ehci splatter in 2.6.26-rc2

ehci splatter in 2.6.26-rc2

[Lennert Buytenhek]

On 2.6.26-rc2, plugging in a certain USB device (haven't tested yet
with other devices) gives me (on two different ARM boards) the oops
below.

Anyone else seeing the same?


usb 1-1: new low speed USB device using orion-ehci and address 2
Unable to handle kernel NULL pointer dereference at virtual address 00000000
pgd = c0004000
[00000000] *pgd=00000000
Internal error: Oops: 17 [#1] PREEMPT
Modules linked in:
CPU: 0    Not tainted  (2.6.26-rc2 #340)
PC is at qh_append_tds+0x24c/0x44c
LR is at ehci_qtd_alloc+0x30/0x5c
pc : [<c02238b4>]    lr : [<c02235a8>]    psr: 00000093
sp : c7c3bcb0  ip : c7dd86c0  fp : c7c3bcfc
r10: ffc42080  r9 : 00000008  r8 : c7fec820
r7 : 80000080  r6 : 00000080  r5 : 00000000  r4 : 00000002
r3 : c7d69c00  r2 : 00000000  r1 : 40800000  r0 : 08085000
Flags: nzcv  IRQs off  FIQs on  Mode SVC_32  ISA ARM  Segment kernel
Control: a005317f  Table: 06a1c000  DAC: 00000017
Process khubd (pid: 72, stack limit = 0xc7c3a268)
Stack: (0xc7c3bcb0 to 0xc7c3c000)
[...]
Backtrace: 
[<c0223668>] (qh_append_tds+0x0/0x44c) from [<c0225470>] (ehci_urb_enqueue+0x100
/0xfb8)
[<c0225370>] (ehci_urb_enqueue+0x0/0xfb8) from [<c02163e8>] (usb_hcd_submit_urb+
0x824/0x91c)
[<c0215bc4>] (usb_hcd_submit_urb+0x0/0x91c) from [<c0216850>] (usb_submit_urb+0x
224/0x260)
[<c021662c>] (usb_submit_urb+0x0/0x260) from [<c02172e8>] (usb_start_wait_urb+0x
44/0xac)
 r6:c7fec820 r5:c7c3be80 r4:00000000
[<c02172a4>] (usb_start_wait_urb+0x0/0xac) from [<c0217538>] (usb_control_msg+0x
c8/0xec)
 r8:00000000 r7:00000100 r6:fffffff4 r5:00000040 r4:c7df4540
[<c0217470>] (usb_control_msg+0x0/0xec) from [<c021206c>] (hub_port_init+0x274/0
x5e4)
[<c0211df8>] (hub_port_init+0x0/0x5e4) from [<c0213408>] (hub_thread+0x60c/0xc1c
)
[<c0212dfc>] (hub_thread+0x0/0xc1c) from [<c0058844>] (kthread+0x5c/0x94)
[<c00587e8>] (kthread+0x0/0x94) from [<c0046484>] (do_exit+0x0/0x72c)
 r6:00000000 r5:00000000 r4:00000000
Code: e51bc040 e5932000 e51c309c e1520003 (15923000)
---[ end trace e1e1758047d6bb3f ]---
note: khubd[72] exited with preempt_count 1

Re: ehci splatter in 2.6.26-rc2

[David Brownell]

On Wednesday 14 May 2008, Lennert Buytenhek wrote:
> On 2.6.26-rc2, plugging in a certain USB device (haven't tested yet
> with other devices) gives me (on two different ARM boards) the oops
> below.
> 
> Anyone else seeing the same?

I have no ARM running EHCI, but I can report it's OK
for me on x86 (limited testing) ... I'd expect to have
heard *very* load screams by now if this was common.


> usb 1-1: new low speed USB device using orion-ehci and address 2
> Unable to handle kernel NULL pointer dereference at virtual address 00000000
> pgd = c0004000
> [00000000] *pgd=00000000
> Internal error: Oops: 17 [#1] PREEMPT
> Modules linked in:
> CPU: 0    Not tainted  (2.6.26-rc2 #340)
> PC is at qh_append_tds+0x24c/0x44c
> LR is at ehci_qtd_alloc+0x30/0x5c
> ...
> [<c0223668>] (qh_append_tds+0x0/0x44c) from [<c0225470>]
>		(ehci_urb_enqueue+0x100 /0xfb8) 
> [<c0225370>] (ehci_urb_enqueue+0x0/0xfb8) from [<c02163e8>]
>		(usb_hcd_submit_urb+ 0x824/0x91c) 

Nothing in that vicinity should have changed in ages,
which makes me wonder if it's really EHCI which is
triggering this.

The only thing coming vaguely to mind is that this may
have to do with dma-coherent memory allocations.  If
the platform support for that has any goofage, you might
be able to elicit different behaviors with dmapool debug
(enable CONFIG_DEBUG_SLAB or CONFIG_SLUB_DEBUG_ON).

- Dave