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Subject[patch 21/23] tty serialize flush_to_ldisc
-stable review patch.  If anyone has any objections, please let us know.

------------------
From: Paul Fulghum <paulkf@microgate.com>

Serialize processing of tty buffers in flush_to_ldisc
to fix (very rare) corruption of tty buffer free list
on SMP systems.

Signed-off-by: Paul Fulghum <paulkf@microgate.com>
Acked-by: Alan Cox <alan@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>


---
drivers/char/tty_io.c | 14 +++++++++-----
1 file changed, 9 insertions(+), 5 deletions(-)

--- linux-2.6.17.7.orig/drivers/char/tty_io.c
+++ linux-2.6.17.7/drivers/char/tty_io.c
@@ -2776,7 +2776,7 @@ 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;
+ struct tty_buffer *tbuf, *head;
int count;
char *char_buf;
unsigned char *flag_buf;
@@ -2793,7 +2793,9 @@ static void flush_to_ldisc(void *private
goto out;
}
spin_lock_irqsave(&tty->buf.lock, flags);
- while((tbuf = tty->buf.head) != NULL) {
+ head = tty->buf.head;
+ tty->buf.head = NULL;
+ while((tbuf = 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;
@@ -2802,10 +2804,12 @@ static void flush_to_ldisc(void *private
disc->receive_buf(tty, char_buf, flag_buf, count);
spin_lock_irqsave(&tty->buf.lock, flags);
}
- if (tbuf->active)
+ if (tbuf->active) {
+ tty->buf.head = head;
break;
- tty->buf.head = tbuf->next;
- if (tty->buf.head == NULL)
+ }
+ head = tbuf->next;
+ if (head == NULL)
tty->buf.tail = NULL;
tty_buffer_free(tty, tbuf);
}
--
-
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