- Use for() instead of while() loop in some functions
   to make the code simpler.

 - Use this_cpu_ptr() instead of per_cpu_ptr() to make the code
   cleaner and a bit faster.
Suggested-by: NPeter Zijlstra <peterz@infradead.org>
Signed-off-by: NZhao Lei <zhaolei@cn.fujitsu.com>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Tejun Heo <htejun@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/d8a7ef9592f55224630cb26dea239f05b6398a4e.1458187654.git.zhaolei@cn.fujitsu.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

Now we don't need cpuacct_init(), and instead we just initialize
root_cpuacct when it's defined.
Signed-off-by: NLi Zefan <lizefan@huawei.com>
Cc: Tejun Heo <tj@kernel.org>
Acked-by: NPeter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/51553834.9090701@huawei.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

Now most of the code in cpuacct.h can be moved to cpuacct.c
Signed-off-by: NLi Zefan <lizefan@huawei.com>
Acked-by: NPeter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/515536D5.2080401@huawei.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

This is a micro optimazation for a hot path.

- We don't need to check if @CA returned from task_ca() is NULL.
- We don't need to check if @CA returned from parent_ca() is NULL.
Signed-off-by: NLi Zefan <lizefan@huawei.com>
Acked-by: NPeter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/515536B7.6060602@huawei.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

This is a micro optimization for the hot path.

- We don't need to check if @CA is NULL in parent_ca().
- We don't need to check if @CA is NULL in the beginning of the for loop.
Signed-off-by: NLi Zefan <lizefan@huawei.com>
Acked-by: NPeter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/515536A9.5000700@huawei.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

So we can remove open-coded cpuacct code in cputime.c.
Signed-off-by: NLi Zefan <lizefan@huawei.com>
Acked-by: NPeter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/51553692.9060008@huawei.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

So we don't open-coded initialization of cpuacct in core.c.
Signed-off-by: NLi Zefan <lizefan@huawei.com>
Acked-by: NPeter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/51553687.1060906@huawei.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

Add cpuacct.h and let sched.h include it.
Signed-off-by: NLi Zefan <lizefan@huawei.com>
Acked-by: NPeter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/5155367B.2060506@huawei.comSigned-off-by: NIngo Molnar <mingo@kernel.org>