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Commit 4d18e6ef authored by Peter Hurley's avatar Peter Hurley Committed by Greg Kroah-Hartman
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tty: Enable configurable tty flip buffer limit 



Allow driver to configure its maximum flip buffer memory
consumption/limit. This is necessary for very-high speed line
rates (in excess of 10MB/sec) because the flip buffers can
be saturated before the line discipline has a chance to
throttle the input.

Signed-off-by: default avatarPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 82f91fe0

drivers/tty/tty_buffer.c

+21 −3
Original line number Diff line number Diff line
@@ -26,7 +26,7 @@ 
 * Byte threshold to limit memory consumption for flip buffers.

 * The actual memory limit is > 2x this amount.

 */

#define TTYB_MEM_LIMIT	65536

#define TTYB_DEFAULT_MEM_LIMIT	65536



/*

 * We default to dicing tty buffer allocations to this many characters
@@ -89,7 +89,7 @@ void tty_buffer_unlock_exclusive(struct tty_port *port) 


int tty_buffer_space_avail(struct tty_port *port)

{

	int space = TTYB_MEM_LIMIT - atomic_read(&port->buf.memory_used);

	int space = port->buf.mem_limit - atomic_read(&port->buf.memory_used);

	return max(space, 0);

}
@@ -162,7 +162,7 @@ static struct tty_buffer *tty_buffer_alloc(struct tty_port *port, size_t size) 


	/* Should possibly check if this fails for the largest buffer we

	   have queued and recycle that ? */

	if (atomic_read(&port->buf.memory_used) > TTYB_MEM_LIMIT)

	if (atomic_read(&port->buf.memory_used) > port->buf.mem_limit)

		return NULL;

	p = kmalloc(sizeof(struct tty_buffer) + 2 * size, GFP_ATOMIC);

	if (p == NULL)
@@ -536,4 +536,22 @@ void tty_buffer_init(struct tty_port *port) 
	atomic_set(&buf->memory_used, 0);

	atomic_set(&buf->priority, 0);

	INIT_WORK(&buf->work, flush_to_ldisc);

	buf->mem_limit = TTYB_DEFAULT_MEM_LIMIT;

}



/**

 *	tty_buffer_set_limit	-	change the tty buffer memory limit

 *	@port: tty port to change

 *

 *	Change the tty buffer memory limit.

 *	Must be called before the other tty buffer functions are used.

 */



int tty_buffer_set_limit(struct tty_port *port, int limit)

{

	if (limit < MIN_TTYB_SIZE)

		return -EINVAL;

	port->buf.mem_limit = limit;

	return 0;

}

EXPORT_SYMBOL_GPL(tty_buffer_set_limit);

include/linux/tty.h

+1 −0
Original line number Diff line number Diff line
@@ -61,6 +61,7 @@ struct tty_bufhead { 
	struct tty_buffer sentinel;

	struct llist_head free;		/* Free queue head */

	atomic_t	   memory_used; /* In-use buffers excluding free list */

	int		   mem_limit;

	struct tty_buffer *tail;	/* Active buffer */

};

/*

include/linux/tty_flip.h

+1 −0
Original line number Diff line number Diff line 
#ifndef _LINUX_TTY_FLIP_H

#define _LINUX_TTY_FLIP_H



extern int tty_buffer_set_limit(struct tty_port *port, int limit);

extern int tty_buffer_space_avail(struct tty_port *port);

extern int tty_buffer_request_room(struct tty_port *port, size_t size);

extern int tty_insert_flip_string_flags(struct tty_port *port,