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SubjectRe: [PATCH] sched: fix env->src_cpu for active migration
Hi,

I tested this on top of 3.8-rc7 and this made the machine (x86_64, Core
i7 920) unable to boot (very early as nothing at all is displayed on
screen). Nothing in the kernel log (after booting with a working
kernel).

Double-checked by just backing out only this patch and this made the
machine boot again.

Damien

> need_active_balance uses env->src_cpu which is set only if there is more
> than 1 task on the run queue. We must set the src_cpu field unconditionnally
> otherwise the test "env->src_cpu > env->dst_cpu" will always fail if there is
> only 1 task on the run queue
>
> Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
> ---
> kernel/sched/fair.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 81fa536..32938ea 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -5044,6 +5044,10 @@ redo:
>
> ld_moved = 0;
> lb_iterations = 1;
> +
> + env.src_cpu = busiest->cpu;
> + env.src_rq = busiest;
> +
> if (busiest->nr_running > 1) {
> /*
> * Attempt to move tasks. If find_busiest_group has found
> @@ -5052,8 +5056,6 @@ redo:
> * correctly treated as an imbalance.
> */
> env.flags |= LBF_ALL_PINNED;
> - env.src_cpu = busiest->cpu;
> - env.src_rq = busiest;
> env.loop_max = min(sysctl_sched_nr_migrate, busiest->nr_running);
>
> update_h_load(env.src_cpu);


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