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[PATCH] add receive_room flow control to flush_to_ldisc 

Flush data serially to line discipline in blocks no larger than
tty->receive_room to avoid losing data if line discipline is busy (such as
N_TTY operating at high speed on heavily loaded system) or does not accept
data in large blocks (such as N_MOUSE).

Signed-off-by: Paul Fulghum <paulkf@microgate.com>
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 04:26:48 -07:00 committed by Linus Torvalds
parent 817d6d3bce
commit 2c3bb20f46
1 changed files with 24 additions and 13 deletions
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37
drivers/char/tty_io.c
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@ -2771,8 +2771,7 @@ static void flush_to_ldisc(void *private_)
struct tty_struct *tty = (struct tty_struct *) private_;
unsigned long flags;
struct tty_ldisc *disc;
struct tty_buffer *tbuf;
int count;
struct tty_buffer *tbuf, *head;
char *char_buf;
unsigned char *flag_buf;
@ -2781,21 +2780,33 @@ static void flush_to_ldisc(void *private_)
return;
spin_lock_irqsave(&tty->buf.lock, flags);
while((tbuf = tty->buf.head) != NULL) {
while ((count = tbuf->commit - tbuf->read) != 0) {
char_buf = tbuf->char_buf_ptr + tbuf->read;
flag_buf = tbuf->flag_buf_ptr + tbuf->read;
tbuf->read += count;
head = tty->buf.head;
if (head != NULL) {
tty->buf.head = NULL;
for (;;) {
int count = head->commit - head->read;
if (!count) {
if (head->next == NULL)
break;
tbuf = head;
head = head->next;
tty_buffer_free(tty, tbuf);
continue;
}
if (!tty->receive_room) {
schedule_delayed_work(&tty->buf.work, 1);
break;
}
if (count > tty->receive_room)
count = tty->receive_room;
char_buf = head->char_buf_ptr + head->read;
flag_buf = head->flag_buf_ptr + head->read;
head->read += count;
spin_unlock_irqrestore(&tty->buf.lock, flags);
disc->receive_buf(tty, char_buf, flag_buf, count);
spin_lock_irqsave(&tty->buf.lock, flags);
}
if (tbuf->active)
break;
tty->buf.head = tbuf->next;
if (tty->buf.head == NULL)
tty->buf.tail = NULL;
tty_buffer_free(tty, tbuf);
tty->buf.head = head;
}
spin_unlock_irqrestore(&tty->buf.lock, flags);