Re: [PATCH v8 12/13] perf record: implement control commands handling

Alexey Budankov
2020-06-24T14:00:19Z

On 23.06.2020 17:54, Jiri Olsa wrote:
> On Wed, Jun 17, 2020 at 11:43:58AM +0300, Alexey Budankov wrote:
>>
>> Implement handling of 'enable' and 'disable' control commands
>> coming from control file descriptor.
>>
>> Signed-off-by: Alexey Budankov <alexey.budankov@linux.intel.com>
>> ---
>> tools/perf/builtin-record.c | 16 ++++++++++++++++
>> 1 file changed, 16 insertions(+)
>>
>> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
>> index d0b29a1070a0..0394e068dde8 100644
>> --- a/tools/perf/builtin-record.c
>> +++ b/tools/perf/builtin-record.c
>> @@ -1527,6 +1527,7 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
>> bool disabled = false, draining = false;
>> int fd;
>> float ratio = 0;
>> + enum evlist_ctl_cmd cmd = EVLIST_CTL_CMD_UNSUPPORTED;
>>
>> atexit(record__sig_exit);
>> signal(SIGCHLD, sig_handler);
>> @@ -1830,6 +1831,21 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
>> alarm(rec->switch_output.time);
>> }
>>
>> + if (evlist__ctlfd_process(rec->evlist, &cmd) > 0) {
>> + switch (cmd) {
>> + case EVLIST_CTL_CMD_ENABLE:
>> + pr_info(EVLIST_ENABLED_MSG);
>> + break;
>> + case EVLIST_CTL_CMD_DISABLE:
>> + pr_info(EVLIST_DISABLED_MSG);
>> + break;
>> + case EVLIST_CTL_CMD_ACK:
>> + case EVLIST_CTL_CMD_UNSUPPORTED:
>> + default:
>> + break;
>> + }
>> + }
>
> so there's still the filter call like:
>
> if (evlist__filter_pollfd(rec->evlist, POLLERR | POLLHUP) == 0)
> draining = true;
>
> it will never be 0 if the control fds are stil alive no?

Due to change in filter_pollfd() and preceding evlist__ctlfd_process() call
now control fd is not counted by filter_pollfd().

However event fds with .revents == 0 are not counted either and this breaks
the algorithm thus something more is still required to cover this gap.

~Alexey

>
> jirka
>