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authorPaul Fulghum <paulkf@microgate.com>2006-02-10 01:51:14 -0800
committerLinus Torvalds <torvalds@g5.osdl.org>2006-02-10 08:13:12 -0800
commit8977d929e49021d9a6e031310aab01fa72f849c2 (patch)
tree13697e607b1153666139114242964f9982acc328
parentf0188f47482efdbd2e005103bb4f0224a835dfad (diff)
downloadlinux-2.6.34-ux500-8977d929e49021d9a6e031310aab01fa72f849c2.tar.gz
[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>
-rw-r--r--drivers/char/tty_io.c30
-rw-r--r--include/linux/kbd_kern.h4
-rw-r--r--include/linux/tty.h2
-rw-r--r--include/linux/tty_flip.h4
4 files changed, 30 insertions, 10 deletions
diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
index 076e07c1da3..a23816d3e9a 100644
--- a/drivers/char/tty_io.c
+++ b/drivers/char/tty_io.c
@@ -268,6 +268,8 @@ static struct tty_buffer *tty_buffer_alloc(size_t size)
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 @@ static struct tty_buffer *tty_buffer_find(struct tty_struct *tty, size_t size)
*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 @@ int tty_buffer_request_room(struct tty_struct *tty, size_t size)
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 @@ static void flush_to_ldisc(void *private_)
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 @@ static void flush_to_ldisc(void *private_)
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 @@ void tty_flip_buffer_push(struct tty_struct *tty)
{
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)
diff --git a/include/linux/kbd_kern.h b/include/linux/kbd_kern.h
index 3aed37314ab..e87c32a5c86 100644
--- a/include/linux/kbd_kern.h
+++ b/include/linux/kbd_kern.h
@@ -153,8 +153,10 @@ 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)
+ if (t->buf.tail != NULL) {
t->buf.tail->active = 0;
+ t->buf.tail->commit = t->buf.tail->used;
+ }
spin_unlock_irqrestore(&t->buf.lock, flags);
schedule_work(&t->buf.work);
}
diff --git a/include/linux/tty.h b/include/linux/tty.h
index a7bd3b4558d..f45cd74e6f2 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -58,6 +58,8 @@ struct tty_buffer {
int used;
int size;
int active;
+ int commit;
+ int read;
/* Data points here */
unsigned long data[0];
};
diff --git a/include/linux/tty_flip.h b/include/linux/tty_flip.h
index 82961eb1988..222faf97d5f 100644
--- a/include/linux/tty_flip.h
+++ b/include/linux/tty_flip.h
@@ -29,8 +29,10 @@ _INLINE_ void tty_schedule_flip(struct tty_struct *tty)
{
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);
schedule_delayed_work(&tty->buf.work, 1);
}