Re: [patch] NE2000

[Jorge Nerin <comandante@zaralinux.com>]

Paul Gortmaker wrote:
> 
> Jorge Nerin wrote:
> 
> >
> > Ok, I reported it several times, but it gets ignored. I have a Realtek
> > 8029 (ne2k-pci), and with both drivers ne and ne2k-pci I can easily get
> > it stuck by doing a ping -f to a host in the local net, and sometimes it
> > happens doing copies to/from nfs shared resources.
> >
> > rmmod & insmod don't cure the problem, it seems that no interrupts are
> > delivered from the card, and there are no log messages, so a reboot is
> > needed to restore net access.
> >
> > System is dual 2x200mmx 96Mb ide discs no interrupts shared, and as far
> > as I can remember all kernel from 2.2.x, 2.3.x up to 2.4.0-testx exhibit
> > this problem.
> 
> Any messages from the driver whatsoever?   Does running a non-SMP
> kernel make the problem go away?
> 
> Paul.
> 

Well, I have tried it with 2.4.0-test10, both SMP and non-SMP, and the
result is a little confusing.

Under SMP a ping -s 50000 -f other_host takes down the network access
with no messages (ne2k-pci), and no possibility of being restored
without a reboot.

Under UP the same command works ok, but after a while the dots stop for
30sec, then ping prints an 'E' and the dots continue. strace revealed
this:

sendmsg(4, {msg_name(16)={sin_family=AF_INET, sin_port=htons(0),
sin_addr=inet_addr("192.168.1.20")}},
msg_iov(1)=[{"\10\0\305~|\23\231\0\v\317\2:\177\236\r\0\10\t\n\v\f\r"...,
50008}], msg_controllen=0, msg_flags=0}, 0x800) = 50008 <30.016855>

ping has been waiting for sendmsg to end for 30 seconds! I don't know if
this could be caused by filling the network buffers, and then waiting a
while while the nic sends it out. As the packet size increases (the -s
option) the stops are more frequent, there is still activity on the
network, but I don't know if they are my packets or the replies.

When ping is stopped it's stuck in sock_wait_for_wmem, and when it's
running it's (usually) in wait_for_packet.

So I think that it could be a little window near sock_wait_for_wmem that
could be SMP insecure wich is affecting me.

The code of sock_wait_for_wmem in 2.4.0-test10 is this:

static long sock_wait_for_wmem(struct sock * sk, long timeo)
{
	DECLARE_WAITQUEUE(wait, current);

	clear_bit(SOCK_ASYNC_NOSPACE, &sk->socket->flags);
	add_wait_queue(sk->sleep, &wait);
	for (;;) {
		if (signal_pending(current))
			break;
		set_bit(SOCK_NOSPACE, &sk->socket->flags);
		set_current_state(TASK_INTERRUPTIBLE);
		if (atomic_read(&sk->wmem_alloc) < sk->sndbuf)
			break;
		if (sk->shutdown & SEND_SHUTDOWN)
			break;
		if (sk->err)
			break;
		timeo = schedule_timeout(timeo);
	}
	__set_current_state(TASK_RUNNING);
	remove_wait_queue(sk->sleep, &wait);
	return timeo;
}

Does someone see something SMP insecure? Perhaps I'm totally wrong, this
could also be somewhere in the interrupt handling, don't know.

-- 
Jorge Nerin
<comandante@zaralinux.com>
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