From 0e4f7f920a5c6bfe5e851e989f27b35a0cc7fb7e Mon Sep 17 00:00:00 2001 From: Leo Yan Date: Wed, 27 Nov 2019 22:15:43 +0800 Subject: tty: serial: msm_serial: Fix lockup for sysrq and oops As the commit 677fe555cbfb ("serial: imx: Fix recursive locking bug") has mentioned the uart driver might cause recursive locking between normal printing and the kernel debugging facilities (e.g. sysrq and oops). In the commit it gave out suggestion for fixing recursive locking issue: "The solution is to avoid locking in the sysrq case and trylock in the oops_in_progress case." This patch follows the suggestion (also used the exactly same code with other serial drivers, e.g. amba-pl011.c) to fix the recursive locking issue, this can avoid stuck caused by deadlock and print out log for sysrq and oops. Fixes: 04896a77a97b ("msm_serial: serial driver for MSM7K onboard serial peripheral.") Signed-off-by: Leo Yan Reviewed-by: Jeffrey Hugo Link: https://lore.kernel.org/r/20191127141544.4277-2-leo.yan@linaro.org Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/msm_serial.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/drivers/tty/serial/msm_serial.c b/drivers/tty/serial/msm_serial.c index 1cbae0768b1f..f6c45a796433 100644 --- a/drivers/tty/serial/msm_serial.c +++ b/drivers/tty/serial/msm_serial.c @@ -1580,6 +1580,7 @@ static void __msm_console_write(struct uart_port *port, const char *s, int num_newlines = 0; bool replaced = false; void __iomem *tf; + int locked = 1; if (is_uartdm) tf = port->membase + UARTDM_TF; @@ -1592,7 +1593,13 @@ static void __msm_console_write(struct uart_port *port, const char *s, num_newlines++; count += num_newlines; - spin_lock(&port->lock); + if (port->sysrq) + locked = 0; + else if (oops_in_progress) + locked = spin_trylock(&port->lock); + else + spin_lock(&port->lock); + if (is_uartdm) msm_reset_dm_count(port, count); @@ -1628,7 +1635,9 @@ static void __msm_console_write(struct uart_port *port, const char *s, iowrite32_rep(tf, buf, 1); i += num_chars; } - spin_unlock(&port->lock); + + if (locked) + spin_unlock(&port->lock); } static void msm_console_write(struct console *co, const char *s, -- cgit v1.2.3