linux-kernel - Re: [patch V3 5/7] rtmutex: Confine deadlock logic to futex

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Date:	Tue, 10 Jun 2014 19:39:39 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Steven Rostedt <rostedt@...dmis.org>
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 5/7] rtmutex: Confine deadlock logic to futex

On Mon, 9 Jun 2014, Steven Rostedt wrote:
> On Mon, 09 Jun 2014 20:28:09 -0000
> Thomas Gleixner <tglx@...utronix.de> wrote:
>   
> > +/*
> > + * Futex variant to allow full deadlock detection.
> > + */
> > +int __rt_mutex_timed_lock(struct rt_mutex *lock,
> > +			  struct hrtimer_sleeper *timeout)
> > +{
> > +	might_sleep();
> > +
> > +	return rt_mutex_timed_fastlock(lock, TASK_INTERRUPTIBLE, timeout, 0,
> > +				       rt_mutex_slowlock);
> > +}
> > +
> >  /**
> >   * rt_mutex_timed_lock - lock a rt_mutex interruptible
> >   *			the timeout structure is provided
> >   *			by the caller
> >   *
> > - * @lock: 		the rt_mutex to be locked
> > + * @lock:		the rt_mutex to be locked
> >   * @timeout:		timeout structure or NULL (no timeout)
> > - * @detect_deadlock:	deadlock detection on/off
> >   *
> >   * Returns:
> > - *  0 		on success
> > - * -EINTR 	when interrupted by a signal
> > + *  0		on success
> > + * -EINTR	when interrupted by a signal
> >   * -ETIMEDOUT	when the timeout expired
> > - * -EDEADLK	when the lock would deadlock (when deadlock detection is on)
> >   */
> >  int
> > -rt_mutex_timed_lock(struct rt_mutex *lock, struct hrtimer_sleeper *timeout,
> > -		    int detect_deadlock)
> > +rt_mutex_timed_lock(struct rt_mutex *lock, struct hrtimer_sleeper *timeout)
> >  {
> >  	might_sleep();
> >  
> > -	return rt_mutex_timed_fastlock(lock, TASK_INTERRUPTIBLE, timeout,
> > -				       detect_deadlock, rt_mutex_slowlock);
> > +	return rt_mutex_timed_fastlock(lock, TASK_INTERRUPTIBLE, timeout, 0,
> > +				       rt_mutex_slowlock);
> >  }
> >  EXPORT_SYMBOL_GPL(rt_mutex_timed_lock);
> >  
> 
> I must be missing something. What's the difference between the above
> and the futex variant one? They both do the exact same thing:
> 
> 
> int foo(struct rt_mutex *lock, struct hrtimer_sleeper *timeout)
> {
> 	might_sleep();
> 
> 	return rt_mutex_timed_fastlock(lock, TASK_INTERRUPTIBLE, timout,
> 				       0, rt_mutex_slowlock);
> }

Right. The one for futex must have s/0/1/. Fixed.

Thanks,

	tglx
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