From: Andrea Arcangeli <aarcange@redhat.com>
To: linux-kernel@vger.kernel.org, linux-mm@kvack.org
Cc: Hillf Danton <dhillf@gmail.com>, Dan Smith <danms@us.ibm.com>,
        Peter Zijlstra <a.p.zijlstra@chello.nl>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@elte.hu>,
        Paul Turner <pjt@google.com>,
        Suresh Siddha <suresh.b.siddha@intel.com>,
        Mike Galbraith <efault@gmx.de>,
        "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
        Lai Jiangshan <laijs@cn.fujitsu.com>,
        Bharata B Rao <bharata.rao@gmail.com>,
        Lee Schermerhorn <Lee.Schermerhorn@hp.com>,
        Rik van Riel <riel@redhat.com>, Johannes Weiner <hannes@cmpxchg.org>,
        Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>,
        Christoph Lameter <cl@linux.com>, Alex Shi <alex.shi@intel.com>,
        Mauricio Faria de Oliveira <mauricfo@linux.vnet.ibm.com>,
        Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
        Don Morris <don.morris@hp.com>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>
Subject: [PATCH 21/40] autonuma: avoid CFS select_task_rq_fair to return -1
Date: Thu, 28 Jun 2012 14:56:01 +0200
Message-Id: <1340888180-15355-22-git-send-email-aarcange@redhat.com>
In-Reply-To: <1340888180-15355-1-git-send-email-aarcange@redhat.com>
References: <1340888180-15355-1-git-send-email-aarcange@redhat.com>
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1133
Lines: 36

Fix to avoid -1 retval.

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

Signed-off-by: Andrea Arcangeli <aarcange@redhat.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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