From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx205.postini.com [74.125.245.205]) by kanga.kvack.org (Postfix) with SMTP id 555DC6B004A for ; Mon, 26 Mar 2012 14:57:11 -0400 (EDT) From: Andrea Arcangeli Subject: [PATCH 21/39] autonuma: fix selecting task runqueue Date: Mon, 26 Mar 2012 19:46:08 +0200 Message-Id: <1332783986-24195-22-git-send-email-aarcange@redhat.com> In-Reply-To: <1332783986-24195-1-git-send-email-aarcange@redhat.com> References: <1332783986-24195-1-git-send-email-aarcange@redhat.com> Sender: owner-linux-mm@kvack.org List-ID: To: linux-kernel@vger.kernel.org, linux-mm@kvack.org Cc: Hillf Danton , Dan Smith , Peter Zijlstra , Linus Torvalds , Andrew Morton , Thomas Gleixner , Ingo Molnar , Paul Turner , Suresh Siddha , Mike Galbraith , "Paul E. McKenney" , Lai Jiangshan , Bharata B Rao , Lee Schermerhorn , Rik van Riel , Johannes Weiner From: Hillf Danton Without coments, the following three hunks, I guess, ====== @@ -2788,6 +2801,7 @@ select_task_rq_fair(struct task_struct *p, goto unlock; } + prev_cpu = new_cpu; while (sd) { int load_idx = sd->forkexec_idx; struct sched_group *group; @@ -2811,6 +2825,7 @@ select_task_rq_fair(struct task_struct *p, if (new_cpu == -1 || new_cpu == cpu) { /* Now try balancing at a lower domain level of cpu */ sd = sd->child; + new_cpu = prev_cpu; continue; } @@ -2826,6 +2841,7 @@ select_task_rq_fair(struct task_struct *p, } /* while loop will break here if sd == NULL */ } + BUG_ON(new_cpu < 0); unlock: rcu_read_unlock(); ====== were added for certain that selected cpu is valid, based on BUG_ON. But question raised, why prev_cpu is changed? Andrea's answer: yes the BUG_ON was introduced to verify the function wouldn't return -1. This patch fixes the problem too. Signed-off-by: Hillf Danton Signed-off-by: Andrea Arcangeli --- kernel/sched/fair.c | 6 ++++-- 1 files changed, 4 insertions(+), 2 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 25e9e5b..a8498e0 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -2769,7 +2769,6 @@ select_task_rq_fair(struct task_struct *p, int sd_flag, int wake_flags) goto unlock; } - prev_cpu = new_cpu; while (sd) { int load_idx = sd->forkexec_idx; struct sched_group *group; @@ -2793,7 +2792,10 @@ 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; - new_cpu = prev_cpu; + if (new_cpu == -1) { + /* Only for certain that new cpu is valid */ + new_cpu = prev_cpu; + } continue; } -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org