sched/rt: Use container_of() to get root domain in rto_push_irq_work_func()

When the rto_push_irq_work_func() is called, it looks at the RT overloaded
bitmask in the root domain via the runqueue (rq->rd). The problem is that
during CPU up and down, nothing here stops rq->rd from changing between
taking the rq->rd->rto_lock and releasing it. That means the lock that is
released is not the same lock that was taken.

Instead of using this_rq()->rd to get the root domain, as the irq work is
part of the root domain, we can simply get the root domain from the irq work
that is passed to the routine:

 container_of(work, struct root_domain, rto_push_work)

This keeps the root domain consistent.

Change-Id: Id4803e4d0dc7877e9435a7ccb6da9c53be5dc9d9
Link: http://lkml.kernel.org/r/CAEU1=PkiHO35Dzna8EQqNSKW1fr1y1zRQ5y66X117MG06sQtNA@mail.gmail.com


Cc: stable@vger.kernel.org
Fixes: 4bdced5c9a292 ("sched/rt: Simplify the IPI based RT balancing logic")
Reported-by: Pavan Kondeti <pkondeti@codeaurora.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Patch-mainline: linux-kernel @ 01/24/18, 7:15
Signed-off-by: Pavankumar Kondeti <pkondeti@codeaurora.org>