Commit 853a9ae2 authored by Johan Hovold's avatar Johan Hovold Committed by Greg Kroah-Hartman
Browse files

serial: 8250: fix handle_irq locking 



The 8250 handle_irq callback is not just called from the interrupt
handler but also from a timer callback when polling (e.g. for ports
without an interrupt line). Consequently the callback must explicitly
disable interrupts to avoid a potential deadlock with another interrupt
in polled mode.

Add back an irqrestore-version of the sysrq port-unlock helper and use
it in the 8250 callbacks that need it.

Fixes: 75f4e830 ("serial: do not restore interrupt state in sysrq helper")
Cc: stable@vger.kernel.org	# 5.13
Cc: Joel Stanley <joel@jms.id.au>
Cc: Andrew Jeffery <andrew@aj.id.au>
Reported-by: default avatarkernel test robot <oliver.sang@intel.com>
Signed-off-by: default avatarJohan Hovold <johan@kernel.org>
Link: https://lore.kernel.org/r/20210714080427.28164-1-johan@kernel.org


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent cc9ca4d9

drivers/tty/serial/8250/8250_aspeed_vuart.c

+3 −2
Original line number Diff line number Diff line
@@ -329,6 +329,7 @@ static int aspeed_vuart_handle_irq(struct uart_port *port) 
{

	struct uart_8250_port *up = up_to_u8250p(port);

	unsigned int iir, lsr;

	unsigned long flags;

	unsigned int space, count;



	iir = serial_port_in(port, UART_IIR);
@@ -336,7 +337,7 @@ static int aspeed_vuart_handle_irq(struct uart_port *port) 
	if (iir & UART_IIR_NO_INT)

		return 0;



	spin_lock(&port->lock);

	spin_lock_irqsave(&port->lock, flags);



	lsr = serial_port_in(port, UART_LSR);
@@ -370,7 +371,7 @@ static int aspeed_vuart_handle_irq(struct uart_port *port) 
	if (lsr & UART_LSR_THRE)

		serial8250_tx_chars(up);



	uart_unlock_and_check_sysrq(port);

	uart_unlock_and_check_sysrq_irqrestore(port, flags);



	return 1;

}

drivers/tty/serial/8250/8250_fsl.c

+3 −2
Original line number Diff line number Diff line
@@ -30,10 +30,11 @@ struct fsl8250_data { 
int fsl8250_handle_irq(struct uart_port *port)

{

	unsigned char lsr, orig_lsr;

	unsigned long flags;

	unsigned int iir;

	struct uart_8250_port *up = up_to_u8250p(port);



	spin_lock(&up->port.lock);

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



	iir = port->serial_in(port, UART_IIR);

	if (iir & UART_IIR_NO_INT) {
@@ -82,7 +83,7 @@ int fsl8250_handle_irq(struct uart_port *port) 


	up->lsr_saved_flags = orig_lsr;



	uart_unlock_and_check_sysrq(&up->port);

	uart_unlock_and_check_sysrq_irqrestore(&up->port, flags);



	return 1;

}

drivers/tty/serial/8250/8250_port.c

+3 −2
Original line number Diff line number Diff line
@@ -1899,11 +1899,12 @@ int serial8250_handle_irq(struct uart_port *port, unsigned int iir) 
	unsigned char status;

	struct uart_8250_port *up = up_to_u8250p(port);

	bool skip_rx = false;

	unsigned long flags;



	if (iir & UART_IIR_NO_INT)

		return 0;



	spin_lock(&port->lock);

	spin_lock_irqsave(&port->lock, flags);



	status = serial_port_in(port, UART_LSR);
@@ -1929,7 +1930,7 @@ int serial8250_handle_irq(struct uart_port *port, unsigned int iir) 
		(up->ier & UART_IER_THRI))

		serial8250_tx_chars(up);



	uart_unlock_and_check_sysrq(port);

	uart_unlock_and_check_sysrq_irqrestore(port, flags);



	return 1;

}

include/linux/serial_core.h

+24 −0
Original line number Diff line number Diff line
@@ -518,6 +518,25 @@ static inline void uart_unlock_and_check_sysrq(struct uart_port *port) 
	if (sysrq_ch)

		handle_sysrq(sysrq_ch);

}



static inline void uart_unlock_and_check_sysrq_irqrestore(struct uart_port *port,

		unsigned long flags)

{

	int sysrq_ch;



	if (!port->has_sysrq) {

		spin_unlock_irqrestore(&port->lock, flags);

		return;

	}



	sysrq_ch = port->sysrq_ch;

	port->sysrq_ch = 0;



	spin_unlock_irqrestore(&port->lock, flags);



	if (sysrq_ch)

		handle_sysrq(sysrq_ch);

}

#else	/* CONFIG_MAGIC_SYSRQ_SERIAL */

static inline int uart_handle_sysrq_char(struct uart_port *port, unsigned int ch)

{
@@ -531,6 +550,11 @@ static inline void uart_unlock_and_check_sysrq(struct uart_port *port) 
{

	spin_unlock(&port->lock);

}

static inline void uart_unlock_and_check_sysrq_irqrestore(struct uart_port *port,

		unsigned long flags)

{

	spin_unlock_irqrestore(&port->lock, flags);

}

#endif	/* CONFIG_MAGIC_SYSRQ_SERIAL */



/*