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Commit 0f56bd2f authored by Peter Hurley's avatar Peter Hurley Committed by Greg Kroah-Hartman
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tty: Use non-atomic state to signal flip buffer flush pending 



Atomic bit ops are no longer required to indicate a flip buffer
flush is pending, as the flush_mutex is sufficient barrier.

Remove the unnecessary port .iflags field and localize flip buffer
state to struct tty_bufhead.

Signed-off-by: default avatarPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 8c1fb49b

drivers/tty/tty_buffer.c

+4 −3
Original line number Diff line number Diff line
@@ -189,11 +189,11 @@ void tty_buffer_flush(struct tty_struct *tty) 
	struct tty_port *port = tty->port;

	struct tty_bufhead *buf = &port->buf;



	set_bit(TTYP_FLUSHPENDING, &port->iflags);

	buf->flushpending = 1;



	mutex_lock(&buf->flush_mutex);

	__tty_buffer_flush(port);

	clear_bit(TTYP_FLUSHPENDING, &port->iflags);

	buf->flushpending = 0;

	mutex_unlock(&buf->flush_mutex);

}
@@ -426,7 +426,7 @@ static void flush_to_ldisc(struct work_struct *work) 
		int count;



		/* Ldisc or user is trying to flush the buffers. */

		if (test_bit(TTYP_FLUSHPENDING, &port->iflags))

		if (buf->flushpending)

			break;



		count = head->commit - head->read;
@@ -505,6 +505,7 @@ void tty_buffer_init(struct tty_port *port) 
	buf->tail = &buf->sentinel;

	init_llist_head(&buf->free);

	atomic_set(&buf->memory_used, 0);

	buf->flushpending = 0;

	INIT_WORK(&buf->work, flush_to_ldisc);

}

include/linux/tty.h

+1 −2
Original line number Diff line number Diff line
@@ -68,6 +68,7 @@ struct tty_bufhead { 
	struct tty_buffer *head;	/* Queue head */

	struct work_struct work;

	struct mutex flush_mutex;

	unsigned int flushpending:1;

	struct tty_buffer sentinel;

	struct llist_head free;		/* Free queue head */

	atomic_t	   memory_used; /* In-use buffers excluding free list */
@@ -212,8 +213,6 @@ struct tty_port { 
	wait_queue_head_t	close_wait;	/* Close waiters */

	wait_queue_head_t	delta_msr_wait;	/* Modem status change */

	unsigned long		flags;		/* TTY flags ASY_*/

	unsigned long		iflags;		/* TTYP_ internal flags */

#define TTYP_FLUSHPENDING		2  /* Queued buffer flush pending */

	unsigned char		console:1,	/* port is a console */

				low_latency:1;	/* direct buffer flush */

	struct mutex		mutex;		/* Locking */