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SubjectOOPS: PPA ZIP 2.4.3 (semi-debugged)
[resent because it didn't turn up in my mail *after* successfully
having subscribed to lk and another mail of mine already turned up in archive]

Hi,

I'm (still) getting a reproducible crash with PPA ZIP on my
Dell Inspiron 5000e notebook.
AFAIR I already noticed an OOPS upon module removal with disconnected
drive a looong time ago when using 2.2.x.

System: Debian Unstable, stock 2.4.3 kernel, gcc 2.95.3 (problem !!?)

Steps to reproduce:
1. mount zip
2. unmount zip
3. unplug zip with ppa module etc. still loaded
3. close the lid -> APM Suspend-To-RAM
4. resume -> printk("ppa: Parallel port cable is unplugged!!\n");
5. to get rid of this annoying message, I naively tried a rmmod ppa -> OOPS


Unable to handle kernel paging request at virtual address 0xd0a0f434
ip c018bc74 batch_entropy_store()+0x90
ax 00000046 bx 00000c47 cx 0000004e dx d0a0f434
si c027bd80 di b737a624 bp 0000009f sp c575bbd8

Process rmmod
Trace:
add_timer_randomness+0xcb
add_keyboard_randomness+0x22
handle_scancode+0x64
handle_kbd_event+0x111
keyboard_interrupt+0xf
handle_IRQ_event+0x2f
do_IRQ+0x6e
ret_from_intr
panic+0xd0
__switch_to+0xb
die+0x42
do_page_fault+0x323
do_page_fault
load_elf_binary+0x907
load_elf_binary
bread+0x18
do_signal+0xe0
d0a0f434
free_initmem+0x6c
__run_task_queue+0x12
do_timer+0x23
tqueue_bh+0x16
number+0x254
unmap_underlying_metadata+0x18
vsprintf+0x2e
d09c1310
.
.
.

(int handler killed)


Simple analysis of crashing function:

%esp+4 = a
%esp+8 = b
%esp+c = num
0xc027bd64 = batch_head
0xc027bd58 = batch_entropy_pool
0xc027bd5c = batch_entropy_credit
0xc027bd60 = batch_max


void batch_entropy_store(u32 a, u32 b, int num)
{
int new;

0xc018bbe4:
if (!batch_max)
return;

0xc018bbf1:
batch_entropy_pool[2*batch_head] = a;

0xc018bc04:
batch_entropy_pool[(2*batch_head) + 1] = b;

0xc018bc18:
batch_entropy_credit[batch_head] = num;

0xc018bc2b:
new = (batch_head+1) & (batch_max-1);

0xc018bc3a:
if (new != batch_tail) {

0xc018bc42:
queue_task(&batch_tqueue, &tq_timer);
batch_head = new;
} else {
#if 0
printk(KERN_NOTICE "random: batch entropy buffer full\n");
#endif
}
}

Complicated (i.e.: better) analysis of crashing function ;-) :

This contains the whole assembler dump, indented to reflect call depth,
comments with C code, etc.

Dump of assembler code for function batch_entropy_store:
if (!batch_max) return;:
0xc018bbe4 <batch_entropy_store>: cmpl $0x0,0xc027bd60
0xc018bbeb <batch_entropy_store+7>:
je 0xc018bc86 <batch_entropy_store+162>

batch_entropy_pool[2*batch_head] = a;:
0xc018bbf1 <batch_entropy_store+13>: mov 0xc027bd64,%ecx
0xc018bbf7 <batch_entropy_store+19>: mov 0xc027bd58,%edx
0xc018bbfd <batch_entropy_store+25>: mov 0x4(%esp,1),%eax
0xc018bc01 <batch_entropy_store+29>: mov %eax,(%edx,%ecx,8)

batch_entropy_pool[(2*batch_head) + 1] = b;:
0xc018bc04 <batch_entropy_store+32>: mov 0xc027bd64,%ecx
0xc018bc0a <batch_entropy_store+38>: mov 0xc027bd58,%edx
0xc018bc10 <batch_entropy_store+44>: mov 0x8(%esp,1),%eax
0xc018bc14 <batch_entropy_store+48>: mov %eax,0x4(%edx,%ecx,8)

batch_entropy_credit[batch_head] = num;:
0xc018bc18 <batch_entropy_store+52>: mov 0xc027bd64,%ecx
0xc018bc1e <batch_entropy_store+58>: mov 0xc027bd5c,%edx
0xc018bc24 <batch_entropy_store+64>: mov 0xc(%esp,1),%eax
0xc018bc28 <batch_entropy_store+68>: mov %eax,(%edx,%ecx,4)

new = (batch_head+1) & (batch_max-1);:
0xc018bc2b <batch_entropy_store+71>: mov 0xc027bd64 [batch_head],%ecx
0xc018bc31 <batch_entropy_store+77>: mov 0xc027bd60 [batch_max],%eax
0xc018bc36 <batch_entropy_store+82>: inc %ecx
0xc018bc37 <batch_entropy_store+83>: dec %eax
0xc018bc38 <batch_entropy_store+84>: and %eax,%ecx

if (new != batch_tail) {:
0xc018bc3a <batch_entropy_store+86>: cmp 0xc027bd68 [batch_tail],%ecx
0xc018bc40 <batch_entropy_store+92>:
je 0xc018bc86 <batch_entropy_store+162>

queue_task(&batch_tqueue, &tq_timer);:
0xc018bc42 <batch_entropy_store+94>: xor %eax,%eax
0xc018bc44 <batch_entropy_store+96>: bts %eax,0xc027bd74 [&batch_tqueue->sync]
0xc018bc4b <batch_entropy_store+103>: sbb %eax,%eax
0xc018bc4d <batch_entropy_store+105>: test %eax,%eax
0xc018bc4f <batch_entropy_store+107>:
jne 0xc018bc80 <batch_entropy_store+156>

spin_lock_irqsave(&tqueue_lock, flags);:
local_irq_save(flags);:
0xc018bc51 <batch_entropy_store+109>: pushf
0xc018bc52 <batch_entropy_store+110>: pop %eax
0xc018bc53 <batch_entropy_store+111>: cli
spin_lock(lock);:
/* hmm, not much here, maybe because no SMP ?? */

list_add_tail(&batch_tqueue->list, &tq_timer);:
__list_add(&batch_tqueue->list, (&tq_timer)->prev, &tq_timer);:
(&tq_timer)->prev = &batch_tqueue->list;
(&batch_tqueue->list)->next = &tq_timer;
(&batch_tqueue->list)->prev = (&tq_timer)->prev;
(&(&tq_timer)->prev)->next = &batch_tqueue->list;
0xc018bc54 <batch_entropy_store+112>: mov 0xc0227e94 [(&tq_timer)->prev],%edx
0xc018bc5a <batch_entropy_store+118>: movl $0xc027bd6c [&batch_tqueue->list],0xc0227e94 [(&tq_timer)->prev]
0xc018bc64 <batch_entropy_store+128>: movl $0xc0227e90,0xc027bd6c [batch_tqueue]
0xc018bc6e <batch_entropy_store+138>: mov %edx [(&tq_timer)->prev],0xc027bd70 [(&batch_tqueue->list)->prev]

**********CRASH**********, EDX == 0xd0a0f434:
0xc018bc74 <batch_entropy_store+144>: movl $0xc027bd6c [&batch_tqueue->list],(%edx) [(&(&tq_timer)->prev)->next == (&tq_timer)->prev]

spin_unlock_irqrestore(&tqueue_lock, flags);:
spin_unlock(&tqueue_lock);:
local_irq_restore(flags);:
0xc018bc7a <batch_entropy_store+150>: push %eax
0xc018bc7b <batch_entropy_store+151>: popf

what's that ??? gcc problem ?:
0xc018bc7c <batch_entropy_store+152>: lea 0x0(%esi,1),%esi

batch_head = new;:
0xc018bc80 <batch_entropy_store+156>: mov %ecx,0xc027bd64 [batch_head]
0xc018bc86 <batch_entropy_store+162>: ret
0xc018bc87 <batch_entropy_store+163>: nop

So can anybody tell me why it crashes at 0xc018bc74 ?

Note that I'm not sure whether the suspend is required for the OOPS;
I don't know any other way of triggering the OOPS, though.

BTW, if I reconnect the cable instead of unloading ppa, I get:
root@note:/root# ppa: Parallel port cable is unplugged!!
ppa: Parallel port cable is unplugged!!
ppa: Parallel port cable is unplugged!!
sda : READ CAPACITY failed.
sda : status = 0, message = 00, host = 1, driver = 00
sda : sense not available.
sda : block size assumed to be 512 bytes, disk size 1GB.
/dev/scsi/host0/bus0/target6/lun0: I/O error: dev 08:00, sector 0

So it seems to try to do a READ CAPACITY call at this moment upon resume,
which maybe blocks the kernel somehow when no cable is available...

Thank you for any suggestions !

I'm subscribed to the list, so no need to CC.

--
Andreas Mohr Stauferstr. 6, D-71272 Renningen, Germany
Tel. +49 7159 800604 http://home.germany.net/100-30936/
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