[printk,v2,02/38] printk: Convert console_drivers list to hlist

Message ID 20221019145600.1282823-3-john.ogness@linutronix.de
State New
Headers
Series reduce console_lock scope |

Commit Message

John Ogness Oct. 19, 2022, 2:55 p.m. UTC
  Replace the open coded single linked list with a hlist so a conversion
to SRCU protected list walks can reuse the existing primitives.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
---
 fs/proc/consoles.c      |  3 +-
 include/linux/console.h |  8 ++--
 kernel/printk/printk.c  | 99 +++++++++++++++++++++++------------------
 3 files changed, 63 insertions(+), 47 deletions(-)
  

Comments

Greg KH Oct. 19, 2022, 3:44 p.m. UTC | #1
On Wed, Oct 19, 2022 at 05:01:24PM +0206, John Ogness wrote:
> Replace the open coded single linked list with a hlist so a conversion
> to SRCU protected list walks can reuse the existing primitives.
> 
> Signed-off-by: John Ogness <john.ogness@linutronix.de>
> ---
>  fs/proc/consoles.c      |  3 +-
>  include/linux/console.h |  8 ++--
>  kernel/printk/printk.c  | 99 +++++++++++++++++++++++------------------
>  3 files changed, 63 insertions(+), 47 deletions(-)
> 
> diff --git a/fs/proc/consoles.c b/fs/proc/consoles.c
> index dfe6ce3505ce..cf2e0788f9c7 100644
> --- a/fs/proc/consoles.c
> +++ b/fs/proc/consoles.c
> @@ -74,8 +74,9 @@ static void *c_start(struct seq_file *m, loff_t *pos)
>  static void *c_next(struct seq_file *m, void *v, loff_t *pos)
>  {
>  	struct console *con = v;
> +
>  	++*pos;
> -	return con->next;
> +	return hlist_entry_safe(con->node.next, struct console, node);
>  }
>  
>  static void c_stop(struct seq_file *m, void *v)
> diff --git a/include/linux/console.h b/include/linux/console.h
> index 8c1686e2c233..7b5f21f9e469 100644
> --- a/include/linux/console.h
> +++ b/include/linux/console.h
> @@ -15,6 +15,7 @@
>  #define _LINUX_CONSOLE_H_ 1
>  
>  #include <linux/atomic.h>
> +#include <linux/list.h>
>  #include <linux/types.h>
>  
>  struct vc_data;
> @@ -154,14 +155,16 @@ struct console {
>  	u64	seq;
>  	unsigned long dropped;
>  	void	*data;
> -	struct	 console *next;
> +	struct hlist_node node;
>  };
>  
> +extern struct hlist_head console_list;
> +
>  /*
>   * for_each_console() allows you to iterate on each console
>   */
>  #define for_each_console(con) \
> -	for (con = console_drivers; con != NULL; con = con->next)
> +	hlist_for_each_entry(con, &console_list, node)
>  
>  extern int console_set_on_cmdline;
>  extern struct console *early_console;
> @@ -174,7 +177,6 @@ enum con_flush_mode {
>  extern int add_preferred_console(char *name, int idx, char *options);
>  extern void register_console(struct console *);
>  extern int unregister_console(struct console *);
> -extern struct console *console_drivers;
>  extern void console_lock(void);
>  extern int console_trylock(void);
>  extern void console_unlock(void);
> diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
> index e4f1e7478b52..867becc40021 100644
> --- a/kernel/printk/printk.c
> +++ b/kernel/printk/printk.c
> @@ -79,13 +79,12 @@ int oops_in_progress;
>  EXPORT_SYMBOL(oops_in_progress);
>  
>  /*
> - * console_sem protects the console_drivers list, and also
> - * provides serialisation for access to the entire console
> - * driver system.
> + * console_sem protects console_list and console->flags updates, and also
> + * provides serialization for access to the entire console driver system.
>   */
>  static DEFINE_SEMAPHORE(console_sem);
> -struct console *console_drivers;
> -EXPORT_SYMBOL_GPL(console_drivers);
> +HLIST_HEAD(console_list);
> +EXPORT_SYMBOL_GPL(console_list);
>  
>  /*
>   * System may need to suppress printk message under certain
> @@ -2556,7 +2555,7 @@ static int console_cpu_notify(unsigned int cpu)
>   * console_lock - lock the console system for exclusive use.
>   *
>   * Acquires a lock which guarantees that the caller has
> - * exclusive access to the console system and the console_drivers list.
> + * exclusive access to the console system and console_list.
>   *
>   * Can sleep, returns nothing.
>   */
> @@ -2576,7 +2575,7 @@ EXPORT_SYMBOL(console_lock);
>   * console_trylock - try to lock the console system for exclusive use.
>   *
>   * Try to acquire a lock which guarantees that the caller has exclusive
> - * access to the console system and the console_drivers list.
> + * access to the console system and console_list.
>   *
>   * returns 1 on success, and 0 on failure to acquire the lock.
>   */
> @@ -2940,11 +2939,20 @@ void console_flush_on_panic(enum con_flush_mode mode)
>  	console_may_schedule = 0;
>  
>  	if (mode == CONSOLE_REPLAY_ALL) {
> +		struct hlist_node *tmp;
>  		struct console *c;
>  		u64 seq;
>  
>  		seq = prb_first_valid_seq(prb);
> -		for_each_console(c)
> +		/*
> +		 * This cannot use for_each_console() because it's not established
> +		 * that the current context has console locked and neither there is
> +		 * a guarantee that there is no concurrency in that case.
> +		 *
> +		 * Open code it for documentation purposes and pretend that
> +		 * it works.
> +		 */
> +		hlist_for_each_entry_safe(c, tmp, &console_list, node)
>  			c->seq = seq;
>  	}
>  	console_unlock();
> @@ -3081,6 +3089,9 @@ static void try_enable_default_console(struct console *newcon)
>  	       (con->flags & CON_BOOT) ? "boot" : "",	\
>  	       con->name, con->index, ##__VA_ARGS__)
>  
> +#define console_first()				\
> +	hlist_entry(console_list.first, struct console, node)
> +
>  /*
>   * The console driver calls this routine during kernel initialization
>   * to register the console printing procedure with printk() and to
> @@ -3140,8 +3151,8 @@ void register_console(struct console *newcon)
>  	 * flag set and will be first in the list.
>  	 */
>  	if (preferred_console < 0) {
> -		if (!console_drivers || !console_drivers->device ||
> -		    console_drivers->flags & CON_BOOT) {
> +		if (hlist_empty(&console_list) || !console_first()->device ||
> +		    console_first()->flags & CON_BOOT) {
>  			try_enable_default_console(newcon);
>  		}
>  	}
> @@ -3169,20 +3180,22 @@ void register_console(struct console *newcon)
>  	}
>  
>  	/*
> -	 *	Put this console in the list - keep the
> -	 *	preferred driver at the head of the list.
> +	 * Put this console in the list - keep the
> +	 * preferred driver at the head of the list.
>  	 */
>  	console_lock();
> -	if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) {
> -		newcon->next = console_drivers;
> -		console_drivers = newcon;
> -		if (newcon->next)
> -			newcon->next->flags &= ~CON_CONSDEV;
> -		/* Ensure this flag is always set for the head of the list */
> +	if (hlist_empty(&console_list)) {
> +		/* Ensure CON_CONSDEV is always set for the head. */
>  		newcon->flags |= CON_CONSDEV;
> +		hlist_add_head(&newcon->node, &console_list);
> +
> +	} else if (newcon->flags & CON_CONSDEV) {
> +		/* Only the new head can have CON_CONSDEV set. */
> +		console_first()->flags &= ~CON_CONSDEV;
> +		hlist_add_head(&newcon->node, &console_list);
> +
>  	} else {
> -		newcon->next = console_drivers->next;
> -		console_drivers->next = newcon;
> +		hlist_add_behind(&newcon->node, console_list.first);
>  	}
>  
>  	newcon->dropped = 0;
> @@ -3209,16 +3222,18 @@ void register_console(struct console *newcon)
>  	if (bootcon_enabled &&
>  	    ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV) &&
>  	    !keep_bootcon) {
> -		for_each_console(con)
> +		struct hlist_node *tmp;
> +
> +		hlist_for_each_entry_safe(con, tmp, &console_list, node) {
>  			if (con->flags & CON_BOOT)
>  				unregister_console(con);
> +		}
>  	}
>  }
>  EXPORT_SYMBOL(register_console);
>  
>  int unregister_console(struct console *console)
>  {
> -	struct console *con;
>  	int res;
>  
>  	con_printk(KERN_INFO, console, "disabled\n");
> @@ -3229,32 +3244,30 @@ int unregister_console(struct console *console)
>  	if (res > 0)
>  		return 0;
>  
> -	res = -ENODEV;
>  	console_lock();
> -	if (console_drivers == console) {
> -		console_drivers=console->next;
> -		res = 0;
> -	} else {
> -		for_each_console(con) {
> -			if (con->next == console) {
> -				con->next = console->next;
> -				res = 0;
> -				break;
> -			}
> -		}
> +
> +	/* Disable it unconditionally */
> +	console->flags &= ~CON_ENABLED;
> +
> +	if (hlist_unhashed(&console->node)) {

How can this ever be hit?  The console lock is held, so it shouldn't
have gone away already.  Or am I missing something else here?

Other than that minor question, looks good to me!

Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  
John Ogness Oct. 19, 2022, 9:46 p.m. UTC | #2
On 2022-10-19, Greg Kroah-Hartman <gregkh@linuxfoundation.org> wrote:
>> diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
>> index e4f1e7478b52..867becc40021 100644
>> --- a/kernel/printk/printk.c
>> +++ b/kernel/printk/printk.c
>> @@ -3229,32 +3244,30 @@ int unregister_console(struct console *console)
>>  	if (res > 0)
>>  		return 0;
>>  
>> -	res = -ENODEV;
>>  	console_lock();
>> -	if (console_drivers == console) {
>> -		console_drivers=console->next;
>> -		res = 0;
>> -	} else {
>> -		for_each_console(con) {
>> -			if (con->next == console) {
>> -				con->next = console->next;
>> -				res = 0;
>> -				break;
>> -			}
>> -		}
>> +
>> +	/* Disable it unconditionally */
>> +	console->flags &= ~CON_ENABLED;
>> +
>> +	if (hlist_unhashed(&console->node)) {
>
> How can this ever be hit?  The console lock is held, so it shouldn't
> have gone away already.  Or am I missing something else here?

Mainline also has this check. I expect it is for the case that some code
tries to call unregister_console() for a console that is not
registered.

Since register_console() does not return if it succeeded, I suppose some
code somewhere my try to unregister without knowing that it never
registered in the first place.

> Other than that minor question, looks good to me!
>
> Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Thanks!

John
  
Greg KH Oct. 20, 2022, 7:43 a.m. UTC | #3
On Wed, Oct 19, 2022 at 11:52:53PM +0206, John Ogness wrote:
> On 2022-10-19, Greg Kroah-Hartman <gregkh@linuxfoundation.org> wrote:
> >> diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
> >> index e4f1e7478b52..867becc40021 100644
> >> --- a/kernel/printk/printk.c
> >> +++ b/kernel/printk/printk.c
> >> @@ -3229,32 +3244,30 @@ int unregister_console(struct console *console)
> >>  	if (res > 0)
> >>  		return 0;
> >>  
> >> -	res = -ENODEV;
> >>  	console_lock();
> >> -	if (console_drivers == console) {
> >> -		console_drivers=console->next;
> >> -		res = 0;
> >> -	} else {
> >> -		for_each_console(con) {
> >> -			if (con->next == console) {
> >> -				con->next = console->next;
> >> -				res = 0;
> >> -				break;
> >> -			}
> >> -		}
> >> +
> >> +	/* Disable it unconditionally */
> >> +	console->flags &= ~CON_ENABLED;
> >> +
> >> +	if (hlist_unhashed(&console->node)) {
> >
> > How can this ever be hit?  The console lock is held, so it shouldn't
> > have gone away already.  Or am I missing something else here?
> 
> Mainline also has this check. I expect it is for the case that some code
> tries to call unregister_console() for a console that is not
> registered.
> 
> Since register_console() does not return if it succeeded, I suppose some
> code somewhere my try to unregister without knowing that it never
> registered in the first place.

Ick, ok, that's fine for now.

What a mess, thanks for working to unwind it!

greg k-h
  
Petr Mladek Oct. 20, 2022, 12:36 p.m. UTC | #4
On Wed 2022-10-19 17:01:24, John Ogness wrote:
> Replace the open coded single linked list with a hlist so a conversion
> to SRCU protected list walks can reuse the existing primitives.
> 
> Signed-off-by: John Ogness <john.ogness@linutronix.de>

Reviewed-by: Petr Mladek <pmladek@suse.com>

Just one nit below.

> @@ -3229,32 +3244,30 @@ int unregister_console(struct console *console)
>  	if (res > 0)
>  		return 0;
>  
> -	res = -ENODEV;
>  	console_lock();
> -	if (console_drivers == console) {
> -		console_drivers=console->next;
> -		res = 0;
> -	} else {
> -		for_each_console(con) {
> -			if (con->next == console) {
> -				con->next = console->next;
> -				res = 0;
> -				break;
> -			}
> -		}
> +
> +	/* Disable it unconditionally */
> +	console->flags &= ~CON_ENABLED;
> +
> +	if (hlist_unhashed(&console->node)) {
> +		res = -ENODEV;
> +		goto out_unlock;

Nit: It might make sense to replace this with:

		console_unlock();
		return -ENODEV;

This is the only code path using the extra goto target.

It is just an idea. I do not resist on this change.

>  	}
>  
> -	if (res)
> -		goto out_disable_unlock;
> +	hlist_del_init(&console->node);
>  
>  	/*
> +	 * <HISTORICAL>
>  	 * If this isn't the last console and it has CON_CONSDEV set, we
>  	 * need to set it on the next preferred console.
> +	 * </HISTORICAL>
> +	 *
> +	 * The above makes no sense as there is no guarantee that the next
> +	 * console has any device attached. Oh well....
>  	 */
> -	if (console_drivers != NULL && console->flags & CON_CONSDEV)
> -		console_drivers->flags |= CON_CONSDEV;
> +	if (!hlist_empty(&console_list) && console->flags & CON_CONSDEV)
> +		console_first()->flags |= CON_CONSDEV;
>  
> -	console->flags &= ~CON_ENABLED;
>  	console_unlock();
>  	console_sysfs_notify();
>  
> @@ -3263,10 +3276,8 @@ int unregister_console(struct console *console)
>  
>  	return res;
>  
> -out_disable_unlock:
> -	console->flags &= ~CON_ENABLED;
> +out_unlock:
>  	console_unlock();
> -
>  	return res;
>  }
>  EXPORT_SYMBOL(unregister_console);

Best Regards,
Petr
  
Sergey Senozhatsky Oct. 24, 2022, 5:23 a.m. UTC | #5
On (22/10/19 17:01), John Ogness wrote:
> Replace the open coded single linked list with a hlist so a conversion
> to SRCU protected list walks can reuse the existing primitives.
> 
> Signed-off-by: John Ogness <john.ogness@linutronix.de>

Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
  

Patch

diff --git a/fs/proc/consoles.c b/fs/proc/consoles.c
index dfe6ce3505ce..cf2e0788f9c7 100644
--- a/fs/proc/consoles.c
+++ b/fs/proc/consoles.c
@@ -74,8 +74,9 @@  static void *c_start(struct seq_file *m, loff_t *pos)
 static void *c_next(struct seq_file *m, void *v, loff_t *pos)
 {
 	struct console *con = v;
+
 	++*pos;
-	return con->next;
+	return hlist_entry_safe(con->node.next, struct console, node);
 }
 
 static void c_stop(struct seq_file *m, void *v)
diff --git a/include/linux/console.h b/include/linux/console.h
index 8c1686e2c233..7b5f21f9e469 100644
--- a/include/linux/console.h
+++ b/include/linux/console.h
@@ -15,6 +15,7 @@ 
 #define _LINUX_CONSOLE_H_ 1
 
 #include <linux/atomic.h>
+#include <linux/list.h>
 #include <linux/types.h>
 
 struct vc_data;
@@ -154,14 +155,16 @@  struct console {
 	u64	seq;
 	unsigned long dropped;
 	void	*data;
-	struct	 console *next;
+	struct hlist_node node;
 };
 
+extern struct hlist_head console_list;
+
 /*
  * for_each_console() allows you to iterate on each console
  */
 #define for_each_console(con) \
-	for (con = console_drivers; con != NULL; con = con->next)
+	hlist_for_each_entry(con, &console_list, node)
 
 extern int console_set_on_cmdline;
 extern struct console *early_console;
@@ -174,7 +177,6 @@  enum con_flush_mode {
 extern int add_preferred_console(char *name, int idx, char *options);
 extern void register_console(struct console *);
 extern int unregister_console(struct console *);
-extern struct console *console_drivers;
 extern void console_lock(void);
 extern int console_trylock(void);
 extern void console_unlock(void);
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index e4f1e7478b52..867becc40021 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -79,13 +79,12 @@  int oops_in_progress;
 EXPORT_SYMBOL(oops_in_progress);
 
 /*
- * console_sem protects the console_drivers list, and also
- * provides serialisation for access to the entire console
- * driver system.
+ * console_sem protects console_list and console->flags updates, and also
+ * provides serialization for access to the entire console driver system.
  */
 static DEFINE_SEMAPHORE(console_sem);
-struct console *console_drivers;
-EXPORT_SYMBOL_GPL(console_drivers);
+HLIST_HEAD(console_list);
+EXPORT_SYMBOL_GPL(console_list);
 
 /*
  * System may need to suppress printk message under certain
@@ -2556,7 +2555,7 @@  static int console_cpu_notify(unsigned int cpu)
  * console_lock - lock the console system for exclusive use.
  *
  * Acquires a lock which guarantees that the caller has
- * exclusive access to the console system and the console_drivers list.
+ * exclusive access to the console system and console_list.
  *
  * Can sleep, returns nothing.
  */
@@ -2576,7 +2575,7 @@  EXPORT_SYMBOL(console_lock);
  * console_trylock - try to lock the console system for exclusive use.
  *
  * Try to acquire a lock which guarantees that the caller has exclusive
- * access to the console system and the console_drivers list.
+ * access to the console system and console_list.
  *
  * returns 1 on success, and 0 on failure to acquire the lock.
  */
@@ -2940,11 +2939,20 @@  void console_flush_on_panic(enum con_flush_mode mode)
 	console_may_schedule = 0;
 
 	if (mode == CONSOLE_REPLAY_ALL) {
+		struct hlist_node *tmp;
 		struct console *c;
 		u64 seq;
 
 		seq = prb_first_valid_seq(prb);
-		for_each_console(c)
+		/*
+		 * This cannot use for_each_console() because it's not established
+		 * that the current context has console locked and neither there is
+		 * a guarantee that there is no concurrency in that case.
+		 *
+		 * Open code it for documentation purposes and pretend that
+		 * it works.
+		 */
+		hlist_for_each_entry_safe(c, tmp, &console_list, node)
 			c->seq = seq;
 	}
 	console_unlock();
@@ -3081,6 +3089,9 @@  static void try_enable_default_console(struct console *newcon)
 	       (con->flags & CON_BOOT) ? "boot" : "",	\
 	       con->name, con->index, ##__VA_ARGS__)
 
+#define console_first()				\
+	hlist_entry(console_list.first, struct console, node)
+
 /*
  * The console driver calls this routine during kernel initialization
  * to register the console printing procedure with printk() and to
@@ -3140,8 +3151,8 @@  void register_console(struct console *newcon)
 	 * flag set and will be first in the list.
 	 */
 	if (preferred_console < 0) {
-		if (!console_drivers || !console_drivers->device ||
-		    console_drivers->flags & CON_BOOT) {
+		if (hlist_empty(&console_list) || !console_first()->device ||
+		    console_first()->flags & CON_BOOT) {
 			try_enable_default_console(newcon);
 		}
 	}
@@ -3169,20 +3180,22 @@  void register_console(struct console *newcon)
 	}
 
 	/*
-	 *	Put this console in the list - keep the
-	 *	preferred driver at the head of the list.
+	 * Put this console in the list - keep the
+	 * preferred driver at the head of the list.
 	 */
 	console_lock();
-	if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) {
-		newcon->next = console_drivers;
-		console_drivers = newcon;
-		if (newcon->next)
-			newcon->next->flags &= ~CON_CONSDEV;
-		/* Ensure this flag is always set for the head of the list */
+	if (hlist_empty(&console_list)) {
+		/* Ensure CON_CONSDEV is always set for the head. */
 		newcon->flags |= CON_CONSDEV;
+		hlist_add_head(&newcon->node, &console_list);
+
+	} else if (newcon->flags & CON_CONSDEV) {
+		/* Only the new head can have CON_CONSDEV set. */
+		console_first()->flags &= ~CON_CONSDEV;
+		hlist_add_head(&newcon->node, &console_list);
+
 	} else {
-		newcon->next = console_drivers->next;
-		console_drivers->next = newcon;
+		hlist_add_behind(&newcon->node, console_list.first);
 	}
 
 	newcon->dropped = 0;
@@ -3209,16 +3222,18 @@  void register_console(struct console *newcon)
 	if (bootcon_enabled &&
 	    ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV) &&
 	    !keep_bootcon) {
-		for_each_console(con)
+		struct hlist_node *tmp;
+
+		hlist_for_each_entry_safe(con, tmp, &console_list, node) {
 			if (con->flags & CON_BOOT)
 				unregister_console(con);
+		}
 	}
 }
 EXPORT_SYMBOL(register_console);
 
 int unregister_console(struct console *console)
 {
-	struct console *con;
 	int res;
 
 	con_printk(KERN_INFO, console, "disabled\n");
@@ -3229,32 +3244,30 @@  int unregister_console(struct console *console)
 	if (res > 0)
 		return 0;
 
-	res = -ENODEV;
 	console_lock();
-	if (console_drivers == console) {
-		console_drivers=console->next;
-		res = 0;
-	} else {
-		for_each_console(con) {
-			if (con->next == console) {
-				con->next = console->next;
-				res = 0;
-				break;
-			}
-		}
+
+	/* Disable it unconditionally */
+	console->flags &= ~CON_ENABLED;
+
+	if (hlist_unhashed(&console->node)) {
+		res = -ENODEV;
+		goto out_unlock;
 	}
 
-	if (res)
-		goto out_disable_unlock;
+	hlist_del_init(&console->node);
 
 	/*
+	 * <HISTORICAL>
 	 * If this isn't the last console and it has CON_CONSDEV set, we
 	 * need to set it on the next preferred console.
+	 * </HISTORICAL>
+	 *
+	 * The above makes no sense as there is no guarantee that the next
+	 * console has any device attached. Oh well....
 	 */
-	if (console_drivers != NULL && console->flags & CON_CONSDEV)
-		console_drivers->flags |= CON_CONSDEV;
+	if (!hlist_empty(&console_list) && console->flags & CON_CONSDEV)
+		console_first()->flags |= CON_CONSDEV;
 
-	console->flags &= ~CON_ENABLED;
 	console_unlock();
 	console_sysfs_notify();
 
@@ -3263,10 +3276,8 @@  int unregister_console(struct console *console)
 
 	return res;
 
-out_disable_unlock:
-	console->flags &= ~CON_ENABLED;
+out_unlock:
 	console_unlock();
-
 	return res;
 }
 EXPORT_SYMBOL(unregister_console);
@@ -3317,10 +3328,11 @@  void __init console_init(void)
  */
 static int __init printk_late_init(void)
 {
+	struct hlist_node *tmp;
 	struct console *con;
 	int ret;
 
-	for_each_console(con) {
+	hlist_for_each_entry_safe(con, tmp, &console_list, node) {
 		if (!(con->flags & CON_BOOT))
 			continue;
 
@@ -3340,6 +3352,7 @@  static int __init printk_late_init(void)
 			unregister_console(con);
 		}
 	}
+
 	ret = cpuhp_setup_state_nocalls(CPUHP_PRINTK_DEAD, "printk:dead", NULL,
 					console_cpu_notify);
 	WARN_ON(ret < 0);