linux-kernel - Re: [PATCH] rtmutex: multiple candidate owners without unrelated boosting

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Date:	Tue, 14 Dec 2010 18:16:46 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Lai Jiangshan <laijs@...fujitsu.com>
Cc:	Ingo Molnar <mingo@...e.hu>, Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Dave Young <hidave.darkstar@...il.com>,
	Darren Hart <dvhart@...ux.intel.com>,
	Namhyung Kim <namhyung@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH] rtmutex: multiple candidate owners without unrelated
 boosting

On Tue, 2010-12-14 at 17:04 +0800, Lai Jiangshan wrote:

>  	/* Release the task */
>  	raw_spin_unlock_irqrestore(&task->pi_lock, flags);
> +	if (!rt_mutex_owner(lock)) {
> +		/*
> +		 * the lock is free and has waiters, set the top waiter
> +		 * as a new candidate owner when it is not set.
> +		 */
> +		if (top_waiter != rt_mutex_top_waiter(lock)) {
> +			top_waiter = rt_mutex_top_waiter(lock);
> +			top_waiter->cand_seq = lock->cand_seq;

Shouldn't this be:

			top_waiter->cand_seq = ++lock->cand_seq;

?

-- Steve

> +			if (!top_waiter->cand_owner) {
> +				top_waiter->cand_owner = 1;
> +				wake_up_process(top_waiter->task);
> +			}
> +		}
> +		raw_spin_unlock(&lock->wait_lock);
> +		goto out_put_task;
> +	}
>  	put_task_struct(task);
>  
>  	/* Grab the next task */
> @@ -296,78 +303,16 @@ static int rt_mutex_adjust_prio_chain(struct task_struct *task,
>  }
>  


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