lowmemorykiller: don't unregister notifier from atomic context

The lowmemorykiller registers an atomic notifier for notfication of when
the task is freed.  From this atomic notifier callback, it removes the
atomic notifier via task_free_unregister().  This is incorrect because
atomic_notifier_chain_unregister() calls syncronize_rcu(), which can
sleep, which shouldn't be done from an atomic notifier.

Fix this by registering the notifier during init, and only unregister it
if the lowmemorykiller is unloaded.

Change-Id: I1577b04e617bc2b2e39dcb490fcfc9ce660eb7ec
Signed-off-by: Rabin Vincent <rabin.vincent@stericsson.com>
Signed-off-by: Christian Bejram <christian.bejram@stericsson.com>
staging: android: lowmemorykiller: Don't wait more than one second for a process to die

If a process forked and the child process was killed by the
lowmemorykiller, the lowmemory killer would be disabled until
the parent process reaped the child or it died itself.

Change-Id: I709b1a4e1b1a1970e51d26a39fcbee57977bbc7f
Signed-off-by: Arve Hjønnevåg <arve@android.com>
staging: android: lowmemorykiller: Ignore shmem pages in page-cache

Change-Id: Ia54fc50b7dcabfeb71eb487c652803f83e2f3d8e
Signed-off-by: Arve Hjønnevåg <arve@android.com>