linux-kernel - Re: [PATCH v3 2/6] sched/rtmutex/deadline: Fix a PI crash for deadline tasks

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Date:	Wed, 20 Apr 2016 21:49:42 +0800
From:	Xunlei Pang <xpang@...hat.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	Juri Lelli <juri.lelli@....com>,
	Ingo Molnar <mingo@...hat.com>,
	Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [PATCH v3 2/6] sched/rtmutex/deadline: Fix a PI crash for
 deadline tasks

On 2016/04/20 at 21:19, Peter Zijlstra wrote:
> On Thu, Apr 14, 2016 at 07:37:03PM +0800, Xunlei Pang wrote:
>> +	/* Updated under pi_lock and rtmutex lock */
>>  	struct rb_node *pi_waiters_leftmost;
>> +	struct rb_node *pi_waiters_leftmost_copy;
>>  struct task_struct *rt_mutex_get_top_task(struct task_struct *task)
>>  {
>> +	if (!task->pi_waiters_leftmost_copy)
>>  		return NULL;
>>  
>> +	return rb_entry(task->pi_waiters_leftmost_copy,
>> +				struct rt_mutex_waiter, pi_tree_entry)->task;
>>  }
> why ?! Why not keep a regular task_struct pointer and avoid this stuff?

I meant to make it semantically consistent, but I can change it since you think task_struct is better.

Regards,
Xunlei