* HDLC driver - dev_free_skb_irq causes Segfault
@ 2008-02-10 2:32 Russell McGuire
2008-02-13 14:11 ` Laurent Pinchart
2008-02-15 16:21 ` Jochen Friedrich
0 siblings, 2 replies; 3+ messages in thread
From: Russell McGuire @ 2008-02-10 2:32 UTC (permalink / raw)
To: linuxppc-embedded
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All,
So I am in the process of debugging my newly established HDLC driver.
More or less modeled after a simplified gianfar / ucc_geth idea.
However, after loading, etc. and using the following commands
-> insmod hdlc-8360.ko
-> sethdlc hdlc0 hdlc-eth
-> ifconfig hdlc0 up 192.168.1.100
All is well, and I am seeing IDL interrupts. Great.
Now I go to ping an address like,
ping 192.168.1.101
I can see that I get the start_xmit function, the IRQ from the QE comes back
and reports the TXBD as successfully sent.
Here is the problem, when I goto free the skb in the tx_handler, I get a
'Unable to Handle Kernel Paging Request for data at address 0x00000000'
Even though for the life of me, I can't see any pointers that are at address
zero.
I have checked the pointer value I am passing in, and indeed it is the exact
same pointer I am receiving from the original
start-xmit call..
Are we supposed to copy the skb? And free it immediately in the start_xmit?
Some special way to store the pointer?
I have tried
txbd->buf = skb->data;
txbd->buf = virt_to_phys(skb->data);
etc.. and various other ways to save that I have seen in the gianfar and
ucc_geth drivers.
My tx_sk_buff** is identical as alloced the same way.
Anyone have any ideas?
-Russ
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* Re: HDLC driver - dev_free_skb_irq causes Segfault
2008-02-10 2:32 HDLC driver - dev_free_skb_irq causes Segfault Russell McGuire
@ 2008-02-13 14:11 ` Laurent Pinchart
2008-02-15 16:21 ` Jochen Friedrich
1 sibling, 0 replies; 3+ messages in thread
From: Laurent Pinchart @ 2008-02-13 14:11 UTC (permalink / raw)
To: linuxppc-embedded, rmcguire
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Hi Russ,
On Sunday 10 February 2008 03:32, Russell McGuire wrote:
> All,
>
> So I am in the process of debugging my newly established HDLC driver.
> More or less modeled after a simplified gianfar / ucc_geth idea.
>
> However, after loading, etc. and using the following commands
>
> -> insmod hdlc-8360.ko
> -> sethdlc hdlc0 hdlc-eth
> -> ifconfig hdlc0 up 192.168.1.100
>
> All is well, and I am seeing IDL interrupts. Great.
>
> Now I go to ping an address like,
> ping 192.168.1.101
>
> I can see that I get the start_xmit function, the IRQ from the QE comes
> back and reports the TXBD as successfully sent.
>
> Here is the problem, when I goto free the skb in the tx_handler, I get a
> 'Unable to Handle Kernel Paging Request for data at address 0x00000000'
> Even though for the life of me, I can't see any pointers that are at
> address zero.
I'm experiencing a similar problem here with a in-house HDLC driver. The
kernel oopses after some time under high HDLC loads.
Could you please post a backtrace to see if our problems are related ? How do
you free the skb ? Posting code snippet (or even the whole source code) would
help.
> I have checked the pointer value I am passing in, and indeed it is the
> exact same pointer I am receiving from the original
> start-xmit call..
>
> Are we supposed to copy the skb? And free it immediately in the start_xmit?
> Some special way to store the pointer?
My understanding is that the skb is supposed to be freed in the TX interrupt
handler.
> I have tried
> txbd->buf = skb->data;
> txbd->buf = virt_to_phys(skb->data);
> etc.. and various other ways to save that I have seen in the gianfar and
> ucc_geth drivers.
You should map the skb data buffer using dma_map_single. Don't forget to unmap
it with dma_unmap_single in the TX interrupt handler.
> My tx_sk_buff** is identical as alloced the same way.
>
> Anyone have any ideas?
Best regards,
--
Laurent Pinchart
CSE Semaphore Belgium
Chaussée de Bruxelles, 732A
B-1410 Waterloo
Belgium
T +32 (2) 387 42 59
F +32 (2) 387 42 75
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^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: HDLC driver - dev_free_skb_irq causes Segfault
2008-02-10 2:32 HDLC driver - dev_free_skb_irq causes Segfault Russell McGuire
2008-02-13 14:11 ` Laurent Pinchart
@ 2008-02-15 16:21 ` Jochen Friedrich
1 sibling, 0 replies; 3+ messages in thread
From: Jochen Friedrich @ 2008-02-15 16:21 UTC (permalink / raw)
To: rmcguire; +Cc: linuxppc-embedded
Hi Russell,
> ‘Unable to Handle Kernel Paging Request for data at address 0x00000000’
You need to check where the crash happens and what data is 0.
> Anyone have any ideas?
Is the source of this driver available somewhere?
Thanks,
Jochen
^ permalink raw reply [flat|nested] 3+ messages in thread
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2008-02-10 2:32 HDLC driver - dev_free_skb_irq causes Segfault Russell McGuire
2008-02-13 14:11 ` Laurent Pinchart
2008-02-15 16:21 ` Jochen Friedrich
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