linux-kernel - [PATCH] Revert "printk: wake up all waiters"

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Message-Id: <20220526203056.81123-1-john.ogness@linutronix.de>
Date:   Thu, 26 May 2022 22:36:56 +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] Revert "printk: wake up all waiters"

This reverts commit 938ba4084abcf6fdd21d9078513c52f8fb9b00d0.

The wait queue @log_wait never has exclusive waiters, so there
is no need to use wake_up_interruptible_all(). Using
wake_up_interruptible() was the correct function to wake all
waiters.

Since there are no exclusive waiters, erroneously changing
wake_up_interruptible() to wake_up_interruptible_all() did not
result in any behavior change. However, using
wake_up_interruptible_all() on a wait queue without exclusive
waiters is fundamentally wrong.

Go back to using wake_up_interruptible() to wake all waiters.

Signed-off-by: John Ogness <john.ogness@...utronix.de>
---
 kernel/printk/printk.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index a3e1035929b0..ea3dd55709e7 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -3904,7 +3904,7 @@ static void wake_up_klogd_work_func(struct irq_work *irq_work)
 	}

 	if (pending & PRINTK_PENDING_WAKEUP)
-		wake_up_interruptible_all(&log_wait);
+		wake_up_interruptible(&log_wait);
 }

 static DEFINE_PER_CPU(struct irq_work, wake_up_klogd_work) =
-- 
2.30.2