From: "Tzvetomir Stoyanov (VMware)" <tz.stoyanov@xxxxxxxxx>
The first record in a ring buffer page may not allways be at the
beginning of the page. There could be time-extends injected before it.
In this case kbuffer_start_of_data() will not return the first record,
as expected. Additional field "start" is added in kbuffer struct, to hold
the offset of the first record from the page and kbuffer_start_of_data()
is modified to use it.
Link: https://lore.kernel.org/linux-trace-devel/20200706154714.27566-1-tz.stoyanov@xxxxxxxxx
Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
[ Finished the patch from Steven ]
Signed-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@xxxxxxxxx>
---
lib/traceevent/kbuffer-parse.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/lib/traceevent/kbuffer-parse.c b/lib/traceevent/kbuffer-parse.c
index 2c5f00a9e786..844db976b38c 100644
--- a/lib/traceevent/kbuffer-parse.c
+++ b/lib/traceevent/kbuffer-parse.c
@@ -35,6 +35,7 @@ enum {
* @next - offset from @data to the start of next event
* @size - The size of data on @data
* @start - The offset from @subbuffer where @data lives
+ * @first - The offset from @subbuffer where the first non time stamp event lives
*
* @read_4 - Function to read 4 raw bytes (may swap)
* @read_8 - Function to read 8 raw bytes (may swap)
@@ -51,6 +52,7 @@ struct kbuffer {
unsigned int next;
unsigned int size;
unsigned int start;
+ unsigned int first;
unsigned int (*read_4)(void *ptr);
unsigned long long (*read_8)(void *ptr);
@@ -546,6 +548,9 @@ int kbuffer_load_subbuffer(struct kbuffer *kbuf, void *subbuffer)
next_event(kbuf);
+ /* save the first record from the page */
+ kbuf->first = kbuf->curr;
+
return 0;
}
@@ -755,7 +760,7 @@ void kbuffer_set_old_format(struct kbuffer *kbuf)
*/
int kbuffer_start_of_data(struct kbuffer *kbuf)
{
- return kbuf->start;
+ return kbuf->first + kbuf->start;
}
/**
--
2.26.2
|