Re: [RFC][PATCH 12/11] sched: Add preempt_count invariant check

[Peter Zijlstra]

On Tue, Sep 29, 2015 at 12:27:55PM +0200, Peter Zijlstra wrote:
> 
> Ingo requested I keep my debug check for the preempt_count invariant.
> 
> Requested-by: Ingo Molnar <mingo@xxxxxxxxxx>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
> ---
>  kernel/sched/core.c |    5 +++++
>  1 file changed, 5 insertions(+)
> 
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -2503,6 +2503,11 @@ static struct rq *finish_task_switch(str
>  	struct mm_struct *mm = rq->prev_mm;
>  	long prev_state;
>  
> +	if (unlikely(WARN_ONCE(preempt_count() != 2,

That should have: s/2/2*PREEMPT_DISABLE_OFFSET/ or something, otherwise
!PREEMPT_COUNT kernels will go funny.

> +			       "corrupted preempt_count: %s/%d/0x%x\n",
> +			       current->comm, current->pid, preempt_count())))
> +		preempt_count_set(INIT_PREEMPT_COUNT);
> +
>  	rq->prev_mm = NULL;
>  
>  	/*
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