref_put + remove from lookup
structure. Furthermore, RCU implementations become extremely tricky.
With a lookup followed by a kref_get_unless_zero *with return value check*
locking in the kref_put path can be deferred to the actual removal from
the lookup structure and RCU lookups become trivial.

v2: Formatting fixes.
v3: Invert the return value.

Change-Id: I391623ee7458428eab6d7f361630f8646d6790b0
Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Git-commit: 4b20db3de8dab005b07c74161cb041db8c5ff3a7
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
[shrenujb@codeaurora.org: resolve trivial merge conflicts]
Signed-off-by: Shrenuj Bansal <shrenujb@codeaurora.org>