linux-kernel - [PATCH] tty: Remove pointless synchronize_irq() in uart_port

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Date:   Tue, 10 May 2022 15:54:00 +0200
From:   Thomas Pfaff <tpfaff@....com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>
CC:     Thomas Gleixner <tglx@...utronix.de>,
        <linux-kernel@...r.kernel.org>
Subject: [PATCH] tty: Remove pointless synchronize_irq() in
 uart_port_shutdown()

From: Thomas Pfaff <tpfaff@....com>

Calling synchronize_irq() after free_irq() is pointless, the context to
the irq is already lost.
It was noticed while creating the bugfix "genirq: Synchronize interrupt 
thread startup".

Signed-off-by: Thomas Pfaff <tpfaff@....com>
---
diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index 57840cf90388..b76e76e650ba 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -1704,12 +1704,6 @@ static void uart_port_shutdown(struct tty_port *port)
 	 */
 	if (uport)
 		uport->ops->shutdown(uport);
-
-	/*
-	 * Ensure that the IRQ handler isn't running on another CPU.
-	 */
-	if (uport)
-		synchronize_irq(uport->irq);
 }
 
 static int uart_carrier_raised(struct tty_port *port)