Re: [STABLE] kernel oops which can be fixed by peterz's patches

[Ben Hutchings]

On Wed, 2016-02-17 at 04:02 +0100, Mike Galbraith wrote:
[...]
> @stable: Kernels that predate SCHED_DEADLINE can use this simple (and tested)
> check in lieu of backport of the full 18 patch mainline treatment.
> 
> Signed-off-by: Mike Galbraith <umgwanakikbuti@xxxxxxxxx>
> ---
> Âkernel/sched/fair.c |ÂÂÂÂ9 +++++++++
> Â1 file changed, 9 insertions(+)
> 
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -4008,6 +4008,7 @@ int can_migrate_task(struct task_struct
> Â	Â* 2) cannot be migrated to this CPU due to cpus_allowed, or
> Â	Â* 3) running (obviously), or
> Â	Â* 4) are cache-hot on their current CPU.
> +	Â* 5) p->pi_lock is held.
> Â	Â*/
> Â	if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
> Â		return 0;
> @@ -4049,6 +4050,14 @@ int can_migrate_task(struct task_struct
> Â	}
> Â
> Â	/*
> +	Â* rt -> fair class change may be in progress.ÂÂIf we sneak in should
> +	Â* double_lock_balance() release rq->lock, and move the task, we will
> +	Â* cause switched_to_fair() to meet a passed but no longer valid rq.
> +	Â*/
> +	if (raw_spin_is_locked(&p->pi_lock))
> +		return 0;
> +
> +	/*
> Â	Â* Aggressive migration if:
> Â	Â* 1) task is cache cold, or
> Â	Â* 2) too many balance attempts have failed.

Queued up for 3.2, thanks.

Ben.

-- 
Ben Hutchings
Any smoothly functioning technology is indistinguishable from a rigged demo.

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