[PATCH] tty buffering stall fix
Prevent stalled processing of received data when a driver allocates tty
buffer space but does not immediately follow the allocation with more data
and a call to schedule receive tty processing. (example: hvc_console) This
bug was introduced by the first locking patch for the new tty buffering.
Signed-off-by: Paul Fulghum <paulkf@microgate.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
index 076e07c..a23816d 100644
--- a/drivers/char/tty_io.c
+++ b/drivers/char/tty_io.c
@@ -268,6 +268,8 @@
p->size = size;
p->next = NULL;
p->active = 0;
+ p->commit = 0;
+ p->read = 0;
p->char_buf_ptr = (char *)(p->data);
p->flag_buf_ptr = (unsigned char *)p->char_buf_ptr + size;
/* printk("Flip create %p\n", p); */
@@ -298,6 +300,8 @@
*tbh = t->next;
t->next = NULL;
t->used = 0;
+ t->commit = 0;
+ t->read = 0;
/* DEBUG ONLY */
memset(t->data, '*', size);
/* printk("Flip recycle %p\n", t); */
@@ -335,6 +339,7 @@
if (b != NULL) {
b->next = n;
b->active = 0;
+ b->commit = b->used;
} else
tty->buf.head = n;
tty->buf.tail = n;
@@ -2752,6 +2757,9 @@
unsigned long flags;
struct tty_ldisc *disc;
struct tty_buffer *tbuf;
+ int count;
+ char *char_buf;
+ unsigned char *flag_buf;
disc = tty_ldisc_ref(tty);
if (disc == NULL) /* !TTY_LDISC */
@@ -2765,16 +2773,20 @@
goto out;
}
spin_lock_irqsave(&tty->buf.lock, flags);
- while((tbuf = tty->buf.head) != NULL && !tbuf->active) {
+ 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;
+ 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;
- spin_unlock_irqrestore(&tty->buf.lock, flags);
- /* printk("Process buffer %p for %d\n", tbuf, tbuf->used); */
- disc->receive_buf(tty, tbuf->char_buf_ptr,
- tbuf->flag_buf_ptr,
- tbuf->used);
- spin_lock_irqsave(&tty->buf.lock, flags);
tty_buffer_free(tty, tbuf);
}
spin_unlock_irqrestore(&tty->buf.lock, flags);
@@ -2871,8 +2883,10 @@
{
unsigned long flags;
spin_lock_irqsave(&tty->buf.lock, flags);
- if (tty->buf.tail != NULL)
+ if (tty->buf.tail != NULL) {
tty->buf.tail->active = 0;
+ tty->buf.tail->commit = tty->buf.tail->used;
+ }
spin_unlock_irqrestore(&tty->buf.lock, flags);
if (tty->low_latency)