Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751396AbaDOWcl (ORCPT ); Tue, 15 Apr 2014 18:32:41 -0400 Received: from mx1.redhat.com ([209.132.183.28]:63483 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750919AbaDOWck (ORCPT ); Tue, 15 Apr 2014 18:32:40 -0400 Date: Tue, 15 Apr 2014 18:29:51 -0400 From: Dave Jones To: "Paul E. McKenney" Cc: cl@linux.com, linux-kernel@vger.kernel.org, mingo@kernel.org, tj@kernel.org, grygorii.strashko@ti.com, peterz@infradead.org Subject: Re: How do I increment a per-CPU variable without warning? Message-ID: <20140415222951.GA742@redhat.com> Mail-Followup-To: Dave Jones , "Paul E. McKenney" , cl@linux.com, linux-kernel@vger.kernel.org, mingo@kernel.org, tj@kernel.org, grygorii.strashko@ti.com, peterz@infradead.org References: <20140415221755.GA27188@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140415221755.GA27188@linux.vnet.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 Tue, Apr 15, 2014 at 03:17:55PM -0700, Paul E. McKenney wrote: > My current admittedly crude workaround is as follows: > > static inline bool rcu_should_resched(void) > { > int t; > > #ifdef CONFIG_DEBUG_PREEMPT > preempt_disable(); > #endif /* #ifdef CONFIG_DEBUG_PREEMPT */ > t = __this_cpu_read(rcu_cond_resched_count) + 1; > if (t < RCU_COND_RESCHED_LIM) { > __this_cpu_write(rcu_cond_resched_count, t); > #ifdef CONFIG_DEBUG_PREEMPT > preempt_enable(); > #endif /* #ifdef CONFIG_DEBUG_PREEMPT */ > return false; > } > #ifdef CONFIG_DEBUG_PREEMPT > preempt_enable(); > #endif /* #ifdef CONFIG_DEBUG_PREEMPT */ > return true; > } Won't using DEBUG_PREEMPT instead of just CONFIG_PREEMPT here make this silently do the wrong thing if preemption is enabled, but debugging isn't ? I'm not seeing why you need the ifdefs at all, unless the implied barrier() is a problem ? Dave -- 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/