UPSTREAM: sched/fair: Avoid pulling all tasks in idle balancing

In idle balancing where a CPU going idle pulls tasks from another CPU,
a livelock may happen if the CPU pulls all tasks from another, makes
it idle, and this iterates. So just avoid this.

Reported-by: Rabin Vincent <rabin.vincent@axis.com>
Signed-off-by: Yuyang Du <yuyang.du@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Ben Segall <bsegall@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Mike Galbraith <umgwanakikbuti@gmail.com>
Cc: Morten Rasmussen <morten.rasmussen@arm.com>
Cc: Paul Turner <pjt@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20150705221151.GF5197@intel.com


Signed-off-by: Ingo Molnar <mingo@kernel.org>
(cherry picked from commit 985d3a4c11cd28251bcc7925aa2d7a9038910384)
Signed-off-by: Ricky Liang <jcliang@chromium.org>

BUG=chrome-os-partner:45410
TEST=Boot kernel on Oak. Run tests for days and doesn't see kernel lock-ups.

Change-Id: I4e39dd14189fbf27afcc64de255f7d1b7b822b34
Reviewed-on: https://chromium-review.googlesource.com/309510


Commit-Ready: Ricky Liang <jcliang@chromium.org>
Tested-by: Ricky Liang <jcliang@chromium.org>
Reviewed-by: Daniel Kurtz <djkurtz@chromium.org>