linux-kernel - [RFC][PATCH 4/5] sh: Add support for sampling counters

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Message-Id: <b8f8fabb61505b10360b358016e97283ba8a621f.1283123521.git.matt@console-pimps.org>
Date:	Mon, 30 Aug 2010 13:13:46 +0100
From:	Matt Fleming <matt@...sole-pimps.org>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Zhang Rui <rui.zhang@...el.com>, linux-kernel@...r.kernel.org,
	Ingo Molnar <mingo@...e.hu>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Robert Richter <robert.richter@....com>,
	Lin Ming <ming.m.lin@...el.com>,
	Paul Mackerras <paulus@...ba.org>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Don Zickus <dzickus@...hat.com>,
	Cyrill Gorcunov <gorcunov@...il.com>,
	Len Brown <lenb@...nel.org>,
	Matthew Garrett <mjg59@...f.ucam.org>
Subject: [RFC][PATCH 4/5] sh: Add support for sampling counters

SH performance counters cannot generate any form of interrupt and so
require hrtimer assistance for sampling counter values. Event groups
periodically sample counters when a hrtimer fires which allows the use
of sampling counters on SH.

Signed-off-by: Matt Fleming <matt@...sole-pimps.org>
---
 arch/sh/kernel/perf_event.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/arch/sh/kernel/perf_event.c b/arch/sh/kernel/perf_event.c
index 7a3dc35..1f77de6 100644
--- a/arch/sh/kernel/perf_event.c
+++ b/arch/sh/kernel/perf_event.c
@@ -114,7 +114,8 @@ static int __hw_perf_event_init(struct perf_event *event)
 	 * no interrupts, and are therefore unable to do sampling without
 	 * further work and timer assistance.
 	 */
-	if (hwc->sample_period)
+	if (!(attr->read_format & PERF_FORMAT_GROUP) &&
+	    hwc->sample_period && event->group_leader == event)
 		return -EINVAL;
 
 	/*
-- 
1.7.1

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