linux-kernel - Re: [patch v2 3/5] rtmutex: Confine deadlock logic to futex

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Date:	Sat, 31 May 2014 15:54:37 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Lai Jiangshan <laijs@...fujitsu.com>,
	Jason Low <jason.low2@...com>
Subject: Re: [patch v2 3/5] rtmutex: Confine deadlock logic to futex

On Sat, 31 May 2014 15:57:50 -0000
Thomas Gleixner <tglx@...utronix.de> wrote:

> ===================================================================
> --- tip.orig/kernel/locking/rtmutex.c
> +++ tip/kernel/locking/rtmutex.c
> @@ -904,16 +904,15 @@ rt_mutex_slowunlock(struct rt_mutex *loc
>   */
>  static inline int
>  rt_mutex_fastlock(struct rt_mutex *lock, int state,
> -		  enum rtmutex_chainwalk detect_deadlock,
>  		  int (*slowfn)(struct rt_mutex *lock, int state,
>  				struct hrtimer_sleeper *timeout,
>  				enum rtmutex_chainwalk detect_deadlock))
>  {
> -	if (!detect_deadlock && likely(rt_mutex_cmpxchg(lock, NULL, current))) {
> +	if (likely(rt_mutex_cmpxchg(lock, NULL, current))) {
>  		rt_mutex_deadlock_account_lock(lock, current);
>  		return 0;
>  	} else
> -		return slowfn(lock, state, NULL, detect_deadlock);
> +		return slowfn(lock, state, NULL, RT_MUTEX_MIN_CHAINWALK);
>  }
>  
>  static inline int
> @@ -924,7 +923,7 @@ rt_mutex_timed_fastlock(struct rt_mutex
>  				      struct hrtimer_sleeper *timeout,
>  				      enum rtmutex_chainwalk detect_deadlock))
>  {
> -	if (!detect_deadlock && likely(rt_mutex_cmpxchg(lock, NULL, current))) {
> +	if (detect_deadlock && likely(rt_mutex_cmpxchg(lock, NULL, current))) {

Did you mean to remove that "!"? Don't we want to call the slowfn all
the time if detect_deadlock is FULL?

-- Steve


>  		rt_mutex_deadlock_account_lock(lock, current);
>  		return 0;
>  	} else
> @@ -961,55 +960,59 @@ void __sched rt_mutex_lock(struct rt_mut
>  {
>  	might_sleep();
>  
> -	rt_mutex_fastlock(lock, TASK_UNINTERRUPTIBLE, RT_MUTEX_MIN_CHAINWALK,
> -			  rt_mutex_slowlock);
> +	rt_mutex_fastlock(lock, TASK_UNINTERRUPTIBLE, rt_mutex_slowlock);
>  }
>  EXPORT_SYMBOL_GPL(rt_mutex_lock);
--
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