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

Jiri Olsa
2020-06-25T17:07:50Z

On Wed, Jun 24, 2020 at 05:55:02PM +0300, Alexey Budankov wrote:
>
> On 24.06.2020 17:00, Alexey Budankov wrote:
> >
> > 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().
> And evlist__ctlfd_process() still should be called second time right
> after evlist_poll() but prior filter_polfd().

aaah it's set to zero in here:

if (entries[ctlfd_pos].revents & (POLLHUP | POLLERR))
evlist__finalize_ctlfd(evlist);
else
entries[ctlfd_pos].revents = 0;

yea, that's bad.. another reason to call it a hack

jirka

>
> ~Alexey
>
> >
> > 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
> >>
>