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SubjectRe: [PATCH 1/2] kernel/SRCU: provide a static initializer
On Fri, May 25, 2018 at 12:19 PM, Sebastian Andrzej Siewior
<bigeasy@linutronix.de> 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.
>
> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

I cannot apply this without an ACK from Paul.

> ---
> include/linux/notifier.h | 34 +++++++++++++++++++++++++++++-----
> include/linux/srcutiny.h | 6 +++---
> include/linux/srcutree.h | 6 +++---
> 3 files changed, 35 insertions(+), 11 deletions(-)
>
> diff --git a/include/linux/notifier.h b/include/linux/notifier.h
> index 6d731110e0db..f35c7bf76143 100644
> --- a/include/linux/notifier.h
> +++ b/include/linux/notifier.h
> @@ -43,9 +43,7 @@
> * 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;
> @@ -91,7 +89,7 @@ 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);
> @@ -104,7 +102,13 @@ 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), \
> + }
>
> #define ATOMIC_NOTIFIER_HEAD(name) \
> struct atomic_notifier_head name = \
> @@ -116,6 +120,26 @@ extern void srcu_init_notifier_head(struct srcu_notifier_head *nh);
> struct raw_notifier_head name = \
> RAW_NOTIFIER_INIT(name)
>
> +#ifdef CONFIG_TREE_SRCU
> +#define _SRCU_NOTIFIER_HEAD(name, mod) \
> + static DEFINE_PER_CPU(struct srcu_data, \
> + name##_head_srcu_data); \
> + mod struct srcu_notifier_head name = \
> + SRCU_NOTIFIER_INIT(name, name##_head_srcu_data)
> +
> +#else
> +#define _SRCU_NOTIFIER_HEAD(name, mod) \
> + mod struct srcu_notifier_head name = \
> + SRCU_NOTIFIER_INIT(name, name)
> +
> +#endif
> +
> +#define SRCU_NOTIFIER_HEAD(name) \
> + _SRCU_NOTIFIER_HEAD(name, /* not static */)
> +
> +#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/srcutiny.h b/include/linux/srcutiny.h
> index 261471f407a5..f41d2fb09f87 100644
> --- a/include/linux/srcutiny.h
> +++ b/include/linux/srcutiny.h
> @@ -43,7 +43,7 @@ struct srcu_struct {
>
> void srcu_drive_gp(struct work_struct *wp);
>
> -#define __SRCU_STRUCT_INIT(name) \
> +#define __SRCU_STRUCT_INIT(name, __ignored) \
> { \
> .srcu_wq = __SWAIT_QUEUE_HEAD_INITIALIZER(name.srcu_wq), \
> .srcu_cb_tail = &name.srcu_cb_head, \
> @@ -56,9 +56,9 @@ void srcu_drive_gp(struct work_struct *wp);
> * Tree SRCU, which needs some per-CPU data.
> */
> #define DEFINE_SRCU(name) \
> - struct srcu_struct name = __SRCU_STRUCT_INIT(name)
> + struct srcu_struct name = __SRCU_STRUCT_INIT(name, name)
> #define DEFINE_STATIC_SRCU(name) \
> - static struct srcu_struct name = __SRCU_STRUCT_INIT(name)
> + static struct srcu_struct name = __SRCU_STRUCT_INIT(name, name)
>
> void synchronize_srcu(struct srcu_struct *sp);
>
> diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h
> index 4eda108abee0..745d4ca4dd50 100644
> --- a/include/linux/srcutree.h
> +++ b/include/linux/srcutree.h
> @@ -104,9 +104,9 @@ struct srcu_struct {
> #define SRCU_STATE_SCAN1 1
> #define SRCU_STATE_SCAN2 2
>
> -#define __SRCU_STRUCT_INIT(name) \
> +#define __SRCU_STRUCT_INIT(name, pcpu_name) \
> { \
> - .sda = &name##_srcu_data, \
> + .sda = &pcpu_name, \
> .lock = __SPIN_LOCK_UNLOCKED(name.lock), \
> .srcu_gp_seq_needed = 0 - 1, \
> __SRCU_DEP_MAP_INIT(name) \
> @@ -133,7 +133,7 @@ struct srcu_struct {
> */
> #define __DEFINE_SRCU(name, is_static) \
> static DEFINE_PER_CPU(struct srcu_data, name##_srcu_data);\
> - is_static struct srcu_struct name = __SRCU_STRUCT_INIT(name)
> + is_static struct srcu_struct name = __SRCU_STRUCT_INIT(name, name##_srcu_data)
> #define DEFINE_SRCU(name) __DEFINE_SRCU(name, /* not static */)
> #define DEFINE_STATIC_SRCU(name) __DEFINE_SRCU(name, static)
>
> --
> 2.17.0
>

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