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SubjectRe: [PATCH v12 05/15] perf evlist: implement control command handling functions
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On 22.07.2020 15:34, Arnaldo Carvalho de Melo wrote:
> Em Wed, Jul 22, 2020 at 09:27:34AM -0300, Arnaldo Carvalho de Melo escreveu:
>> Em Fri, Jul 17, 2020 at 10:01:33AM +0300, Alexey Budankov escreveu:
>>>
>>> Implement functions of initialization, finalization and processing
>>> of control command messages coming from control file descriptors.
>>> Allocate control file descriptor as descriptor at struct pollfd
>>> object of evsel_list for atomic poll() operation.
>>>
>>> Signed-off-by: Alexey Budankov <alexey.budankov@linux.intel.com>
>>> Acked-by: Jiri Olsa <jolsa@redhat.com>
>>> Acked-by: Namhyung Kim <namhyung@kernel.org>
>>
>> I'm applying locally for testing, but can you answer what is the reason
>> for that newline in the CMD_ACK_TAG? I tried looking at previous
>> discussion but couldn't quickly find any reasoning for that
>>
>> - Arnaldo
>>
>>> +++ b/tools/perf/util/evlist.h
>>> @@ -359,4 +359,22 @@ void perf_evlist__force_leader(struct evlist *evlist);
>>> struct evsel *perf_evlist__reset_weak_group(struct evlist *evlist,
>>> struct evsel *evsel,
>>> bool close);
>>> +#define EVLIST_CTL_CMD_ENABLE_TAG "enable"
>>> +#define EVLIST_CTL_CMD_DISABLE_TAG "disable"
>>> +#define EVLIST_CTL_CMD_ACK_TAG "ack\n"
>>
>> What for? That '\n'?
>
> Oh, I see, this is not a _command_, it is a _response_, and the sender
> expects a newline, right?

Right. Shell commands can expect strings terminated by \n, e.g. 'read -u'.
See sample bash script in 00/15 for example.

>
> So I think this needs to be marked clearly as:
>
> // Commands accepted by 'perf record'
>
> #define EVLIST_CTL_CMD_ENABLE_TAG "enable"
> #define EVLIST_CTL_CMD_DISABLE_TAG "disable"
>
>
> // Responses sent by 'perf record'
>
> #define EVLIST_CTL_RSP_ACK "ack"
>
> And then make the response add the newline, as conceivably we could have
> something like "nack", "invalid", "enoperm", etc, no?

That above makes sense.

>
> Anyway, this can be done on top of this series, so I'm continuing
> processing it locally.
>
> - Arnaldo
>

Alexei

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