From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753712Ab2LJO3Y (ORCPT ); Mon, 10 Dec 2012 09:29:24 -0500 Received: from e39.co.us.ibm.com ([32.97.110.160]:60391 "EHLO e39.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752020Ab2LJO3W (ORCPT ); Mon, 10 Dec 2012 09:29:22 -0500 Date: Mon, 10 Dec 2012 06:29:14 -0800 From: "Paul E. McKenney" To: Frank Rowand Cc: "linux-kernel@vger.kernel.org" , "linux-rt-users@vger.kernel.org" , "tglx@linutronix.de" , "dipankar@in.ibm.com" , "linux-arm-kernel@lists.infradead.org" Subject: Re: [PATCH RT 2/2][RFC] let RCU stall messages escape with CONFIG_PREEMPT_RT_FULL Message-ID: <20121210142914.GP2516@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <50BED1DA.7070907@am.sony.com> <50BED305.9090308@am.sony.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <50BED305.9090308@am.sony.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-Content-Scanned: Fidelis XPS MAILER x-cbid: 12121014-3620-0000-0000-00000096FB7C Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Dec 04, 2012 at 08:52:21PM -0800, Frank Rowand wrote: > > The printk()s in RCU stall warnings do not get flushed to the console > on ARM. Add the oops_in_progress flag back into the special trylock case in > console_trylock_for_printk(), and set the flag using "bust_spinlocks(1)". > This allows the printk() output to be flushed to the console. > > Signed-off-by: Frank Rowand Is bust_spinlocks(1) appropriate for all architectures, or should this be conditioned on architectures that need oops_in_progress to be set? Thanx, Paul > --- > kernel/printk.c | 5 3 + 2 - 0 ! > kernel/rcutree.c | 14 14 + 0 - 0 ! > 2 files changed, 17 insertions(+), 2 deletions(-) > > Index: b/kernel/printk.c > =================================================================== > --- a/kernel/printk.c > +++ b/kernel/printk.c > @@ -1390,8 +1390,9 @@ static int console_trylock_for_printk(un > { > int retval = 0, wake = 0; > #ifdef CONFIG_PREEMPT_RT_FULL > - int lock = !early_boot_irqs_disabled && !irqs_disabled_flags(flags) && > - (preempt_count() <= 1); > + int lock = oops_in_progress || ( > + !early_boot_irqs_disabled && !irqs_disabled_flags(flags) && > + (preempt_count() <= 1)); > #else > int lock = 1; > #endif > Index: b/kernel/rcutree.c > =================================================================== > --- a/kernel/rcutree.c > +++ b/kernel/rcutree.c > @@ -758,6 +758,11 @@ static void print_other_cpu_stall(struct > raw_spin_unlock_irqrestore(&rnp->lock, flags); > > /* > + * Allow printk() to flush to device > + */ > + bust_spinlocks(1); > + > + /* > * OK, time to rat on our buddy... > * See Documentation/RCU/stallwarn.txt for info on how to debug > * RCU CPU stall warnings. > @@ -799,6 +804,8 @@ static void print_other_cpu_stall(struct > > rcu_print_detail_task_stall(rsp); > > + bust_spinlocks(0); > + > force_quiescent_state(rsp, 0); /* Kick them all. */ > } > > @@ -808,6 +815,11 @@ static void print_cpu_stall(struct rcu_s > struct rcu_node *rnp = rcu_get_root(rsp); > > /* > + * Allow printk() to flush to device > + */ > + bust_spinlocks(1); > + > + /* > * OK, time to rat on ourselves... > * See Documentation/RCU/stallwarn.txt for info on how to debug > * RCU CPU stall warnings. > @@ -820,6 +832,8 @@ static void print_cpu_stall(struct rcu_s > if (!trigger_all_cpu_backtrace()) > dump_stack(); > > + bust_spinlocks(0); > + > raw_spin_lock_irqsave(&rnp->lock, flags); > if (ULONG_CMP_GE(jiffies, rsp->jiffies_stall)) > rsp->jiffies_stall = jiffies + >