sched: using dst_rq instead of this_rq during load balance

As we already have dst_rq in lb_env, using or changing "this_rq" do not
make sense.

This patch will replace "this_rq" with dst_rq in load_balance, and we
don't need to change "this_rq" while process LBF_SOME_PINNED any more.

Signed-off-by: Michael Wang <wangyun@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/501F8357.3070102@linux.vnet.ibm.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

kernel/sched/fair.c

@@ -4283,7 +4283,7 @@ static int load_balance(int this_cpu, struct rq *this_rq,
 		goto out_balanced;
 	}
 
-	BUG_ON(busiest == this_rq);
+	BUG_ON(busiest == env.dst_rq);
 
 	schedstat_add(sd, lb_imbalance[idle], env.imbalance);
 
@@ -4304,15 +4304,15 @@ static int load_balance(int this_cpu, struct rq *this_rq,
 		update_h_load(env.src_cpu);
 more_balance:
 		local_irq_save(flags);
-		double_rq_lock(this_rq, busiest);
+		double_rq_lock(env.dst_rq, busiest);
 
 		/*
 		 * cur_ld_moved - load moved in current iteration
 		 * ld_moved     - cumulative load moved across iterations
 		 */
 		cur_ld_moved = move_tasks(&env);
 		ld_moved += cur_ld_moved;
-		double_rq_unlock(this_rq, busiest);
+		double_rq_unlock(env.dst_rq, busiest);
 		local_irq_restore(flags);
 
 		if (env.flags & LBF_NEED_BREAK) {
@@ -4348,8 +4348,7 @@ static int load_balance(int this_cpu, struct rq *this_rq,
 		if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0 &&
 				lb_iterations++ < max_lb_iterations) {
 
-			this_rq		 = cpu_rq(env.new_dst_cpu);
-			env.dst_rq	 = this_rq;
+			env.dst_rq	 = cpu_rq(env.new_dst_cpu);
 			env.dst_cpu	 = env.new_dst_cpu;
 			env.flags	&= ~LBF_SOME_PINNED;
 			env.loop	 = 0;