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Commit b85fa01e authored by Lai Jiangshan's avatar Lai Jiangshan Committed by Steven Rostedt
Browse files

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: default avatarLai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: default avatarSteven Rostedt <srostedt@redhat.com>
parent 34cd4998

kernel/trace/ring_buffer.c

+4 −5
Original line number Diff line number Diff line
@@ -2406,7 +2406,7 @@ void ring_buffer_free_read_page(struct ring_buffer *buffer, void *data) 
 * 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 @@ int ring_buffer_read_page(struct ring_buffer *buffer, 
	 */

	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);