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Message-ID: <4FEDFAB1.8050305@redhat.com>
Date: Fri, 29 Jun 2012 14:57:53 -0400
From: Rik van Riel <riel@...hat.com>
To: Andrea Arcangeli <aarcange@...hat.com>
CC: linux-kernel@...r.kernel.org, linux-mm@...ck.org,
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>,
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: Re: [PATCH 21/40] autonuma: avoid CFS select_task_rq_fair to return
-1
On 06/28/2012 08:56 AM, Andrea Arcangeli wrote:
> 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 */
Wait, what?
Either this is a scheduler bugfix, in which case you
are better off submitting it separately and reducing
the size of your autonuma patch queue, or this is a
behaviour change in the scheduler that needs better
arguments than a 1-line changelog.
--
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