linux-kernel - Re: [PATCH 1/2] watchdog: rename watchdog_suspend() and watchdog

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Date:	Fri, 7 Aug 2015 11:11:20 +0100
From:	Aaron Tomlin <atomlin@...hat.com>
To:	Ulrich Obergfell <uobergfe@...hat.com>
Cc:	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	dzickus@...hat.com, jolsa@...nel.org, mhocko@...e.cz,
	eranian@...gle.com, cmetcalf@...hip.com, fweisbec@...il.com,
	linux@...ck-us.net
Subject: Re: [PATCH 1/2] watchdog: rename watchdog_suspend() and
 watchdog_resume()

On Fri 2015-08-07 11:58 +0200, Ulrich Obergfell wrote:
> Rename watchdog_suspend() to lockup_detector_suspend() and
> watchdog_resume() to lockup_detector_resume() to avoid
> confusion with the watchdog subsystem and to be consistent
> with the existing name lockup_detector_init().
> 
> Also provide comment blocks to explain the watchdog_running
> and watchdog_suspended variables and their relationship.
> 
> Signed-off-by: Ulrich Obergfell <uobergfe@...hat.com>
> ---
>  arch/x86/kernel/cpu/perf_event_intel.c |  4 ++--
>  include/linux/nmi.h                    |  8 ++++----
>  kernel/watchdog.c                      | 26 ++++++++++++++++++++++----
>  3 files changed, 28 insertions(+), 10 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/perf_event_intel.c b/arch/x86/kernel/cpu/perf_event_intel.c
> index d4e1b0c..0357bf7 100644
> --- a/arch/x86/kernel/cpu/perf_event_intel.c
> +++ b/arch/x86/kernel/cpu/perf_event_intel.c
> @@ -3368,7 +3368,7 @@ static __init int fixup_ht_bug(void)
>  		return 0;
>  	}
>  
> -	if (watchdog_suspend() != 0) {
> +	if (lockup_detector_suspend() != 0) {
>  		pr_info("failed to disable PMU erratum BJ122, BV98, HSD29 workaround\n");
>  		return 0;
>  	}
> @@ -3379,7 +3379,7 @@ static __init int fixup_ht_bug(void)
>  	x86_pmu.commit_scheduling = NULL;
>  	x86_pmu.stop_scheduling = NULL;
>  
> -	watchdog_resume();
> +	lockup_detector_resume();
>  
>  	get_online_cpus();
>  
> diff --git a/include/linux/nmi.h b/include/linux/nmi.h
> index 46e28e9e..78488e0 100644
> --- a/include/linux/nmi.h
> +++ b/include/linux/nmi.h
> @@ -84,15 +84,15 @@ extern int proc_watchdog_thresh(struct ctl_table *, int ,
>  				void __user *, size_t *, loff_t *);
>  extern int proc_watchdog_cpumask(struct ctl_table *, int,
>  				 void __user *, size_t *, loff_t *);
> -extern int watchdog_suspend(void);
> -extern void watchdog_resume(void);
> +extern int lockup_detector_suspend(void);
> +extern void lockup_detector_resume(void);
>  #else
> -static inline int watchdog_suspend(void)
> +static inline int lockup_detector_suspend(void)
>  {
>  	return 0;
>  }
>  
> -static inline void watchdog_resume(void)
> +static inline void lockup_detector_resume(void)
>  {
>  }
>  #endif
> diff --git a/kernel/watchdog.c b/kernel/watchdog.c
> index 69666f4..64ed1c3 100644
> --- a/kernel/watchdog.c
> +++ b/kernel/watchdog.c
> @@ -67,8 +67,26 @@ unsigned long *watchdog_cpumask_bits = cpumask_bits(&watchdog_cpumask);
>  #define for_each_watchdog_cpu(cpu) \
>  	for_each_cpu_and((cpu), cpu_online_mask, &watchdog_cpumask)
>  
> -static int __read_mostly watchdog_suspended;
> +/*
> + * The 'watchdog_running' variable is set to 1 when the watchdog threads
> + * are registered/started and is set to 0 when the watchdog threads are
> + * unregistered/stopped, so it is an indicator whether the threads exist.
> + */
>  static int __read_mostly watchdog_running;
> +/*
> + * If a subsystem has a need to deactivate the watchdog temporarily, it
> + * can use the suspend/resume interface to achieve this. The content of
> + * the 'watchdog_suspended' variable reflects this state. Existing threads
> + * are parked/unparked by the lockup_detector_{suspend|resume} functions
> + * (see comment blocks pertaining to those functions for further details).
> + *
> + * 'watchdog_suspended' also prevents threads from being registered/started
> + * or unregistered/stopped via parameters in /proc/sys/kernel, so the state
> + * of 'watchdog_running' cannot change while the watchdog is deactivated
> + * temporarily (see related code in 'proc' handlers).
> + */
> +static int __read_mostly watchdog_suspended;
> +
>  static u64 __read_mostly sample_period;
>  
>  static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts);
> @@ -669,7 +687,7 @@ static void watchdog_unpark_threads(void)
>  /*
>   * Suspend the hard and soft lockup detector by parking the watchdog threads.
>   */
> -int watchdog_suspend(void)
> +int lockup_detector_suspend(void)
>  {
>  	int ret = 0;
>  
> @@ -679,7 +697,7 @@ int watchdog_suspend(void)
>  	 * the 'watchdog_suspended' variable). If the watchdog threads are
>  	 * running, the first caller takes care that they will be parked.
>  	 * The state of 'watchdog_running' cannot change while a suspend
> -	 * request is active (see related changes in 'proc' handlers).
> +	 * request is active (see related code in 'proc' handlers).
>  	 */
>  	if (watchdog_running && !watchdog_suspended)
>  		ret = watchdog_park_threads();
> @@ -695,7 +713,7 @@ int watchdog_suspend(void)
>  /*
>   * Resume the hard and soft lockup detector by unparking the watchdog threads.
>   */
> -void watchdog_resume(void)
> +void lockup_detector_resume(void)
>  {
>  	mutex_lock(&watchdog_proc_mutex);
>  

Reviewed-by: Aaron Tomlin <atomlin@...hat.com>

-- 
Aaron Tomlin

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