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From: Vince Weaver <vincent.weaver@maine.edu>
To: Peter Zijlstra <peterz@infradead.org>, linux-kernel@vger.kernel.org
Cc: 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: [perf] perf_event.h ABI visibility question
Date: Thu, 23 Aug 2018 14:25:06 -0400 (EDT)	[thread overview]
Message-ID: <alpine.DEB.2.21.1808231401440.28868@macbook-air> (raw)


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.

Vince


             reply	other threads:[~2018-08-23 18:25 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-08-23 18:25 Vince Weaver [this message]
2018-08-24  8:50 ` [perf] perf_event.h ABI visibility question Peter Zijlstra
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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