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| author | Steven Rostedt <srostedt@redhat.com> | 2009-03-03 23:52:42 -0500 |
|---|---|---|
| committer | Steven Rostedt <srostedt@redhat.com> | 2009-03-04 19:01:45 -0500 |
| commit | 4f3640f8a358f2183a8c966f299eeb55ca523e06 (patch) | |
| tree | ff8b1a10b449fbb823523b09a192e6b5563d56e8 | |
| parent | e543ad76914abec1acf6631604a4154cd7a2ca6b (diff) | |
| download | linux-4f3640f8a358f2183a8c966f299eeb55ca523e06.tar.gz linux-4f3640f8a358f2183a8c966f299eeb55ca523e06.tar.bz2 linux-4f3640f8a358f2183a8c966f299eeb55ca523e06.zip | |
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@redhat.com>
| -rw-r--r-- | 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 f2a163db52f9..f7473645b9c6 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; |