From: Stephen Hemminger <shemminger@vyatta•com>
To: Yegor Yefremov <yegorslists@googlemail•com>
Cc: "Figo.zhang" <figo1802@gmail•com>,
Dick Hollenbeck <dick@softplc•com>,
netdev@vger•kernel.org, zealcook@gmail•com
Subject: Re: KS8695: possible NAPI issue
Date: Fri, 5 Mar 2010 08:22:18 -0800 [thread overview]
Message-ID: <20100305082218.4f734857@nehalam> (raw)
In-Reply-To: <f69abfc31003050700y57718a6aje3c1ff41d04748ae@mail.gmail.com>
On Fri, 5 Mar 2010 16:00:11 +0100
Yegor Yefremov <yegorslists@googlemail•com> wrote:
> >> My tests look like following:
> >>
> >> 1. system start
> >> 2. ping one host: O.K.
> >> 3. nc -l -p 5000 > /var/test (about 1Mb): O.K.
> >> 4. ping the same host: failed
> > 1. type "arp" command, see the arp is exit or expire?
>
> debian:~# nc -l -p 5000 > /var/zImage
>
> debian:~# ping -c 1 192.168.1.38
>
> PING 192.168.1.38 (192.168.1.38) 56(84) bytes of data.
>
> From 192.168.1.66 icmp_seq=1 Destination Host Unreachable
>
>
>
> --- 192.168.1.38 ping statistics ---
>
> 1 packets transmitted, 0 received, +1 errors, 100% packet loss, time 0ms
>
>
>
> debian:~# arp
>
> Address HWtype HWaddress Flags Mask Iface
> 192.168.1.38 (incomplete) eth0
>
> 192.168.1.36 ether 00:10:18:39:19:aa C eth0
>
>
> > 2. at this point, see is it still have RX interrpt and receive packet in
> > ks8695_rx()? (in some watchpoint add printk).
>
> I've inserted some printks and I can see that interrupts are coming
> and the received count will be increased. I can also see my system
> sending arp requests. Even this ping request is visible in wireshark
> and its reply, but the ping utility sees nothing of it.
One of the requirements for NAPI to work is that the IRQ is level triggered.
Otherwise there can be a race between packet arrival and the end of
NAPI processing:
static int ks8695_poll(struct napi_struct *napi, int budget)
{
struct ks8695_priv *ksp = container_of(napi, struct ks8695_priv, napi);
unsigned long work_done;
unsigned long isr = readl(KS8695_IRQ_VA + KS8695_INTEN);
unsigned long mask_bit = 1 << ks8695_get_rx_enable_bit(ksp);
work_done = ks8695_rx(ksp, budget);
if (work_done < budget) {
unsigned long flags;
spin_lock_irqsave(&ksp->rx_lock, flags);
>>> packet arrives >>
/*enable rx interrupt*/
writel(isr | mask_bit, KS8695_IRQ_VA + KS8695_INTEN);
>>> or here >>
__napi_complete(napi);
spin_unlock_irqrestore(&ksp->rx_lock, flags);
If the hardware can't be reprogrammed to level mode;
the solution used in some drivers is to poll for lost packet after re-enabling
NAPI.
--
next prev parent reply other threads:[~2010-03-05 16:22 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-03-02 12:04 KS8695: possible NAPI issue Yegor Yefremov
2010-03-02 14:09 ` Dick Hollenbeck
2010-03-03 1:46 ` figo zhang
2010-03-03 5:01 ` Dick Hollenbeck
2010-03-03 8:28 ` Yegor Yefremov
2010-03-04 10:10 ` Yegor Yefremov
2010-03-05 6:54 ` figo zhang
2010-03-05 10:06 ` Yegor Yefremov
2010-03-05 13:52 ` Figo.zhang
2010-03-05 15:03 ` Yegor Yefremov
2010-03-05 14:07 ` Figo.zhang
2010-03-05 15:00 ` Yegor Yefremov
2010-03-05 16:22 ` Stephen Hemminger [this message]
2010-03-06 2:40 ` Figo.zhang
2010-03-08 9:04 ` figo zhang
2010-03-08 14:10 ` Yegor Yefremov
2010-03-08 14:11 ` Yegor Yefremov
2010-03-09 1:50 ` figo zhang
2010-03-15 9:19 ` Yegor Yefremov
2010-08-04 14:40 ` Yegor Yefremov
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