Re: [PATCH 03/11] perf tool: Use PERF_EVENT_IOC_ID perf ioctl to read event id

From: Namhyung Kim
Date: Mon Oct 22 2012 - 03:57:18 EST


Just a minor nitpicking..

On Sat, 20 Oct 2012 16:33:11 +0200, Jiri Olsa wrote:
> Changing the way we retrieve the event ID. Instead of parsing out
> the ID out of the read data, using the PERF_EVENT_IOC_ID ioctl.
> Keeping the old way in place to support kernels without
> PERF_EVENT_IOC_ID ioctl support.
> + } else if (errno)
> + return -1;

Is this check really needed? I think that returning non-zero from the
ioctl always sets the errno, no? How about this:

ret = ioctl(fd, PERF_EVENT_IOC_ID, &id);
if (!ret)
goto add;

if (errno != ENOTTY)
return -1;


I guess that it'll show you better diff stat. :)


> - perf_evlist__id_add(evlist, evsel, cpu, thread, read_data[id_idx]);
> + add:
> + perf_evlist__id_add(evlist, evsel, cpu, thread, id);
> return 0;
> }
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