LKML Archive on lore.kernel.org
 help / color / Atom feed
From: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
To: Petr Mladek <pmladek@suse.com>, Steven Rostedt <rostedt@goodmis.org>
Cc: Jan Kara <jack@suse.cz>,
	Andrew Morton <akpm@linux-foundation.org>,
	Peter Zijlstra <peterz@infradead.org>,
	"Rafael J . Wysocki" <rjw@rjwysocki.net>,
	Eric Biederman <ebiederm@xmission.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Jiri Slaby <jslaby@suse.com>, Pavel Machek <pavel@ucw.cz>,
	Andreas Mohr <andi@lisas.de>,
	Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>,
	linux-kernel@vger.kernel.org,
	Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
	Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Subject: [RFC][PATCHv5 06/13] printk: register PM notifier
Date: Tue, 15 Aug 2017 11:56:18 +0900
Message-ID: <20170815025625.1977-7-sergey.senozhatsky@gmail.com> (raw)
In-Reply-To: <20170815025625.1977-1-sergey.senozhatsky@gmail.com>

It's not always possible/safe to wake_up() printk kernel
thread. For example, late suspend/early resume may printk()
while timekeeping is not initialized yet, so calling into the
scheduler may result in recursive warnings.

Another thing to notice is the fact that PM at some point
freezes user space and kernel threads: freeze_processes()
and freeze_kernel_threads(), correspondingly. Thus we need
printk() to operate in emergency mode there and attempt to
immediately flush pending kernel message to the console.

This patch registers PM notifier, so PM can switch printk
to emergency mode from PM_FOO_PREPARE notifiers and return
back to printk threaded mode from PM_POST_FOO notifiers.

Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Suggested-by: Andreas Mohr <andi@lisas.de>
---
 kernel/printk/printk.c | 35 +++++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 05165f008bc8..d3f149fad85c 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -49,6 +49,7 @@
 #include <linux/sched/debug.h>
 #include <linux/sched/task_stack.h>
 #include <linux/kthread.h>
+#include <linux/suspend.h>
 
 #include <linux/uaccess.h>
 #include <asm/sections.h>
@@ -2913,6 +2914,33 @@ static DEFINE_PER_CPU(struct irq_work, wake_up_klogd_work) = {
 	.flags = IRQ_WORK_LAZY,
 };
 
+static int printk_pm_notify(struct notifier_block *notify_block,
+			    unsigned long mode, void *unused)
+{
+	switch (mode) {
+	case PM_HIBERNATION_PREPARE:
+	case PM_SUSPEND_PREPARE:
+	case PM_RESTORE_PREPARE:
+		printk_emergency_begin_sync();
+		break;
+
+	case PM_POST_SUSPEND:
+	case PM_POST_HIBERNATION:
+	case PM_POST_RESTORE:
+		printk_emergency_end_sync();
+		break;
+
+	default:
+		return NOTIFY_DONE;
+	}
+
+	return NOTIFY_OK;
+}
+
+static struct notifier_block printk_pm_nb = {
+	.notifier_call = printk_pm_notify,
+};
+
 static int printk_kthread_func(void *data)
 {
 	while (1) {
@@ -2960,9 +2988,16 @@ static int __init init_printk_kthread(void)
 	if (!alloc_cpumask_var(&printk_offload_cpus, GFP_KERNEL))
 		return -ENOMEM;
 
+	if (register_pm_notifier(&printk_pm_nb) != 0) {
+		pr_err("printk: unable to register PM notifier\n");
+		free_cpumask_var(printk_offload_cpus);
+		return -EINVAL;
+	}
+
 	thread = kthread_run(printk_kthread_func, NULL, "printk");
 	if (IS_ERR(thread)) {
 		pr_err("printk: unable to create printing thread\n");
+		unregister_pm_notifier(&printk_pm_nb);
 		free_cpumask_var(printk_offload_cpus);
 		return PTR_ERR(thread);
 	}
-- 
2.14.1

  parent reply index

Thread overview: 94+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-08-15  2:56 [RFC][PATCHv5 00/13] printk: introduce printing kernel thread Sergey Senozhatsky
2017-08-15  2:56 ` [RFC][PATCHv5 01/13] printk: move printk_pending out of per-cpu Sergey Senozhatsky
2017-08-15  2:56 ` [RFC][PATCHv5 02/13] printk: introduce printing kernel thread Sergey Senozhatsky
2017-08-15  2:56 ` [RFC][PATCHv5 03/13] printk: add sync printk_emergency API Sergey Senozhatsky
2017-08-15  2:56 ` [RFC][PATCHv5 04/13] printk: add enforce_emergency parameter Sergey Senozhatsky
2017-08-15  2:56 ` [RFC][PATCHv5 05/13] printk: enable printk offloading Sergey Senozhatsky
2017-08-15  2:56 ` Sergey Senozhatsky [this message]
2017-08-15 11:51   ` [RFC][PATCHv5 06/13] printk: register PM notifier Rafael J. Wysocki
2017-08-16  7:31     ` Sergey Senozhatsky
2017-08-16 12:58       ` Rafael J. Wysocki
2017-08-17  5:55         ` Sergey Senozhatsky
2017-08-17 15:43           ` Rafael J. Wysocki
2017-08-17 23:19             ` Sergey Senozhatsky
2017-08-15  2:56 ` [RFC][PATCHv5 07/13] printk: register syscore notifier Sergey Senozhatsky
2017-08-15 11:56   ` Rafael J. Wysocki
2017-08-16  6:55     ` Sergey Senozhatsky
2017-08-16 12:59       ` Rafael J. Wysocki
2017-08-15  2:56 ` [RFC][PATCHv5 08/13] printk: set watchdog_thresh as maximum value for atomic_print_limit Sergey Senozhatsky
2017-08-15  2:56 ` [RFC][PATCHv5 09/13] printk: add auto-emergency enforcement mechanism Sergey Senozhatsky
2017-08-15  2:56 ` [RFC][PATCHv5 10/13] printk: force printk_kthread to offload printing Sergey Senozhatsky
2017-08-15  2:56 ` [RFC][PATCHv5 11/13] printk: always offload printing from user-space processes Sergey Senozhatsky
2017-08-15  2:56 ` [RFC][PATCHv5 12/13] printk: do not cond_resched() when we can offload Sergey Senozhatsky
2017-08-15  2:56 ` [RFC][PATCHv5 13/13] printk: move offloading logic to per-cpu Sergey Senozhatsky
2017-08-23  8:33 ` [RFC][PATCHv5 00/13] printk: introduce printing kernel thread Sergey Senozhatsky
2017-08-28  9:05 ` printk: what is going on with additional newlines? Pavel Machek
2017-08-28 10:28   ` Sergey Senozhatsky
2017-08-28 12:21     ` Sergey Senozhatsky
2017-08-28 12:38       ` Sergey Senozhatsky
2017-08-28 12:46       ` Pavel Machek
2017-08-29 13:40         ` Sergey Senozhatsky
2017-08-29 16:37           ` Joe Perches
2017-08-29 17:00           ` Linus Torvalds
2017-08-29 17:12             ` Linus Torvalds
2017-08-29 20:41               ` Tetsuo Handa
2017-08-29 20:51                 ` Linus Torvalds
2017-09-02  6:12                   ` Tetsuo Handa
2017-09-02 17:06                     ` Linus Torvalds
2017-08-29 23:50               ` Steven Rostedt
2017-08-29 23:59                 ` Linus Torvalds
2017-08-30  1:03                 ` Sergey Senozhatsky
2017-08-30  1:10                   ` Steven Rostedt
2017-08-30  1:51                     ` Sergey Senozhatsky
2017-08-30  1:52                     ` Joe Perches
2017-08-30  2:25                       ` Sergey Senozhatsky
2017-08-30  2:31                         ` Joe Perches
2017-08-30  2:47                           ` Sergey Senozhatsky
2017-08-30  2:58                             ` Joe Perches
2017-08-30  5:37                               ` Sergey Senozhatsky
2017-09-08 10:18                                 ` Pavel Machek
2017-09-05  9:44                             ` Petr Mladek
2017-09-05  9:59                               ` Sergey Senozhatsky
2017-09-05 12:21                                 ` Petr Mladek
2017-09-05 12:35                                   ` Tetsuo Handa
2017-09-05 14:18                                     ` Sergey Senozhatsky
2017-09-05 13:42                                   ` Sergey Senozhatsky
2017-09-06  7:55                                     ` Petr Mladek
2017-09-17  6:26                                       ` Sergey Senozhatsky
2017-09-17  9:27                                         ` Sergey Senozhatsky
2017-09-17 15:35                                         ` Linus Torvalds
2017-09-18  0:46                                           ` Sergey Senozhatsky
2017-09-18  2:22                                             ` Joe Perches
2017-09-18  2:41                                               ` Sergey Senozhatsky
2017-09-18  2:45                                                 ` Joe Perches
2017-09-18  2:55                                                   ` Sergey Senozhatsky
2017-09-18  3:07                                                     ` Joe Perches
2017-09-18  4:42                                                       ` Sergey Senozhatsky
2017-09-01 13:19                     ` Sergey Senozhatsky
2017-09-01 17:32                       ` Joe Perches
2017-09-01 20:21                         ` Linus Torvalds
2017-09-04  5:22                           ` Sergey Senozhatsky
2017-09-04  5:41                             ` Joe Perches
2017-09-05 14:54                             ` Steven Rostedt
2017-09-06  2:14                               ` Sergey Senozhatsky
2017-09-06  2:36                               ` Linus Torvalds
2017-09-04  4:30                         ` Sergey Senozhatsky
2017-09-04  5:24                           ` Sergey Senozhatsky
2017-08-29 17:33             ` Sergey Senozhatsky
2017-08-29 17:52               ` Linus Torvalds
2017-08-29 18:09                 ` Joe Perches
2017-08-30  1:07                   ` Sergey Senozhatsky
2017-08-30  0:58                 ` Sergey Senozhatsky
2017-08-29 16:48   ` Linus Torvalds
2017-08-29 17:10     ` Joe Perches
2017-08-29 17:20       ` Linus Torvalds
2017-08-29 17:33         ` Joe Perches
2017-08-29 17:36           ` Linus Torvalds
2017-08-29 17:48             ` Joe Perches
2017-08-29 20:24     ` Pavel Machek
2017-09-01  1:40       ` Sergey Senozhatsky
2017-09-01  2:04         ` Joe Perches
2017-09-01  6:59           ` Pavel Machek
2017-09-01  7:23             ` Joe Perches
2017-09-01  7:29         ` Pavel Machek
2017-09-01 11:13           ` Steven Rostedt

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20170815025625.1977-7-sergey.senozhatsky@gmail.com \
    --to=sergey.senozhatsky@gmail.com \
    --cc=akpm@linux-foundation.org \
    --cc=andi@lisas.de \
    --cc=ebiederm@xmission.com \
    --cc=gregkh@linuxfoundation.org \
    --cc=jack@suse.cz \
    --cc=jslaby@suse.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=pavel@ucw.cz \
    --cc=penguin-kernel@I-love.SAKURA.ne.jp \
    --cc=peterz@infradead.org \
    --cc=pmladek@suse.com \
    --cc=rjw@rjwysocki.net \
    --cc=rostedt@goodmis.org \
    --cc=sergey.senozhatsky.work@gmail.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

LKML Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/lkml/0 lkml/git/0.git
	git clone --mirror https://lore.kernel.org/lkml/1 lkml/git/1.git
	git clone --mirror https://lore.kernel.org/lkml/2 lkml/git/2.git
	git clone --mirror https://lore.kernel.org/lkml/3 lkml/git/3.git
	git clone --mirror https://lore.kernel.org/lkml/4 lkml/git/4.git
	git clone --mirror https://lore.kernel.org/lkml/5 lkml/git/5.git
	git clone --mirror https://lore.kernel.org/lkml/6 lkml/git/6.git
	git clone --mirror https://lore.kernel.org/lkml/7 lkml/git/7.git
	git clone --mirror https://lore.kernel.org/lkml/8 lkml/git/8.git
	git clone --mirror https://lore.kernel.org/lkml/9 lkml/git/9.git
	git clone --mirror https://lore.kernel.org/lkml/10 lkml/git/10.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 lkml lkml/ https://lore.kernel.org/lkml \
		linux-kernel@vger.kernel.org
	public-inbox-index lkml

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-kernel


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git