Re: [PATCH 1/4] Extend notifier_call_chain to count nr_calls made.

Randy Dunlap
2006-11-14T18:18:52Z

On Tue, 14 Nov 2006 17:50:51 +0530 Gautham R Shenoy wrote:

> Provide notifier_call_chain with an option to call only a specified number of
> notifiers and also record the number of call to notifiers made.
>
> The need for this enhancement was identified in the post entitled
> "Slab - Eliminate lock_cpu_hotplug from slab"
> (http://lkml.org/lkml/2006/10/28/92) by Ravikiran G Thirumalai and
> Andrew Morton.
>
> This patch adds two additional parameters to notifier_call_chain API namely
> - int nr_to_calls : Number of notifier_functions to be called.
> The don't care value is -1.
>
> - unsigned int *nr_calls : Records the total number of notifier_funtions
> called by notifier_call_chain. The don't care
> value is NULL.

Those could (should?) be the same data type.

> Credit : Andrew Morton <akpm@osdl.org>
> Signed-off-by: Gautham R Shenoy <ego@in.ibm.com>
>
> --
> include/linux/notifier.h | 8 +++
> kernel/sys.c | 97 +++++++++++++++++++++++++++++++++++++++-------- 2 files changed, 89 insertions(+), 16 deletions(-)
>
> Index: hotplug/kernel/sys.c
> ===================================================================
> --- hotplug.orig/kernel/sys.c
> +++ hotplug/kernel/sys.c
> @@ -134,19 +134,41 @@ static int notifier_chain_unregister(str
> return -ENOENT;
> }
>
> +/*
> + * notifier_call_chain - Informs the registered notifiers about an event.
> + *
> + * @nl: Pointer to head of the blocking notifier chain
> + * @val: Value passed unmodified to notifier function
> + * @v: Pointer passed unmodified to notifier function
> + * @nr_to_call: Number of notifier functions to be called. Don't care
> + * value of this parameter is -1.
> + * @nr_calls: Records the number of notifications sent. Don't care
> + * value of this field is NULL.
> + *
> + * RETURN VALUE: notifier_call_chain returns the value returned by the
> + * last notifier function called.
> + */

You can make that comment block be kernel-doc format by using
/**
as the comment introduction and removing the blank line after the
function name & short description.

> static int __kprobes notifier_call_chain(struct notifier_block **nl,
> - unsigned long val, void *v)
> + unsigned long val, void *v,
> + int nr_to_call, unsigned int *nr_calls)
> {
> int ret = NOTIFY_DONE;
> struct notifier_block *nb, *next_nb;
...
> }
> @@ -205,10 +227,13 @@ int atomic_notifier_chain_unregister(str
> EXPORT_SYMBOL_GPL(atomic_notifier_chain_unregister);
>
> /**
> - * atomic_notifier_call_chain - Call functions in an atomic notifier chain
> + * __atomic_notifier_call_chain - Call functions in an atomic notifier
> + * chain

Don't break the short function description line; kernel-doc does not
support that.

> * @nh: Pointer to head of the atomic notifier chain
> * @val: Value passed unmodified to notifier function
> * @v: Pointer passed unmodified to notifier function
> + * @nr_to_call: See the comment for notifier_call_chain.
> + * @nr_calls: See the comment for notifier_call_chain.
> *
> * Calls each function in a notifier chain in turn. The functions
> * run in an atomic context, so they must not block.
> @@ -222,19 +247,27 @@ EXPORT_SYMBOL_GPL(atomic_notifier_chain_
> * of the last notifier function called.
> */
>
> -int __kprobes atomic_notifier_call_chain(struct atomic_notifier_head *nh,
> - unsigned long val, void *v)
> +int __kprobes __atomic_notifier_call_chain(struct atomic_notifier_head *nh,
> + unsigned long val, void *v,
> + int nr_to_call, unsigned int *nr_calls)
> {
...
> }
>
> -EXPORT_SYMBOL_GPL(atomic_notifier_call_chain);
> +EXPORT_SYMBOL_GPL(__atomic_notifier_call_chain);
>
> +int __kprobes atomic_notifier_call_chain(struct atomic_notifier_head *nh,
> + unsigned long val, void *v)
> +{
> + return __atomic_notifier_call_chain(nh, val, v, -1, NULL);
> +}
> +
> +EXPORT_SYMBOL_GPL(atomic_notifier_call_chain);
> /*
> * Blocking notifier chain routines. All access to the chain is
> * synchronized by an rwsem.
> @@ -304,10 +337,13 @@ int blocking_notifier_chain_unregister(s
> EXPORT_SYMBOL_GPL(blocking_notifier_chain_unregister);
>
> /**
> - * blocking_notifier_call_chain - Call functions in a blocking notifier chain
> + * __blocking_notifier_call_chain - Call functions in a blocking notifier
> + * chain

kernel-doc requires that the function description fit on one source line,
so don't break it (even if it is > 80 columns; yes, I know it needs to be
fixed)

> * @nh: Pointer to head of the blocking notifier chain
> * @val: Value passed unmodified to notifier function
> * @v: Pointer passed unmodified to notifier function
> + * @nr_to_call: See comment for notifier_call_chain.
> + * @nr_calls: See comment for notifier_call_chain.
> *
> * Calls each function in a notifier chain in turn. The functions
> * run in a process context, so they are allowed to block.

> Index: hotplug/include/linux/notifier.h
> ===================================================================
> --- hotplug.orig/include/linux/notifier.h
> +++ hotplug/include/linux/notifier.h
> @@ -132,12 +132,20 @@ extern int srcu_notifier_chain_unregiste
>
> extern int atomic_notifier_call_chain(struct atomic_notifier_head *,
> unsigned long val, void *v);
> +extern int __atomic_notifier_call_chain(struct atomic_notifier_head *,

While you are changing these lines, please put a prototype parameter
name for all parameters; i.e., add something like "notifier"
or "nh" after the '*' on all of these.

> + unsigned long val, void *v, int nr_to_call, unsigned int *nr_calls);
> extern int blocking_notifier_call_chain(struct blocking_notifier_head *,
> unsigned long val, void *v);
> +extern int __blocking_notifier_call_chain(struct blocking_notifier_head *,
> + unsigned long val, void *v, int nr_to_call, unsigned int *nr_calls);
> extern int raw_notifier_call_chain(struct raw_notifier_head *,
> unsigned long val, void *v);
> +extern int __raw_notifier_call_chain(struct raw_notifier_head *,
> + unsigned long val, void *v, int nr_to_call, unsigned int *nr_calls);
> extern int srcu_notifier_call_chain(struct srcu_notifier_head *,
> unsigned long val, void *v);
> +extern int __srcu_notifier_call_chain(struct srcu_notifier_head *,
> + unsigned long val, void *v, int nr_to_call, unsigned int *nr_calls);
>
> #define NOTIFY_DONE 0x0000 /* Don't care */
> #define NOTIFY_OK 0x0001 /* Suits me */
> --

---
~Randy