ring_buffer: fix typing mistake
Impact: Fix bug
I found several very very curious line.
It's so curious that it may be brought by typing mistake.
When (cpu_buffer->reader_page == cpu_buffer->commit_page):
1) We haven't copied it for bpage is changed:
bpage = cpu_buffer->reader_page->page;
memcpy(bpage->data, cpu_buffer->reader_page->page->data + read ... )
2) We need update cpu_buffer->reader_page->read, but
"cpu_buffer->reader_page += read;" is not right.
[
This bug was a typo. The commit->reader_page is a page pointer
and not an index into the page. The line should have been
commit->reader_page->read += read. The other changes
by Lai are nice clean ups to the code. - SDR
]
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 53ba3a6..eca2827 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -2406,7 +2406,7 @@
* to swap with a page in the ring buffer.
*
* for example:
- * rpage = ring_buffer_alloc_page(buffer);
+ * rpage = ring_buffer_alloc_read_page(buffer);
* if (!rpage)
* return error;
* ret = ring_buffer_read_page(buffer, &rpage, cpu, 0);
@@ -2461,18 +2461,17 @@
*/
if (cpu_buffer->reader_page == cpu_buffer->commit_page) {
unsigned int read = cpu_buffer->reader_page->read;
+ unsigned int commit = rb_page_commit(cpu_buffer->reader_page);
if (full)
goto out;
/* The writer is still on the reader page, we must copy */
- bpage = cpu_buffer->reader_page->page;
memcpy(bpage->data,
cpu_buffer->reader_page->page->data + read,
- local_read(&bpage->commit) - read);
+ commit - read);
/* consume what was read */
- cpu_buffer->reader_page += read;
-
+ cpu_buffer->reader_page->read = commit;
} else {
/* swap the pages */
rb_init_page(bpage);