serial: imx: drop workaround for forced irq threading

Force-threaded interrupt handlers used to run with interrupts enabled,
something which could lead to deadlocks in case a threaded handler
shared a lock with code running in hard interrupt context (e.g. timer
callbacks) and did not explicitly disable interrupts.

This was specifically the case for serial drivers that take the port
lock in their console write path as printk can be called from hard
interrupt context also with forced threading ("threadirqs").

Since commit 81e2073c175b ("genirq: Disable interrupts for force
threaded handlers") interrupt handlers always run with interrupts
disabled on non-RT so that drivers no longer need to do handle this.

Drop the now obsolete workaround added by commit 33f16855dcb9 ("tty:
serial: imx: fix potential deadlock").

Cc: Sam Nobs <samuel.nobs@taitradio.com>
Cc: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Johan Hovold <johan@kernel.org>
Link: https://lore.kernel.org/r/20210322111036.31966-1-johan@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index 3f69356937ef99fbb95e580ba97b41d372c1c362..7d5a8dfa3e91e28d2e2ee6debf1f51f7b52e8712 100644 (file)
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -918,14 +918,8 @@ 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;
 
-       /*
-        * 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);
+       spin_lock(&sport->port.lock);
 
        usr1 = imx_uart_readl(sport, USR1);
        usr2 = imx_uart_readl(sport, USR2);
@@ -995,7 +989,7 @@ static irqreturn_t imx_uart_int(int irq, void *dev_id)
                ret = IRQ_HANDLED;
        }
 
-       spin_unlock_irqrestore(&sport->port.lock, flags);
+       spin_unlock(&sport->port.lock);
 
        return ret;
 }