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[PATCH] remove active field from tty buffer structure 

Remove 'active' field from tty buffer structure.  This was added in 2.6.16
as part of a patch to make the new tty buffering SMP safe.  This field is
unnecessary with the more intelligently written flush_to_ldisc that adds
receive_room handling.

Removing this field reverts to simpler logic where the tail buffer is
always the 'active' buffer, which should not be freed by flush_to_ldisc.
(active == buffer being filled with new data)

The result is simpler, smaller, and faster tty buffer code.

Signed-off-by: Paul Fulghum <paulkf@microgate.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Paul Fulghum 2006-06-28 04:26:49 -07:00 committed by Linus Torvalds
parent 2c3bb20f46
commit 33b37a33c2
4 changed files with 6 additions and 17 deletions
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16
drivers/char/tty_io.c
View File

@ -267,7 +267,6 @@ static struct tty_buffer *tty_buffer_alloc(size_t size)
p->used = 0;
p->size = size;
p->next = NULL;
p->active = 0;
p->commit = 0;
p->read = 0;
p->char_buf_ptr = (char *)(p->data);
@ -327,10 +326,9 @@ int tty_buffer_request_room(struct tty_struct *tty, size_t size)
/* OPTIMISATION: We could keep a per tty "zero" sized buffer to
remove this conditional if its worth it. This would be invisible
to the callers */
if ((b = tty->buf.tail) != NULL) {
if ((b = tty->buf.tail) != NULL)
left = b->size - b->used;
b->active = 1;
} else
else
left = 0;
if (left < size) {
@ -338,12 +336,10 @@ int tty_buffer_request_room(struct tty_struct *tty, size_t size)
if ((n = tty_buffer_find(tty, size)) != NULL) {
if (b != NULL) {
b->next = n;
b->active = 0;
b->commit = b->used;
} else
tty->buf.head = n;
tty->buf.tail = n;
n->active = 1;
} else
size = left;
}
@ -404,10 +400,8 @@ void tty_schedule_flip(struct tty_struct *tty)
{
unsigned long flags;
spin_lock_irqsave(&tty->buf.lock, flags);
if (tty->buf.tail != NULL) {
tty->buf.tail->active = 0;
if (tty->buf.tail != NULL)
tty->buf.tail->commit = tty->buf.tail->used;
}
spin_unlock_irqrestore(&tty->buf.lock, flags);
schedule_delayed_work(&tty->buf.work, 1);
}
@ -2902,10 +2896,8 @@ void tty_flip_buffer_push(struct tty_struct *tty)
{
unsigned long flags;
spin_lock_irqsave(&tty->buf.lock, flags);
if (tty->buf.tail != NULL) {
tty->buf.tail->active = 0;
if (tty->buf.tail != NULL)
tty->buf.tail->commit = tty->buf.tail->used;
}
spin_unlock_irqrestore(&tty->buf.lock, flags);
if (tty->low_latency)

4
include/linux/kbd_kern.h
View File

@ -155,10 +155,8 @@ static inline void con_schedule_flip(struct tty_struct *t)
{
unsigned long flags;
spin_lock_irqsave(&t->buf.lock, flags);
if (t->buf.tail != NULL) {
t->buf.tail->active = 0;
if (t->buf.tail != NULL)
t->buf.tail->commit = t->buf.tail->used;
}
spin_unlock_irqrestore(&t->buf.lock, flags);
schedule_work(&t->buf.work);
}

1
include/linux/tty.h
View File

@ -57,7 +57,6 @@ struct tty_buffer {
unsigned char *flag_buf_ptr;
int used;
int size;
int active;
int commit;
int read;
/* Data points here */

2
include/linux/tty_flip.h
View File

@ -12,7 +12,7 @@ static inline int tty_insert_flip_char(struct tty_struct *tty,
unsigned char ch, char flag)
{
struct tty_buffer *tb = tty->buf.tail;
if (tb && tb->active && tb->used < tb->size) {
if (tb && tb->used < tb->size) {
tb->flag_buf_ptr[tb->used] = flag;
tb->char_buf_ptr[tb->used++] = ch;
return 1;