open("/dev/ttyO2", O_RDONLY) never returns on the 2.6.38-1000-linaro-omap

[Ken Werner]

When using the 2.6.38-1000-linaro-omap kernel the process hangs as the open call never returns. Here is a small testcase:

#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
int main (int argc, char **argv){
  int fd;
  fd = open("/dev/ttyO2", O_RDONLY);
  if (fd == -1) {
    perror ("open failed");
    exit(EXIT_FAILURE);
  }
  close(fd);
  return 0;
}

Here is the stack trace of this task:
[ 651.671020] open S c059b724 0 642 532 0x00000000
[ 651.671051] [<c059b724>] (schedule+0x3f4/0x778) from [<c0387678>] (tty_port_block_til_ready+0x138/0x2f4)
[ 651.671081] [<c0387678>] (tty_port_block_til_ready+0x138/0x2f4) from [<c0380aac>] (tty_open+0x178/0x420)
[ 651.671081] [<c0380aac>] (tty_open+0x178/0x420) from [<c016b2a8>] (chrdev_open+0x114/0x1ec)
[ 651.671112] [<c016b2a8>] (chrdev_open+0x114/0x1ec) from [<c0165918>] (__dentry_open+0x100/0x2b8)
[ 651.671142] [<c0165918>] (__dentry_open+0x100/0x2b8) from [<c01668fc>] (nameidata_to_filp+0x60/0x68)
[ 651.671142] [<c01668fc>] (nameidata_to_filp+0x60/0x68) from [<c0174688>] (finish_open+0xa0/0x174)
[ 651.671173] [<c0174688>] (finish_open+0xa0/0x174) from [<c0174bec>] (do_filp_open+0x18c/0x5f8)
[ 651.671173] [<c0174bec>] (do_filp_open+0x18c/0x5f8) from [<c0166960>] (do_sys_open+0x5c/0x138)
[ 651.671203] [<c0166960>] (do_sys_open+0x5c/0x138) from [<c0065c40>] (ret_fast_syscall+0x0/0x30)

[Dr. David Alan Gilbert (davidgil-uk)]

I can confirm the same on my panda; note that when this hangs I did a ctrl-d in the serial console and got the following oops:

[20361.272521] Unable to handle kernel NULL pointer dereference at virtual address 0000009c
[20361.281005] pgd = d9d14000
[20361.283843] [0000009c] *pgd=8160c831, *pte=00000000, *ppte=00000000
[20361.290405] Internal error: Oops: 17 [#1] SMP
[20361.294921] last sysfs file: /sys/devices/system/cpu/cpu1/topology/core_siblings
[20361.302642] Modules linked in: smsc95xx usbnet omap_wdt omap2_mcspi leds_gpio twl4030_pwrbutton twl6030_usb usbhid usb_storage hid uas
[20361.315307] CPU: 0 Tainted: G W (2.6.38-1000-linaro-omap #1-Ubuntu)
[20361.322998] PC is at uart_update_termios+0xb0/0xc0
[20361.328033] LR is at tty_port_block_til_ready+0x170/0x2f4
[20361.333648] pc : [<c03973d8>] lr : [<c03876b0>] psr: 600f0013
[20361.333648] sp : da85dd70 ip : 00000000 fp : c1742800
[20361.345642] r10: 00000000 r9 : d9f89950 r8 : d9f8995c
[20361.351074] r7 : c1742800 r6 : da85c000 r5 : 00000000 r4 : c1403c00
[20361.357879] r3 : 00000000 r2 : 00000002 r1 : d9f89948 r0 : 00000002
[20361.364685] Flags: nZCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment user
[20361.372131] Control: 10c53c7d Table: 99d1404a DAC: 00000015
[20361.378112] Process a.out (pid: 1371, stack limit = 0xda85c2f8)
[20361.384277] Stack: (0xda85dd70 to 0xda85e000)
[20361.388824] dd60: d9f89948 c14888c0 da85c000 c03876b0
[20361.397369] dd80: c1742800 c015e720 80000013 d9f89948 00000002 00000000 c14ccf60 c00c6574
[20361.405883] dda0: da85dda0 da85dda0 00000000 0fc00002 c14888c0 00000000 da85c000 c1408060
[20361.414428] ddc0: c07e6b0c c0380aac 00000105 00000000 da0d9000 00000002 d9f6b788 d9f6b788
[20361.422943] dde0: 00000000 c1408060 00000000 c14888c0 da85c000 00000000 00000000 c016b2a8
[20361.431488] de00: c1408060 00000000 da85c000 c14888c0 da4ac800 c1488640 c1408060 00000000
[20361.440002] de20: da85c000 c016b194 00000000 c0165918 00000000 d9d4e700 00000000 c14888c0
[20361.448516] de40: da85ded4 00000024 da85c000 00000000 00000000 c01668fc d9d4e700 c01744f4
[20361.457061] de60: da85ded4 da85ded4 00000000 00000000 00000000 c0174688 da85ded4 00000000
[20361.465576] de80: 00000000 00000024 00000101 da85ded4 c16b4000 c0174bec 00100100 00200200
[20361.474121] dea0: 00000000 00000000 d9d15000 400effff c07ff960 ffffff9c 400f0000 da85df34
[20361.482635] dec0: c1729860 400e1000 d9c92318 da612d80 da612d70 c1488640 da4ac800 da612d70
[20361.491149] dee0: c6569a00 00000000 00000000 da5a6c00 00000000 c1408060 00000101 00000002
[20361.499694] df00: 00000001 00000000 400e0000 c005b4d4 00000010 c0168914 00000020 00000000
[20361.508209] df20: 400e1000 00000000 00000000 00000001 00000000 00000000 d9c92318 c07ababc
[20361.516754] df40: da82f380 da82f388 00000000 c16b4000 ffffff9c 00000003 00000005 00000000
[20361.525268] df60: da85c000 00000000 00000000 c0166960 00000000 400e1000 c1729860 beade91c
[20361.533813] df80: da85c000 00000000 beade7d8 000083a5 00000005 c0065e08 da85c000 00000000
[20361.542327] dfa0: 00000000 c0065c40 00000000 beade7d8 000084c0 00000000 beade91c 00008425
[20361.550872] dfc0: 00000000 beade7d8 0000...

[warmcat (andy-warmcat)]

I could reproduce this with strace cat /dev/ttyO2, it hung at the open() but responded to ^C.

I couldn't reproduce the OOPS.

[Ken Werner (kwerner)]

I've got the Oops but only once. It looked very similar to what David posted.

[Chase Qi (chase-qi)]

Migrated to bugzilla: https://bugs.linaro.org/show_bug.cgi?id=566