linux-kernel - Re: [PATCH 20/48] perf tools: Make ordered

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Date:	Wed, 24 Feb 2016 15:18:45 +0100
From:	Jiri Olsa <jolsa@...hat.com>
To:	Wang Nan <wangnan0@...wei.com>
Cc:	Alexei Starovoitov <ast@...nel.org>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Brendan Gregg <brendan.d.gregg@...il.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Cody P Schafer <dev@...yps.com>,
	"David S. Miller" <davem@...emloft.net>,
	He Kuang <hekuang@...wei.com>,
	Jérémie Galarneau 
	<jeremie.galarneau@...icios.com>, Jiri Olsa <jolsa@...nel.org>,
	Kirill Smelkov <kirr@...edi.com>,
	Li Zefan <lizefan@...wei.com>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Namhyung Kim <namhyung@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>, pi3orama@....com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 20/48] perf tools: Make ordered_events reusable

On Mon, Feb 22, 2016 at 09:10:47AM +0000, Wang Nan wrote:
> ordered_events__free() leaves linked lists and timestamps not cleared,
> so unable to be reused after ordered_events__free(). Which is inconvenient
> after 'perf record' supports generating multiple perf.data output and
> process build-ids for each of them.
> 
> Calls ordered_events__init() in ordered_events__free() so ordered_events
> can be reused.
> 
> Signed-off-by: Wang Nan <wangnan0@...wei.com>
> Signed-off-by: He Kuang <hekuang@...wei.com>
> Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
> Cc: Jiri Olsa <jolsa@...nel.org>
> Cc: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
> Cc: Namhyung Kim <namhyung@...nel.org>
> Cc: Zefan Li <lizefan@...wei.com>
> Cc: pi3orama@....com
> ---
>  tools/perf/util/ordered-events.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/tools/perf/util/ordered-events.c b/tools/perf/util/ordered-events.c
> index b1b9e23..70c0dc8 100644
> --- a/tools/perf/util/ordered-events.c
> +++ b/tools/perf/util/ordered-events.c
> @@ -299,6 +299,8 @@ void ordered_events__init(struct ordered_events *oe, ordered_events__deliver_t d
>  
>  void ordered_events__free(struct ordered_events *oe)
>  {
> +	ordered_events__deliver_t old_deliver = oe->deliver;
> +
>  	while (!list_empty(&oe->to_free)) {
>  		struct ordered_event *event;
>  
> @@ -307,4 +309,7 @@ void ordered_events__free(struct ordered_events *oe)
>  		free_dup_event(oe, event->event);
>  		free(event);
>  	}
> +
> +	memset(oe, '\0', sizeof(*oe));
> +	ordered_events__init(oe, old_deliver);
>  }

I think it'd be better to put that memset call into ordered_events__init

and introduce ordered_events__reinit that calls ordered_events__free
and ordered_events__init with oe->deliver as you do above

that way it'll be apparent when you reuse the ordered_events struct

thanks,
jirka