tty: Make driver-side flip buffers lockless (e8437d7e) · Commits · 戴 / test

drivers/tty/tty_buffer.c

+4 −27

Original line number	Diff line number	Diff line
		@@ -62,8 +62,6 @@ static void tty_buffer_reset(struct tty_buffer *p, size_t size)
		*
		* Remove all the buffers pending on a tty whether queued with data
		* or in the free ring. Must be called when the tty is no longer in use
		*
		* Locking: none
		*/

		void tty_buffer_free_all(struct tty_port *port)
		@@ -216,29 +214,26 @@ void tty_buffer_flush(struct tty_struct *tty)
		*
		* Make at least size bytes of linear space available for the tty
		* buffer. If we fail return the size we managed to find.
		*
		* Locking: Takes port->buf.lock
		*/
		int tty_buffer_request_room(struct tty_port *port, size_t size)
		{
		struct tty_bufhead *buf = &port->buf;
		struct tty_buffer b, n;
		int left;
		unsigned long flags;
		spin_lock_irqsave(&buf->lock, flags);

		b = buf->tail;
		left = b->size - b->used;

		if (left < size) {
		/* This is the slow path - looking for new buffers to use */
		if ((n = tty_buffer_alloc(port, size)) != NULL) {
		b->next = n;
		b->commit = b->used;
		buf->tail = n;
		b->commit = b->used;
		smp_mb();
		b->next = n;
		} else
		size = left;
		}
		spin_unlock_irqrestore(&buf->lock, flags);
		return size;
		}
		EXPORT_SYMBOL_GPL(tty_buffer_request_room);
		@@ -252,8 +247,6 @@ EXPORT_SYMBOL_GPL(tty_buffer_request_room);
		*
		* Queue a series of bytes to the tty buffering. All the characters
		* passed are marked with the supplied flag. Returns the number added.
		*
		* Locking: Called functions may take port->buf.lock
		*/

		int tty_insert_flip_string_fixed_flag(struct tty_port *port,
		@@ -288,8 +281,6 @@ EXPORT_SYMBOL(tty_insert_flip_string_fixed_flag);
		* Queue a series of bytes to the tty buffering. For each character
		* the flags array indicates the status of the character. Returns the
		* number added.
		*
		* Locking: Called functions may take port->buf.lock
		*/

		int tty_insert_flip_string_flags(struct tty_port *port,
		@@ -324,19 +315,14 @@ EXPORT_SYMBOL(tty_insert_flip_string_flags);
		* processing by the line discipline.
		* Note that this function can only be used when the low_latency flag
		* is unset. Otherwise the workqueue won't be flushed.
		*
		* Locking: Takes port->buf.lock
		*/

		void tty_schedule_flip(struct tty_port *port)
		{
		struct tty_bufhead *buf = &port->buf;
		unsigned long flags;
		WARN_ON(port->low_latency);

		spin_lock_irqsave(&buf->lock, flags);
		buf->tail->commit = buf->tail->used;
		spin_unlock_irqrestore(&buf->lock, flags);
		schedule_work(&buf->work);
		}
		EXPORT_SYMBOL(tty_schedule_flip);
		@@ -352,8 +338,6 @@ EXPORT_SYMBOL(tty_schedule_flip);
		* accounted for as ready for normal characters. This is used for drivers
		* that need their own block copy routines into the buffer. There is no
		* guarantee the buffer is a DMA target!
		*
		* Locking: May call functions taking port->buf.lock
		*/

		int tty_prepare_flip_string(struct tty_port port, unsigned char *chars,
		@@ -382,8 +366,6 @@ EXPORT_SYMBOL_GPL(tty_prepare_flip_string);
		* accounted for as ready for characters. This is used for drivers
		* that need their own block copy routines into the buffer. There is no
		* guarantee the buffer is a DMA target!
		*
		* Locking: May call functions taking port->buf.lock
		*/

		int tty_prepare_flip_string_flags(struct tty_port *port,
		@@ -511,18 +493,13 @@ void tty_flush_to_ldisc(struct tty_struct *tty)
		*
		* In the event of the queue being busy for flipping the work will be
		* held off and retried later.
		*
		* Locking: tty buffer lock. Driver locks in low latency mode.
		*/

		void tty_flip_buffer_push(struct tty_port *port)
		{
		struct tty_bufhead *buf = &port->buf;
		unsigned long flags;

		spin_lock_irqsave(&buf->lock, flags);
		buf->tail->commit = buf->tail->used;
		spin_unlock_irqrestore(&buf->lock, flags);

		if (port->low_latency)
		flush_to_ldisc(&buf->work);

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