Re: [PATCH 2/3] perf tools: Allow to enable/disable events via control file

Jiri Olsa
2020-12-10T16:26:43Z

On Mon, Dec 07, 2020 at 08:02:20PM +0300, Alexei Budankov wrote:
> Hi,
>
> On 06.12.2020 20:05, Jiri Olsa wrote:
> > Adding new control events to enable/disable specific event.
> > The interface string for control file are:
> >
> > 'enable-<EVENT NAME>'
> > 'disable-<EVENT NAME>'
>
> <SNIP>
>
> >
> > when received the command, perf will scan the current evlist
> > for <EVENT NAME> and if found it's enabled/disabled.
>
> <SNIP>
>
> > diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
> > index 70aff26612a9..05723227bebf 100644
> > --- a/tools/perf/util/evlist.c
> > +++ b/tools/perf/util/evlist.c
> > @@ -1915,7 +1915,13 @@ static int evlist__ctlfd_recv(struct evlist *evlist, enum evlist_ctl_cmd *cmd,
> > bytes_read == data_size ? "" : c == '\n' ? "\\n" : "\\0");
> >
> > if (bytes_read > 0) {
> > - if (!strncmp(cmd_data, EVLIST_CTL_CMD_ENABLE_TAG,
> > + if (!strncmp(cmd_data, EVLIST_CTL_CMD_ENABLE_EVSEL_TAG,
> > + (sizeof(EVLIST_CTL_CMD_ENABLE_EVSEL_TAG)-1))) {
> > + *cmd = EVLIST_CTL_CMD_ENABLE_EVSEL;
> > + } else if (!strncmp(cmd_data, EVLIST_CTL_CMD_DISABLE_EVSEL_TAG,
> > + (sizeof(EVLIST_CTL_CMD_DISABLE_EVSEL_TAG)-1))) {
> > + *cmd = EVLIST_CTL_CMD_DISABLE_EVSEL;
> > + } else if (!strncmp(cmd_data, EVLIST_CTL_CMD_ENABLE_TAG,
> > (sizeof(EVLIST_CTL_CMD_ENABLE_TAG)-1))) {
> > *cmd = EVLIST_CTL_CMD_ENABLE;
> > } else if (!strncmp(cmd_data, EVLIST_CTL_CMD_DISABLE_TAG,
> > @@ -1952,6 +1958,8 @@ int evlist__ctlfd_process(struct evlist *evlist, enum evlist_ctl_cmd *cmd)
> > char cmd_data[EVLIST_CTL_CMD_MAX_LEN];
> > int ctlfd_pos = evlist->ctl_fd.pos;
> > struct pollfd *entries = evlist->core.pollfd.entries;
> > + struct evsel *evsel;
> > + char *evsel_name;
> >
> > if (!evlist__ctlfd_initialized(evlist) || !entries[ctlfd_pos].revents)
> > return 0;
> > @@ -1967,6 +1975,26 @@ int evlist__ctlfd_process(struct evlist *evlist, enum evlist_ctl_cmd *cmd)
> > case EVLIST_CTL_CMD_DISABLE:
> > evlist__disable(evlist);
> > break;
> > + case EVLIST_CTL_CMD_ENABLE_EVSEL:
> > + evsel_name = cmd_data + sizeof(EVLIST_CTL_CMD_ENABLE_EVSEL_TAG) - 1;
>
> It makes sense to check that evsel_name still points
> into cmd_data buffer after assigning to event name.

right, will add that

thanks,
jirka