linux-kernel - [PATCH v7 01/13] printk: Avoid delaying messages that aren't solicited by any console

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Message-ID: <8c69a5fccc15a512e5ba6385f3c933e3d2f8a96b.1763492585.git.chris@chrisdown.name>
Date: Wed, 19 Nov 2025 03:06:50 +0800
From: Chris Down <chris@...isdown.name>
To: Petr Mladek <pmladek@...e.com>
Cc: linux-kernel@...r.kernel.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Sergey Senozhatsky <senozhatsky@...omium.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	John Ogness <john.ogness@...utronix.de>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Tony Lindgren <tony.lindgren@...ux.intel.com>, kernel-team@...com
Subject: [PATCH v7 01/13] printk: Avoid delaying messages that aren't
 solicited by any console

printk_delay() may introduce delays even when no console wants to emit
the message, which is unnecessary and may hold back messages we actually
care about. Add a check in printk_delay() to determine if any console
will print the message to avoid introducing unnecessary delays. This
change aligns with the existing behaviour of boot-delayed printk
messages, which already have a similar check.

Reviewed-by: Petr Mladek <pmladek@...e.com>
Signed-off-by: Chris Down <chris@...isdown.name>
---
 kernel/printk/printk.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 5aee9ffb16b9..ff8b6dbb29a7 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -1307,14 +1307,12 @@ static int __init boot_delay_setup(char *str)
 }
 early_param("boot_delay", boot_delay_setup);
 
-static void boot_delay_msec(int level)
+static void boot_delay_msec(void)
 {
 	unsigned long long k;
 	unsigned long timeout;
-	bool suppress = !is_printk_force_console() &&
-			suppress_message_printing(level);
 
-	if ((boot_delay == 0 || system_state >= SYSTEM_RUNNING) || suppress)
+	if (boot_delay == 0 || system_state >= SYSTEM_RUNNING)
 		return;
 
 	k = (unsigned long long)loops_per_msec * boot_delay;
@@ -1334,7 +1332,7 @@ static void boot_delay_msec(int level)
 	}
 }
 #else
-static inline void boot_delay_msec(int level)
+static inline void boot_delay_msec(void)
 {
 }
 #endif
@@ -2116,7 +2114,11 @@ int printk_delay_msec __read_mostly;
 
 static inline void printk_delay(int level)
 {
-	boot_delay_msec(level);
+	/* If the message is forced (e.g. panic), we must delay */
+	if (!is_printk_force_console() && suppress_message_printing(level))
+		return;
+
+	boot_delay_msec();
 
 	if (unlikely(printk_delay_msec)) {
 		int m = printk_delay_msec;
-- 
2.51.2