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Re: [PATCH -tip v8 6/7] tracing: ftrace dynamic ftrace_event_call support


On Thu, 28 May 2009, Masami Hiramatsu wrote:

> Add dynamic ftrace_event_call support to ftrace. Trace engines can adds new
> ftrace_event_call to ftrace on the fly. Each operator functions of the call
> takes a ftrace_event_call data structure as an argument, because these
> functions may be shared among several ftrace_event_calls.
> 
> Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
> Cc: Steven Rostedt <rostedt@goodmis.org>
> Cc: Ingo Molnar <mingo@elte.hu>
> Cc: Tom Zanussi <tzanussi@gmail.com>
> Cc: Frederic Weisbecker <fweisbec@gmail.com>
> ---
> 
>  include/linux/ftrace_event.h |   13 ++++++----
>  include/trace/ftrace.h       |   22 +++++++++--------
>  kernel/trace/trace_events.c  |   54 +++++++++++++++++++++++++++++-------------
>  kernel/trace/trace_export.c  |   27 ++++++++++-----------
>  4 files changed, 69 insertions(+), 47 deletions(-)
> 
> diff --git a/include/linux/ftrace_event.h b/include/linux/ftrace_event.h
> index bbf40f6..e25f3a4 100644
> --- a/include/linux/ftrace_event.h
> +++ b/include/linux/ftrace_event.h
> @@ -108,12 +108,13 @@ struct ftrace_event_call {
>  	struct dentry		*dir;
>  	struct trace_event	*event;
>  	int			enabled;
> -	int			(*regfunc)(void);
> -	void			(*unregfunc)(void);
> +	int			(*regfunc)(struct ftrace_event_call *);
> +	void			(*unregfunc)(struct ftrace_event_call *);
>  	int			id;
> -	int			(*raw_init)(void);
> -	int			(*show_format)(struct trace_seq *s);
> -	int			(*define_fields)(void);
> +	int			(*raw_init)(struct ftrace_event_call *);
> +	int			(*show_format)(struct ftrace_event_call *,
> +					       struct trace_seq *);
> +	int			(*define_fields)(struct ftrace_event_call *);
>  	struct list_head	fields;
>  	int			filter_active;
>  	void			*filter;
> @@ -138,6 +139,8 @@ extern int filter_current_check_discard(struct ftrace_event_call *call,
>  
>  extern int trace_define_field(struct ftrace_event_call *call, char *type,
>  			      char *name, int offset, int size, int is_signed);
> +extern int trace_add_event_call(struct ftrace_event_call *call);
> +extern void trace_remove_event_call(struct ftrace_event_call *call);
>  
>  #define is_signed_type(type)	(((type)(-1)) < 0)
>  
> diff --git a/include/trace/ftrace.h b/include/trace/ftrace.h
> index b4ec83a..de3ee7c 100644
> --- a/include/trace/ftrace.h
> +++ b/include/trace/ftrace.h
> @@ -229,7 +229,8 @@ ftrace_raw_output_##call(struct trace_iterator *iter, int flags)	\
>  #undef TRACE_EVENT
>  #define TRACE_EVENT(call, proto, args, tstruct, func, print)		\
>  static int								\
> -ftrace_format_##call(struct trace_seq *s)				\
> +ftrace_format_##call(struct ftrace_event_call *event_call,		\
> +		     struct trace_seq *s)				\
>  {									\
>  	struct ftrace_raw_##call field __attribute__((unused));		\
>  	int ret = 0;							\
> @@ -269,10 +270,9 @@ ftrace_format_##call(struct trace_seq *s)				\
>  #undef TRACE_EVENT
>  #define TRACE_EVENT(call, proto, args, tstruct, func, print)		\
>  int									\
> -ftrace_define_fields_##call(void)					\
> +ftrace_define_fields_##call(struct ftrace_event_call *event_call)	\
>  {									\
>  	struct ftrace_raw_##call field;					\
> -	struct ftrace_event_call *event_call = &event_##call;		\
>  	int ret;							\
>  									\
>  	__common_field(int, type, 1);					\
> @@ -298,7 +298,7 @@ ftrace_define_fields_##call(void)					\
>   *	event_trace_printk(_RET_IP_, "<call>: " <fmt>);
>   * }
>   *
> - * static int ftrace_reg_event_<call>(void)
> + * static int ftrace_reg_event_<call>(struct ftrace_event_call *dummy)

I would prefer "unused" or similar as a variable name over "dummy".

>   * {
>   *	int ret;
>   *
> @@ -309,7 +309,7 @@ ftrace_define_fields_##call(void)					\
>   *	return ret;
>   * }
>   *
> - * static void ftrace_unreg_event_<call>(void)
> + * static void ftrace_unreg_event_<call>(struct ftrace_event_call *dummy)
>   * {
>   *	unregister_trace_<call>(ftrace_event_<call>);
>   * }
> @@ -342,7 +342,7 @@ ftrace_define_fields_##call(void)					\
>   *	trace_current_buffer_unlock_commit(event, irq_flags, pc);
>   * }
>   *
> - * static int ftrace_raw_reg_event_<call>(void)
> + * static int ftrace_raw_reg_event_<call>(struct ftrace_event_call *dummy)
>   * {
>   *	int ret;
>   *
> @@ -353,7 +353,7 @@ ftrace_define_fields_##call(void)					\
>   *	return ret;
>   * }
>   *
> - * static void ftrace_unreg_event_<call>(void)
> + * static void ftrace_unreg_event_<call>(struct ftrace_event_call *dummy)
>   * {
>   *	unregister_trace_<call>(ftrace_raw_event_<call>);
>   * }
> @@ -362,7 +362,7 @@ ftrace_define_fields_##call(void)					\
>   *	.trace			= ftrace_raw_output_<call>, <-- stage 2
>   * };
>   *
> - * static int ftrace_raw_init_event_<call>(void)
> + * static int ftrace_raw_init_event_<call>(struct ftrace_event_call *dummy)
>   * {
>   *	int id;
>   *
> @@ -477,7 +477,7 @@ static void ftrace_raw_event_##call(proto)				\
>  		trace_nowake_buffer_unlock_commit(event, irq_flags, pc); \
>  }									\
>  									\
> -static int ftrace_raw_reg_event_##call(void)				\
> +static int ftrace_raw_reg_event_##call(struct ftrace_event_call *dummy)	\
>  {									\
>  	int ret;							\
>  									\
> @@ -488,7 +488,7 @@ static int ftrace_raw_reg_event_##call(void)				\
>  	return ret;							\
>  }									\
>  									\
> -static void ftrace_raw_unreg_event_##call(void)				\
> +static void ftrace_raw_unreg_event_##call(struct ftrace_event_call *dummy)\
>  {									\
>  	unregister_trace_##call(ftrace_raw_event_##call);		\
>  }									\
> @@ -497,7 +497,7 @@ static struct trace_event ftrace_event_type_##call = {			\
>  	.trace			= ftrace_raw_output_##call,		\
>  };									\
>  									\
> -static int ftrace_raw_init_event_##call(void)				\
> +static int ftrace_raw_init_event_##call(struct ftrace_event_call *dummy)\
>  {									\
>  	int id;								\
>  									\
> diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
> index 6c81f9c..5d0a324 100644
> --- a/kernel/trace/trace_events.c
> +++ b/kernel/trace/trace_events.c
> @@ -60,9 +60,7 @@ err:
>  }
>  EXPORT_SYMBOL_GPL(trace_define_field);
>  
> -#ifdef CONFIG_MODULES
> -
> -static void trace_destroy_fields(struct ftrace_event_call *call)
> +void trace_destroy_fields(struct ftrace_event_call *call)
>  {
>  	struct ftrace_event_field *field, *next;
>  
> @@ -74,8 +72,6 @@ static void trace_destroy_fields(struct ftrace_event_call *call)
>  	}
>  }
>  
> -#endif /* CONFIG_MODULES */
> -
>  static void ftrace_event_enable_disable(struct ftrace_event_call *call,
>  					int enable)
>  {
> @@ -84,14 +80,14 @@ static void ftrace_event_enable_disable(struct ftrace_event_call *call,
>  		if (call->enabled) {
>  			call->enabled = 0;
>  			tracing_stop_cmdline_record();
> -			call->unregfunc();
> +			call->unregfunc(call);
>  		}
>  		break;
>  	case 1:
>  		if (!call->enabled) {
>  			call->enabled = 1;
>  			tracing_start_cmdline_record();
> -			call->regfunc();
> +			call->regfunc(call);

Cute.

>  		}
>  		break;
>  	}
> @@ -558,7 +554,7 @@ event_format_read(struct file *filp, char __user *ubuf, size_t cnt,
>  	trace_seq_printf(s, "format:\n");
>  	trace_write_header(s);
>  
> -	r = call->show_format(s);
> +	r = call->show_format(call, s);
>  	if (!r) {
>  		/*
>  		 * ug!  The format output is bigger than a PAGE!!
> @@ -905,7 +901,7 @@ event_create_dir(struct ftrace_event_call *call, struct dentry *d_events,
>  		d_events = event_subsystem_dir(call->system, d_events);
>  
>  	if (call->raw_init) {
> -		ret = call->raw_init();
> +		ret = call->raw_init(call);
>  		if (ret < 0) {
>  			pr_warning("Could not initialize trace point"
>  				   " events/%s\n", call->name);
> @@ -929,7 +925,7 @@ event_create_dir(struct ftrace_event_call *call, struct dentry *d_events,
>  					  id);
>  
>  	if (call->define_fields) {
> -		ret = call->define_fields();
> +		ret = call->define_fields(call);
>  		if (ret < 0) {
>  			pr_warning("Could not initialize trace point"
>  				   " events/%s\n", call->name);
> @@ -949,6 +945,36 @@ event_create_dir(struct ftrace_event_call *call, struct dentry *d_events,
>  	return 0;
>  }
>  
> +/* Add an additional event_call dynamically */
> +int trace_add_event_call(struct ftrace_event_call *call)
> +{
> +	struct dentry *d_events;
> +
> +	if (!call->name)
> +		return -EINVAL;
> +
> +	d_events = event_trace_events_dir();
> +	if (!d_events)
> +		return -ENOENT;
> +
> +	list_add(&call->list, &ftrace_events);

ftrace_events needs to be protected by the event_mutex.

> +	return event_create_dir(call, d_events, &ftrace_event_id_fops,
> +				&ftrace_enable_fops, &ftrace_event_filter_fops,
> +				&ftrace_event_format_fops);
> +}
> +
> +/* Remove an event_call */
> +void trace_remove_event_call(struct ftrace_event_call *event_call)
> +{
> +	ftrace_event_enable_disable(event_call, 0);
> +	if (event_call->event)
> +		unregister_ftrace_event(event_call->event);
> +	debugfs_remove_recursive(event_call->dir);
> +	list_del(&event_call->list);

Same here.

> +	trace_destroy_fields(event_call);
> +	destroy_preds(event_call);
> +}
> +
>  #define for_each_event(event, start, end)			\
>  	for (event = start;					\
>  	     (unsigned long)event < (unsigned long)end;		\
> @@ -1053,13 +1079,7 @@ static void trace_module_remove_events(struct module *mod)
>  	list_for_each_entry_safe(call, p, &ftrace_events, list) {
>  		if (call->mod == mod) {
>  			found = true;
> -			ftrace_event_enable_disable(call, 0);
> -			if (call->event)
> -				unregister_ftrace_event(call->event);
> -			debugfs_remove_recursive(call->dir);
> -			list_del(&call->list);
> -			trace_destroy_fields(call);
> -			destroy_preds(call);
> +			trace_remove_event_call(call);

We'll need a version that does not take the event_mutex, because it is 
held at this point.

-- Steve

>  		}
>  	}
>  
> diff --git a/kernel/trace/trace_export.c b/kernel/trace/trace_export.c
> index d06cf89..7cee79d 100644
> --- a/kernel/trace/trace_export.c
> +++ b/kernel/trace/trace_export.c
> @@ -60,7 +60,7 @@ extern void __bad_type_size(void);
>  #undef TRACE_EVENT_FORMAT
>  #define TRACE_EVENT_FORMAT(call, proto, args, fmt, tstruct, tpfmt)	\
>  static int								\
> -ftrace_format_##call(struct trace_seq *s)				\
> +ftrace_format_##call(struct ftrace_event_call *dummy, struct trace_seq *s)\
>  {									\
>  	struct args field;						\
>  	int ret;							\
> @@ -76,7 +76,7 @@ ftrace_format_##call(struct trace_seq *s)				\
>  #define TRACE_EVENT_FORMAT_NOFILTER(call, proto, args, fmt, tstruct,	\
>  				    tpfmt)				\
>  static int								\
> -ftrace_format_##call(struct trace_seq *s)				\
> +ftrace_format_##call(struct ftrace_event_call *dummy, struct trace_seq *s)\
>  {									\
>  	struct args field;						\
>  	int ret;							\
> @@ -115,10 +115,16 @@ ftrace_format_##call(struct trace_seq *s)				\
>  #define TRACE_FIELD_SPECIAL(type_item, item, len, cmd)	\
>  	cmd;
>  
> +static int ftrace_raw_init_event(struct ftrace_event_call *event_call)
> +{
> +	INIT_LIST_HEAD(&event_call->fields);
> +	init_preds(event_call);
> +	return 0;
> +}
> +
>  #undef TRACE_EVENT_FORMAT
>  #define TRACE_EVENT_FORMAT(call, proto, args, fmt, tstruct, tpfmt)	\
> -int ftrace_define_fields_##call(void);					\
> -static int ftrace_raw_init_event_##call(void);				\
> +int ftrace_define_fields_##call(struct ftrace_event_call *c);		\
>  									\
>  struct ftrace_event_call __used						\
>  __attribute__((__aligned__(4)))						\
> @@ -126,16 +132,10 @@ __attribute__((section("_ftrace_events"))) event_##call = {		\
>  	.name			= #call,				\
>  	.id			= proto,				\
>  	.system			= __stringify(TRACE_SYSTEM),		\
> -	.raw_init		= ftrace_raw_init_event_##call,		\
> +	.raw_init		= ftrace_raw_init_event,		\
>  	.show_format		= ftrace_format_##call,			\
>  	.define_fields		= ftrace_define_fields_##call,		\
> -};									\
> -static int ftrace_raw_init_event_##call(void)				\
> -{									\
> -	INIT_LIST_HEAD(&event_##call.fields);				\
> -	init_preds(&event_##call);					\
> -	return 0;							\
> -}									\
> +};
>  
>  #undef TRACE_EVENT_FORMAT_NOFILTER
>  #define TRACE_EVENT_FORMAT_NOFILTER(call, proto, args, fmt, tstruct,	\
> @@ -182,9 +182,8 @@ __attribute__((section("_ftrace_events"))) event_##call = {		\
>  #undef TRACE_EVENT_FORMAT
>  #define TRACE_EVENT_FORMAT(call, proto, args, fmt, tstruct, tpfmt)	\
>  int									\
> -ftrace_define_fields_##call(void)					\
> +ftrace_define_fields_##call(struct ftrace_event_call *event_call)	\
>  {									\
> -	struct ftrace_event_call *event_call = &event_##call;		\
>  	struct args field;						\
>  	int ret;							\
>  									\
> 
> 
> -- 
> Masami Hiramatsu
> 
> Software Engineer
> Hitachi Computer Products (America), Inc.
> Software Solutions Division
> 
> e-mail: mhiramat@redhat.com
> 


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