linux-kernel - Re: [RT] Warning from swake_up_all

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Date:	Sat, 2 Apr 2016 22:44:15 -0500
From:	Clark Williams <williams@...hat.com>
To:	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Daniel Wagner <wagi@...om.org>,
	RT <linux-rt-users@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RT] Warning from swake_up_all_locked in rt-4.4.4-rt11

On Fri, 1 Apr 2016 12:33:18 +0200
Sebastian Andrzej Siewior <bigeasy@...utronix.de> wrote:

> * Thomas Gleixner | 2016-03-14 09:49:52 [+0100]:
> 
> >On Sun, 13 Mar 2016, Clark Williams wrote:
> >  
> >> I'm hitting the WARN_ON(wakes > 2) in $SUBJECT when resuming from suspend on my laptop (quad-core i7 with HT on). Looks like the warning gets hit 36 times on resume. E.g.:  
> >If resume is the only case, then we can filter that out and not worry about it
> >at all :)  
> 
> This works with the "mem" and "disk" target:
> 
> --- a/include/linux/suspend.h
> +++ b/include/linux/suspend.h
> @@ -194,6 +194,12 @@ struct platform_freeze_ops {
>  	void (*end)(void);
>  };
>  
> +#if defined(CONFIG_SUSPEND) || defined(CONFIG_HIBERNATION)
> +extern bool pm_in_action;
> +#else
> +# define pm_in_action false
> +#endif
> +
>  #ifdef CONFIG_SUSPEND
>  /**
>   * suspend_set_ops - set platform dependent suspend operations
> diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
> index bfd9e0982f15..fbb23f93e8d6 100644
> --- a/kernel/power/hibernate.c
> +++ b/kernel/power/hibernate.c
> @@ -648,6 +648,10 @@ static void power_down(void)
>  		cpu_relax();
>  }
>  
> +#ifndef CONFIG_SUSPEND
> +bool pm_in_action;
> +#endif
> +
>  /**
>   * hibernate - Carry out system hibernation, including saving the image.
>   */
> @@ -660,6 +664,8 @@ int hibernate(void)
>  		return -EPERM;
>  	}
>  
> +	pm_in_action = true;
> +
>  	lock_system_sleep();
>  	/* The snapshot device should not be opened while we're running */
>  	if (!atomic_add_unless(&snapshot_device_available, -1, 0)) {
> @@ -725,6 +731,7 @@ int hibernate(void)
>  	atomic_inc(&snapshot_device_available);
>   Unlock:
>  	unlock_system_sleep();
> +	pm_in_action = false;
>  	return error;
>  }
>  
> diff --git a/kernel/power/suspend.c b/kernel/power/suspend.c
> index 80ebc0726290..393bc342c586 100644
> --- a/kernel/power/suspend.c
> +++ b/kernel/power/suspend.c
> @@ -522,6 +522,8 @@ static int enter_state(suspend_state_t state)
>  	return error;
>  }
>  
> +bool pm_in_action;
> +
>  /**
>   * pm_suspend - Externally visible function for suspending the system.
>   * @state: System sleep state to enter.
> @@ -536,6 +538,8 @@ int pm_suspend(suspend_state_t state)
>  	if (state <= PM_SUSPEND_ON || state >= PM_SUSPEND_MAX)
>  		return -EINVAL;
>  
> +	pm_in_action = true;
> +
>  	error = enter_state(state);
>  	if (error) {
>  		suspend_stats.fail++;
> @@ -543,6 +547,7 @@ int pm_suspend(suspend_state_t state)
>  	} else {
>  		suspend_stats.success++;
>  	}
> +	pm_in_action = false;
>  	return error;
>  }
>  EXPORT_SYMBOL(pm_suspend);
> diff --git a/kernel/sched/swait.c b/kernel/sched/swait.c
> index 8459561f0379..205fe36868f9 100644
> --- a/kernel/sched/swait.c
> +++ b/kernel/sched/swait.c
> @@ -1,5 +1,6 @@
>  #include <linux/sched.h>
>  #include <linux/swait.h>
> +#include <linux/suspend.h>
>  
>  void __init_swait_queue_head(struct swait_queue_head *q, const char *name,
>  			     struct lock_class_key *key)
> @@ -42,7 +43,9 @@ void swake_up_all_locked(struct swait_queue_head *q)
>  		list_del_init(&curr->task_list);
>  		wakes++;
>  	}
> -	WARN_ON(wakes > 2);
> +	if (pm_in_action)
> +		return;
> +	WARN(wakes > 2, "complate_all() with %d waiters\n", wakes);
>  }
>  EXPORT_SYMBOL(swake_up_all_locked);
>  
> Sebastian

Applied to 4.4.6-rt12, suspended/resumed multiple times with no warnings from swake_up_all_locked().

Tested-by: Clark Williams <williams@...hat.com>

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