Commit 4bf3631c authored Apr 23, 2007 by Jiri Kosina Committed by Linus Torvalds Apr 24, 2007

8250: fix possible deadlock between serial8250_handle_port() and serial8250_interrupt()



Commit 40b36daa introduced possibility that serial8250_backup_timeout() ->
serial8250_handle_port() locks port.lock without disabling irqs, thus
allowing deadlock against interrupt handler (port.lock is acquired in
serial8250_interrupt()).

Spotted by lockdep.

Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Cc: Dave Jones <davej@codemonkey.org.uk>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Alex Williamson <alex.williamson@hp.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent c5408b88

drivers/serial/8250.c

+3 −2

Original line number	Original line	Diff line number	Diff line
	@@ -1334,8 +1334,9 @@ static inline void
	serial8250_handle_port(struct uart_8250_port *up)		serial8250_handle_port(struct uart_8250_port *up)
	{		{
	unsigned int status;		unsigned int status;
			unsigned long flags;

	spin_lock(&up->port.lock);		spin_lock_irqsave(&up->port.lock, flags);

	status = serial_inp(up, UART_LSR);		status = serial_inp(up, UART_LSR);

	@@ -1347,7 +1348,7 @@ serial8250_handle_port(struct uart_8250_port *up)
	if (status & UART_LSR_THRE)		if (status & UART_LSR_THRE)
	transmit_chars(up);		transmit_chars(up);

	spin_unlock(&up->port.lock);		spin_unlock_irqrestore(&up->port.lock, flags);
	}		}

	/*		/*