linux-kernel - Re: [patch V3 4/7] rtmutex: Siplify remove

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Message-ID: <20140609205329.52b8c0d5@gandalf.local.home>
Date:	Mon, 9 Jun 2014 20:53:29 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>,
	Lai Jiangshan <laijs@...fujitsu.com>,
	Jason Low <jason.low2@...com>, Brad Mouring <bmouring@...com>
Subject: Re: [patch V3 4/7] rtmutex: Siplify remove_waiter()

On Mon, 09 Jun 2014 20:28:08 -0000
Thomas Gleixner <tglx@...utronix.de> wrote:

> Exit right away, when the removed waiter was not the top prioriy
> waiter on the lock. Get rid of the extra indent level.
> 
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> ---
>  kernel/locking/rtmutex.c |   26 ++++++++++----------------
>  1 file changed, 10 insertions(+), 16 deletions(-)
> 
> Index: tip/kernel/locking/rtmutex.c
> ===================================================================
> --- tip.orig/kernel/locking/rtmutex.c
> +++ tip/kernel/locking/rtmutex.c
> @@ -780,7 +780,7 @@ static void remove_waiter(struct rt_mute
>  {
>  	int first = (waiter == rt_mutex_top_waiter(lock));
>  	struct task_struct *owner = rt_mutex_owner(lock);
> -	struct rt_mutex *next_lock = NULL;
> +	struct rt_mutex *next_lock;
>  	unsigned long flags;
>  
>  	raw_spin_lock_irqsave(&current->pi_lock, flags);
> @@ -788,28 +788,22 @@ static void remove_waiter(struct rt_mute
>  	current->pi_blocked_on = NULL;
>  	raw_spin_unlock_irqrestore(&current->pi_lock, flags);
>  

Add comment here, something like...

	/*
	 * Only update priority if this task was the highest priority
	 * task waiting on the lock, and there is an owner to update.
	 */

Rest looks good.

Reviewed-by: Steven Rostedt <rostedt@...dmis.org>

-- Steve


> -	if (!owner)
> +	if (!owner || !first)
>  		return;
>  
> -	if (first) {
> +	raw_spin_lock_irqsave(&owner->pi_lock, flags);
>  
> -		raw_spin_lock_irqsave(&owner->pi_lock, flags);
> +	rt_mutex_dequeue_pi(owner, waiter);
>  
> -		rt_mutex_dequeue_pi(owner, waiter);
> +	if (rt_mutex_has_waiters(lock))
> +		rt_mutex_enqueue_pi(owner, rt_mutex_top_waiter(lock));
>  
> -		if (rt_mutex_has_waiters(lock)) {
> -			struct rt_mutex_waiter *next;
> +	__rt_mutex_adjust_prio(owner);
>  
> -			next = rt_mutex_top_waiter(lock);
> -			rt_mutex_enqueue_pi(owner, next);
> -		}
> -		__rt_mutex_adjust_prio(owner);
> +	/* Store the lock on which owner is blocked or NULL */
> +	next_lock = task_blocked_on_lock(owner);
>  
> -		/* Store the lock on which owner is blocked or NULL */
> -		next_lock = task_blocked_on_lock(owner);
> -
> -		raw_spin_unlock_irqrestore(&owner->pi_lock, flags);
> -	}
> +	raw_spin_unlock_irqrestore(&owner->pi_lock, flags);
>  
>  	if (!next_lock)
>  		return;
> 

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