linux-kernel - [PATCH 02/25] kernel/printk: Convert to hotplug state machine

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Date:   Thu,  3 Nov 2016 15:49:58 +0100
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     linux-kernel@...r.kernel.org
Cc:     rt@...utronix.de,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH 02/25] kernel/printk: Convert to hotplug state machine

Install the callbacks via the state machine.

Cc: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
 include/linux/cpuhotplug.h |  1 +
 kernel/printk/printk.c     | 27 ++++++++++++---------------
 2 files changed, 13 insertions(+), 15 deletions(-)

diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index 69b74fa0da60..4174083280d7 100644
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -31,6 +31,7 @@ enum cpuhp_state {
 	CPUHP_S390_PFAULT_DEAD,
 	CPUHP_BLK_MQ_DEAD,
 	CPUHP_FS_BUFF_DEAD,
+	CPUHP_PRINTK_DEAD,
 	CPUHP_WORKQUEUE_PREP,
 	CPUHP_POWER_NUMA_PREPARE,
 	CPUHP_HRTIMERS_PREPARE,
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index de08fc90baaf..4487ffcd42d5 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -2185,27 +2185,18 @@ void resume_console(void)
 
 /**
  * console_cpu_notify - print deferred console messages after CPU hotplug
- * @self: notifier struct
- * @action: CPU hotplug event
- * @hcpu: unused
+ * @cpu: unused
  *
  * If printk() is called from a CPU that is not online yet, the messages
  * will be spooled but will not show up on the console.  This function is
  * called when a new CPU comes online (or fails to come up), and ensures
  * that any such output gets printed.
  */
-static int console_cpu_notify(struct notifier_block *self,
-	unsigned long action, void *hcpu)
+static int console_cpu_notify(unsigned int cpu)
 {
-	switch (action) {
-	case CPU_ONLINE:
-	case CPU_DEAD:
-	case CPU_DOWN_FAILED:
-	case CPU_UP_CANCELED:
-		console_lock();
-		console_unlock();
-	}
-	return NOTIFY_OK;
+	console_lock();
+	console_unlock();
+	return 0;
 }
 
 /**
@@ -2843,6 +2834,7 @@ EXPORT_SYMBOL(unregister_console);
 static int __init printk_late_init(void)
 {
 	struct console *con;
+	int ret;
 
 	for_each_console(con) {
 		if (!keep_bootcon && con->flags & CON_BOOT) {
@@ -2857,7 +2849,12 @@ static int __init printk_late_init(void)
 				unregister_console(con);
 		}
 	}
-	hotcpu_notifier(console_cpu_notify, 0);
+	ret = cpuhp_setup_state_nocalls(CPUHP_PRINTK_DEAD, "printk:dead", NULL,
+					console_cpu_notify);
+	WARN_ON(ret < 0);
+	ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN, "printk:online",
+					console_cpu_notify, NULL);
+	WARN_ON(ret < 0);
 	return 0;
 }
 late_initcall(printk_late_init);
-- 
2.10.2