Re: [PATCH tip 1/1] trace: assign defaults at register_ftrace_event

[Frederic Weisbecker <fweisbec@gmail.com>]

On Wed, Feb 04, 2009 at 08:16:39PM -0200, Arnaldo Carvalho de Melo wrote:
> Impact: simplification of tracers
> 
> As all tracers are doing this we might as well do it in
> register_ftrace_event and save one branch each time we call these
> callbacks.
> 
> Cc: Ingo Molnar <mingo@elte.hu>
> Cc: Frédéric Weisbecker <fweisbec@gmail.com>
> Cc: Jens Axboe <jens.axboe@oracle.com>
> Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
> ---
>  block/blktrace.c            |    2 --
>  kernel/trace/trace.c        |   13 +++++--------
>  kernel/trace/trace_branch.c |    3 ---
>  kernel/trace/trace_output.c |   13 +++++++++++--
>  4 files changed, 16 insertions(+), 15 deletions(-)
> 
> diff --git a/block/blktrace.c b/block/blktrace.c
> index c7698d1..1ebd068 100644
> --- a/block/blktrace.c
> +++ b/block/blktrace.c
> @@ -1243,8 +1243,6 @@ static struct trace_event trace_blk_event = {
>  	.type	 	= TRACE_BLK,
>  	.trace		= blk_trace_event_print,
>  	.latency_trace	= blk_trace_event_print,
> -	.raw		= trace_nop_print,
> -	.hex		= trace_nop_print,
>  	.binary		= blk_trace_event_print_binary,
>  };
>  
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index fd51cf0..a5e4c0a 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -1412,7 +1412,7 @@ static enum print_line_t print_lat_fmt(struct trace_iterator *iter)
>  			goto partial;
>  	}
>  
> -	if (event && event->latency_trace)
> +	if (event)
>  		return event->latency_trace(iter, sym_flags);
>  
>  	if (!trace_seq_printf(s, "Unknown type %d\n", entry->type))
> @@ -1441,7 +1441,7 @@ static enum print_line_t print_trace_fmt(struct trace_iterator *iter)
>  			goto partial;
>  	}
>  
> -	if (event && event->trace)
> +	if (event)
>  		return event->trace(iter, sym_flags);
>  
>  	if (!trace_seq_printf(s, "Unknown type %d\n", entry->type))
> @@ -1467,7 +1467,7 @@ static enum print_line_t print_raw_fmt(struct trace_iterator *iter)
>  	}
>  
>  	event = ftrace_find_event(entry->type);
> -	if (event && event->raw)
> +	if (event)
>  		return event->raw(iter, 0);
>  
>  	if (!trace_seq_printf(s, "%d ?\n", entry->type))
> @@ -1494,7 +1494,7 @@ static enum print_line_t print_hex_fmt(struct trace_iterator *iter)
>  	}
>  
>  	event = ftrace_find_event(entry->type);
> -	if (event && event->hex) {
> +	if (event) {
>  		enum print_line_t ret = event->hex(iter, 0);
>  		if (ret != TRACE_TYPE_HANDLED)
>  			return ret;
> @@ -1536,10 +1536,7 @@ static enum print_line_t print_bin_fmt(struct trace_iterator *iter)
>  	}
>  
>  	event = ftrace_find_event(entry->type);
> -	if (event && event->binary)
> -		return event->binary(iter, 0);
> -
> -	return TRACE_TYPE_HANDLED;
> +	return event ? event->binary(iter, 0) : TRACE_TYPE_HANDLED;
>  }
>  
>  static int trace_empty(struct trace_iterator *iter)
> diff --git a/kernel/trace/trace_branch.c b/kernel/trace/trace_branch.c
> index 7ac72a4..297deb2 100644
> --- a/kernel/trace/trace_branch.c
> +++ b/kernel/trace/trace_branch.c
> @@ -182,9 +182,6 @@ static struct trace_event trace_branch_event = {
>  	.type	 	= TRACE_BRANCH,
>  	.trace		= trace_branch_print,
>  	.latency_trace	= trace_branch_print,
> -	.raw		= trace_nop_print,
> -	.hex		= trace_nop_print,
> -	.binary		= trace_nop_print,
>  };
>  
>  static struct tracer branch_trace __read_mostly =
> diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c
> index b7380ee..b6e99af 100644
> --- a/kernel/trace/trace_output.c
> +++ b/kernel/trace/trace_output.c
> @@ -435,6 +435,17 @@ int register_ftrace_event(struct trace_event *event)
>  	if (ftrace_find_event(event->type))
>  		goto out;
>  
> +	if (event->trace == NULL)
> +		event->trace = trace_nop_print;
> +	if (event->latency_trace == NULL)
> +		event->latency_trace = trace_nop_print;
> +	if (event->raw == NULL)
> +		event->raw = trace_nop_print;
> +	if (event->hex == NULL)
> +		event->hex = trace_nop_print;
> +	if (event->binary == NULL)
> +		event->binary = trace_nop_print;
> +
>  	key = event->type & (EVENT_HASHSIZE - 1);
>  
>  	hlist_add_head_rcu(&event->node, &event_hash[key]);
> @@ -874,8 +885,6 @@ static struct trace_event trace_print_event = {
>  	.trace		= trace_print_print,
>  	.latency_trace	= trace_print_print,
>  	.raw		= trace_print_raw,
> -	.hex		= trace_nop_print,
> -	.binary		= trace_nop_print,
>  };
>  
>  static struct trace_event *events[] __initdata = {
> -- 
> 1.6.0.6
> 


Nice! This avoids one branch for each entry printed.