From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753583Ab3A2F45 (ORCPT ); Tue, 29 Jan 2013 00:56:57 -0500 Received: from e32.co.us.ibm.com ([32.97.110.150]:57326 "EHLO e32.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753330Ab3A2F4z (ORCPT ); Tue, 29 Jan 2013 00:56:55 -0500 Date: Mon, 28 Jan 2013 21:56:43 -0800 From: "Paul E. McKenney" To: Josh Triplett Cc: linux-kernel@vger.kernel.org, mingo@elte.hu, laijs@cn.fujitsu.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@polymtl.ca, niv@us.ibm.com, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, Valdis.Kletnieks@vt.edu, dhowells@redhat.com, edumazet@google.com, darren@dvhart.com, fweisbec@gmail.com, sbw@mit.edu, "Paul E. McKenney" Subject: Re: [PATCH tip/core/rcu 1/2] rcu: Provide RCU CPU stall warnings for tiny RCU Message-ID: <20130129055643.GS6395@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20130127002328.GA4847@linux.vnet.ibm.com> <1359246227-5770-1-git-send-email-paulmck@linux.vnet.ibm.com> <20130127105708.GD3119@leaf> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130127105708.GD3119@leaf> User-Agent: Mutt/1.5.21 (2010-09-15) X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13012905-5406-0000-0000-000004A90834 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Jan 27, 2013 at 09:57:08PM +1100, Josh Triplett wrote: > On Sat, Jan 26, 2013 at 04:23:46PM -0800, Paul E. McKenney wrote: > > From: "Paul E. McKenney" > > > > Tiny RCU has historically omitted RCU CPU stall warnings in order to > > reduce memory requirements, however, lack of these warnings caused > > Thomas Gleixner some debugging pain recently. Therefore, this commit > > adds RCU CPU stall warnings to tiny RCU if RCU_TRACE=y. This keeps > > the memory footprint small, while still enabling CPU stall warnings > > in kernels built to enable them. > > > > Updated to include Josh Triplett's suggested use of RCU_STALL_COMMON > > config variable to simplify #if expressions. > > > > Reported-by: Thomas Gleixner > > Signed-off-by: Paul E. McKenney > > Signed-off-by: Paul E. McKenney > > One suggestion below; with that change, > Reviewed-by: Josh Triplett > > > --- a/init/Kconfig > > +++ b/init/Kconfig > > @@ -486,6 +486,14 @@ config PREEMPT_RCU > > This option enables preemptible-RCU code that is common between > > the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations. > > > > +config RCU_STALL_COMMON > > + def_bool ( TREE_RCU || TREE_PREEMPT_RCU || RCU_TRACE ) > > + help > > + This option enables RCU CPU stall code that is common between > > + the TINY and TREE variants of RCU. The purpose is to allow > > + the tiny variants to disable RCU CPU stall warnings, while > > + making these warnings mandatory for the tree variants. > > + > [...] > > --- a/lib/Kconfig.debug > > +++ b/lib/Kconfig.debug > > @@ -970,7 +970,7 @@ config RCU_TORTURE_TEST_RUNNABLE > > > > config RCU_CPU_STALL_TIMEOUT > > int "RCU CPU stall timeout in seconds" > > - depends on TREE_RCU || TREE_PREEMPT_RCU > > + depends on TREE_RCU || TREE_PREEMPT_RCU || RCU_TRACE > > depends on RCU_STALL_COMMON Good catch, fixed! Thanx, Paul