Commit-ID: 4f3640f8a358f2183a8c966f299eeb55ca523e06
Gitweb: http://git.kernel.org/tip/4f3640f8a358f2183a8c966f299eeb55ca523e06
Author: "Steven Rostedt" <srostedt@xxxxxxxxxx>
AuthorDate: Tue, 3 Mar 2009 23:52:42 -0500
Commit: Steven Rostedt <srostedt@xxxxxxxxxx>
CommitDate: Wed, 4 Mar 2009 19:01:45 -0500
ring-buffer: fix timestamp in partial ring_buffer_page_read
If a partial ring_buffer_page_read happens, then some of the
incremental timestamps may be lost. This patch writes the
recent timestamp into the page that is passed back to the caller.
A partial ring_buffer_page_read is where the full page would not
be written back to the user, and instead, just part of the page
is copied to the user. A full page would be a page swap with the
ring buffer and the timestamps would be correct.
Signed-off-by: Steven Rostedt <srostedt@xxxxxxxxxx>
---
kernel/trace/ring_buffer.c | 6 +++++-
1 files changed, 5 insertions(+), 1 deletions(-)
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index f2a163d..f747364 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -2461,6 +2461,7 @@ int ring_buffer_read_page(struct ring_buffer *buffer,
unsigned long flags;
unsigned int commit;
unsigned int read;
+ u64 save_timestamp;
int ret = -1;
/*
@@ -2515,6 +2516,9 @@ int ring_buffer_read_page(struct ring_buffer *buffer,
if (len < size)
goto out;
+ /* save the current timestamp, since the user will need it */
+ save_timestamp = cpu_buffer->read_stamp;
+
/* Need to copy one event at a time */
do {
memcpy(bpage->data + pos, rpage->data + rpos, size);
@@ -2531,7 +2535,7 @@ int ring_buffer_read_page(struct ring_buffer *buffer,
/* update bpage */
local_set(&bpage->commit, pos);
- bpage->time_stamp = rpage->time_stamp;
+ bpage->time_stamp = save_timestamp;
/* we copied everything to the beginning */
read = 0;
--
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