linux-kernel - Re: [PATCH 2/3] kernel/SRCU: provide a static initializer

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Date:	Fri, 05 Apr 2013 15:21:29 +0800
From:	Lai Jiangshan <laijs@...fujitsu.com>
To:	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
CC:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org, tglx@...utronix.de
Subject: Re: [PATCH 2/3] kernel/SRCU: provide a static initializer



On 03/19/2013 10:16 PM, Sebastian Andrzej Siewior wrote:
> There are macros for static initializer for the three out of four
> possible notifier types, that are:
> 	ATOMIC_NOTIFIER_HEAD()
> 	BLOCKING_NOTIFIER_HEAD()
> 	RAW_NOTIFIER_HEAD()
> 
> This patch provides a static initilizer for the forth type to make it
> complete.
> 
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
> ---
>  include/linux/notifier.h |   26 +++++++++++++++++++++-----
>  include/linux/srcu.h     |    6 +++---
>  2 files changed, 24 insertions(+), 8 deletions(-)
> 
> diff --git a/include/linux/notifier.h b/include/linux/notifier.h
> index d65746e..6bfd703 100644
> --- a/include/linux/notifier.h
> +++ b/include/linux/notifier.h
> @@ -42,9 +42,7 @@
>   * in srcu_notifier_call_chain(): no cache bounces and no memory barriers.
>   * As compensation, srcu_notifier_chain_unregister() is rather expensive.
>   * SRCU notifier chains should be used when the chain will be called very
> - * often but notifier_blocks will seldom be removed.  Also, SRCU notifier
> - * chains are slightly more difficult to use because they require special
> - * runtime initialization.
> + * often but notifier_blocks will seldom be removed.
>   */
>  
>  struct notifier_block {
> @@ -85,7 +83,7 @@ struct srcu_notifier_head {
>  		(name)->head = NULL;		\
>  	} while (0)
>  
> -/* srcu_notifier_heads must be initialized and cleaned up dynamically */
> +/* srcu_notifier_heads must be cleaned up dynamically */
>  extern void srcu_init_notifier_head(struct srcu_notifier_head *nh);
>  #define srcu_cleanup_notifier_head(name)	\
>  		cleanup_srcu_struct(&(name)->srcu);
> @@ -98,7 +96,13 @@ extern void srcu_init_notifier_head(struct srcu_notifier_head *nh);
>  		.head = NULL }
>  #define RAW_NOTIFIER_INIT(name)	{				\
>  		.head = NULL }
> -/* srcu_notifier_heads cannot be initialized statically */
> +
> +#define SRCU_NOTIFIER_INIT(name, pcpu)				\
> +	{							\
> +		.mutex = __MUTEX_INITIALIZER(name.mutex),	\
> +		.head = NULL,					\
> +		.srcu = __SRCU_STRUCT_INIT(name.srcu, pcpu),	\
> +	}


Hi, Sebastian

I don't want to expose __SRCU_STRUCT_INIT(),
due to it has strong coupling with the percpu array.

I hope other structure which uses SRCU should use init_srcu_struct().

Thanks,
Lai

>  
>  #define ATOMIC_NOTIFIER_HEAD(name)				\
>  	struct atomic_notifier_head name =			\
> @@ -110,6 +114,18 @@ extern void srcu_init_notifier_head(struct srcu_notifier_head *nh);
>  	struct raw_notifier_head name =				\
>  		RAW_NOTIFIER_INIT(name)
>  
> +#define _SRCU_NOTIFIER_HEAD(name, mod)				\
> +	static DEFINE_PER_CPU(struct srcu_struct_array,		\
> +			name##_head_srcu_array);		\
> +	mod struct srcu_notifier_head name =			\
> +			SRCU_NOTIFIER_INIT(name, name##_head_srcu_array)
> +
> +#define SRCU_NOTIFIER_HEAD(name)				\
> +	_SRCU_NOTIFIER_HEAD(name, )
> +
> +#define SRCU_NOTIFIER_HEAD_STATIC(name)				\
> +	_SRCU_NOTIFIER_HEAD(name, static)
> +
>  #ifdef __KERNEL__
>  
>  extern int atomic_notifier_chain_register(struct atomic_notifier_head *nh,
> diff --git a/include/linux/srcu.h b/include/linux/srcu.h
> index d04acb8..fe9efd4 100644
> --- a/include/linux/srcu.h
> +++ b/include/linux/srcu.h
> @@ -84,10 +84,10 @@ int init_srcu_struct(struct srcu_struct *sp);
>  
>  void process_srcu(struct work_struct *work);
>  
> -#define __SRCU_STRUCT_INIT(name)					\
> +#define __SRCU_STRUCT_INIT(name, pcpu_name)				\
>  	{								\
>  		.completed = -300,					\
> -		.per_cpu_ref = &name##_srcu_array,			\
> +		.per_cpu_ref = &pcpu_name,				\
>  		.queue_lock = __SPIN_LOCK_UNLOCKED(name.queue_lock),	\
>  		.running = false,					\
>  		.batch_queue = RCU_BATCH_INIT(name.batch_queue),	\
> @@ -105,7 +105,7 @@ void process_srcu(struct work_struct *work);
>  #define _DEFINE_SRCU(name, mod)						\
>  	static DEFINE_PER_CPU(struct srcu_struct_array, name##_srcu_array);\
>  	mod struct srcu_struct name =					\
> -				__SRCU_STRUCT_INIT(name);
> +				__SRCU_STRUCT_INIT(name, name##_srcu_array);
>  
>  #define DEFINE_SRCU(name)		_DEFINE_SRCU(name, )
>  #define DEFINE_STATIC_SRCU(name)	_DEFINE_SRCU(name, static)

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