On 10/23/2015 12:17 AM, Sergei Shtylyov wrote:
[...]
If memory is not yet available
when the controller is trying to use the invalid descriptor, the
controller will see it and DMA will stop.
That means leaving RACT=0 and that's what the driver is even doing...
Hm, then I don't understand how the error you've described can occur,
unless we encounter OOM during sh_eth_ring_format()...
Is it acceptable path to go?
I'm not seeing a bug in this function, perhaps I'm missing something?
Nevermind, I'm seeing the bug now -- occurred to me before I went to bed
yesterday.
To achieve zero copy, the driver push the sk_buffs filled with
received packet to the netdev core with netif_receive_skb() then
netdev_alloc_skb() sk_buffs in the sh_eth_rx(), the poll method of the
driver, and update the corresponding descriptor.
If the allocation failed, it just leave the function, leaving old
pointer in the descriptor as is.
Yes, but note that it also leaves RACT=0, which basically means an invalid
descriptor, encountering which the reception should just stop.
The problem is that the first loop has no way of identifying the bad
descriptors. Looks like we only can fix that by checking rx_skbuff[entry] for
NULL.
MBR, Sergei
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