Revert "tty: tty_port: add workqueue to flip TTY buffer"

This reverts commit d000422.

It is reported by many to cause boot failures, so must be reverted.

Cc: Xin Zhao <jackzxcui1989@163.com>
Cc: Jiri Slaby <jirislaby@kernel.org>
Link: https://lore.kernel.org/r/d1942304-ee30-478d-90fb-279519f3ae81@samsung.com
Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reported-by: Tommaso Merciai <tommaso.merciai.xr@bp.renesas.com>
Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: gregkh

drivers/tty/pty.c

@@ -403,8 +403,6 @@ static int pty_common_install(struct tty_driver *driver, struct tty_struct *tty,
 	o_tty->link = tty;
 	tty_port_init(ports[0]);
 	tty_port_init(ports[1]);
-	tty_port_link_wq(ports[0], system_dfl_wq);
-	tty_port_link_wq(ports[1], system_dfl_wq);
 	tty_buffer_set_limit(ports[0], 8192);
 	tty_buffer_set_limit(ports[1], 8192);
 	o_tty->port = ports[0];
@@ -534,16 +532,14 @@ static void __init legacy_pty_init(void)
 	pty_driver = tty_alloc_driver(legacy_count,
 			TTY_DRIVER_RESET_TERMIOS |
 			TTY_DRIVER_REAL_RAW |
-			TTY_DRIVER_DYNAMIC_ALLOC |
-			TTY_DRIVER_CUSTOM_WORKQUEUE);
+			TTY_DRIVER_DYNAMIC_ALLOC);
 	if (IS_ERR(pty_driver))
 		panic("Couldn't allocate pty driver");
 
 	pty_slave_driver = tty_alloc_driver(legacy_count,
 			TTY_DRIVER_RESET_TERMIOS |
 			TTY_DRIVER_REAL_RAW |
-			TTY_DRIVER_DYNAMIC_ALLOC |
-			TTY_DRIVER_CUSTOM_WORKQUEUE);
+			TTY_DRIVER_DYNAMIC_ALLOC);
 	if (IS_ERR(pty_slave_driver))
 		panic("Couldn't allocate pty slave driver");
 
@@ -853,17 +849,15 @@ static void __init unix98_pty_init(void)
 			TTY_DRIVER_REAL_RAW |
 			TTY_DRIVER_DYNAMIC_DEV |
 			TTY_DRIVER_DEVPTS_MEM |
-			TTY_DRIVER_DYNAMIC_ALLOC |
-			TTY_DRIVER_CUSTOM_WORKQUEUE);
+			TTY_DRIVER_DYNAMIC_ALLOC);
 	if (IS_ERR(ptm_driver))
 		panic("Couldn't allocate Unix98 ptm driver");
 	pts_driver = tty_alloc_driver(NR_UNIX98_PTY_MAX,
 			TTY_DRIVER_RESET_TERMIOS |
 			TTY_DRIVER_REAL_RAW |
 			TTY_DRIVER_DYNAMIC_DEV |
 			TTY_DRIVER_DEVPTS_MEM |
-			TTY_DRIVER_DYNAMIC_ALLOC |
-			TTY_DRIVER_CUSTOM_WORKQUEUE);
+			TTY_DRIVER_DYNAMIC_ALLOC);
 	if (IS_ERR(pts_driver))
 		panic("Couldn't allocate Unix98 pts driver");
 

drivers/tty/tty_buffer.c

@@ -76,7 +76,7 @@ void tty_buffer_unlock_exclusive(struct tty_port *port)
 	mutex_unlock(&buf->lock);
 
 	if (restart)
-		queue_work(buf->flip_wq, &buf->work);
+		queue_work(system_dfl_wq, &buf->work);
 }
 EXPORT_SYMBOL_GPL(tty_buffer_unlock_exclusive);
 
@@ -530,7 +530,7 @@ void tty_flip_buffer_push(struct tty_port *port)
 	struct tty_bufhead *buf = &port->buf;
 
 	tty_flip_buffer_commit(buf->tail);
-	queue_work(buf->flip_wq, &buf->work);
+	queue_work(system_dfl_wq, &buf->work);
 }
 EXPORT_SYMBOL(tty_flip_buffer_push);
 
@@ -560,7 +560,7 @@ int tty_insert_flip_string_and_push_buffer(struct tty_port *port,
 		tty_flip_buffer_commit(buf->tail);
 	spin_unlock_irqrestore(&port->lock, flags);
 
-	queue_work(buf->flip_wq, &buf->work);
+	queue_work(system_dfl_wq, &buf->work);
 
 	return size;
 }
@@ -613,7 +613,7 @@ void tty_buffer_set_lock_subclass(struct tty_port *port)
 
 bool tty_buffer_restart_work(struct tty_port *port)
 {
-	return queue_work(port->buf.flip_wq, &port->buf.work);
+	return queue_work(system_dfl_wq, &port->buf.work);
 }
 
 bool tty_buffer_cancel_work(struct tty_port *port)

drivers/tty/tty_io.c

@@ -3446,23 +3446,10 @@ int tty_register_driver(struct tty_driver *driver)
 	if (error < 0)
 		goto err;
 
-	if (!(driver->flags & TTY_DRIVER_CUSTOM_WORKQUEUE)) {
-		driver->flip_wq = alloc_workqueue("%s-flip-wq", WQ_UNBOUND | WQ_SYSFS,
-						  0, driver->name);
-		if (!driver->flip_wq) {
-			error = -ENOMEM;
-			goto err_unreg_char;
-		}
-		for (i = 0; i < driver->num; i++) {
-			if (driver->ports[i])
-				tty_port_link_driver_wq(driver->ports[i], driver);
-		}
-	}
-
 	if (driver->flags & TTY_DRIVER_DYNAMIC_ALLOC) {
 		error = tty_cdev_add(driver, dev, 0, driver->num);
 		if (error)
-			goto err_destroy_wq;
+			goto err_unreg_char;
 	}
 
 	scoped_guard(mutex, &tty_mutex)
@@ -3488,10 +3475,6 @@ int tty_register_driver(struct tty_driver *driver)
 	scoped_guard(mutex, &tty_mutex)
 		list_del(&driver->tty_drivers);
 
-err_destroy_wq:
-	if (!(driver->flags & TTY_DRIVER_CUSTOM_WORKQUEUE))
-		destroy_workqueue(driver->flip_wq);
-
 err_unreg_char:
 	unregister_chrdev_region(dev, driver->num);
 err:
@@ -3511,8 +3494,6 @@ void tty_unregister_driver(struct tty_driver *driver)
 				driver->num);
 	scoped_guard(mutex, &tty_mutex)
 		list_del(&driver->tty_drivers);
-	if (!(driver->flags & TTY_DRIVER_CUSTOM_WORKQUEUE))
-		destroy_workqueue(driver->flip_wq);
 }
 EXPORT_SYMBOL(tty_unregister_driver);
 

drivers/tty/tty_port.c

@@ -99,26 +99,6 @@ void tty_port_init(struct tty_port *port)
 }
 EXPORT_SYMBOL(tty_port_init);
 
-/**
- * tty_port_link_wq - link tty_port and flip workqueue
- * @port: tty_port of the device
- * @flip_wq: workqueue to queue flip buffer work on
- *
- * When %TTY_DRIVER_CUSTOM_WORKQUEUE is used, every tty_port shall be linked to
- * a workqueue manually by this function, otherwise tty_flip_buffer_push() will
- * see %NULL flip_wq pointer on queue_work.
- * When %TTY_DRIVER_CUSTOM_WORKQUEUE is NOT used, the function can be used to
- * link a certain port to a specific workqueue, instead of using the workqueue
- * allocated in tty_register_driver().
- *
- * Note that TTY port API will NOT destroy the workqueue.
- */
-void tty_port_link_wq(struct tty_port *port, struct workqueue_struct *flip_wq)
-{
-	port->buf.flip_wq = flip_wq;
-}
-EXPORT_SYMBOL_GPL(tty_port_link_wq);
-
 /**
  * tty_port_link_device - link tty and tty_port
  * @port: tty_port of the device
@@ -177,7 +157,6 @@ struct device *tty_port_register_device_attr(struct tty_port *port,
 		const struct attribute_group **attr_grp)
 {
 	tty_port_link_device(port, driver, index);
-	tty_port_link_driver_wq(port, driver);
 	return tty_register_device_attr(driver, index, device, drvdata,
 			attr_grp);
 }
@@ -204,7 +183,6 @@ struct device *tty_port_register_device_attr_serdev(struct tty_port *port,
 	struct device *dev;
 
 	tty_port_link_device(port, driver, index);
-	tty_port_link_driver_wq(port, driver);
 
 	dev = serdev_tty_port_register(port, host, parent, driver, index);
 	if (PTR_ERR(dev) != -ENODEV) {
@@ -725,7 +703,6 @@ int tty_port_install(struct tty_port *port, struct tty_driver *driver,
 		struct tty_struct *tty)
 {
 	tty->port = port;
-	tty_port_link_driver_wq(port, driver);
 	return tty_standard_install(driver, tty);
 }
 EXPORT_SYMBOL_GPL(tty_port_install);

include/linux/tty_buffer.h

@@ -34,7 +34,6 @@ static inline u8 *flag_buf_ptr(struct tty_buffer *b, unsigned int ofs)
 
 struct tty_bufhead {
 	struct tty_buffer *head;	/* Queue head */
-	struct workqueue_struct *flip_wq;
 	struct work_struct work;
 	struct mutex	   lock;
 	atomic_t	   priority;

include/linux/tty_driver.h

@@ -69,10 +69,6 @@ struct serial_struct;
  *	Do not create numbered ``/dev`` nodes. For example, create
  *	``/dev/ttyprintk`` and not ``/dev/ttyprintk0``. Applicable only when a
  *	driver for a single tty device is being allocated.
- *
- * @TTY_DRIVER_CUSTOM_WORKQUEUE:
- *	Do not create workqueue when tty_register_driver(). When set, flip
- *	buffer workqueue shall be set by tty_port_link_wq() for every port.
  */
 enum tty_driver_flag {
 	TTY_DRIVER_INSTALLED		= BIT(0),
@@ -83,7 +79,6 @@ enum tty_driver_flag {
 	TTY_DRIVER_HARDWARE_BREAK	= BIT(5),
 	TTY_DRIVER_DYNAMIC_ALLOC	= BIT(6),
 	TTY_DRIVER_UNNUMBERED_NODE	= BIT(7),
-	TTY_DRIVER_CUSTOM_WORKQUEUE	= BIT(8),
 };
 
 enum tty_driver_type {
@@ -511,7 +506,6 @@ struct tty_operations {
  * @flags: tty driver flags (%TTY_DRIVER_)
  * @proc_entry: proc fs entry, used internally
  * @other: driver of the linked tty; only used for the PTY driver
- * @flip_wq: workqueue to queue flip buffer work on
  * @ttys: array of active &struct tty_struct, set by tty_standard_install()
  * @ports: array of &struct tty_port; can be set during initialization by
  *	   tty_port_link_device() and similar
@@ -545,7 +539,6 @@ struct tty_driver {
 	unsigned long	flags;
 	struct proc_dir_entry *proc_entry;
 	struct tty_driver *other;
-	struct workqueue_struct *flip_wq;
 
 	/*
 	 * Pointer to the tty data structures

include/linux/tty_port.h

@@ -138,7 +138,6 @@ struct tty_port {
 					   kernel */
 
 void tty_port_init(struct tty_port *port);
-void tty_port_link_wq(struct tty_port *port, struct workqueue_struct *flip_wq);
 void tty_port_link_device(struct tty_port *port, struct tty_driver *driver,
 		unsigned index);
 struct device *tty_port_register_device(struct tty_port *port,
@@ -166,18 +165,6 @@ static inline struct tty_port *tty_port_get(struct tty_port *port)
 	return NULL;
 }
 
-/*
- * Never overwrite the workqueue set by tty_port_link_wq().
- * No effect when %TTY_DRIVER_CUSTOM_WORKQUEUE is set, as driver->flip_wq is
- * %NULL.
- */
-static inline void tty_port_link_driver_wq(struct tty_port *port,
-					   struct tty_driver *driver)
-{
-	if (!port->buf.flip_wq)
-		port->buf.flip_wq = driver->flip_wq;
-}
-
 /* If the cts flow control is enabled, return true. */
 static inline bool tty_port_cts_enabled(const struct tty_port *port)
 {