From a838b2e634405fb89ddbf4fa9412acb33911911f Mon Sep 17 00:00:00 2001
From: Steven Rostedt <srostedt@redhat.com>
Date: Tue, 27 Apr 2010 13:26:58 -0400
Subject: [PATCH] ring-buffer: Make benchmark handle missed events

With the addition of the "missed events" flags that is stored in the
commit field of the ring buffer page, the ring_buffer_benchmark
was not updated to handle this. If events are missed, then the
missed events flag is set in the ring buffer page, the benchmark
will count that flag as part of the size of the page and will hit the BUG()
when it tries to read beyond the page.

The solution is simply to have the ring buffer benchmark mask off
the extra bits.

Reported-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 kernel/trace/ring_buffer_benchmark.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/ring_buffer_benchmark.c b/kernel/trace/ring_buffer_benchmark.c
index dc56556b55a2..302f8a614635 100644
--- a/kernel/trace/ring_buffer_benchmark.c
+++ b/kernel/trace/ring_buffer_benchmark.c
@@ -113,7 +113,8 @@ static enum event_status read_page(int cpu)
 	ret = ring_buffer_read_page(buffer, &bpage, PAGE_SIZE, cpu, 1);
 	if (ret >= 0) {
 		rpage = bpage;
-		commit = local_read(&rpage->commit);
+		/* The commit may have missed event flags set, clear them */
+		commit = local_read(&rpage->commit) & 0xfffff;
 		for (i = 0; i < commit && !kill_test; i += inc) {
 
 			if (i >= (PAGE_SIZE - offsetof(struct rb_page, data))) {