Re: NAPI poll routine happens in interrupt context?

[Joshua Wise]

It has come to my attention that the link that I posted previously was 
nonfunctional. It has been fixed.

As well, here are some other pertinent details:

This is kernel 2.6.13-rc2, the latest that works with MIPS SMP.

Here is a trace:
Debug: sleeping function called from invalid context at 
arch/mips/math-emu/dsemul.c:137
in_atomic():1, irqs_disabled():0
Call Trace:
 [<ffffffff801406e0>] __might_sleep+0x180/0x198
 [<ffffffff802cec00>] ipv6_rcv+0xc0/0x440
 [<ffffffff80140428>] do_dsemulret+0x68/0x1a0
 [<ffffffff8010b3a4>] do_ade+0x24/0x550
 [<ffffffff80102964>] handle_adel_int+0x3c/0x58
 [<ffffffff80268160>] netif_receive_skb+0x1b0/0x2e0
 [<ffffffff802cec04>] ipv6_rcv+0xc4/0x440
 [<ffffffff80268160>] netif_receive_skb+0x1b0/0x2e0
 [<ffffffff802572c8>] lanlan_poll+0x3e0/0x440
 [<ffffffff8026868c>] net_rx_action+0x16c/0x370
 [<ffffffff802686a8>] net_rx_action+0x188/0x370
 [<ffffffff80154f28>] __do_softirq+0x118/0x250
 [<ffffffff80154f28>] __do_softirq+0x118/0x250
 [<ffffffff80155110>] do_softirq+0xb0/0xe0
 [<ffffffff80101930>] mipsIRQ+0x130/0x1e0
 [<ffffffff80101c90>] r4k_wait+0x0/0x10
 [<ffffffff80103e6c>] cpu_idle+0x4c/0x68
 [<ffffffff80103e64>] cpu_idle+0x44/0x68
 [<ffffffff8037fcfc>] start_kernel+0x454/0x4e8
 [<ffffffff8037fcf4>] start_kernel+0x44c/0x4e8

Apologies for any inconvenience.

joshua

On Wednesday 17 August 2005 09:32, Joshua Wise wrote:
> Hello LKML,
>
> I have recently been working on a network driver for an emulated
> ultra-simple network card, and I've run into a few snags with the NAPI. My
> current issue is that it seems to me that my poll routine is being called
> from an atomic context, so when poll calls rx, and rx calls
> netif_receive_skb, I end up with lots of __might_sleep warnings in the
> various network layers.
>
> This is not so good. I need every cycle I can get, as this emulator is
> incredibly slow, so burning cycles by printing out the reported badness is
> not really acceptible. Conceivably the badness itself is also an issue.
>
> Before posting here, I did search Google for "lkml napi poll interrupt",
> although I did not find anything relevant to my issue.
>
> If interested, the code is available at http://joshuawise.com/lanlan.c .
> Some notes:
>
> The virtual lan-lan is a very very simple device. It consists of an ioreg
> that maintains state of the device, as described by the ioreg bit defines.
> It also has an ioctlreg that can pass through ioctls to the Linux kernel
> tap device that it's sitting on top of. (This goes with the ifreq seen in
> the struct.) One must always write and read in word-aligned chunks to and
> from it, for simplicity's sake.
>
> Feel free to suggest any modifications that this device might need to make
> it more fully functional. Hopefully we can bring this driver to such a
> state where it will be usable as a replacement skeleton driver for the
> NAPI.
>
> Please cc: Aaron and myself, as neither of us are subscribed to lkml.
>
> Thanks in advance,
> joshua
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