Revert "printk: Wait for the global console lock when the system is going down"

This reverts commit b87f02307d3cfbda768520f0687c51ca77e14fc3.

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/20220623145157.21938-2-pmladek@suse.com

1 files changed, 0 insertions, 32 deletions

diff --git a/kernel/printk/printk_safe.c b/kernel/printk/printk_safe.c
index caac4de1ea59..ef0f9a2044da 100644
--- a/kernel/printk/printk_safe.c
+++ b/kernel/printk/printk_safe.c
@@ -8,9 +8,7 @@
 #include <linux/smp.h>
 #include <linux/cpumask.h>
 #include <linux/printk.h>
-#include <linux/console.h>
 #include <linux/kprobes.h>
-#include <linux/delay.h>
 
 #include "internal.h"
 
@@ -52,33 +50,3 @@ asmlinkage int vprintk(const char *fmt, va_list args)
 	return vprintk_default(fmt, args);
 }
 EXPORT_SYMBOL(vprintk);
-
-/**
- * try_block_console_kthreads() - Try to block console kthreads and
- *	make the global console_lock() avaialble
- *
- * @timeout_ms:        The maximum time (in ms) to wait.
- *
- * Prevent console kthreads from starting processing new messages. Wait
- * until the global console_lock() become available.
- *
- * Context: Can be called in any context.
- */
-void try_block_console_kthreads(int timeout_ms)
-{
-	block_console_kthreads = true;
-
-	/* Do not wait when the console lock could not be safely taken. */
-	if (this_cpu_read(printk_context) || in_nmi())
-		return;
-
-	while (timeout_ms > 0) {
-		if (console_trylock()) {
-			console_unlock();
-			return;
-		}
-
-		udelay(1000);
-		timeout_ms -= 1;
-	}
-}