[PATCH] xhci: dbgtty: convert rx push tasklet to BH workqueue

[Kun Luo <luokun485@gmail.com>]

The kernel is converting remaining tasklet users to BH workqueues so
softirq handling can go through the workqueue path. The dbc TTY rx
push path is a straightforward bottom-half: schedule from IRQ /
unthrottle, run the same work, kill on port teardown.

Replace the tasklet with system_bh_wq. Behavior stays in softirq
context, so existing locking is unchanged.

Compile-tested only.

Signed-off-by: Kun Luo <luokun485@gmail.com>
---
 drivers/usb/host/xhci-dbgcap.h |  2 +-
 drivers/usb/host/xhci-dbgtty.c | 17 +++++++++--------
 2 files changed, 10 insertions(+), 9 deletions(-)

diff --git a/drivers/usb/host/xhci-dbgcap.h b/drivers/usb/host/xhci-dbgcap.h
index 5b18efb2c1ea..78e9b5e674a3 100644
--- a/drivers/usb/host/xhci-dbgcap.h
+++ b/drivers/usb/host/xhci-dbgcap.h
@@ -127,7 +127,7 @@ struct dbc_port {
 	struct list_head		read_pool;
 	struct list_head		read_queue;
 	unsigned int			n_read;
-	struct tasklet_struct		push;
+	struct work_struct		push;
 
 	struct list_head		write_pool;
 	unsigned int			tx_boundary;
diff --git a/drivers/usb/host/xhci-dbgtty.c b/drivers/usb/host/xhci-dbgtty.c
index 3d51e8d82659..c18215751d92 100644
--- a/drivers/usb/host/xhci-dbgtty.c
+++ b/drivers/usb/host/xhci-dbgtty.c
@@ -11,6 +11,7 @@
 #include <linux/tty.h>
 #include <linux/tty_flip.h>
 #include <linux/idr.h>
+#include <linux/workqueue.h>
 
 #include "xhci.h"
 #include "xhci-dbgcap.h"
@@ -189,9 +190,9 @@ dbc_read_complete(struct xhci_dbc *dbc, struct dbc_request *req)
 		}
 	}
 
-	/* defer moving data from req to tty buffer to a tasklet */
+	/* defer moving data from req to tty buffer to BH workqueue */
 	list_add_tail(&req->list_pool, &port->read_queue);
-	tasklet_schedule(&port->push);
+	queue_work(system_bh_wq, &port->push);
 out:
 	spin_unlock_irqrestore(&port->port_lock, flags);
 }
@@ -384,7 +385,7 @@ static void dbc_tty_unthrottle(struct tty_struct *tty)
 	unsigned long		flags;
 
 	spin_lock_irqsave(&port->port_lock, flags);
-	tasklet_schedule(&port->push);
+	queue_work(system_bh_wq, &port->push);
 	spin_unlock_irqrestore(&port->port_lock, flags);
 }
 
@@ -400,13 +401,13 @@ static const struct tty_operations dbc_tty_ops = {
 	.unthrottle		= dbc_tty_unthrottle,
 };
 
-static void dbc_rx_push(struct tasklet_struct *t)
+static void dbc_rx_push(struct work_struct *work)
 {
 	struct dbc_request	*req;
 	struct tty_struct	*tty;
 	unsigned long		flags;
 	bool			disconnect = false;
-	struct dbc_port		*port = from_tasklet(port, t, push);
+	struct dbc_port		*port = from_work(port, work, push);
 	struct list_head	*queue = &port->read_queue;
 	int			untransferred;
 
@@ -438,7 +439,7 @@ static void dbc_rx_push(struct tasklet_struct *t)
 	}
 
 	if (!list_empty(queue))
-		tasklet_schedule(&port->push);
+		queue_work(system_bh_wq, &port->push);
 
 	if (!disconnect)
 		dbc_start_rx(port);
@@ -467,7 +468,7 @@ xhci_dbc_tty_init_port(struct xhci_dbc *dbc, struct dbc_port *port)
 {
 	tty_port_init(&port->port);
 	spin_lock_init(&port->port_lock);
-	tasklet_setup(&port->push, dbc_rx_push);
+	INIT_WORK(&port->push, dbc_rx_push);
 	INIT_LIST_HEAD(&port->read_pool);
 	INIT_LIST_HEAD(&port->read_queue);
 	INIT_LIST_HEAD(&port->write_pool);
@@ -479,7 +480,7 @@ xhci_dbc_tty_init_port(struct xhci_dbc *dbc, struct dbc_port *port)
 static void
 xhci_dbc_tty_exit_port(struct dbc_port *port)
 {
-	tasklet_kill(&port->push);
+	cancel_work_sync(&port->push);
 	tty_port_destroy(&port->port);
 }
 
-- 
2.54.0