From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761133AbaGYTeV (ORCPT ); Fri, 25 Jul 2014 15:34:21 -0400 Received: from mail-lb0-f178.google.com ([209.85.217.178]:55444 "EHLO mail-lb0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753235AbaGYTeT (ORCPT ); Fri, 25 Jul 2014 15:34:19 -0400 MIME-Version: 1.0 In-Reply-To: <20140725180632.GA6230@linux.vnet.ibm.com> References: <1406248652-17416-1-git-send-email-bobby.prani@gmail.com> <1406248652-17416-2-git-send-email-bobby.prani@gmail.com> <20140725152551.GC11241@linux.vnet.ibm.com> <20140725180632.GA6230@linux.vnet.ibm.com> From: Pranith Kumar Date: Fri, 25 Jul 2014 15:33:48 -0400 Message-ID: Subject: Re: [PATCH v2 2/2] rcu: Check the return value of rcu_nocb_mask cpumask allocation To: Paul McKenney Cc: Josh Triplett , Steven Rostedt , Mathieu Desnoyers , Lai Jiangshan , "open list:READ-COPY UPDATE..." Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jul 25, 2014 at 2:06 PM, Paul E. McKenney wrote: > On Fri, Jul 25, 2014 at 08:25:51AM -0700, Paul E. McKenney wrote: >> On Thu, Jul 24, 2014 at 08:37:32PM -0400, Pranith Kumar wrote: >> > This commit checks the return value of the zalloc_cpumask_var() used for >> > allocating cpumask for rcu_nocb_mask. >> > >> > Signed-off-by: Pranith Kumar >> >> Hmmm... I saw the check in the previous patch, but didn't see removal >> of the later have_rcu_nocb_mask check. Please see below. > > And events overtook this one. Turns out that commit b58cc46c5f6b > (rcu: Don't offload callbacks unless specifically requested) was not > one of my best efforts. > > I will adapt your patch 2/2 in this series and apply it with your > Signed-off-by. Patch 1/2 is obsoleted by the current fix for > commit b58cc46c5f6b. > OK. I am curious to see what problem you found in that commit. I look forward to see your updated patch. >> > --- >> > v2: no change from v1 >> > >> > kernel/rcu/tree_plugin.h | 23 ++++++++++++----------- >> > 1 file changed, 12 insertions(+), 11 deletions(-) >> > >> > diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h >> > index 520538a..9c9a01c 100644 >> > --- a/kernel/rcu/tree_plugin.h >> > +++ b/kernel/rcu/tree_plugin.h >> > @@ -54,7 +54,10 @@ static void __init rcu_bootup_announce_oddness_nocb(void) >> > { >> > #ifndef CONFIG_RCU_NOCB_CPU_NONE >> > if (!have_rcu_nocb_mask) { >> > - zalloc_cpumask_var(&rcu_nocb_mask, GFP_KERNEL); >> > + if (!zalloc_cpumask_var(&rcu_nocb_mask, GFP_KERNEL)) { >> > + pr_info("rcu_nocb_mask allocation failed\n"); >> > + return; >> > + } >> > have_rcu_nocb_mask = true; >> > } >> > #ifdef CONFIG_RCU_NOCB_CPU_ZERO >> > @@ -66,17 +69,15 @@ static void __init rcu_bootup_announce_oddness_nocb(void) >> > cpumask_copy(rcu_nocb_mask, cpu_possible_mask); >> > #endif /* #ifdef CONFIG_RCU_NOCB_CPU_ALL */ >> > #endif /* #ifndef CONFIG_RCU_NOCB_CPU_NONE */ >> > - if (have_rcu_nocb_mask) { >> > - if (!cpumask_subset(rcu_nocb_mask, cpu_possible_mask)) { >> > - pr_info("\tNote: kernel parameter 'rcu_nocbs=' contains nonexistent CPUs.\n"); >> > - cpumask_and(rcu_nocb_mask, cpu_possible_mask, >> > - rcu_nocb_mask); >> > - } >> > - cpulist_scnprintf(nocb_buf, sizeof(nocb_buf), rcu_nocb_mask); >> > - pr_info("\tOffload RCU callbacks from CPUs: %s.\n", nocb_buf); >> > - if (rcu_nocb_poll) >> > - pr_info("\tPoll for callbacks from no-CBs CPUs.\n"); >> > + if (!cpumask_subset(rcu_nocb_mask, cpu_possible_mask)) { >> >> What happens if CONFIG_RCU_NOCB_CPU_NONE=y and the rcu_nocbs= boot >> parameter is not specified and we get here? >> >> In order to get visible failures when testing, build with >> CONFIG_CPUMASK_OFFSTACK=y. >> >> > + pr_info("\tNote: kernel parameter 'rcu_nocbs=' contains nonexistent CPUs.\n"); >> > + cpumask_and(rcu_nocb_mask, cpu_possible_mask, >> > + rcu_nocb_mask); >> > } >> > + cpulist_scnprintf(nocb_buf, sizeof(nocb_buf), rcu_nocb_mask); >> > + pr_info("\tOffload RCU callbacks from CPUs: %s.\n", nocb_buf); >> > + if (rcu_nocb_poll) >> > + pr_info("\tPoll for callbacks from no-CBs CPUs.\n"); >> > } >> > >> > /* >> > -- >> > 2.0.1 >> > > -- Pranith