Hi Jiri,
On Fri, 29 Nov 2013 12:45:04 +0100, Jiri Olsa wrote:
> hi,
> Andi reported wrong error message for :S modifier
> on kernel without event ID ioctl support.
>
> The reason was that the ioctl failed, but the error was
> printed like the mmap would:
>
> $ perf.old record -e '{cycles,cache-misses}:S' ls
> failed to mmap with 25 (Inappropriate ioctl for device)
> ls: Terminated
I see same confusing error message..
>
> I experimentally added sort of 'libc errno' interface for
> perf_evlist to be able to get proper error message, like:
>
> $ perf record -e '{cycles,cache-misses}:S' ls
> Cannot read event group on this kernel.
> Please consider kernel update (v3.12+).
> ls: Terminated
>
> I'm not sure about this approach. Maybe it'd be better be more
> global..? So before throwing this out, sending it as RFC ;-)
I like it. :) We still need to improve this user-visible error handling.
But what you mean by 'more global'? I think the evlist APIs are pretty
global alreay. And we have same error handling in perf_target code too.
But I think it'd be better making it thread-safe even though it's not
needed for now. The code is growing really fast.. ;-)
Thanks,
Namhyung
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