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Date: Mon, 27 Jul 2009 22:42:14 +0530
From: "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
To: Alan Cox <alan@...rguk.ukuu.org.uk>
Cc: OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>,
Linus Torvalds <torvalds@...ux-foundation.org>,
"Rafael J. Wysocki" <rjw@...k.pl>, Ray Lee <ray-lk@...rabbit.org>,
LKML <linux-kernel@...r.kernel.org>,
Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] kdesu broken
On Mon, Jul 27, 2009 at 05:42:52PM +0100, Alan Cox wrote:
>
> > > - if (count > tty->receive_room) {
> > > + if (count > tty->receive_room)
> > > count = tty->receive_room;
> > > - done = 0;
> > > - }
> > > char_buf = head->char_buf_ptr + head->read;
> > > flag_buf = head->flag_buf_ptr + head->read;
> > > head->read += count;
> > > _
> >
> >
> > I still have the "compile in emacs" bug. So this patch along with
> > http://article.gmane.org/gmane.linux.kernel/869824 doesn't fix the
> > bug for me.
>
> Can you stick some printk calls in and debug it further then because at
> with the fixes Ogawa provided I'm finding it impossible to reproduce even
> on an 8 way x86.
>
> What hardware are you using ?
My T60p lenovo laptop. If you can send me a debug prink patch i can redo the
test with the patches. I don't know what data i should start collecting so
that it make sense. This is the patch i tried
diff -ru /home/opensource/sources/linux-2.6/drivers/char/n_tty.c /home/opensource/build/linux-2.6-distro/drivers/char/n_tty.c
--- /home/opensource/sources/linux-2.6/drivers/char/n_tty.c 2009-07-17 10:07:40.210991073 +0530
+++ /home/opensource/build/linux-2.6-distro/drivers/char/n_tty.c 2009-07-27 18:56:14.518330502 +0530
@@ -1777,7 +1777,8 @@
tty->minimum_to_wake = (minimum - (b - buf));
if (!input_available_p(tty, 0)) {
- if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
+ if (test_bit(TTY_EOF, &tty->flags)) {
+ /* PTY pair closed and all data consumed */
retval = -EIO;
break;
}
diff -ru /home/opensource/sources/linux-2.6/drivers/char/pty.c /home/opensource/build/linux-2.6-distro/drivers/char/pty.c
--- /home/opensource/sources/linux-2.6/drivers/char/pty.c 2009-07-26 22:45:50.354419907 +0530
+++ /home/opensource/build/linux-2.6-distro/drivers/char/pty.c 2009-07-27 21:29:26.217922778 +0530
@@ -38,6 +38,9 @@
static void pty_close(struct tty_struct *tty, struct file *filp)
{
+ struct tty_struct *pair;
+ unsigned long flags;
+
BUG_ON(!tty);
if (tty->driver->subtype == PTY_TYPE_MASTER)
WARN_ON(tty->count > 1);
@@ -47,13 +50,23 @@
}
wake_up_interruptible(&tty->read_wait);
wake_up_interruptible(&tty->write_wait);
+
tty->packet = 0;
- if (!tty->link)
+ pair = tty->link;
+ if (!pair)
return;
- tty->link->packet = 0;
- set_bit(TTY_OTHER_CLOSED, &tty->link->flags);
- wake_up_interruptible(&tty->link->read_wait);
- wake_up_interruptible(&tty->link->write_wait);
+
+ spin_lock_irqsave(&pair->buf.lock, flags);
+ pair->packet = 0;
+ /* Indicate that the other end is now closed, set the
+ ENDPENDING marker so that the true end can be processed by
+ the line discipline */
+ set_bit(TTY_EOFPENDING, &pair->flags);
+ set_bit(TTY_OTHER_CLOSED, &pair->flags);
+ spin_unlock_irqrestore(&pair->buf.lock, flags);
+ tty_flip_buffer_push(pair);
+ wake_up_interruptible(&pair->read_wait);
+ wake_up_interruptible(&pair->write_wait);
if (tty->driver->subtype == PTY_TYPE_MASTER) {
set_bit(TTY_OTHER_CLOSED, &tty->flags);
#ifdef CONFIG_UNIX98_PTYS
@@ -180,7 +193,6 @@
if (!to)
return;
- /* tty_buffer_flush(to); FIXME */
if (to->packet) {
spin_lock_irqsave(&tty->ctrl_lock, flags);
tty->ctrl_status |= TIOCPKT_FLUSHWRITE;
@@ -191,23 +203,30 @@
static int pty_open(struct tty_struct *tty, struct file *filp)
{
- int retval = -ENODEV;
+ int retval = -EIO;
+ unsigned long flags;
+ struct tty_struct *pair;
- if (!tty || !tty->link)
- goto out;
+ if (tty == NULL || (pair = tty->link) == NULL)
+ return -ENODEV;
- retval = -EIO;
if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
+ return -EIO;
+ spin_lock_irqsave(&pair->buf.lock, flags);
+ if (test_bit(TTY_PTY_LOCK, &pair->flags))
goto out;
- if (test_bit(TTY_PTY_LOCK, &tty->link->flags))
- goto out;
- if (tty->link->count != 1)
+ if (pair->count != 1)
goto out;
- clear_bit(TTY_OTHER_CLOSED, &tty->link->flags);
+ clear_bit(TTY_OTHER_CLOSED, &pair->flags);
+ /* The buf.lock stops this racing a flush_to_ldisc from
+ the other end */
+ clear_bit(TTY_EOFPENDING, &pair->flags);
+ clear_bit(TTY_EOF, &pair->flags);
set_bit(TTY_THROTTLED, &tty->flags);
retval = 0;
out:
+ spin_unlock_irqrestore(&pair->buf.lock, flags);
return retval;
}
diff -ru /home/opensource/sources/linux-2.6/drivers/char/tty_buffer.c /home/opensource/build/linux-2.6-distro/drivers/char/tty_buffer.c
--- /home/opensource/sources/linux-2.6/drivers/char/tty_buffer.c 2009-04-28 21:21:06.964692375 +0530
+++ /home/opensource/build/linux-2.6-distro/drivers/char/tty_buffer.c 2009-07-27 21:29:26.229922140 +0530
@@ -119,6 +119,12 @@
tty_buffer_free(tty, thead);
}
tty->buf.tail = NULL;
+ /* We can EOF a pty/tty pair with a flush as well as by consuming
+ all the data left over */
+ if (test_bit(TTY_EOFPENDING, &tty->flags)) {
+ set_bit(TTY_EOF, &tty->flags);
+ wake_up(&tty->read_wait);
+ }
}
/**
@@ -405,6 +411,7 @@
struct tty_buffer *tbuf, *head;
char *char_buf;
unsigned char *flag_buf;
+ int done = 1;
disc = tty_ldisc_ref(tty);
if (disc == NULL) /* !TTY_LDISC */
@@ -433,6 +440,7 @@
break;
if (!tty->receive_room) {
schedule_delayed_work(&tty->buf.work, 1);
+ done = 0;
break;
}
if (count > tty->receive_room)
@@ -454,6 +462,10 @@
__tty_buffer_flush(tty);
clear_bit(TTY_FLUSHPENDING, &tty->flags);
wake_up(&tty->read_wait);
+ } else if (done && test_bit(TTY_EOFPENDING, &tty->flags)) {
+ /* The last bits hit the ldisc so set EOF */
+ wake_up(&tty->read_wait);
+ set_bit(TTY_EOF, &tty->flags);
}
clear_bit(TTY_FLUSHING, &tty->flags);
spin_unlock_irqrestore(&tty->buf.lock, flags);
--
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