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Date:   Mon, 25 May 2020 11:43:00 +1000
From:   "Anand K. Mistry" <>
To:     Andi Kleen <>
        Alexander Shishkin <>,
        Arnaldo Carvalho de Melo <>,
        Ingo Molnar <>, Jiri Olsa <>,
        Mark Rutland <>,
        Namhyung Kim <>,
        Peter Zijlstra <>,
Subject: Re: [PATCH v3] perf record: Use an eventfd to wakeup when done

On Sat, 23 May 2020 at 23:35, Andi Kleen <> wrote:
> Anand K Mistry <> writes:
> >       }
> >
> > +     done_fd = eventfd(0, EFD_NONBLOCK);
> This will make perf depend on a recent glibc or other library
> that implements eventfd. Wouldn't surprise me if some kind
> of build time check is needed for this to pass all of Arnaldo's
> built tests.

Looks like Arnaldo made that change when merging:

This makes me curious. How old a kernel should modern tools support?
>From the man page, eventfd was added in 2.6.22 (and eventfd2 in
2.6.27), which was 2007 (or 2008 for eventfd2) and glibc-2.8 which was
2008. I understand the kernel's policy of never breaking userspace,
but what about userspace tools?

> -Andi

Anand K. Mistry
Software Engineer
Google Australia

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