linux-kernel - Re: [PATCH -rt] Updates-from-Jon-Masters-for-hwlat

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Date:	Mon, 2 Nov 2009 16:43:12 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	John Kacur <jkacur@...hat.com>
cc:	linux-kernel@...r.kernel.org, Jon Masters <jcm@...hat.com>,
	linux-rt-users@...r.kernel.org,
	Clark Williams <williams@...hat.com>
Subject: Re: [PATCH -rt]
 Updates-from-Jon-Masters-for-hwlat_detector.c.patch

Hi,

On Fri, 23 Oct 2009, John Kacur wrote:
> I took Jon Masters' latest hwlat_detector patch for upstream, and grabbed 
> the bits that aren't currently in -rt. The patch is fairly small.
> 
> Please consider it for the next -rt release.

Not really.

> diff --git a/drivers/misc/hwlat_detector.c b/drivers/misc/hwlat_detector.c
> index be6553f..7191e17 100644
> --- a/drivers/misc/hwlat_detector.c
> +++ b/drivers/misc/hwlat_detector.c
> @@ -262,6 +262,8 @@ static int get_sample(void *unused)
>  		/* Keep a running maximum ever recorded hardware latency */
>  		if (sample > data.max_sample)
>  			data.max_sample = sample;
> +
> +		wake_up(&data.wq); /* wake up reader(s) */
>  	}
>  
>  	ret = 0;
> @@ -299,8 +301,6 @@ static int kthread_fn(void *unused)
>  			goto err_out;
>  		}
>  
> -		wake_up(&data.wq); /* wake up reader(s) */
> -

This reverts -rt commit 5fc485f6341c177e9d5f641c6fb9e33ca465aa84. 

CONFIG_DEBUG_SPINLOCK_SLEEP resp. CONFIG_DEBUG_PREEMPT will tell you
why this is a bad idea on -rt :)

Thanks,

	tglx
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