Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754196Ab3G2MNV (ORCPT ); Mon, 29 Jul 2013 08:13:21 -0400 Received: from merlin.infradead.org ([205.233.59.134]:40423 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751644Ab3G2MNU (ORCPT ); Mon, 29 Jul 2013 08:13:20 -0400 Date: Mon, 29 Jul 2013 14:13:05 +0200 From: Peter Zijlstra To: Xie XiuQi 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 Message-ID: <20130729121305.GE3008@twins.programming.kicks-ass.net> References: <51F5D399.3050609@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <51F5D399.3050609@huawei.com> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1843 Lines: 55 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(). > 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? -- 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/