From: Leo Yan leo.yan@linaro.org
commit 0e4f7f920a5c6bfe5e851e989f27b35a0cc7fb7e upstream.
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 leo.yan@linaro.org Reviewed-by: Jeffrey Hugo jeffrey.l.hugo@gmail.com Link: https://lore.kernel.org/r/20191127141544.4277-2-leo.yan@linaro.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/tty/serial/msm_serial.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-)
--- a/drivers/tty/serial/msm_serial.c +++ b/drivers/tty/serial/msm_serial.c @@ -1588,6 +1588,7 @@ static void __msm_console_write(struct u int num_newlines = 0; bool replaced = false; void __iomem *tf; + int locked = 1;
if (is_uartdm) tf = port->membase + UARTDM_TF; @@ -1600,7 +1601,13 @@ static void __msm_console_write(struct u 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);
@@ -1636,7 +1643,9 @@ static void __msm_console_write(struct u 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,