Messages in this thread Patch in this message | | | Date | Mon, 09 Feb 2009 14:21:14 +0800 | From | Lai Jiangshan <> | Subject | [PATCH 1/2] ring_buffer: fix typing mistake |
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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.
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> --- ring_buffer.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index bd38c5c..e97acae 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -2377,7 +2377,7 @@ 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); @@ -2432,18 +2432,17 @@ 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);
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