linux-kernel - [PATCH 2/2] ring-buffer: Fix accounting of entries when removing pages

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Date:	Fri, 29 Jun 2012 17:35:47 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	linux-kernel@...r.kernel.org
Cc:	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Vaibhav Nagarnaik <vnagarnaik@...gle.com>,
	Justin Teravest <teravest@...gle.com>,
	David Sharp <dhsharp@...gle.com>
Subject: [PATCH 2/2] ring-buffer: Fix accounting of entries when removing pages

From: Vaibhav Nagarnaik <vnagarnaik@...gle.com>

When removing pages from the ring buffer, its state is not reset. This
means that the counters need to be correctly updated to account for the
pages removed.

Update the overrun counter to reflect the removed events from the pages.

Link: http://lkml.kernel.org/r/1340998301-1715-1-git-send-email-vnagarnaik@google.com

Cc: Justin Teravest <teravest@...gle.com>
Cc: David Sharp <dhsharp@...gle.com>
Signed-off-by: Vaibhav Nagarnaik <vnagarnaik@...gle.com>
Signed-off-by: Steven Rostedt <rostedt@...dmis.org>
---
 kernel/trace/ring_buffer.c |    5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index ba39cba..f765465 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -1347,10 +1347,9 @@ rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned int nr_pages)
 			 * If something was added to this page, it was full
 			 * since it is not the tail page. So we deduct the
 			 * bytes consumed in ring buffer from here.
-			 * No need to update overruns, since this page is
-			 * deleted from ring buffer and its entries are
-			 * already accounted for.
+			 * Increment overrun to account for the lost events.
 			 */
+			local_add(page_entries, &cpu_buffer->overrun);
 			local_sub(BUF_PAGE_SIZE, &cpu_buffer->entries_bytes);
 		}
 
-- 
1.7.10



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