Revert "printk: extend console_lock for per-console locking"

This reverts commit 8e27473.

The testing of 5.19 release candidates revealed missing synchronization
between early and regular console functionality.

It would be possible to start the console kthreads later as a workaround.
But it is clear that console lock serialized console drivers between
each other. It opens a big area of possible problems that were not
considered by people involved in the development and review.

printk() is crucial for debugging kernel issues and console output is
very important part of it. The number of consoles is huge and a proper
review would take some time. As a result it need to be reverted for 5.19.

Link: https://lore.kernel.org/r/YrBdjVwBOVgLfHyb@alley
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20220623145157.21938-5-pmladek@suse.com

Author: pmladek

include/linux/console.h

@@ -16,7 +16,6 @@
 
 #include <linux/atomic.h>
 #include <linux/types.h>
-#include <linux/mutex.h>
 
 struct vc_data;
 struct console_font_op;
@@ -155,20 +154,6 @@ struct console {
 	u64	seq;
 	unsigned long dropped;
 	struct task_struct *thread;
-	bool	blocked;
-
-	/*
-	 * The per-console lock is used by printing kthreads to synchronize
-	 * this console with callers of console_lock(). This is necessary in
-	 * order to allow printing kthreads to run in parallel to each other,
-	 * while each safely accessing the @blocked field and synchronizing
-	 * against direct printing via console_lock/console_unlock.
-	 *
-	 * Note: For synchronizing against direct printing via
-	 *       console_trylock/console_unlock, see the static global
-	 *       variable @console_kthreads_active.
-	 */
-	struct mutex lock;
 
 	void	*data;
 	struct	 console *next;