Re: Using netconsole for debugging suspend/resume

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



Matt Mackall wrote:
That's odd. Netpoll holds a reference to the device, of course, but so
does a normal "up" interface. So that shouldn't be the problem.
Another possibility is that outgoing packets from printks in the
driver are causing difficulty. Not sure what can be done about that.
I only tried once; maybe I misunderstood what was going on. I'll try again tonight.
Oh, I think I see what's happening.  The e1000 suspend routine does this:

	if (netif_running(netdev))
		e1000_down(adapter);

This leaves the interface up, but it stops the queue. Then netpoll_send_skb() has this loop:
	do {
		npinfo->tries--;
		spin_lock(&np->dev->xmit_lock);
		np->dev->xmit_lock_owner = smp_processor_id();

		/*
		 * network drivers do not expect to be called if the queue is
		 * stopped.
		 */
		if (netif_queue_stopped(np->dev)) {
			np->dev->xmit_lock_owner = -1;
			spin_unlock(&np->dev->xmit_lock);
			netpoll_poll(np);
			udelay(50);
			continue;
		}
/* ... */
again: /* proposed */
	} while (npinfo->tries > 0);


so this will end up in an infinite loop, since netif_queue_stopped() will always return true, and it never looks at npinfo->tries. Should the "continue" be "goto again"?
Also, e1000_down does a netif_poll_disable(), but I'm not sure what that
actually does... Should it prevent netpoll from even trying to send?
It's generally going to suck, because unlike a polled serial port, the
device needs to be put to sleep. But if you're doing suspend to RAM,
I'm interested in suspend-to-ram. I presume that with suspend-to-disk, booting with built-in netconsole will tell me useful stuff; that'll be the next experiment.
you might be able to do something like this:

- unhook net device from suspend machinery (possibly just return success)
- bounce out of suspend before the final call to ACPI is made

Net effect is you do OS-level suspend and resume of everything but the
NIC without actually powering down the core. Which should let you
debug just about everything.
Well, the machine has to really suspend so that I can see (and debug) a
mostly normal resume. In particular, I need the hardware to be zapped
so I can see if it is being restarted properly.
What might work is to change the e1000 suspend routine to save enough
state for resume to work, but keep the interface up so that netconsole
can keep transmitting all the way up to the point that the final acpi
call powers off the machine.
Then the e1000 would resume normally, including restarting the xmit
queue so that netconsole can start again immediately; any netconsole
output before the e1000 resume would be lost, of course (I guess it
could be buffered). That would suit me for now.
   J

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

[Index of Archives]     [Kernel Newbies]     [Netfilter]     [Bugtraq]     [Photo]     [Stuff]     [Gimp]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux RAID]     [Video 4 Linux]     [Linux for the blind]     [Linux Resources]
  Powered by Linux