linux-kernel - [PATCH 21/40] autonuma: avoid CFS select_task_rq

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Date:	Thu, 28 Jun 2012 14:56:01 +0200
From:	Andrea Arcangeli <aarcange@...hat.com>
To:	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Cc:	Hillf Danton <dhillf@...il.com>, Dan Smith <danms@...ibm.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>, Paul Turner <pjt@...gle.com>,
	Suresh Siddha <suresh.b.siddha@...el.com>,
	Mike Galbraith <efault@....de>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Lai Jiangshan <laijs@...fujitsu.com>,
	Bharata B Rao <bharata.rao@...il.com>,
	Lee Schermerhorn <Lee.Schermerhorn@...com>,
	Rik van Riel <riel@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>,
	Christoph Lameter <cl@...ux.com>,
	Alex Shi <alex.shi@...el.com>,
	Mauricio Faria de Oliveira <mauricfo@...ux.vnet.ibm.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Don Morris <don.morris@...com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>
Subject: [PATCH 21/40] autonuma: avoid CFS select_task_rq_fair to return -1

Fix to avoid -1 retval.

Includes fixes from Hillf Danton <dhillf@...il.com>.

Signed-off-by: Andrea Arcangeli <aarcange@...hat.com>
---
 kernel/sched/fair.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index c099cc6..fa96810 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -2789,6 +2789,9 @@ select_task_rq_fair(struct task_struct *p, int sd_flag, int wake_flags)
 		if (new_cpu == -1 || new_cpu == cpu) {
 			/* Now try balancing at a lower domain level of cpu */
 			sd = sd->child;
+			if (new_cpu < 0)
+				/* Return prev_cpu is find_idlest_cpu failed */
+				new_cpu = prev_cpu;
 			continue;
 		}
 
@@ -2807,6 +2810,7 @@ select_task_rq_fair(struct task_struct *p, int sd_flag, int wake_flags)
 unlock:
 	rcu_read_unlock();
 
+	BUG_ON(new_cpu < 0);
 	return new_cpu;
 }
 #endif /* CONFIG_SMP */
--
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