From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752412AbbE0VTi (ORCPT ); Wed, 27 May 2015 17:19:38 -0400 Received: from e39.co.us.ibm.com ([32.97.110.160]:38563 "EHLO e39.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752278AbbE0VTf (ORCPT ); Wed, 27 May 2015 17:19:35 -0400 Date: Wed, 27 May 2015 14:19:31 -0700 From: "Paul E. McKenney" To: Nicholas Mc Guire Cc: Lai Jiangshan , Josh Triplett , Steven Rostedt , Joe Perches , Mathieu Desnoyers , linux-kernel@vger.kernel.org Subject: Re: [PATCH V2] rcu: change return type to bool Message-ID: <20150527211931.GQ5989@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <1432709785-8472-1-git-send-email-hofrat@osadl.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1432709785-8472-1-git-send-email-hofrat@osadl.org> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 15052721-0033-0000-0000-000004A45918 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, May 27, 2015 at 08:56:25AM +0200, Nicholas Mc Guire wrote: > Type-checking coccinelle spatches are being used to locate type mismatches > between function signatures and return values in this case this produced: > ./kernel/rcu/srcu.c:271 WARNING: return of wrong type > int != unsigned long, > > srcu_readers_active() returns an int that is the sum of per_cpu unsigned > long but the only user is cleanup_srcu_struct() which is using it as a > boolean (condition) to see if there is any readers rather than actually > using the approximate number of readers. The theoretically possible > unsigned long overflow case does not need to be handled explicitly - if > we had 4G++ readers then something else went wrong a long time ago. > > proposal: change the return type to boolean. The function name is left > unchanged as it fits the naming expectation for a boolean. > > patch was compile tested for x86_64_defconfig (implies CONFIG_SRCU=y) > > patch is against 4.1-rc5 (localversion-next is -next-20150525) > > Signed-off-by: Nicholas Mc Guire OK, I have queued this for testing. If Lai Jiangshan is OK with it, I am OK with it. Thanx, Paul > --- > > V2: dropped the unnecessary !! conversion to boolean. for the details > see Joe Perches clarification at > http://lkml.org/lkml/2015/5/24/47 > > kernel/rcu/srcu.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > diff --git a/kernel/rcu/srcu.c b/kernel/rcu/srcu.c > index fb33d35..de35087 100644 > --- a/kernel/rcu/srcu.c > +++ b/kernel/rcu/srcu.c > @@ -252,14 +252,15 @@ static bool srcu_readers_active_idx_check(struct srcu_struct *sp, int idx) > } > > /** > - * srcu_readers_active - returns approximate number of readers. > + * srcu_readers_active - returns true if there are readers. and false > + * otherwise > * @sp: which srcu_struct to count active readers (holding srcu_read_lock). > * > * Note that this is not an atomic primitive, and can therefore suffer > * severe errors when invoked on an active srcu_struct. That said, it > * can be useful as an error check at cleanup time. > */ > -static int srcu_readers_active(struct srcu_struct *sp) > +static bool srcu_readers_active(struct srcu_struct *sp) > { > int cpu; > unsigned long sum = 0; > -- > 1.7.10.4 >