introduce for_each_thread() to replace the buggy while_each_thread()

while_each_thread() and next_thread() should die, almost every lockless
usage is wrong.

1. Unless g == current, the lockless while_each_thread() is not safe.

   while_each_thread(g, t) can loop forever if g exits, next_thread()
   can't reach the unhashed thread in this case. Note that this can
   happen even if g is the group leader, it can exec.

2. Even if while_each_thread() itself was correct, people often use
   it wrongly.

   It was never safe to just take rcu_read_lock() and loop unless
   you verify that pid_alive(g) == T, even the first next_thread()
   can point to the already freed/reused memory.

This patch adds signal_struct->thread_head and task->thread_node to
create the normal rcu-safe list with the stable head.  The new
for_each_thread(g, t) helper is always safe under rcu_read_lock() as
long as this task_struct can't go away.

Note: of course it is ugly to have both task_struct->thread_node and the
old task_struct->thread_group, we will kill it later, after we change
the users of while_each_thread() to use for_each_thread().

Perhaps we can kill it even before we convert all users, we can
reimplement next_thread(t) using the new thread_head/thread_node.  But
we can't do this right now because this will lead to subtle behavioural
changes.  For example, do/while_each_thread() always sees at least one
task, while for_each_thread() can do nothing if the whole thread group
has died.  Or thread_group_empty(), currently its semantics is not clear
unless thread_group_leader(p) and we need to audit the callers before we
can change it.

So this patch adds the new interface which has to coexist with the old
one for some time, hopefully the next changes will be more or less
straightforward and the old one will go away soon.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Sergey Dyasly <dserrg@gmail.com>
Tested-by: Sergey Dyasly <dserrg@gmail.com>
Reviewed-by: Sameer Nanda <snanda@chromium.org>
Acked-by: David Rientjes <rientjes@google.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Mandeep Singh Baines <msb@chromium.org>
Cc: "Ma, Xindong" <xindong.ma@intel.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: "Tu, Xiaobing" <xiaobing.tu@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Paul Reioux <reioux@gmail.com>

backported to Linux 3.4

Conflicts:
	kernel/fork.c
introduce for_each_thread() to replace the buggy while_each_thread() (fix)

fix a merge derp. pointed out by neobuddy89

Signed-off-by: Paul Reioux <reioux@gmail.com>
lowmemorykiller.c: convert to use for_each_thread

Signed-off-by: Paul Reioux <reioux@gmail.com>
kernel/power/powersuspend: new PM kernel driver for Android w/o early_suspend

Android early_suspend/late_resume PM kernel driver framework has been
deprecated by Google. This new powersuspend PM kernel driver is a replacement
for it and existing early_suspend drivers can be easily adapted to use this
new replacement driver

Signen-off-by: Paul Reioux <reioux@gmail.com>

Conflicts:

	kernel/power/Kconfig
powersuspend: fix logci derps :p

Signed-off-by: Paul Reioux <reioux@gmail.com>
kernel/power/powersuspend: remove userspace dependency from powersuspend

make powersuspend not depend on a userspace initiator anymore, but use a hook
in autosleep instead.

Signed-off-by: Paul Reioux <reioux@gmail.com>
kernel/power/powersuspend: add back userpace control w/ default kernel control

make kernel / userspace mode switchable

Signed-off-by: Paul Reioux <reioux@gmail.com>
kernel/power/powersuspend: default to userspace for now

Signed-off-by: Paul Reioux <reioux@gmail.com>
kernel/power/powersuspend: new PM kernel driver for Android w/o early_suspend v1.3 (Yank555.lu)

- add an alternative hook for screen on / off detection in the display pannel driver
  (sleeps  ~0.1s sooner, wakes up ~1s later then autosleep)

Conflicts:
	drivers/video/msm/mdss/mdss_samsung_dsi_panel.c
kernel/power/powersuspend: new PM kernel driver for Android w/o early_suspend v1.4 (Yank555.lu)

- add hybrid-kernel mode (autosleep and panel, first wins)
- default to hybrid-kernel mode
- harmonize debug message with my other stuff
- include all 3 modes as default, so it's only commenting out to change

- add an alternative hook for screen on / off detection in the display panel driver
(sleeps ~0.1s sooner, wakes up ~1s later then autosleep)

kernel/power/powersuspend: new PM kernel driver for Android w/o early_suspend v1.2 (Yank555.lu)

- make kernel / userspace mode switchable

kernel/power/powersuspend: new PM kernel driver for Android w/o early_suspend v1.1 (Yank555.lu)

- make powersuspend not depend on a userspace initiator anymore, but use a hook in autosleep instead.

kernel/power/powersuspend: new PM kernel driver for Android w/o early_suspend (faux123)

Android early_suspend/late_resume PM kernel driver framework has been
deprecated by Google. This new powersuspend PM kernel driver is a replacement
for it and existing early_suspend drivers can be easily adapted to use this
new replacement driver

Signen-off-by: Paul Reioux <reioux@gmail.com>;
kernel/power/powersuspend: new PM kernel driver for Android w/o early_suspend v1.5 (Yank555.lu)

- fix hybrid-kernel mode cannot be set through sysfs

kernel/power/powersuspend: new PM kernel driver for Android w/o early_suspend v1.4 (Yank555.lu)

- add hybrid-kernel mode (autosleep and panel, first wins)
- default to hybrid-kernel mode
- harmonize debug message with my other stuff
- include all 3 modes as default, so it's only commenting out to change

kernel/power/powersuspend: new PM kernel driver for Android w/o early_suspend v1.3 (Yank555.lu)

- fix stupid typo
- add an alternative hook for screen on / off detection in the display panel driver
(sleeps ~0.1s sooner, wakes up ~1s later then autosleep)

kernel/power/powersuspend: new PM kernel driver for Android w/o early_suspend v1.2 (Yank555.lu)

- make kernel / userspace mode switchable

kernel/power/powersuspend: new PM kernel driver for Android w/o early_suspend v1.1 (Yank555.lu)

- make powersuspend not depend on a userspace initiator anymore, but use a hook in autosleep instead.

kernel/power/powersuspend: new PM kernel driver for Android w/o early_suspend (faux123)

Android early_suspend/late_resume PM kernel driver framework has been
deprecated by Google. This new powersuspend PM kernel driver is a replacement
for it and existing early_suspend drivers can be easily adapted to use this
new replacement driver

Signen-off-by: Paul Reioux <reioux@gmail.com>;
sched: remove redundant update_runtime notifier

migration_call() will do all the things that update_runtime() does.
So it seems update_runtime() is a redundant notifier, remove it.

Furthermore, there is potential risk that the current code will catch
BUG_ON at line 687 of rt.c when do cpu hotplug while there are realtime
threads running because of enable runtime twice.

Change-Id: I0fdad8d5a1cebb845d3f308b205dbd6517c3e4de
Cc: bitbucket@online.de
Signed-off-by: Neil Zhang <zhangwm@marvell.com>
Reviewed-on: http://git-master/r/215596
(cherry picked from commit 8f646de983f24361814d9a6ca679845fb2265807)
Reviewed-on: http://git-master/r/223067
Reviewed-by: Peter Boonstoppel <pboonstoppel@nvidia.com>
Tested-by: Peter Boonstoppel <pboonstoppel@nvidia.com>
Reviewed-by: Paul Walmsley <pwalmsley@nvidia.com>
Reviewed-by: Automatic_Commit_Validation_User
GVS: Gerrit_Virtual_Submit
Reviewed-by: Diwakar Tundlam <dtundlam@nvidia.com>
nohz: stat: Fix CPU idle time accounting

Since cpustat[CPUTIME_IDLE] is never connected to ts->idle_sleeptime,
never read from cpustat[CPUTIME_IDLE] when reporting stats in
/proc/stat.

Note this was rejected by Michal Hocko when it was initially proposed
by Martin Schwidefsky in LKML, so if you want to upstream it, better
find an alternative (either completely disable cpustat[CPUTIME_IDLE]
for CONFIG_NO_HZ or somehow connect them to keep them in sync.)

bug 1190321

Change-Id: Idc92488910b826aff850a010016d8326c7ab9e6c
Signed-off-by: Bo Yan <byan@nvidia.com>
Reviewed-on: http://git-master/r/214638
Reviewed-by: Automatic_Commit_Validation_User
GVS: Gerrit_Virtual_Submit
Reviewed-by: Liang Cheng (SW) <licheng@nvidia.com>
Tested-by: Liang Cheng (SW) <licheng@nvidia.com>

Conflicts:
	fs/proc/stat.c
timekeeping: Fix time moving backwards

Changed the calculation logic that sometimes calculates
the time wrong.

Sometimes there is an overflow when the tv_nsec field in
the timespec structure is being added since it is 32-bit.

To resolve this issue nsec variable is being added first
so that the addition is performed in 64 bit signed format.

Bug 1217429

Change-Id: I9c65da88f02596ba73c47be6342ed909e650db22
Signed-off-by: Ajay Nandakumar <anandakumarm@nvidia.com>
Reviewed-on: http://git-master/r/195092
Reviewed-by: Automatic_Commit_Validation_User
Reviewed-by: Prashant Gaikwad <pgaikwad@nvidia.com>
Reviewed-by: Shridhar Rasal <srasal@nvidia.com>
Reviewed-by: Bo Yan <byan@nvidia.com>
GVS: Gerrit_Virtual_Submit
Reviewed-by: Bharat Nihalani <bnihalani@nvidia.com>
Tested-by: Shridhar Rasal <srasal@nvidia.com>

Conflicts:
	kernel/time/timekeeping.c
screen hooks for powersuspend
Linux 3.4.94