Messages in this thread Patches in this message | | | From | Andrea Arcangeli <> | Subject | [PATCH 21/39] autonuma: fix selecting task runqueue | Date | Mon, 26 Mar 2012 19:46:08 +0200 |
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From: Hillf Danton <dhillf@gmail.com>
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 <dhillf@gmail.com> Signed-off-by: Andrea Arcangeli <aarcange@redhat.com> --- 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; }
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