From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755583AbdC2JaG (ORCPT ); Wed, 29 Mar 2017 05:30:06 -0400 Received: from mail-pg0-f65.google.com ([74.125.83.65]:34055 "EHLO mail-pg0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754894AbdC2J3x (ORCPT ); Wed, 29 Mar 2017 05:29:53 -0400 From: Sergey Senozhatsky To: Steven Rostedt , Petr Mladek Cc: Jan Kara , Andrew Morton , Linus Torvalds , Peter Zijlstra , "Rafael J . Wysocki" , Eric Biederman , Greg Kroah-Hartman , Jiri Slaby , Pavel Machek , Len Brown , linux-kernel@vger.kernel.org, Sergey Senozhatsky , Sergey Senozhatsky Subject: [RFC][PATCHv2 7/8] printk: add printk emergency_mode parameter Date: Wed, 29 Mar 2017 18:25:10 +0900 Message-Id: <20170329092511.3958-8-sergey.senozhatsky@gmail.com> X-Mailer: git-send-email 2.12.2 In-Reply-To: <20170329092511.3958-1-sergey.senozhatsky@gmail.com> References: <20170329092511.3958-1-sergey.senozhatsky@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This param permits user-space to forcibly on/off printk emergency mode via /sys/module/printk/parameters/emergency_mode node. We have annotated sections in the kernel that switch printk to emergency, but there might be places/cases when user space would want to have printk operate in emergency mode all the time. Signed-off-by: Sergey Senozhatsky --- kernel/printk/printk.c | 20 +++++++++++++++++++- 1 file changed, 19 insertions(+), 1 deletion(-) diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index 1927b5cb5cbe..0d96839bb450 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -455,7 +455,7 @@ static struct task_struct *printk_kthread __read_mostly; static atomic_t printk_emergency __read_mostly; /* * Disable printk_kthread permanently. Unlike `oops_in_progress' - * it doesn't go back to 0. + * it doesn't go back to 0 (unless enforced by user-space). */ static bool printk_kthread_disabled __read_mostly; @@ -483,6 +483,24 @@ void printk_emergency_end(void) atomic_dec(&printk_emergency); } +static int printk_kthread_disabled_set(const char *val, + const struct kernel_param *kp) +{ + return param_set_bool(val, kp); +} + +static const struct kernel_param_ops printk_kthread_disabled_ops = { + .set = printk_kthread_disabled_set, + .get = param_get_bool, +}; + +module_param_cb(emergency_mode, + &printk_kthread_disabled_ops, + &printk_kthread_disabled, + 0644); +MODULE_PARM_DESC(emergency_mode, + "don't offload message printing to printk kthread"); + /* Return log buffer address */ char *log_buf_addr_get(void) { -- 2.12.2