>>> On Tue, Jun 24, 2008 at 10:16 AM, in message
<20080624141602.28487.81775.stgit@xxxxxxxxxxxxxxxxxxxxxx>, Gregory Haskins
<ghaskins@xxxxxxxxxx> wrote:
> Load-balancing will never terminate if all cpus are "all_pinned" with
> the current algorithm. This would be pretty unlikely to occur, but we
> should protect against it nonetheless.
Hmm...after thinking about this some more, I think I was wrong and this is unfounded.
The code would eventually terminate when the f_b_g()/f_b_q() cant find a good target.
Pls ignore this patch.
Regards,
-Greg
>
> Signed-off-by: Gregory Haskins <ghaskins@xxxxxxxxxx>
> ---
>
> kernel/sched.c | 19 ++++++++++---------
> 1 files changed, 10 insertions(+), 9 deletions(-)
>
> diff --git a/kernel/sched.c b/kernel/sched.c
> index 31f91d9..54b27b4 100644
> --- a/kernel/sched.c
> +++ b/kernel/sched.c
> @@ -3178,7 +3178,8 @@ static int load_balance(int this_cpu, struct rq
> *this_rq,
> struct sched_group *group;
> unsigned long imbalance;
> struct rq *busiest;
> - cpumask_t cpus = CPU_MASK_ALL;
> + cpumask_t cpus = sd->span;
> + int remain = cpus_weight(sd->span) - 1;
> unsigned long flags;
>
> /*
> @@ -3237,11 +3238,10 @@ redo:
> resched_cpu(this_cpu);
>
> /* All tasks on this runqueue were pinned by CPU affinity */
> - if (unlikely(all_pinned)) {
> + if (unlikely(all_pinned && remain)) {
> cpu_clear(cpu_of(busiest), cpus);
> - if (!cpus_empty(cpus))
> - goto redo;
> - goto out_balanced;
> + remain--;
> + goto redo;
> }
> }
>
> @@ -3332,7 +3332,8 @@ load_balance_newidle(int this_cpu, struct rq *this_rq,
> struct sched_domain *sd)
> int ld_moved = 0;
> int sd_idle = 0;
> int all_pinned = 0;
> - cpumask_t cpus = CPU_MASK_ALL;
> + cpumask_t cpus = sd->span;
> + int remain = cpus_weight(sd->span) - 1;
>
> /*
> * When power savings policy is enabled for the parent domain, idle
> @@ -3375,10 +3376,10 @@ redo:
> &all_pinned);
> spin_unlock(&busiest->lock);
>
> - if (unlikely(all_pinned)) {
> + if (unlikely(all_pinned && remain)) {
> cpu_clear(cpu_of(busiest), cpus);
> - if (!cpus_empty(cpus))
> - goto redo;
> + remain--;
> + goto redo;
> }
> }
>
>
> --
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