From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752612Ab3GFFsF (ORCPT ); Sat, 6 Jul 2013 01:48:05 -0400 Received: from mail-pd0-f171.google.com ([209.85.192.171]:42249 "EHLO mail-pd0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751900Ab3GFFsD (ORCPT ); Sat, 6 Jul 2013 01:48:03 -0400 Date: Sat, 6 Jul 2013 13:45:53 +0800 From: Wang YanQing To: Preeti U Murthy Cc: xiaoguangrong@cn.fujitsu.com, mingo@elte.hu, paulmck@linux.vnet.ibm.com, linux-kernel@vger.kernel.org, a.p.zijlstra@chello.nl, npiggin@suse.de, deepthi@linux.vnet.ibm.com, peterz@infradead.org, rusty@rustcorp.com.au, heiko.carstens@de.ibm.com, rostedt@goodmis.org, miltonm@bga.com, srivatsa.bhat@linux.vnet.ibm.com, jens.axboe@oracle.com, tj@kernel.org, akpm@linux-foundation.org, svaidy@linux.vnet.ibm.com, shli@kernel.org, tglx@linutronix.de, lig.fnst@cn.fujitsu.com, anton@samba.org Subject: Re: [PATCH 3/3] smp/ipi:Remove check around csd lock in handler for smp_call_function variants Message-ID: <20130706054552.GA2929@udknight> Mail-Followup-To: Wang YanQing , Preeti U Murthy , xiaoguangrong@cn.fujitsu.com, mingo@elte.hu, paulmck@linux.vnet.ibm.com, linux-kernel@vger.kernel.org, a.p.zijlstra@chello.nl, npiggin@suse.de, deepthi@linux.vnet.ibm.com, peterz@infradead.org, rusty@rustcorp.com.au, heiko.carstens@de.ibm.com, rostedt@goodmis.org, miltonm@bga.com, srivatsa.bhat@linux.vnet.ibm.com, jens.axboe@oracle.com, tj@kernel.org, akpm@linux-foundation.org, svaidy@linux.vnet.ibm.com, shli@kernel.org, tglx@linutronix.de, lig.fnst@cn.fujitsu.com, anton@samba.org References: <20130705162548.16888.18957.stgit@preeti.in.ibm.com> <20130705162720.16888.81958.stgit@preeti.in.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130705162720.16888.81958.stgit@preeti.in.ibm.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jul 05, 2013 at 09:57:21PM +0530, Preeti U Murthy wrote: > call_single_data is always locked by all callers of > arch_send_call_function_single_ipi() or > arch_send_call_function_ipi_mask() which results in execution of > generic_call_function_interrupt() handler. > > Hence remove the check for lock on csd in generic_call_function_interrupt() > handler, before unlocking it. I can't find where is the generic_call_function_interrupt :) > Signed-off-by: Preeti U Murthy > Cc: Peter Zijlstra > Cc: Ingo Molnar > Cc: Xiao Guangrong > Cc: srivatsa.bhat@linux.vnet.ibm.com > Cc: Paul E. McKenney > Cc: Steven Rostedt > Cc: Rusty Russell --- > > kernel/smp.c | 14 +------------- > 1 file changed, 1 insertion(+), 13 deletions(-) > > diff --git a/kernel/smp.c b/kernel/smp.c > index b6981ae..d37581a 100644 > --- a/kernel/smp.c > +++ b/kernel/smp.c > @@ -181,25 +181,13 @@ 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; > - You haven't mention this change in the ChangeLog, don't do it. I can't see any harm to remove csd_flags, but I hope others check it again. > csd->func(csd->info); > > - /* > - * Unlocked CSDs are valid through generic_exec_single(): > - */ > - if (csd_flags & CSD_FLAG_LOCK) > - csd_unlock(csd); > + csd_unlock(csd); I don't like this change, I think check CSD_FLAG_LOCK to make sure we really need csd_unlock is good. Just like you can't know who and how people will use the API, so some robust check code is good.