From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754387AbZBIGVk (ORCPT ); Mon, 9 Feb 2009 01:21:40 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752059AbZBIGVb (ORCPT ); Mon, 9 Feb 2009 01:21:31 -0500 Received: from cn.fujitsu.com ([222.73.24.84]:57667 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1751534AbZBIGVb (ORCPT ); Mon, 9 Feb 2009 01:21:31 -0500 Message-ID: <498FCB5A.5030207@cn.fujitsu.com> Date: Mon, 09 Feb 2009 14:21:14 +0800 From: Lai Jiangshan User-Agent: Thunderbird 2.0.0.19 (Windows/20081209) MIME-Version: 1.0 To: Steven Rostedt , Ingo Molnar , Linux Kernel Mailing List Subject: [PATCH 1/2] ring_buffer: fix typing mistake Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 --- 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);