Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753566Ab3COBnu (ORCPT ); Thu, 14 Mar 2013 21:43:50 -0400 Received: from szxga01-in.huawei.com ([119.145.14.64]:50393 "EHLO szxga01-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753003Ab3COBnt (ORCPT ); Thu, 14 Mar 2013 21:43:49 -0400 Message-ID: <51427CA4.2060803@huawei.com> Date: Fri, 15 Mar 2013 09:43:00 +0800 From: Li Zefan User-Agent: Mozilla/5.0 (Windows NT 6.1; rv:17.0) Gecko/20130307 Thunderbird/17.0.4 MIME-Version: 1.0 To: li guang CC: Oleg Nesterov , , , Subject: Re: [PATCH 2/2] task_work: check callback if it's NULL References: <1363247865-3531-1-git-send-email-lig.fnst@cn.fujitsu.com> <1363247865-3531-2-git-send-email-lig.fnst@cn.fujitsu.com> <20130314144307.GB16136@redhat.com> <1363306834.21129.121.camel@liguang.fnst.cn.fujitsu.com> <514272D3.7040901@huawei.com> <1363310769.21129.132.camel@liguang.fnst.cn.fujitsu.com> In-Reply-To: <1363310769.21129.132.camel@liguang.fnst.cn.fujitsu.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit X-Originating-IP: [10.135.68.215] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1792 Lines: 56 On 2013/3/15 9:26, li guang wrote: > 在 2013-03-15五的 09:01 +0800，Li Zefan写道： >> On 2013/3/15 8:20, li guang wrote: >>> 在 2013-03-14四的 15:43 +0100，Oleg Nesterov写道： >>>> On 03/14, liguang wrote: >>>>> >>>>> Signed-off-by: liguang >>>>> --- >>>>> kernel/task_work.c | 3 ++- >>>>> 1 files changed, 2 insertions(+), 1 deletions(-) >>>>> >>>>> diff --git a/kernel/task_work.c b/kernel/task_work.c >>>>> index 0bf4258..f458b08 100644 >>>>> --- a/kernel/task_work.c >>>>> +++ b/kernel/task_work.c >>>>> @@ -75,7 +75,8 @@ void task_work_run(void) >>>>> >>>>> do { >>>>> next = work->next; >>>>> - work->func(work); >>>>> + if (unlikely(work->func)) >>>>> + work->func(work); >>>> >>>> Why? >>>> >>>> Oleg. >>>> >>> >>> can we believe a callback always be call-able? >>> can it happened to be 0? e.g. wrong initialized. >>> of course, we can complain the caller, be why don't >>> we easily make it more safer? >>> >> >> Because you're not making things safer, but your're trying >> to cover up bugs... >> > > Oh, that's a little harsh to a normal programmer like me :-) > for it seems you are asking me to be coding without any bug. > are you? or it is the theory of kernel coding? > And you make a bug, and you want the kernel to cover up the bug instead of crash on a null pointer deref so you'll know you've made a bug? Why we check if a callback is NULL before calling it? Because it's allowed to be. Why we don't check if a callback is NULL? Because it's not supposed to be. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/