linux-kernel - Re: [PATCH] locking/pvqspinlock: Fix a bug in qstat

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Date:	Wed, 13 Jul 2016 09:50:42 -0400
From:	Waiman Long <waiman.long@....com>
To:	Pan Xinhui <xinhui.pan@...ux.vnet.ibm.com>
CC:	<linux-kernel@...r.kernel.org>, <peterz@...radead.org>,
	<mingo@...hat.com>
Subject: Re: [PATCH] locking/pvqspinlock: Fix a bug in qstat_read()

On 07/13/2016 06:23 AM, Pan Xinhui wrote:
> It's obviously wrong to set stat to NULL. So lets remove it.
> Otherwise it is always zero when we check the latency of kick/wake
>
> Signed-off-by: Pan Xinhui<xinhui.pan@...ux.vnet.ibm.com>
> ---
>   kernel/locking/qspinlock_stat.h | 1 -
>   1 file changed, 1 deletion(-)
>
> diff --git a/kernel/locking/qspinlock_stat.h b/kernel/locking/qspinlock_stat.h
> index 7b0f1b9..8fa1165 100644
> --- a/kernel/locking/qspinlock_stat.h
> +++ b/kernel/locking/qspinlock_stat.h
> @@ -157,7 +157,6 @@ static ssize_t qstat_read(struct file *file, char __user *user_buf,
>   		 */
>   		if ((counter == qstat_pv_latency_kick) ||
>   		    (counter == qstat_pv_latency_wake)) {
> -			stat = 0;
>   			if (kicks)
>   				stat = DIV_ROUND_CLOSEST_ULL(stat, kicks);
>   		}

Thanks for catching that. The statement shouldn't be there.

Reviewed-by: Waiman Long <Waiman.Long@....com>