android/lowmemorykiller: Check all tasks for death pending

The lowmemorykiller uses the TIF_MEMDIE flag to help ensure it doesn't
kill another task until the memory from the previously killed task has
been returned to the system.

However the lowmemorykiller does not currently look at tasks who do not
have a tasks->mm, but just because a process doesn't have a tasks->mm
does not mean that the task's memory has been fully returned to the
system yet.

In order to prevent the lowmemorykiller from unnecessarily killing
multiple applications in a row the lowmemorykiller has been changed to
ensure that previous killed tasks are no longer in the process list
before attempting to kill another task.

Change-Id: I7d8a8fd39ca5625e6448ed2efebfb621f6e93845
Signed-off-by: Liam Mark <lmark@codeaurora.org>
Signed-off-by: Mitchel Humpherys <mitchelh@codeaurora.org>
android/lowmemorykiller: Selectively count free CMA pages

In certain memory configurations there can be a large number of
CMA pages which are not suitable to satisfy certain memory
requests.

This large number of unsuitable pages can cause the
lowmemorykiller to not kill any tasks because the
lowmemorykiller counts all free pages.
In order to ensure the lowmemorykiller properly evaluates the
free memory only count the free CMA pages if they are suitable
for satisfying the memory request.

Change-Id: I7f06d53e2d8cfe7439e5561fe6e5209ce73b1c90
CRs-fixed: 437016
Signed-off-by: Liam Mark <lmark@codeaurora.org>
android/lowmemorykiller: Ignore tasks with freed mm

A killed task can stay in the task list long after its
memory has been returned to the system, therefore
ignore any tasks whose mm struct has been freed.

Change-Id: I76394b203b4ab2312437c839976f0ecb7b6dde4e
CRs-fixed: 450383
Signed-off-by: Liam Mark <lmark@codeaurora.org>

Conflicts:

	drivers/staging/android/lowmemorykiller.c
Staging: android: binder: Fix memory leak on thread/process exit

If a thread or process exited while a reply, one-way transaction or
death notification was pending, the struct holding the pending work
was leaked.

CRs-Fixed: 477612
Change-Id: I8b7a4f77689731a47c9e2f2fffefcac95c412e00
Signed-off-by: Arve Hjønnevåg <arve@android.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Git-commit: 675d66b0ed5fd170d6a44cf8dbb3fa56a5347bdb
Git-repo: https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/
Signed-off-by: Chintan Pandya <cpandya@codeaurora.org>