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Subject: [PATCH] mpx5200_uart: drop port lock across tty_flip_buffer() call
From: Thomas Gleixner <tglx@linutronix.de>
To: linuxppc-embedded@ozlabs.org
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Date: Wed, 25 Jul 2007 21:10:56 +0200
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The port lock needs to be dropped across the tty_flip_buffer call, as it
would lead to a deadlock with the spin_lock(&port->lock) in uart_start()

Uncovered by lockdep / preempt-rt

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>


Index: linux-2.6.22/drivers/serial/mpc52xx_uart.c
===================================================================
--- linux-2.6.22.orig/drivers/serial/mpc52xx_uart.c	2007-07-09 01:32:17.000000000 +0200
+++ linux-2.6.22/drivers/serial/mpc52xx_uart.c	2007-07-25 21:06:11.000000000 +0200
@@ -501,7 +501,9 @@ mpc52xx_uart_int_rx_chars(struct uart_po
 		}
 	}
 
+	spin_unlock(&port->lock);
 	tty_flip_buffer_push(tty);
+	spin_lock(&port->lock);
 
 	return in_be16(&PSC(port)->mpc52xx_psc_status) & MPC52xx_PSC_SR_RXRDY;
 }