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

Alexei Budankov
2020-12-10T18:22:25Z

On 10.12.2020 21:06, Jiri Olsa wrote:
> On Thu, Dec 10, 2020 at 05:24:30PM +0100, Jiri Olsa wrote:
>> 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
>
> actualy it's already checked in evlist__ctlfd_recv, evsel_name at
> worst will be empty string so evlist__find_evsel_by_str will fail
>
> I'll add '' around %s in the error output string:
>
> failed: can't find '%s' event
>
> so it's obvious when it's empty

Looks good to me. Thanks!

Alexei

>
> jirka
>
> .
>