linux-kernel - [tip:perfcounters/core] perf_counter: kerneltop: simplify data

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Date:	Wed, 1 Apr 2009 10:13:07 GMT
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, paulus@...ba.org, hpa@...or.com,
	mingo@...hat.com, a.p.zijlstra@...llo.nl, tglx@...utronix.de,
	mingo@...e.hu
Subject: [tip:perfcounters/core] perf_counter: kerneltop: simplify data_head read

Commit-ID:  b5b7e234c3d14eb614998ce5a96719baf146c71c
Gitweb:     http://git.kernel.org/tip/b5b7e234c3d14eb614998ce5a96719baf146c71c
Author:     Peter Zijlstra <a.p.zijlstra@...llo.nl>
AuthorDate: Mon, 30 Mar 2009 19:07:04 +0200
Committer:  Ingo Molnar <mingo@...e.hu>
CommitDate: Wed, 1 Apr 2009 11:33:33 +0200

perf_counter: kerneltop: simplify data_head read

Now that the kernel side changed, match up again.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Acked-by: Paul Mackerras <paulus@...ba.org>
LKML-Reference: <20090330171023.327144324@...llo.nl>
Signed-off-by: Ingo Molnar <mingo@...e.hu>


---
 Documentation/perf_counter/kerneltop.c |   14 +-------------
 1 files changed, 1 insertions(+), 13 deletions(-)

diff --git a/Documentation/perf_counter/kerneltop.c b/Documentation/perf_counter/kerneltop.c
index fda1438..2779c57 100644
--- a/Documentation/perf_counter/kerneltop.c
+++ b/Documentation/perf_counter/kerneltop.c
@@ -1125,22 +1125,10 @@ struct mmap_data {
 static unsigned int mmap_read_head(struct mmap_data *md)
 {
 	struct perf_counter_mmap_page *pc = md->base;
-	unsigned int seq, head;
-
-repeat:
-	rmb();
-	seq = pc->lock;
-
-	if (unlikely(seq & 1)) {
-		cpu_relax();
-		goto repeat;
-	}
+	int head;
 
 	head = pc->data_head;
-
 	rmb();
-	if (pc->lock != seq)
-		goto repeat;
 
 	return head;
 }
--
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