iv/linux
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

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
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

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. * to swap with a page in the ring buffer.
* *
* for example: * for example:
* rpage = ring_buffer_alloc_page(buffer); * rpage = ring_buffer_alloc_read_page(buffer);
* if (!rpage) * if (!rpage)
* return error; * return error;
* ret = ring_buffer_read_page(buffer, &rpage, cpu, 0); * 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) { if (cpu_buffer->reader_page == cpu_buffer->commit_page) {
unsigned int read = cpu_buffer->reader_page->read; unsigned int read = cpu_buffer->reader_page->read;
unsigned int commit = rb_page_commit(cpu_buffer->reader_page);
if (full) if (full)
goto out; goto out;
/* The writer is still on the reader page, we must copy */ /* The writer is still on the reader page, we must copy */
bpage = cpu_buffer->reader_page->page;
memcpy(bpage->data, memcpy(bpage->data,
cpu_buffer->reader_page->page->data + read, cpu_buffer->reader_page->page->data + read,
local_read(&bpage->commit) - read); commit - read);
/* consume what was read */ /* consume what was read */
cpu_buffer->reader_page += read; cpu_buffer->reader_page->read = commit;
} else { } else {
/* swap the pages */ /* swap the pages */
rb_init_page(bpage); rb_init_page(bpage);