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ring_buffer: fix typing mistake

Browse source 
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>
This commit is contained in:
Lai Jiangshan 2009-02-09 14:21:14 +08:00 committed by Steven Rostedt
parent 34cd4998d3
commit b85fa01ed9
1 changed files with 4 additions and 5 deletions
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9
kernel/trace/ring_buffer.c
View file

@ -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);