From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ingo Molnar Subject: Re: [PATCH RFC] v2 expedited "big hammer" RCU grace periods Date: Sun, 26 Apr 2009 13:27:17 +0200 Message-ID: <20090426112717.GE10391@elte.hu> References: <20090426052340.GA24931@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linux-kernel@vger.kernel.org, netdev@vger.kernel.org, netfilter-devel@vger.kernel.org, akpm@linux-foundation.org, torvalds@linux-foundation.org, davem@davemloft.net, dada1@cosmosbay.com, zbr@ioremap.net, jeff.chua.linux@gmail.com, paulus@samba.org, laijs@cn.fujitsu.com, jengelh@medozas.de, r000n@r000n.net, benh@kernel.crashing.org, mathieu.desnoyers@polymtl.ca To: "Paul E. McKenney" Return-path: Content-Disposition: inline In-Reply-To: <20090426052340.GA24931@linux.vnet.ibm.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: netfilter-devel.vger.kernel.org * Paul E. McKenney wrote: > Second cut of "big hammer" expedited RCU grace periods, but only > for rcu_bh. This creates another softirq vector, so that entering > this softirq vector will have forced an rcu_bh quiescent state (as > noted by Dave Miller). Use smp_call_function() to invoke > raise_softirq() on all CPUs in order to cause this to happen. > Track the CPUs that have passed through a quiescent state (or gone > offline) with a cpumask. hm, i'm still asking whether doing this would be simpler via a reschedule vector - which not only is an existing facility but also forces all RCU domains through a quiescent state - not just bh-RCU participants. Triggering a new softirq is in no way simpler that doing an SMP cross-call - in fact softirqs are a finite resource so using some other facility would be preferred. Am i missing something? Ingo