linux-kernel - Re: [PATCH 3/4] watchdog: disable watchdog when thresh is zero

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Date:	Tue, 17 May 2011 09:10:18 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Mandeep Singh Baines <msb@...omium.org>
Cc:	linux-kernel@...r.kernel.org,
	Marcin Slusarz <marcin.slusarz@...il.com>,
	Don Zickus <dzickus@...hat.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Frederic Weisbecker <fweisbec@...il.com>
Subject: Re: [PATCH 3/4] watchdog: disable watchdog when thresh is zero


* Mandeep Singh Baines <msb@...omium.org> wrote:

> This restores the previous behavior of softlock_thresh.
> 
> Currently, setting watchdog_thresh to zero causes the watchdog
> kthreads to consume a lot of CPU.
> 
> Signed-off-by: Mandeep Singh Baines <msb@...omium.org>
> Cc: Marcin Slusarz <marcin.slusarz@...il.com>
> Cc: Don Zickus <dzickus@...hat.com>
> Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> Cc: Frederic Weisbecker <fweisbec@...il.com>
> Cc: Ingo Molnar <mingo@...e.hu>
> ---
>  kernel/watchdog.c |   15 ++++++++++++++-
>  1 files changed, 14 insertions(+), 1 deletions(-)
> 
> diff --git a/kernel/watchdog.c b/kernel/watchdog.c
> index cf0e09f..50c2f62 100644
> --- a/kernel/watchdog.c
> +++ b/kernel/watchdog.c
> @@ -526,7 +526,20 @@ int proc_dowatchdog_thresh(struct ctl_table *table, int write,
>  			     void __user *buffer,
>  			     size_t *lenp, loff_t *ppos)
>  {
> -	return proc_dointvec_minmax(table, write, buffer, lenp, ppos);
> +	int ret;
> +
> +	ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
> +	if (ret || !write)
> +		goto out;
> +
> +	if (softlockup_thresh)
> +		watchdog_enable_all_cpus();
> +	else
> +		watchdog_disable_all_cpus();

This now adds two similar looking blocks of these 4 lines, one in 
proc_dowatchdog_enabled(), one in proc_dowatchdog_thresh().

They are not the same though. So what happens if the watchdog is disabled but 
the threshold is updated to nonzero - do we enable the watchdog?

Thanks,

	Ingo
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