Messages in this thread | | | Date | Fri, 2 Sep 2011 20:23:00 +0200 | Subject | Re: kernel BUG and freeze on cat /proc/tty/driver/serial | From | Zdenek Kabelac <> |
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2011/3/10 Chuck Ebbert <cebbert@redhat.com>: > On Wed, 16 Feb 2011 17:17:28 +0100 > "Mario 'BitKoenig' Holbe" <Mario.Holbe@TU-Ilmenau.DE> wrote: > >> reading /proc/tty/driver/serial leads to a NULL pointer dereference >> BUG and freeze on a serial-console enabled 2.6.35.{4,10,11} and >> 2.6.37. 2.6.32.28 does fine without BUG and freeze. >> >> Fresh boot 2.6.35.11 into emergency... >> # cat /proc/tty/driver/serial >> [ 73.199568] BUG: unable to handle kernel NULL pointer dereference >> at 00000099 [ 73.227373] IP: [<c11a8969>] tty_ldisc_try+0x10/0x35 > > The oops is here, in uart_handle_dcd_change() in serial_core.h: > > struct tty_ldisc *ld = tty_ldisc_ref(port->tty); > > (port->tty is NULL) > > Called from check_modem_status() in 8250.c: > > if (status & UART_MSR_DDCD) > uart_handle_dcd_change(&up->port, status & UART_MSR_DCD); > > So apparently the port has no tty, until you run "setserial -g", or else > that somehow makes the DCD status appear unchanged later when reading > /proc/tty/driver/serial.
Just noticed the same freeze of my box with 3.1.0-rc4 - thought with just a little bit different stack trace (as I've taken only camera snap - here is just list of function) - happened right after resume.
tty_ldisc_try NULL pointer dereference
tty_ldisc_ref check_modem_status serial8250_get_mctrl uart_proc_show ? seq_read ? kmem_cache_alloc_trace ? seq_read seq_read ? sub_preempt_count ? seq_lseek proc_reg_read vfs_read sys_read system_call_fastpath
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