Fwd: request_module() fails

Fwd: request_module() fails

[Gireesh Kumar M]

Hi,

I'm trying to load some modules upon occurance of a GPIO interrupt.
The ISR checks some register and then schedules a tasklet to act
further on the interrupt.
Inside the tasklet, I call request_module to load a driver. But, here
it's failing. Please see the error log pasted below.
When I tried to load the same module using modprobe and it works fine. I
have edited modules.dep with an entry for my module.

[Note:] The kernel modules installed on the rootfs are from a
different kernel version. So I don't see an entry in /lib/modules/<my
kernel name>. Instead, the rootfs has a different
entry(/lib/modules/<default-kernel>)
Since I have a different kernel version, the "uname -r" gives <my
kernel name> and since that entry is not in /lib/modules/; modprobe
was failing initially.
I fixed this by creating a soft link called /lib/modules/<my kernel
name> that points to /lib/modules/<default-kernel>
After this modification, modprobe worked fine.

Kindly help me if anyone has a clue.

Kernel version: 2.6.10
Architecture: ARM

Thank you,
Gireesh


 =====Error Log=========================================
root@10.24.241.113:/home/gireesh/test_mod# insmod test_mod.ko pin_a=0 pin_b=2
Test module inserted
irq registered successfully

[gireesh] then I generated the interrupt and what I see is as follows.
"In tasklet" is the message I'm printing from the tasklet.

root@10.24.241.113:/home/gireesh/test_mod # In tasklet
BUG: scheduling while atomic: swapper/0x00000103/0
caller is schedule+0xec/0x12c
BUG: scheduling from the idle thread!
Unable to handle kernel NULL pointer dereference at virtual address 00000004
pgd = c0004000
[00000004] *pgd=00000000
Internal error: Oops: 17 [#1]
Modules linked in: test_mod dsplinkk
CPU: 0
PC is at dequeue_task+0xc/0x78
LR is at deactivate_task+0x28/0x34
pc : [<c003c128>]    lr : [<c003c464>]    Tainted: PF
sp : c027fca0  ip : c027fcb0  fp : c027fcac
r10: c027e000  r9 : c02d94f0  r8 : c02800c0
r7 : c027e000  r6 : c027fde4  r5 : c027fd5c  r4 : c02800c0
r3 : 00000001  r2 : 00000000  r1 : 00000000  r0 : c02800c0
Flags: nZCv  IRQs off  FIQs on  Mode SVC_32  Segment kernel
Control: 5317F  Table: 80FD8000  DAC: 00000017
Process swapper (pid: 0, stack limit = 0xc027e1a0)
Stack: (0xc027fca0 to 0xc0280000)
fca0: c027fcc4 c027fcb0 c003c464 c003c12c c0239168 c0239168 c027fd14 c027fcc8
fcc0: c0238c24 c003c44c 00000000 20000093 c027fcfc 03938700 f4e31f00 0000049a
fce0: c0369ed0 c028021c 00000000 c027e000 c027fd5c c027fde4 c027e000 c027fde0
fd00: c02d6ca0 c02de780 c027fd34 c027fd18 c0239168 c0238a50 c02d6ca0 c027fd48
fd20: c027fd5c c027fd48 c027fd8c c027fd38 c02392fc c023908c 00000000 c02800c0
fd40: c003d00c 00000000 00000000 c0238ffc 00000001 c02800c0 c003d00c c027fde4
fd60: c027fde4 c027fde0 c027fd8c c028334c c027fd90 c027fde0 c02de7d0 0000000a
fd80: c027fe0c c027fd90 c0052898 c023923c 00000001 c0369ec8 c0369ec8 c0052774
fda0: c027fdc8 c0369ec0 00000000 00000000 00000000 4b87ad6e 00000000 00000000
fdc0: 00000000 00000000 c027fde0 c028334c c027fe10 c028344c 00000001 00000000
fde0: 00000000 c027fd5c c027fd5c c027fe28 c02de7d0 c02e0240 c02e0244 c027fe28
fe00: c027fe84 c027fe10 c00529b0 c00527f8 c028334c c0244588 c024458c c027fe28
fe20: 00000000 00000000 6273756d 7264685f c0280063 0000000b c027fe74 c027fe48
fe40: c0041c44 c0041840 c0041c44 c027feac e1048000 00000000 c02de7a4 00000001
fe60: c02de7d0 0000000a c027fe84 00000000 c02de7a4 00000001 c027fea4 c027fe98
fe80: bf012360 c00528c8 bf0124b8 c027e000 00000000 00000000 c027febc c027fea8
fea0: c00469a0 bf012344 c027e000 00000103 c027fee4 c027fec0 c0046458 c0046930
fec0: c027e000 00000000 ffffffff 00000002 c027e000 c027ff50 c027fefc c027fee8
fee0: c0046534 c0046414 c027e000 c027e000 c027ff14 c027ff00 c00466ec c004650c
ff00: c027e000 c027ff84 c027ff4c c027ff18 c002d320 c00466b0 c003c424 c003c27c
ff20: 00000000 c027ff84 e1048000 ffffffff 00000002 c027e000 00000001 800240f8
ff40: c027ffac c027ff50 c002b5e0 c002d210 00000000 0005317f 0005217f 60000013
ff60: c027e000 60000093 c02812a8 c02fa450 80024128 41069265 800240f8 c027ffac
ff80: c027ff98 c027ff98 c002ddfc c002de0c 60000013 ffffffff c027e000 c002dd94
ffa0: c027ffcc c027ffb0 c002de78 c002dda4 c027ffcc 00053175 c02d67dc c02e13e4
ffc0: c027fffc c027ffd0 c00087d8 c002de24 c0008304 00000000 00000000 c02d7c30
ffe0: 00000000 00053175 c02d7c1c c0280fd0 00000000 c0280000 8000809c c0008660
Backtrace:
[<c003c11c>] (dequeue_task+0x0/0x78) from [<c003c464>]
(deactivate_task+0x28/0x3
4)
[<c003c43c>] (deactivate_task+0x0/0x34) from [<c0238c24>] (__schedule+0x1e4/0x5a
c)
 r4 = C0239168
[<c0238a40>] (__schedule+0x0/0x5ac) from [<c0239168>] (schedule+0xec/0x12c)
[<c023907c>] (schedule+0x0/0x12c) from [<c02392fc>] (wait_for_completion+0xd0/0x
164)
 r4 = C027FD48
[<c023922c>] (wait_for_completion+0x0/0x164) from [<c0052898>] (call_usermodehel
per+0xb0/0xcc)
 r8 = 0000000A  r7 = C02DE7D0  r6 = C027FDE0  r5 = C027FD90
 r4 = C028334C
[<c00527e8>] (call_usermodehelper+0x0/0xcc) from [<c00529b0>] (request_module+0x
fc/0x140)
 r6 = C027FE28  r5 = C02E0244  r4 = C02E0240
[<c00528b4>] (request_module+0x0/0x140) from [<bf012360>] (load_module_tasklet+0
x2c/0x54 [test_mod])
 r3 = 00000000  r2 = 00000000  r1 = C027E000  r0 = BF0124B8
 r6 = 00000001  r5 = C02DE7A4  r4 = 00000000
[<bf012334>] (load_module_tasklet+0x0/0x54 [test_mod]) from [<c00469a0>] (tas
klet_action+0x80/0xcc)
[<c0046920>] (tasklet_action+0x0/0xcc) from [<c0046458>] (___do_softirq+0x54/0xf
8)
 r5 = 00000103  r4 = C027E000
[<c0046404>] (___do_softirq+0x0/0xf8) from [<c0046534>] (__do_softirq+0x38/0x58)
[<c00464fc>] (__do_softirq+0x0/0x58) from [<c00466ec>] (irq_exit+0x4c/0x60)
 r5 = C027E000  r4 = C027E000
[<c00466a0>] (irq_exit+0x0/0x60) from [<c002d320>] (asm_do_IRQ+0x120/0x138)
 r4 = C027FF84
[<c002d200>] (asm_do_IRQ+0x0/0x138) from [<c002b5e0>] (__irq_svc+0x40/0x74)
[<c002dd94>] (default_idle+0x0/0x80) from [<c002de78>] (cpu_idle+0x64/0xac)
 r5 = C002DD94  r4 = C027E000
[<c002de14>] (cpu_idle+0x0/0xac) from [<c00087d8>] (start_kernel+0x188/0x1cc)
 r6 = C02E13E4  r5 = C02D67DC  r4 = 00053175
[<c0008650>] (start_kernel+0x0/0x1cc) from [<8000809c>] (0x8000809c)
Code: e89da800 e1a0c00d e92dd800 e24cb004 (e5913004)
 <0>Kernel panic - not syncing: Aiee, killing interrupt handler!

Re: Fwd: request_module() fails

[Stephen Hemminger]

On Wed, 1 Aug 2007 13:29:18 +0530
"Gireesh Kumar M" <gireesh.mnair@gmail.com> wrote:

> Hi,
> 
> I'm trying to load some modules upon occurance of a GPIO interrupt.
> The ISR checks some register and then schedules a tasklet to act
> further on the interrupt.
> Inside the tasklet, I call request_module to load a driver. But, here
> it's failing. Please see the error log pasted below.
> When I tried to load the same module using modprobe and it works fine. I
> have edited modules.dep with an entry for my module.

You can't sucessfully load a module from tasklet because tasklet's run
in softirq. You need to use a work queue (or other mechanism) that runs
in process context. Loading a module will require accessing disk, and that
can only be done from process context.

Your whole scheme is pretty daft, because it will be slow and you might
as well have the module already loaded.