sched/fair: Test list head instead of list entry in throttle_cfs_rq()
sched/fair: Test list head instead of list entry in throttle_cfs_rq()

According to the comments, we need to test if this is
the first throttled task, however, list_empty() tests on
the entry cfs_rq->throttled_list, not the head, this is wrong.

This is a bug because we don't re-init the list entry after
removing it from the list, so list_empty() could return false
even if the list is really empty.

Signed-off-by: Cong Wang <0f114804888b88d50037b04b42e57b858d851b87@gmail.com>
Signed-off-by: Cong Wang <2b3b59efb30d692c772b2f93c636eba69bba4f54@twopensource.com>
Signed-off-by: Peter Zijlstra (Intel) <3fddac958924aef220f202ca567388ddab3f14a8@infradead.org>
Reviewed-by: Ben Segall <7dc6b67dc6a1a2319718815cbe6519298041ac95@google.com>
Cc: Linus Torvalds <69652caca27c8b940640ad396ab71f93cacec34f@linux-foundation.org>
Cc: Peter Zijlstra <3fddac958924aef220f202ca567388ddab3f14a8@infradead.org>
Cc: Thomas Gleixner <00e4cf8f46a57000a44449bf9dd8cbbcc209fd2a@linutronix.de>
Link: http://lkml.kernel.org/r/1435174907-432-1-git-send-email-0f114804888b88d50037b04b42e57b858d851b87@gmail.com
Signed-off-by: Ingo Molnar <9dbbbf0688fedc85ad4da37637f1a64b8c718ee2@kernel.org>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs