linux-kernel - Re: [PATCH 2/3] rtmutex: Add rt_mutex_init

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Date:	Mon, 14 Mar 2016 14:16:21 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Davidlohr Bueso <dave@...olabs.net>
Cc:	tglx@...utronix.de, mingo@...nel.org, bigeasy@...utronix.de,
	umgwanakikbuti@...il.com, paulmck@...ux.vnet.ibm.com,
	linux-kernel@...r.kernel.org, Davidlohr Bueso <dbueso@...e.de>
Subject: Re: [PATCH 2/3] rtmutex: Add rt_mutex_init_waiter helper

On Tue, Mar 08, 2016 at 10:20:22AM -0800, Davidlohr Bueso wrote:

> +++ b/kernel/futex.c
> @@ -2778,10 +2778,7 @@ static int futex_wait_requeue_pi(u32 __user *uaddr, unsigned int flags,
>  	 * The waiter is allocated on our stack, manipulated by the requeue
>  	 * code while we sleep on uaddr.
>  	 */
> -	debug_rt_mutex_init_waiter(&rt_waiter);
> -	RB_CLEAR_NODE(&rt_waiter.pi_tree_entry);
> -	RB_CLEAR_NODE(&rt_waiter.tree_entry);
> -	rt_waiter.task = NULL;
> +	rt_mutex_init_waiter(&rt_waiter);
>  
>  	ret = get_futex_key(uaddr2, flags & FLAGS_SHARED, &key2, VERIFY_WRITE);
>  	if (unlikely(ret != 0))


> +static inline void
> +rt_mutex_init_waiter(struct rt_mutex_waiter *waiter)
> +{
> +       debug_rt_mutex_init_waiter(waiter);
> +
> +       RB_CLEAR_NODE(&waiter->pi_tree_entry);
> +       RB_CLEAR_NODE(&waiter->tree_entry);
> +       waiter->task = NULL;
> +}


Just thinking, would not something like:

#define DEFINE_RT_WAITER(name)					\
  struct rt_mutex_waiter name = {				\
	.tree_entry = __INIT_RB_NODE(name.tree_entry),		\
	.pi_tree_entry = __INIT_RB_NODE(name.pi_tree_entry),	\
	__INIT_RT_WAITER_DEBUG(name)				\
  }

Be nicer? That way we're sure the whole structure is initialized.