tty: drop tty_schedule_flip()

stable inclusion
from stable-v4.19.254
commit 3ca62328d9bfaa597397099cb7f5a485a9bebacc
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/I5A5Y1
CVE: CVE-2022-1462

--------------------------------

commit 5db96ef2 upstream.

Since commit a9c3f68f (tty: Fix low_latency BUG) in 2014,
tty_flip_buffer_push() is only a wrapper to tty_schedule_flip(). All
users were converted in the previous patches, so remove
tty_schedule_flip() completely while inlining its body into
tty_flip_buffer_push().

One less exported function.
Reviewed-by: NJohan Hovold <johan@kernel.org>
Signed-off-by: NJiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20211122111648.30379-4-jslaby@suse.czSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NYi Yang <yiyang13@huawei.com>
Reviewed-by: NXiu Jianfeng <xiujianfeng@huawei.com>
Reviewed-by: NWang Weiyang <wangweiyang2@huawei.com>
Signed-off-by: NYongqiang Liu <liuyongqiang13@huawei.com>

drivers/tty/tty_buffer.c

@@ -390,27 +390,6 @@ int __tty_insert_flip_char(struct tty_port *port, unsigned char ch, char flag)
 }
 EXPORT_SYMBOL(__tty_insert_flip_char);
 
-/**
- *	tty_schedule_flip	-	push characters to ldisc
- *	@port: tty port to push from
- *
- *	Takes any pending buffers and transfers their ownership to the
- *	ldisc side of the queue. It then schedules those characters for
- *	processing by the line discipline.
- */
-
-void tty_schedule_flip(struct tty_port *port)
-{
-	struct tty_bufhead *buf = &port->buf;
-
-	/* paired w/ acquire in flush_to_ldisc(); ensures
-	 * flush_to_ldisc() sees buffer data.
-	 */
-	smp_store_release(&buf->tail->commit, buf->tail->used);
-	queue_work(system_unbound_wq, &buf->work);
-}
-EXPORT_SYMBOL(tty_schedule_flip);
-
 /**
  *	tty_prepare_flip_string		-	make room for characters
  *	@port: tty port
@@ -553,7 +532,14 @@ static void flush_to_ldisc(struct work_struct *work)
 
 void tty_flip_buffer_push(struct tty_port *port)
 {
-	tty_schedule_flip(port);
+	struct tty_bufhead *buf = &port->buf;
+
+	/*
+	 * Paired w/ acquire in flush_to_ldisc(); ensures flush_to_ldisc() sees
+	 * buffer data.
+	 */
+	smp_store_release(&buf->tail->commit, buf->tail->used);
+	queue_work(system_unbound_wq, &buf->work);
 }
 EXPORT_SYMBOL(tty_flip_buffer_push);
 

include/linux/tty_flip.h

@@ -12,7 +12,6 @@ extern int tty_insert_flip_string_fixed_flag(struct tty_port *port,
 extern int tty_prepare_flip_string(struct tty_port *port,
 		unsigned char **chars, size_t size);
 extern void tty_flip_buffer_push(struct tty_port *port);
-void tty_schedule_flip(struct tty_port *port);
 int __tty_insert_flip_char(struct tty_port *port, unsigned char ch, char flag);
 
 static inline int tty_insert_flip_char(struct tty_port *port,