From: Peter Zijlstra <a.p.zijlstra@chello.nl>
Date: Mon, 30 Mar 2009 17:07:04 +0000 (+0200)
Subject: perf_counter: kerneltop: simplify data_head read
X-Git-Tag: v2.6.31-rc1~383^2~426
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=195564390210977954fe4ef45b39cdee34f41b59;p=karo-tx-linux.git

perf_counter: kerneltop: simplify data_head read

Now that the kernel side changed, match up again.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Paul Mackerras <paulus@samba.org>
Orig-LKML-Reference: <20090330171023.327144324@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---

diff --git a/Documentation/perf_counter/kerneltop.c b/Documentation/perf_counter/kerneltop.c
index fda1438365dc..2779c57ad4ba 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;
 }