[PATCH 2/3] drivers/tty: convert tty_port to use kthread_worker

[Steven Walter <stevenrwalter@xxxxxxxxx>]

Use kthread_worker instead of workqueues.  For now there is only a
single workqueue, but the intention is to bring back the "low_latency"
tty option, along with a second high-priority kthread worker.

Signed-off-by: Steven Walter <stevenrwalter@xxxxxxxxx>
---
 drivers/tty/tty_buffer.c | 17 +++++++++++------
 drivers/tty/tty_io.c     |  3 ++-
 drivers/tty/tty_port.c   |  2 +-
 include/linux/tty.h      |  5 +++--
 4 files changed, 17 insertions(+), 10 deletions(-)

diff --git a/drivers/tty/tty_buffer.c b/drivers/tty/tty_buffer.c
index ed7b5c8..4564202 100644
--- a/drivers/tty/tty_buffer.c
+++ b/drivers/tty/tty_buffer.c
@@ -3,6 +3,7 @@
  */
 
 #include <linux/types.h>
+#include <linux/kthread.h>
 #include <linux/errno.h>
 #include <linux/tty.h>
 #include <linux/tty_driver.h>
@@ -431,7 +432,7 @@ receive_buf(struct tty_struct *tty, struct tty_buffer *head, int count)
  *		 'consumer'
  */
 
-static void flush_to_ldisc(struct work_struct *work)
+static void flush_to_ldisc(struct kthread_work *work)
 {
 	struct tty_port *port = container_of(work, struct tty_port, buf.work);
 	struct tty_bufhead *buf = &port->buf;
@@ -520,17 +521,21 @@ EXPORT_SYMBOL(tty_flip_buffer_push);
  *	Must be called before the other tty buffer functions are used.
  */
 
+static DEFINE_KTHREAD_WORKER(tty_buffer_worker);
 
 void tty_buffer_queue_work(struct tty_port *port)
 {
-	struct tty_bufhead *buf = &port->buf;
-	schedule_work(&buf->work);
+	queue_kthread_work(&tty_buffer_worker, &port->buf.work);
 }
 
 void tty_buffer_flush_work(struct tty_port *port)
 {
-	struct tty_bufhead *buf = &port->buf;
-	flush_work(&buf->work);
+	flush_kthread_work(&port->buf.work);
+}
+
+void tty_buffer_init_kthread()
+{
+	kthread_run(kthread_worker_fn, &tty_buffer_worker, "tty");
 }
 
 void tty_buffer_init(struct tty_port *port)
@@ -544,7 +549,7 @@ void tty_buffer_init(struct tty_port *port)
 	init_llist_head(&buf->free);
 	atomic_set(&buf->mem_used, 0);
 	atomic_set(&buf->priority, 0);
-	INIT_WORK(&buf->work, flush_to_ldisc);
+	init_kthread_work(&buf->work, flush_to_ldisc);
 	buf->mem_limit = TTYB_DEFAULT_MEM_LIMIT;
 }
 
diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index 0508a1d..abcd9a5 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -1633,7 +1633,7 @@ static void release_tty(struct tty_struct *tty, int idx)
 	tty->port->itty = NULL;
 	if (tty->link)
 		tty->link->port->itty = NULL;
-	cancel_work_sync(&tty->port->buf.work);
+	tty_buffer_flush_work(tty->port);
 
 	if (tty->link)
 		tty_kref_put(tty->link);
@@ -3602,6 +3602,7 @@ void console_sysfs_notify(void)
  */
 int __init tty_init(void)
 {
+	tty_buffer_init_kthread();
 	cdev_init(&tty_cdev, &tty_fops);
 	if (cdev_add(&tty_cdev, MKDEV(TTYAUX_MAJOR, 0), 1) ||
 	    register_chrdev_region(MKDEV(TTYAUX_MAJOR, 0), 1, "/dev/tty") < 0)
diff --git a/drivers/tty/tty_port.c b/drivers/tty/tty_port.c
index 1b93357..d041323 100644
--- a/drivers/tty/tty_port.c
+++ b/drivers/tty/tty_port.c
@@ -131,7 +131,7 @@ EXPORT_SYMBOL(tty_port_free_xmit_buf);
  */
 void tty_port_destroy(struct tty_port *port)
 {
-	cancel_work_sync(&port->buf.work);
+	tty_buffer_flush_work(port);
 	tty_buffer_free_all(port);
 }
 EXPORT_SYMBOL(tty_port_destroy);
diff --git a/include/linux/tty.h b/include/linux/tty.h
index 7bad787..9c19141 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -2,9 +2,9 @@
 #define _LINUX_TTY_H
 
 #include <linux/fs.h>
+#include <linux/kthread.h>
 #include <linux/major.h>
 #include <linux/termios.h>
-#include <linux/workqueue.h>
 #include <linux/tty_driver.h>
 #include <linux/tty_ldisc.h>
 #include <linux/mutex.h>
@@ -59,7 +59,7 @@ static inline char *flag_buf_ptr(struct tty_buffer *b, int ofs)
 
 struct tty_bufhead {
 	struct tty_buffer *head;	/* Queue head */
-	struct work_struct work;
+	struct kthread_work work;
 	struct mutex	   lock;
 	atomic_t	   priority;
 	struct tty_buffer sentinel;
@@ -448,6 +448,7 @@ extern void tty_buffer_flush(struct tty_struct *tty);
 extern void tty_buffer_init(struct tty_port *port);
 extern void tty_buffer_queue_work(struct tty_port *port);
 extern void tty_buffer_flush_work(struct tty_port *port);
+extern void tty_buffer_init_kthread(void);
 extern speed_t tty_termios_baud_rate(struct ktermios *termios);
 extern speed_t tty_termios_input_baud_rate(struct ktermios *termios);
 extern void tty_termios_encode_baud_rate(struct ktermios *termios,
-- 
1.9.1

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