gem csum breakage with 018c5bba (Handle CHECKSUM_COMPLETE more adequately ...)

gem csum breakage with 018c5bba (Handle CHECKSUM_COMPLETE more adequately ...)

[Alexander Graf]

Hi,

With current Linus' master tree my ibook started emitting a lot of annoying csum calculation warnings. I've bisected it down to the commit seen in the subject line, but I suppose the real problem lies somewhere a lot deeper and only gets revealed thanks to the more clever checksum logic applied now.

Any ideas how to dig further into this?


Thanks,

Alex

---

<unknown>: hw csum failure
CPU: 0 PID: 0 Comm: swapper Not tainted 3.12.0+ #1
Call Trace:
[efff1d00] [c00090f0] show_stack+0x48/0x150 (unreliable)
[efff1d40] [c049f794] csum_partial_copy_to_xdr+0xf8/0x168
[efff1d60] [c04a1120] xs_udp_data_ready+0xbc/0x140
[efff1d90] [c03f99f4] sock_queue_rcv_skb+0x144/0x1c0
[efff1db0] [c045aa28] __udp_queue_rcv_skb+0x38/0xd4
[efff1dc0] [c045de5c] udp_queue_rcv_skb+0x260/0x3ac
[efff1de0] [c045e6dc] __udp4_lib_rcv+0x2c8/0x63c
[efff1e20] [c0432a78] ip_local_deliver_finish+0x100/0x268
[efff1e40] [c0408264] __netif_receive_skb_core+0x510/0x690
[efff1ea0] [c040b78c] napi_gro_receive+0xac/0xd8
[efff1eb0] [c0353b94] gem_poll+0x5bc/0x116c
[efff1f50] [c040a60c] net_rx_action+0x118/0x1fc
[efff1f90] [c0046afc] __do_softirq+0xd4/0x1c4
[efff1fe0] [c0046f04] irq_exit+0x94/0xb8
[efff1ff0] [c000ef30] call_do_irq+0x24/0x3c
[c0733e90] [c0006ca4] do_IRQ+0x64/0xb4
[c0733eb0] [c0011b34] ret_from_except+0x0/0x1c
--- Exception: 501 at arch_cpu_idle+0x24/0x6c
    LR = arch_cpu_idle+0x24/0x6c
[c0733f70] [c0082638] rcu_idle_enter+0x84/0xc4 (unreliable)
[c0733f80] [c007c4b0] cpu_startup_entry+0xa4/0x16c
[c0733fb0] [c06caf54] start_kernel+0x308/0x31c
[c0733ff0] [00003d34] 0x3d34

Re: gem csum breakage with 018c5bba (Handle CHECKSUM_COMPLETE more adequately ...)

[Herbert Xu]

On Fri, Nov 22, 2013 at 07:08:16PM +0100, Alexander Graf wrote:
> Hi,
> 
> With current Linus' master tree my ibook started emitting a lot of annoying csum calculation warnings. I've bisected it down to the commit seen in the subject line, but I suppose the real problem lies somewhere a lot deeper and only gets revealed thanks to the more clever checksum logic applied now.
> 
> Any ideas how to dig further into this?

Sorry, I don't have any docs on this device.  Perhaps Dave has
the docs which can tell us what RXDCTRL_TCPCSUM actually returns?

I assume it returns the correct checksum ending at the IP
packet boundary and only goes wrong when extra padding exists.

Hmm, I suppose the question then is what exactly does it do
if the packet isn't an IP packet?

Thanks,
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

Re: gem csum breakage with 018c5bba (Handle CHECKSUM_COMPLETE more adequately ...)

[David Miller]

From: Alexander Graf <agraf@suse.de>
Date: Fri, 22 Nov 2013 19:08:16 +0100

> With current Linus' master tree my ibook started emitting a lot of
> annoying csum calculation warnings. I've bisected it down to the
> commit seen in the subject line, but I suppose the real problem lies
> somewhere a lot deeper and only gets revealed thanks to the more
> clever checksum logic applied now.
> 
> Any ideas how to dig further into this?

Ok, I'm going to revert this commit, for several reasons.

In addition to the problem you are running into, it just occurred to me
that if the __pskb_trim() call fails, we'll leave a corrupted checksum
in the SKB.

Thanks for your report.