linux-kernel - Re: [PATCH v10 07/10] perf record: Read from overwritable ring buffer

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Date:	Thu, 23 Jun 2016 12:38:09 -0500
From:	Nilay Vaish <nilayvaish@...il.com>
To:	pi3orama <pi3orama@....com>
Cc:	Wang Nan <wangnan0@...wei.com>, acme@...nel.org,
	Linux Kernel list <linux-kernel@...r.kernel.org>,
	He Kuang <hekuang@...wei.com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Jiri Olsa <jolsa@...nel.org>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Zefan Li <lizefan@...wei.com>
Subject: Re: [PATCH v10 07/10] perf record: Read from overwritable ring buffer

On 23 June 2016 at 09:31, pi3orama <pi3orama@....com> wrote:
>
>
> 发自我的 iPhone
>
>> 在 2016年6月23日，下午10:27，Nilay Vaish <nilayvaish@...il.com> 写道：
>>
>>> On 23 June 2016 at 00:27, Wang Nan <wangnan0@...wei.com> wrote:
>>> @@ -542,6 +568,79 @@ static struct perf_event_header finished_round_event = {
>>>        .type = PERF_RECORD_FINISHED_ROUND,
>>> };
>>>
>>> +static void
>>> +record__toggle_overwrite_evsels(struct record *rec,
>>> +                               enum overwrite_evt_state state)
>>> +{
>>> +       struct perf_evlist *evlist = rec->overwrite_evlist;
>>> +       enum overwrite_evt_state old_state = rec->overwrite_evt_state;
>>> +       enum action {
>>> +               NONE,
>>> +               PAUSE,
>>> +               RESUME,
>>> +       } action = NONE;
>>> +
>>> +       switch (old_state) {
>>> +       case OVERWRITE_EVT_RUNNING: {
>>> +               switch (state) {
>>> +               case OVERWRITE_EVT_DATA_PENDING:
>>> +                       action = PAUSE;
>>> +                       break;
>>> +               case OVERWRITE_EVT_RUNNING:
>>> +               case OVERWRITE_EVT_EMPTY:
>>> +               default:
>>> +                       goto state_err;
>>> +               }
>>> +               break;
>>> +       }
>>> +       case OVERWRITE_EVT_DATA_PENDING: {
>>> +               switch (state) {
>>> +               case OVERWRITE_EVT_EMPTY:
>>> +                       break;
>>> +               case OVERWRITE_EVT_RUNNING:
>>> +               case OVERWRITE_EVT_DATA_PENDING:
>>> +               default:
>>> +                       goto state_err;
>>> +               }
>>> +               break;
>>> +       }
>>> +       case OVERWRITE_EVT_EMPTY: {
>>> +               switch (state) {
>>> +               case OVERWRITE_EVT_RUNNING:
>>> +                       action = RESUME;
>>> +                       break;
>>> +               case OVERWRITE_EVT_EMPTY:
>>> +               case OVERWRITE_EVT_DATA_PENDING:
>>> +               default:
>>> +                       goto state_err;
>>
>>
>> Wang, thanks for making the changes I suggested.
>> The patch overall looks fine to me.  Just as a matter
>> of style, I probably would not write case labels that
>> do not have any statements associated with them.
>> I'll let default take care of those labels.
>>
>
> I don't like them either.
>
> You have to do this when you start working
> on perf code. It turns on -Wall and -Werror,
> without these case gcc will complain,
> compiling will fail.
>

Oops!  Did not realize that compiler would complain.
I guess we have to leave them as they are.  Patch is good to be committed.

Thanks
Nilay