>>>>> "John" == John Lenton <[EMAIL PROTECTED]> writes:
John> I found to my dismay that it's extremely easy to crash 2.4.4 if
John> it has a Live! in it. I have no way of getting at the oops, but
John> somebody out there probably has both this soundcard and a
John> serial console (or somethin'). I present it in the form of a
John> script, but you'll probably have no problem realizing where the
John> problem is. The number of "writers" never gets past 64. I guess
John> the 65th should probably get the same as the 2nd writer does on
John> other cards...
I have retried this Oops with 2.4.4-ac17. I have the ksymoops'ed file.
The error is happening in "linux/drivers/sound/emu10k1/timer.c". The
function `emu10k1_timer_uninstall' has the following code,
list_del(&timer->list);
Which are the generic kernel list manipulation functions. The `next'
element is NULL and when the statement `next->prev = prev;' is
executed, the processor tries to access 4(NULL) in kernel mode. My
guess is that some sort of race condition is happening and `next' is
NULL when it shouldn't be; but what do I know...
Here is an objdump --disassemble --source --line...
174: fa cli
/usr/src/linux-2.4.4/include/linux/list.h:82
* the prev/next entries already!
*/
static __inline__ void __list_del(struct list_head * prev,
struct list_head * next)
{
175: 8b 52 04 movl 0x4(%edx),%edx
178: 89 54 24 10 movl %edx,0x10(%esp,1)
17c: 8b 54 24 1c movl 0x1c(%esp,1),%edx
180: 8b 02 movl (%edx),%eax
/usr/src/linux-2.4.4/include/linux/list.h:83
next->prev = prev;
182: 8b 54 24 10 movl 0x10(%esp,1),%edx
186: 89 50 04 movl %edx,0x4(%eax)
***** Oops is here ^^^^^^^^^^
/usr/src/linux-2.4.4/include/linux/list.h:84
prev->next = next;
189: 89 02 movl %eax,(%edx)
/usr/src/linux-2.4.4/drivers/sound/emu10k1/timer.c:121
list_del(&timer->list);
list_for_each(entry, &card->timers) {
18b: 8b 97 70 40 00 00 movl 0x4070(%edi),%edx
191: 8d b7 70 40 00 00 leal 0x4070(%edi),%esi
I looked in list.h for a `safe' list delete, where next is checked for
NULL. Should the driver check this before calling `list_delete'?
Here is the opps again,
Unable to handle kernel NULL pointer dereference at virtual address 00000004
printing eip: c01caa92
*pde = 00000000
Oops: 0002
CPU: 0
EIP: 0010:[emu10k1_timer_uninstall+50/236]
EFLAGS: 00010097
eax: 00000000 ebx: ffffffff ecx: c3a9350c edx: 00000000
esi: c11d8000 edi: c11d8000 ebp: 00000097 esp: c3909f38
ds: 0018 es: 0018 ss: 0018
Process cat (pid: 872, stackpage=c3909000)
Stack: c3a93400 c11d8000 c2089ba0 00000000 00000000 c01c7957 c11d8000 c3a93478
c2089ba0 c3a93400 c11d8000 c01c78fa c2089ba0 00000246 c3a93400 00001000
c01c400a c2089ba0 ffffffea c15d6200 00001000 00000000 00001000 c3908000
Call Trace: [emu10k1_waveout_close+27/60]
[emu10k1_waveout_open+102/168]
[emu10k1_audio_write+190/456]
[sys_write+142/196]
[system_call+51/64]
Code: 89 50 04 89 02 8b 97 70 40 00 00 8d b7 70 40 00 00 89 54 24
And the script,
#!/bin/sh
setup () {
dd bs=1M count=10 </dev/urandom >/tmp/noise 2> /dev/null
}
noise () {
cat /tmp/noise > /dev/dsp &
}
setup
i=0
while (noise); do
i=$(( $i+1 ))
echo $i
done
thanks,
Bill
ps, There is no FAQ entry on how to generate a single object with `-g'. I
ended up recompiling my whole tree!
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