ldisc problems with 2.6.32-2.6.37-rc2 (at least)

[Sergey Lapin <slapin@ossfans.org>]

Hi, all!

slapin@slapin:~$ cat >zoo.c
#include <stdio.h>
#include <sys/socket.h>
#include <linux/x25.h>
#include <sys/ioctl.h>
#include <fcntl.h>

int main(int argc, char *argv[])
{
       int fd = open(argv[1], O_RDWR);
       int ldisc = N_X25;
       int ret;
       int s;
       struct sockaddr_x25 loc, rem;
       ret = ioctl(fd, TIOCSETD, &ldisc);
       if (ret < 0)
               goto bad_ioctl;
       char buffer[128];
       s = socket(AF_X25, SOCK_SEQPACKET, 0);
       memset(&loc, 0, sizeof(loc));
       memset(&rem, 0, sizeof(rem));
       loc.sx25_family = AF_X25;
       strcpy(&loc.sx25_addr, "0");
       rem.sx25_family = AF_X25;
       strcpy(&rem.sx25_addr, "0");
       ret = bind(s, (struct sockaddr *)&loc, sizeof(loc));
       if (ret < 0)
               goto bad_bind;
       printf(".\n");
       sleep(30);
       printf(".\n");
       ret = connect(s, (struct sockaddr *)&rem, sizeof(rem));
       if (ret < 0)
               goto bad_connect;
       memset(buffer, 0, sizeof(buffer));
       while(1) {
               write(s, buffer, sizeof(buffer));
               sleep(10);
       }
       close(s);
       printf(".\n");
       sleep(30);
       ldisc = 0;
       ret = ioctl(fd, TIOCSETD, &ldisc);
       if (ret < 0)
               goto bad_ioctl;
       close(fd);
       return 0;
bad_ioctl:
       perror("ioctl");
       return -1;
bad_bind:
       perror("bind");
       return -1;
bad_connect:
       perror("connect");
       return -1;
}
slapin@slapin:~$ ./a.out /dev/ttyUSB1
.
.
connect: Network is unreachable
slapin@slapin:~$ dmesg
 Sent at 4:45 PM on Wednesday
 me:  [2943389.061987] ------------[ cut here ]----------
[2943389.062002] WARNING: at /tmp/buildd/linux-2.6-2.6.32/debian/build/source_i386_none/drivers/char/tty_ldisc.c:445 tty_ldisc_open+0x26/0x38()
[2943389.062008] Hardware name: System Product Name
[2943389.062011] Modules linked in: x25 ax25 x25_asy lapb cp210x btrfs zlib_deflate crc32c libcrc32c ufs qnx4 hfsplus hfs minix ntfs msdos jfs xfs exportfs reiserfs ext4 jbd2 nls_cp437 vfat fat usb_storage nls_utf8 isofs udf crc_itu_t acpi_cpufreq sco parport_pc cpufreq_stats bridge ppdev cpufreq_conservative stp cpufreq_userspace lp cpufreq_powersave parport vboxnetadp bnep rfcomm vboxnetflt l2cap vboxdrv crc16 bluetooth rfkill binfmt_misc fuse ext2 loop snd_hda_codec_intelhdmi snd_hda_codec_realtek snd_hda_intel snd_hda_codec snd_hwdep snd_pcm_oss snd_mixer_oss snd_pcm snd_seq_midi snd_rawmidi snd_seq_midi_event snd_seq snd_timer snd_seq_device i915 drm_kms_helper evdev drm i2c_i801 i2c_algo_bit snd psmouse pl2303 video soundcore joydev asus_atk0110 output usbserial i2c_core snd_page_alloc pcspkr processor button serio_raw ext3 jbd mbcache usbhid hid dm_mod sg sr_mod sd_mod crc_t10dif cdrom ata_generic ata_piix ehci_hcd thermal r8169 pata_jmicron thermal_sys libata scsi_mod mii usbcore nls_base [last unloaded: x25]
[2943389.062162] Pid: 5251, comm: a.out Tainted: G        W  2.6.32-5-686 #1
[2943389.062167] Call Trace:
[2943389.062180]  [<c1030321>] ? warn_slowpath_common+0x5e/0x8a
[2943389.062188]  [<c1030357>] ? warn_slowpath_null+0xa/0xc
[2943389.062195]  [<c119311c>] ? tty_ldisc_open+0x26/0x38
[2943389.062202]  [<c11936c5>] ? tty_set_ldisc+0x218/0x304
[2943389.062212]  [<c101f409>] ? kunmap_atomic+0x51/0x6d
[2943389.062230]  [<f852ee80>] ? usb_serial_generic_chars_in_buffer+0x75/0x9c [usbserial]
[2943389.062244]  [<f852d0df>] ? serial_chars_in_buffer+0x44/0x47 [usbserial]
[2943389.062252]  [<c1191f0e>] ? tty_chars_in_buffer+0x12/0x13
[2943389.062259]  [<c119231a>] ? tty_wait_until_sent+0x1c/0xcb
[2943389.062271]  [<c118efa1>] ? tty_ioctl+0x554/0x6f0
[2943389.062277]  [<c118ea4d>] ? tty_ioctl+0x0/0x6f0
[2943389.062287]  [<c10bd3cc>] ? vfs_ioctl+0x1c/0x5f
[2943389.062294]  [<c10bd960>] ? do_vfs_ioctl+0x4aa/0x4e5
[2943389.062303]  [<c10b1453>] ? do_sys_open+0xd4/0xdf
[2943389.062309]  [<c10adfb0>] ? kmem_cache_free+0x78/0xaf
[2943389.062316]  [<c10b1453>] ? do_sys_open+0xd4/0xdf
[2943389.062323]  [<c10b1448>] ? do_sys_open+0xc9/0xdf
[2943389.062331]  [<c126f01f>] ? do_page_fault+0x2f1/0x307
[2943389.062339]  [<c10bd9dc>] ? sys_ioctl+0x41/0x58
[2943389.062347]  [<c10030fb>] ? sysenter_do_call+0x12/0x28
[2943389.062353] ---[ end trace a7919e7f17c0a72e ]---

What am I doing wrong here? This backtrace is from Debian
slapin@slapin:~$ uname -a
Linux slapin 2.6.32-5-686 #1 SMP Thu Oct 14 17:15:16 UTC 2010 i686 GNU/Linux

But I get similar backtraces from 2.6.37-rc2.

Thanks a lot,
S.