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SubjectRe: [PATCH] tty: remove unused variable canon_change
On Tue, 02 Sep 2008 14:27:21 -0700 Harvey Harrison <harvey.harrison@gmail.com> wrote:

> drivers/char/tty_ioctl.c: In function ___change_termios___:
> drivers/char/tty_ioctl.c:492: warning: unused variable ___canon_change___
>
> Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
> ---
> new warning in next-20080902
>
> drivers/char/tty_ioctl.c | 1 -
> 1 files changed, 0 insertions(+), 1 deletions(-)
>
> diff --git a/drivers/char/tty_ioctl.c b/drivers/char/tty_ioctl.c
> index 17e6a98..a408c8e 100644
> --- a/drivers/char/tty_ioctl.c
> +++ b/drivers/char/tty_ioctl.c
> @@ -489,7 +489,6 @@ EXPORT_SYMBOL(tty_termios_hw_change);
>
> static void change_termios(struct tty_struct *tty, struct ktermios *new_termios)
> {
> - int canon_change;
> struct ktermios old_termios;
> struct tty_ldisc *ld;
> unsigned long flags;

I cannot find the patch which added the canon_change stuff on a mailing
list. If I could, I'd reply to that.


It goes oops. config is at http://userweb.kernel.org/~akpm/config-vmm.txt


From: Andrew Morton <akpm@linux-foundation.org>

BUG: unable to handle kernel NULL pointer dereference at 0000000c
IP: [<c02afc15>] n_tty_set_termios+0x15/0x340
*pde = 00000000
Oops: 0000 [#1] SMP
last sysfs file:
Dumping ftrace buffer:
(ftrace buffer empty)
Modules linked in:

Pid: 1, comm: swapper Tainted: G W (2.6.27-rc5-mm1 #2)
EIP: 0060:[<c02afc15>] EFLAGS: 00010282 CPU: 0
EIP is at n_tty_set_termios+0x15/0x340
EAX: f709cdd0 EBX: f709cdd0 ECX: f64cd468 EDX: 00000000
ESI: 00000000 EDI: f60ee000 EBP: f702fdf4 ESP: f702fde8
DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 0068
Process swapper (pid: 1, ti=f702e000 task=f702d210 task.ti=f702e000)
Stack: f709cdd0 f709cdd0 f60ee000 f702fe04 c02b0299 f7095070 f709cdd0 f702fe18
c02b3493 f7095070 f709cdd0 00000000 f702fe3c c02ae9b5 f7095070 f702fe60
00000000 fffffff4 f7095070 00000000 00500001 f702fe70 c02aedeb f707d078
Call Trace:
[<c02b0299>] ? n_tty_open+0x49/0xa0
[<c02b3493>] ? tty_ldisc_setup+0x23/0x80
[<c02ae9b5>] ? tty_init_dev+0x85/0x150
[<c02aedeb>] ? tty_open+0x36b/0x440
[<c01940fa>] ? chrdev_open+0x9a/0x190
[<c018fded>] ? __dentry_open+0xad/0x230
[<c0190d90>] ? nameidata_to_filp+0x50/0x60
[<c0194060>] ? chrdev_open+0x0/0x190
[<c019c41a>] ? do_filp_open+0x19a/0x700
[<c01158a9>] ? cpa_fill_pool+0x99/0x120
[<c01a4706>] ? alloc_fd+0x26/0xf0
[<c01a47af>] ? alloc_fd+0xcf/0xf0
[<c03e159d>] ? _spin_unlock+0x1d/0x20
[<c018fc0b>] ? do_sys_open+0x4b/0xd0
[<c0126e5b>] ? printk+0x1b/0x20
[<c018fcf9>] ? sys_open+0x29/0x40
[<c01011b7>] ? init_post+0x47/0x140
[<c0103fff>] ? kernel_thread_helper+0x7/0x18
=======================

tty->termios is NULL.

Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

drivers/char/n_tty.c | 12 ------------
1 file changed, 12 deletions(-)

diff -puN drivers/char/n_tty.c~a drivers/char/n_tty.c
--- a/drivers/char/n_tty.c~a
+++ a/drivers/char/n_tty.c
@@ -1039,20 +1039,8 @@ int is_ignored(int sig)

static void n_tty_set_termios(struct tty_struct *tty, struct ktermios *old)
{
- int canon_change;
BUG_ON(!tty);

- canon_change = (old->c_lflag ^ tty->termios->c_lflag) & ICANON;
- if (canon_change) {
- memset(&tty->read_flags, 0, sizeof tty->read_flags);
- tty->canon_head = tty->read_tail;
- tty->canon_data = 0;
- tty->erasing = 0;
- }
-
- if (canon_change && !L_ICANON(tty) && tty->read_cnt)
- wake_up_interruptible(&tty->read_wait);
-
tty->icanon = (L_ICANON(tty) != 0);
if (test_bit(TTY_HW_COOK_IN, &tty->flags)) {
tty->raw = 1;
_


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