From: Johan Hovold johan@kernel.org
commit 853a9ae29e978d37f5dfa72622a68c9ae3d7fa89 upstream.
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: 75f4e830fa9c ("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: kernel test robot oliver.sang@intel.com Signed-off-by: Johan Hovold johan@kernel.org Link: https://lore.kernel.org/r/20210714080427.28164-1-johan@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/tty/serial/8250/8250_aspeed_vuart.c | 5 +++-- drivers/tty/serial/8250/8250_fsl.c | 5 +++-- drivers/tty/serial/8250/8250_port.c | 5 +++-- include/linux/serial_core.h | 24 ++++++++++++++++++++++++ 4 files changed, 33 insertions(+), 6 deletions(-)
--- a/drivers/tty/serial/8250/8250_aspeed_vuart.c +++ b/drivers/tty/serial/8250/8250_aspeed_vuart.c @@ -320,6 +320,7 @@ static int aspeed_vuart_handle_irq(struc { struct uart_8250_port *up = up_to_u8250p(port); unsigned int iir, lsr; + unsigned long flags; int space, count;
iir = serial_port_in(port, UART_IIR); @@ -327,7 +328,7 @@ static int aspeed_vuart_handle_irq(struc 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);
@@ -363,7 +364,7 @@ static int aspeed_vuart_handle_irq(struc 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; } --- a/drivers/tty/serial/8250/8250_fsl.c +++ b/drivers/tty/serial/8250/8250_fsl.c @@ -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
up->lsr_saved_flags = orig_lsr;
- uart_unlock_and_check_sysrq(&up->port); + uart_unlock_and_check_sysrq_irqrestore(&up->port, flags);
return 1; } --- a/drivers/tty/serial/8250/8250_port.c +++ b/drivers/tty/serial/8250/8250_port.c @@ -1899,11 +1899,12 @@ int serial8250_handle_irq(struct uart_po 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_po (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; } --- a/include/linux/serial_core.h +++ b/include/linux/serial_core.h @@ -517,6 +517,25 @@ static inline void uart_unlock_and_check 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) { @@ -530,6 +549,11 @@ static inline void uart_unlock_and_check { 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 */
/*