From: Peter Zijlstra <peterz@infradead.org>
To: Vince Weaver <vincent.weaver@maine.edu>
Cc: linux-kernel@vger.kernel.org,
Josh Poimboeuf <jpoimboe@redhat.com>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Andy Lutomirski <luto@kernel.org>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Arnaldo Carvalho de Melo <acme@redhat.com>,
Jiri Olsa <jolsa@redhat.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Stephane Eranian <eranian@google.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@kernel.org>
Subject: Re: [perf] perf_event.h ABI visibility question
Date: Fri, 24 Aug 2018 10:50:42 +0200 [thread overview]
Message-ID: <20180824085042.GL24124@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <alpine.DEB.2.21.1808231401440.28868@macbook-air>
On Thu, Aug 23, 2018 at 02:25:06PM -0400, Vince Weaver wrote:
>
> I notice that Linux 4.18 has the following changeset which changes the
> user visible perf_event.h file
>
> commit 6cbc304f2f360f25cc8607817239d6f4a2fd3dc5
> Author: Peter Zijlstra <peterz@infradead.org>
> Date: Thu May 10 15:48:41 2018 +0200
>
> perf/x86/intel: Fix unwind errors from PEBS entries (mk-II)
>
> which contains
>
> --- a/include/uapi/linux/perf_event.h
> +++ b/include/uapi/linux/perf_event.h
> @@ -143,6 +143,8 @@ enum perf_event_sample_format {
> PERF_SAMPLE_PHYS_ADDR = 1U << 19,
>
> PERF_SAMPLE_MAX = 1U << 20, /* non-ABI */
> +
> + __PERF_SAMPLE_CALLCHAIN_EARLY = 1ULL << 63,
> };
>
>
> Is this supposed to be a user-visible interface?
>
> I realize that if the user tries to set anything above PERF_SAMPLE_MAX
> it will be caught and flagged as EINVAL.
>
> However even with the double-underscore hint in
> __PERF_SAMPLE_CALLCHAIN_EARLY the value is still in the user-visible
> header so it's now part of the ABI and I guess the manpage has to document it.
Hurphm.. visible yes, but as you say, also quite useless. Does it really
make sense to document that?
next prev parent reply other threads:[~2018-08-24 8:50 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-23 18:25 [perf] perf_event.h ABI visibility question Vince Weaver
2018-08-24 8:50 ` Peter Zijlstra [this message]
2018-08-24 21:09 ` Vince Weaver
2018-08-27 7:52 ` Peter Zijlstra
2018-08-28 17:51 ` Vince Weaver
2018-08-29 12:13 ` Peter Zijlstra
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