From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753410AbdHODAe (ORCPT ); Mon, 14 Aug 2017 23:00:34 -0400 Received: from mail-pg0-f68.google.com ([74.125.83.68]:36733 "EHLO mail-pg0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753208AbdHODAc (ORCPT ); Mon, 14 Aug 2017 23:00:32 -0400 From: Sergey Senozhatsky To: Petr Mladek , Steven Rostedt Cc: Jan Kara , Andrew Morton , Peter Zijlstra , "Rafael J . Wysocki" , Eric Biederman , Greg Kroah-Hartman , Jiri Slaby , Pavel Machek , Andreas Mohr , Tetsuo Handa , linux-kernel@vger.kernel.org, Sergey Senozhatsky , Sergey Senozhatsky Subject: [RFC][PATCHv5 08/13] printk: set watchdog_thresh as maximum value for atomic_print_limit Date: Tue, 15 Aug 2017 11:56:20 +0900 Message-Id: <20170815025625.1977-9-sergey.senozhatsky@gmail.com> X-Mailer: git-send-email 2.14.1 In-Reply-To: <20170815025625.1977-1-sergey.senozhatsky@gmail.com> References: <20170815025625.1977-1-sergey.senozhatsky@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org There is no point in setting `atomic_print_limit' significantly larger than watchdog's lockup threshold. This highly increases the chances of lockups. Watchdog's softlockup threshold is `2 * watchdog_thresh', but we limit `atomic_print_limit' to just `watchdog_thresh'. Signed-off-by: Sergey Senozhatsky --- kernel/printk/printk.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index b14e35f94596..12284aa30025 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -545,6 +545,19 @@ int printk_emergency_end_sync(void) } EXPORT_SYMBOL_GPL(printk_emergency_end_sync); +/* + * We offload to make watchdog lockup detector happy, there is little + * point (no point at all) in setting `atomic_print_limit' larger than + * `watchdog_thresh'. + */ +static inline void adj_atomic_print_limit(void) +{ +#ifdef CONFIG_LOCKUP_DETECTOR + if (watchdog_thresh && atomic_print_limit > watchdog_thresh) + atomic_print_limit = watchdog_thresh; +#endif +} + /* * Under heavy printing load or with a slow serial console (or both) * console_unlock() can stall CPUs, which can result in soft/hard-lockups, @@ -580,6 +593,8 @@ static inline bool console_offload_printing(void) if (current == printk_kthread) return false; + adj_atomic_print_limit(); + if (!time_after_eq(now, printing_start_ts + atomic_print_limit)) return false; -- 2.14.1