linux-kernel - [PATCH v3 1/6] sched: change position of resched_cpu() in load

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Message-Id: <1366705662-3587-2-git-send-email-iamjoonsoo.kim@lge.com>
Date:	Tue, 23 Apr 2013 17:27:37 +0900
From:	Joonsoo Kim <iamjoonsoo.kim@....com>
To:	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>
Cc:	linux-kernel@...r.kernel.org,
	Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>,
	Davidlohr Bueso <davidlohr.bueso@...com>,
	Jason Low <jason.low2@...com>,
	Joonsoo Kim <iamjoonsoo.kim@....com>
Subject: [PATCH v3 1/6] sched: change position of resched_cpu() in load_balance()

cur_ld_moved is reset if env.flags hit LBF_NEED_BREAK.
So, there is possibility that we miss doing resched_cpu().
Correct it as changing position of resched_cpu()
before checking LBF_NEED_BREAK.

Acked-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Tested-by: Jason Low <jason.low2@...com>
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@....com>

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 1c97735..25aaf93 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5080,17 +5080,17 @@ more_balance:
 		double_rq_unlock(env.dst_rq, busiest);
 		local_irq_restore(flags);
 
-		if (env.flags & LBF_NEED_BREAK) {
-			env.flags &= ~LBF_NEED_BREAK;
-			goto more_balance;
-		}
-
 		/*
 		 * some other cpu did the load balance for us.
 		 */
 		if (cur_ld_moved && env.dst_cpu != smp_processor_id())
 			resched_cpu(env.dst_cpu);
 
+		if (env.flags & LBF_NEED_BREAK) {
+			env.flags &= ~LBF_NEED_BREAK;
+			goto more_balance;
+		}
+
 		/*
 		 * Revisit (affine) tasks on src_cpu that couldn't be moved to
 		 * us and move them to an alternate dst_cpu in our sched_group
-- 
1.7.9.5

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