linux-kernel - Re: [seqcount] INFO: trying to register non-static key.

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Date:	Tue, 12 Nov 2013 10:46:44 -0500
From:	Vivek Goyal <vgoyal@...hat.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Fengguang Wu <fengguang.wu@...el.com>,
	John Stultz <john.stultz@...aro.org>,
	Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org,
	Jens Axboe <axboe@...nel.dk>, Tejun Heo <tj@...nel.org>
Subject: Re: [seqcount] INFO: trying to register non-static key.

On Tue, Nov 12, 2013 at 04:29:56PM +0100, Peter Zijlstra wrote:
> On Tue, Nov 12, 2013 at 10:15:41AM -0500, Vivek Goyal wrote:
> > I see that we allocate per cpu stats but don't do any initializations.
> > 
> > static void tg_stats_alloc_fn(struct work_struct *work)
> > {
> >         static struct tg_stats_cpu *stats_cpu;  /* this fn is non-reentrant */
> >         struct delayed_work *dwork = to_delayed_work(work);
> >         bool empty = false;
> > 
> > alloc_stats:
> >         if (!stats_cpu) {
> >                 stats_cpu = alloc_percpu(struct tg_stats_cpu);
> >                 if (!stats_cpu) {
> >                         /* allocation failed, try again after some time */
> >                         schedule_delayed_work(dwork, msecs_to_jiffies(10));
> >                         return;
> >                 }
> >         }
> > 
> >         spin_lock_irq(&tg_stats_alloc_lock);
> 
> Absolutely!
> 
> Something like this perhaps? Did I miss more blkg_[rw]stats? If I read
> the git grep output right, this was the last one.

Looks good to me.

This should be the last one. There are only two users of stats right
now. blk-throttle and cfq-iosched.

Thanks
Vivek

> 
> ---
>  block/blk-throttle.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/block/blk-throttle.c b/block/blk-throttle.c
> index 8331aba9426f..fd743d98c41d 100644
> --- a/block/blk-throttle.c
> +++ b/block/blk-throttle.c
> @@ -256,6 +256,12 @@ static struct throtl_data *sq_to_td(struct throtl_service_queue *sq)
>  	}								\
>  } while (0)
>  
> +static void tg_stats_init(struct tg_stats_cpu *tg_stats)
> +{
> +	blkg_rwstat_init(&tg_stats->service_bytes);
> +	blkg_rwstat_init(&tg_stats->serviced);
> +}
> +
>  /*
>   * Worker for allocating per cpu stat for tgs. This is scheduled on the
>   * system_wq once there are some groups on the alloc_list waiting for
> @@ -269,12 +275,16 @@ static void tg_stats_alloc_fn(struct work_struct *work)
>  
>  alloc_stats:
>  	if (!stats_cpu) {
> +		int cpu;
> +
>  		stats_cpu = alloc_percpu(struct tg_stats_cpu);
>  		if (!stats_cpu) {
>  			/* allocation failed, try again after some time */
>  			schedule_delayed_work(dwork, msecs_to_jiffies(10));
>  			return;
>  		}
> +		for_each_possible_cpu(cpu)
> +			tg_stats_init(per_cpu(stats_cpu, cpu));
>  	}
>  
>  	spin_lock_irq(&tg_stats_alloc_lock);
--
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