Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753493AbaDXNF3 (ORCPT ); Thu, 24 Apr 2014 09:05:29 -0400 Received: from mx1.redhat.com ([209.132.183.28]:24960 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753179AbaDXNF0 (ORCPT ); Thu, 24 Apr 2014 09:05:26 -0400 Date: Thu, 24 Apr 2014 09:04:52 -0400 From: Rik van Riel To: paulmck@linux.vnet.ibm.com Cc: Jiri Kosina , linux-kernel@vger.kernel.org, joern@logfs.org, peterz@infradead.org, Andrew Morton , cxie@redhat.com, Greg Kroah-Hartman , Jiri Slaby Subject: [PATCH RFC] sysrq,rcu: suppress RCU stall warnings while sysrq runs Message-ID: <20140424090452.3482f95c@annuminas.surriel.com> In-Reply-To: <20140424014648.GK4496@linux.vnet.ibm.com> References: <20140423125352.704f9fb2@annuminas.surriel.com> <535833AE.6010505@redhat.com> <20140424014648.GK4496@linux.vnet.ibm.com> Organization: Red Hat, Inc. MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org As suggested by Paul McKenney... This seems small and simple enough that it should not introduce any extra maintenance work in the future. ---8<--- Some sysrq handlers can run for a long time, because they dump a lot of data onto a serial console. Having RCU stall warnings pop up in the middle of them only makes the problem worse. This patch temporarily disables RCU stall warnings while a sysrq request is handled. Signed-off-by: Rik van Riel Suggested-by: Paul McKenney --- drivers/tty/sysrq.c | 2 ++ include/linux/rcupdate.h | 2 ++ kernel/rcu/update.c | 11 +++++++++++ 3 files changed, 15 insertions(+) diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c index 3c61e9b..dd53af9 100644 --- a/drivers/tty/sysrq.c +++ b/drivers/tty/sysrq.c @@ -511,6 +511,7 @@ void __handle_sysrq(int key, bool check_mask) int orig_log_level; int i; + rcu_sysrq_start(); rcu_read_lock(); /* * Raise the apparent loglevel to maximum so that the sysrq header @@ -554,6 +555,7 @@ void __handle_sysrq(int key, bool check_mask) console_loglevel = orig_log_level; } rcu_read_unlock(); + rcu_sysrq_end(); } void handle_sysrq(int key) diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 00a7fd6..b9a95f8 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -227,6 +227,8 @@ void rcu_idle_enter(void); void rcu_idle_exit(void); void rcu_irq_enter(void); void rcu_irq_exit(void); +void rcu_sysrq_start(void); +void rcu_sysrq_end(void); #ifdef CONFIG_RCU_USER_QS void rcu_user_enter(void); diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c index 4c0a9b0..2ac3289 100644 --- a/kernel/rcu/update.c +++ b/kernel/rcu/update.c @@ -320,6 +320,17 @@ int rcu_jiffies_till_stall_check(void) return till_stall_check * HZ + RCU_STALL_DELAY_DELTA; } +void rcu_sysrq_start(void) +{ + rcu_cpu_stall_suppress = 2; +} + +void rcu_sysrq_end(void) +{ + if (rcu_cpu_stall_suppress == 2) + rcu_cpu_stall_suppress = 0; +} + static int rcu_panic(struct notifier_block *this, unsigned long ev, void *ptr) { rcu_cpu_stall_suppress = 1; -- 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/