Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756741Ab3G3Brm (ORCPT ); Mon, 29 Jul 2013 21:47:42 -0400 Received: from szxga01-in.huawei.com ([119.145.14.64]:47108 "EHLO szxga01-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751675Ab3G3Brl (ORCPT ); Mon, 29 Jul 2013 21:47:41 -0400 Message-ID: <51F71AEC.1090709@huawei.com> Date: Tue, 30 Jul 2013 09:46:20 +0800 From: Xie XiuQi User-Agent: Mozilla/5.0 (Windows NT 6.1; rv:17.0) Gecko/20130307 Thunderbird/17.0.4 MIME-Version: 1.0 To: Peter Zijlstra CC: Jens Axboe , Ingo Molnar , Andrew Morton , Hanjun Guo , Li Zefan , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH] smp: kill unnecessary variable - csd_flags References: <51F5D399.3050609@huawei.com> <20130729121305.GE3008@twins.programming.kicks-ass.net> In-Reply-To: <20130729121305.GE3008@twins.programming.kicks-ass.net> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.135.69.18] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2076 Lines: 64 On 2013/7/29 20:13, Peter Zijlstra wrote: > On Mon, Jul 29, 2013 at 10:29:45AM +0800, Xie XiuQi wrote: >> We used csd_flags formerly because we allocated csd_data by >> kmalloc when "wait == 0". When fail to allocation, we will >> fall back to on-stack allocation. "csd_data" might be invalid >> after generic_exec_single return. >> >> But now we use per cpu data for single cpu ipi calls, and >> csd_data can't fall back to on-stack allocation when "wait == 0". >> >> So csd_flags is unnecessary now. Remove it. > > The much simpler argument is that both callsites of > generic_exec_single() do an unconditional csd_lock(). > That's right. All csd_data are protected by csd_lock. >> Signed-off-by: Xie XiuQi >> --- >> kernel/smp.c | 11 +---------- >> 1 files changed, 1 insertions(+), 10 deletions(-) >> >> diff --git a/kernel/smp.c b/kernel/smp.c >> index 4dba0f7..cac2b6e 100644 >> --- a/kernel/smp.c >> +++ b/kernel/smp.c >> @@ -186,25 +186,16 @@ void generic_smp_call_function_single_interrupt(void) >> >> while (!list_empty(&list)) { >> struct call_single_data *csd; >> - unsigned int csd_flags; >> >> csd = list_entry(list.next, struct call_single_data, list); >> list_del(&csd->list); >> >> - /* >> - * 'csd' can be invalid after this call if flags == 0 >> - * (when called through generic_exec_single()), >> - * so save them away before making the call: >> - */ >> - csd_flags = csd->flags; >> - >> csd->func(csd->info); >> >> /* >> * Unlocked CSDs are valid through generic_exec_single(): >> */ >> - if (csd_flags & CSD_FLAG_LOCK) >> - csd_unlock(csd); >> + csd_unlock(csd); > > The comment is completely useless and confusing after this; why do you > leave it in? > Thanks for your comment, I'll remove the comment and send a new version soon. -- 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/