From 33f16855dcb973f745c51882d0e286601ff3be2b Mon Sep 17 00:00:00 2001 From: Sam Nobs Date: Tue, 10 Nov 2020 09:50:06 +1300 Subject: tty: serial: imx: fix potential deadlock MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Enabling the lock dependency validator has revealed that the way spinlocks are used in the IMX serial port could result in a deadlock. Specifically, imx_uart_int() acquires a spinlock without disabling the interrupts, meaning that another interrupt could come along and try to acquire the same spinlock, potentially causing the two to wait for each other indefinitely. Use spin_lock_irqsave() instead to disable interrupts upon acquisition of the spinlock. Fixes: c974991d2620 ("tty:serial:imx: use spin_lock instead of spin_lock_irqsave in isr") Reviewed-by: Uwe Kleine-König Signed-off-by: Sam Nobs Link: https://lore.kernel.org/r/1604955006-9363-1-git-send-email-samuel.nobs@taitradio.com Cc: stable Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/imx.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) (limited to 'drivers/tty/serial/imx.c') diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c index 1731d9728865..3c53a3c89959 100644 --- a/drivers/tty/serial/imx.c +++ b/drivers/tty/serial/imx.c @@ -942,8 +942,14 @@ static irqreturn_t imx_uart_int(int irq, void *dev_id) struct imx_port *sport = dev_id; unsigned int usr1, usr2, ucr1, ucr2, ucr3, ucr4; irqreturn_t ret = IRQ_NONE; + unsigned long flags = 0; - spin_lock(&sport->port.lock); + /* + * IRQs might not be disabled upon entering this interrupt handler, + * e.g. when interrupt handlers are forced to be threaded. To support + * this scenario as well, disable IRQs when acquiring the spinlock. + */ + spin_lock_irqsave(&sport->port.lock, flags); usr1 = imx_uart_readl(sport, USR1); usr2 = imx_uart_readl(sport, USR2); @@ -1013,7 +1019,7 @@ static irqreturn_t imx_uart_int(int irq, void *dev_id) ret = IRQ_HANDLED; } - spin_unlock(&sport->port.lock); + spin_unlock_irqrestore(&sport->port.lock, flags); return ret; } -- cgit From e67c139c488e84e7eae6c333231e791f0e89b3fb Mon Sep 17 00:00:00 2001 From: Fugang Duan Date: Wed, 11 Nov 2020 10:51:36 +0800 Subject: tty: serial: imx: keep console clocks always on MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit For below code, there has chance to cause deadlock in SMP system: Thread 1: clk_enable_lock(); pr_info("debug message"); clk_enable_unlock(); Thread 2: imx_uart_console_write() clk_enable() clk_enable_lock(); Thread 1: Acuired clk enable_lock -> printk -> console_trylock_spinning Thread 2: console_unlock() -> imx_uart_console_write -> clk_disable -> Acquite clk enable_lock So the patch is to keep console port clocks always on like other console drivers. Fixes: 1cf93e0d5488 ("serial: imx: remove the uart_console() check") Acked-by: Uwe Kleine-König Signed-off-by: Fugang Duan Link: https://lore.kernel.org/r/20201111025136.29818-1-fugang.duan@nxp.com Cc: stable [fix up build warning - gregkh] Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/imx.c | 20 +++----------------- 1 file changed, 3 insertions(+), 17 deletions(-) (limited to 'drivers/tty/serial/imx.c') diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c index 3c53a3c89959..cacf7266a262 100644 --- a/drivers/tty/serial/imx.c +++ b/drivers/tty/serial/imx.c @@ -2008,16 +2008,6 @@ imx_uart_console_write(struct console *co, const char *s, unsigned int count) unsigned int ucr1; unsigned long flags = 0; int locked = 1; - int retval; - - retval = clk_enable(sport->clk_per); - if (retval) - return; - retval = clk_enable(sport->clk_ipg); - if (retval) { - clk_disable(sport->clk_per); - return; - } if (sport->port.sysrq) locked = 0; @@ -2053,9 +2043,6 @@ imx_uart_console_write(struct console *co, const char *s, unsigned int count) if (locked) spin_unlock_irqrestore(&sport->port.lock, flags); - - clk_disable(sport->clk_ipg); - clk_disable(sport->clk_per); } /* @@ -2156,15 +2143,14 @@ imx_uart_console_setup(struct console *co, char *options) retval = uart_set_options(&sport->port, co, baud, parity, bits, flow); - clk_disable(sport->clk_ipg); if (retval) { - clk_unprepare(sport->clk_ipg); + clk_disable_unprepare(sport->clk_ipg); goto error_console; } - retval = clk_prepare(sport->clk_per); + retval = clk_prepare_enable(sport->clk_per); if (retval) - clk_unprepare(sport->clk_ipg); + clk_disable_unprepare(sport->clk_ipg); error_console: return retval; -- cgit