linux-kernel - [PATCH printk v3 05/19] printk: Fail pr_flush() if before SYSTEM

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Message-Id: <20240722171939.3349410-6-john.ogness@linutronix.de>
Date: Mon, 22 Jul 2024 19:25:25 +0206
From: John Ogness <john.ogness@...utronix.de>
To: Petr Mladek <pmladek@...e.com>
Cc: Sergey Senozhatsky <senozhatsky@...omium.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org
Subject: [PATCH printk v3 05/19] printk: Fail pr_flush() if before SYSTEM_SCHEDULING

A follow-up change adds pr_flush() to console unregistration.
However, with boot consoles unregistration can happen very
early if there are also regular consoles registering as well.
In this case the pr_flush() is not important because the
regular console manually flushes the boot consoles before
unregistering them.

Allow pr_flush() to fail if @system_state has not yet reached
SYSTEM_SCHEDULING. This avoids might_sleep() and msleep()
explosions that would otherwise occur.

Signed-off-by: John Ogness <john.ogness@...utronix.de>
---
 kernel/printk/printk.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 641c2a8b0a09..39db56a32c5e 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -3946,6 +3946,10 @@ static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progre
 	u64 diff;
 	u64 seq;

+	/* Sorry, pr_flush() will not work this early. */
+	if (system_state < SYSTEM_SCHEDULING)
+		return false;
+
 	might_sleep();

 	seq = prb_next_reserve_seq(prb);
-- 
2.39.2