linux-kernel - [PATCH 2/2] serial: core: Remove BUG_ON(in

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Message-Id: <20210208181615.381861-3-bigeasy@linutronix.de>
Date:   Mon,  8 Feb 2021 19:16:15 +0100
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Ahmed S. Darwish" <a.darwish@...utronix.de>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Subject: [PATCH 2/2] serial: core: Remove BUG_ON(in_interrupt()) check

From: "Ahmed S. Darwish" <a.darwish@...utronix.de>

The usage of in_interrupt() in drivers is phased out for various
reasons.

In both exported functions where BUG_ON(in_interrupt()) is invoked,
there is a mutex_lock() afterwards. mutex_lock() contains a
might_sleep() which will already trigger a stack trace if the target
functions is called from atomic context.

Remove the BUG_ON() and add a "Context: " in the kernel-doc instead.

Signed-off-by: Ahmed S. Darwish <a.darwish@...utronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
---
 drivers/tty/serial/serial_core.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index 7dacdb6a85345..62dc7b5cd60c6 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -2848,6 +2848,8 @@ static const struct attribute_group tty_dev_attr_group = {
  *	@drv: pointer to the uart low level driver structure for this port
  *	@uport: uart port structure to use for this port.
  *
+ *	Context: task context, might sleep
+ *
  *	This allows the driver to register its own uart_port structure
  *	with the core driver.  The main purpose is to allow the low
  *	level uart drivers to expand uart_port, rather than having yet
@@ -2861,8 +2863,6 @@ int uart_add_one_port(struct uart_driver *drv, struct uart_port *uport)
 	struct device *tty_dev;
 	int num_groups;
 
-	BUG_ON(in_interrupt());
-
 	if (uport->line >= drv->nr)
 		return -EINVAL;
 
@@ -2951,6 +2951,8 @@ int uart_add_one_port(struct uart_driver *drv, struct uart_port *uport)
  *	@drv: pointer to the uart low level driver structure for this port
  *	@uport: uart port structure for this port
  *
+ *	Context: task context, might sleep
+ *
  *	This unhooks (and hangs up) the specified port structure from the
  *	core driver.  No further calls will be made to the low-level code
  *	for this port.
@@ -2963,8 +2965,6 @@ int uart_remove_one_port(struct uart_driver *drv, struct uart_port *uport)
 	struct tty_struct *tty;
 	int ret = 0;
 
-	BUG_ON(in_interrupt());
-
 	mutex_lock(&port_mutex);
 
 	/*
-- 
2.30.0