From: Vince Weaver <vweaver1@eecs.utk.edu>
Date: Fri, 3 Jun 2011 21:54:40 +0000 (-0400)
Subject: perf: Comment /proc/sys/kernel/perf_event_paranoid to be part of user ABI
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=aa4a221875873d2a1f9656cb7fd7e545e952b4fa;p=GitHub%2FLineageOS%2Fandroid_kernel_motorola_exynos9610.git

perf: Comment /proc/sys/kernel/perf_event_paranoid to be part of user ABI

Turns out that distro packages use this file as an indicator of
the perf event subsystem - this is easier to check for from scripts
than the existence of the system call.

This is easy enough to keep around for the kernel, so add a
comment to make sure it stays so.

Signed-off-by: Vince Weaver <vweaver1@eecs.utk.edu>
Cc: David Ahern <dsahern@gmail.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: paulus@samba.org
Cc: acme@redhat.com
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/alpine.DEB.2.00.1106031751170.29381@cl320.eecs.utk.edu
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 4fc92445a29c..f175d98bd355 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -938,6 +938,12 @@ static struct ctl_table kern_table[] = {
 	},
 #endif
 #ifdef CONFIG_PERF_EVENTS
+	/*
+	 * User-space scripts rely on the existence of this file
+	 * as a feature check for perf_events being enabled.
+	 *
+	 * So it's an ABI, do not remove!
+	 */
 	{
 		.procname	= "perf_event_paranoid",
 		.data		= &sysctl_perf_event_paranoid,