linux-kernel - Re: [PATCH -mm 2/4] llist, Define macro to check NMI safe cmpxchg

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Date:	Tue, 6 Sep 2011 06:50:26 -0400
From:	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To:	Huang Ying <ying.huang@...el.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, Andi Kleen <andi@...stfloor.org>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH -mm 2/4] llist, Define macro to check NMI safe cmpxchg

* Huang Ying (ying.huang@...el.com) wrote:
> To make code cleaner and reduce code duplication.  Thanks Peter
> Zijlstra for reminding.
> 
> Signed-off-by: Huang Ying <ying.huang@...el.com>
> Cc: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
> Cc: Peter Zijlstra <peterz@...radead.org>
> ---
>  include/linux/llist.h |   22 ++++++++++------------
>  1 file changed, 10 insertions(+), 12 deletions(-)
> 
> --- a/include/linux/llist.h
> +++ b/include/linux/llist.h
> @@ -70,6 +70,12 @@ struct llist_node {
>  #define LLIST_HEAD_INIT(name)	{ NULL }
>  #define LLIST_HEAD(name)	struct llist_head name = LLIST_HEAD_INIT(name)
>  
> +#ifdef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG
> +#define CHECK_NMI_SAFE_CMPXCHG()

Does it have to be in caps ? And can it be turned into a static inline
function ? I'm thinking about something close to might_sleep().

Thanks,

Mathieu

> +#else
> +#define CHECK_NMI_SAFE_CMPXCHG()	BUG_ON(in_nmi())
> +#endif
> +
>  /**
>   * init_llist_head - initialize lock-less list head
>   * @head:	the head for your lock-less list
> @@ -147,9 +153,7 @@ static inline void llist_add(struct llis
>  {
>  	struct llist_node *entry, *old_entry;
>  
> -#ifndef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG
> -	BUG_ON(in_nmi());
> -#endif
> +	CHECK_NMI_SAFE_CMPXCHG();
>  
>  	entry = head->first;
>  	do {
> @@ -171,9 +175,7 @@ static inline void llist_add_batch(struc
>  {
>  	struct llist_node *entry, *old_entry;
>  
> -#ifndef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG
> -	BUG_ON(in_nmi());
> -#endif
> +	CHECK_NMI_SAFE_CMPXCHG();
>  
>  	entry = head->first;
>  	do {
> @@ -201,9 +203,7 @@ static inline struct llist_node *llist_d
>  {
>  	struct llist_node *entry, *old_entry, *next;
>  
> -#ifndef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG
> -	BUG_ON(in_nmi());
> -#endif
> +	CHECK_NMI_SAFE_CMPXCHG();
>  
>  	entry = head->first;
>  	do {
> @@ -227,9 +227,7 @@ static inline struct llist_node *llist_d
>   */
>  static inline struct llist_node *llist_del_all(struct llist_head *head)
>  {
> -#ifndef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG
> -	BUG_ON(in_nmi());
> -#endif
> +	CHECK_NMI_SAFE_CMPXCHG();
>  
>  	return xchg(&head->first, NULL);
>  }

-- 
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com
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