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    SubjectRe: [patch] fix netconsole hang with alt-sysrq-t
    ==> Regarding Re: [patch] fix netconsole hang with alt-sysrq-t; Matt Mackall <> adds:

    mpm> On Fri, Aug 06, 2004 at 03:29:27PM -0400, Jeff Moyer wrote:
    >> Hi, Matt,
    >> Here's the patch. Sorry it took me so long, been busy with other work.
    >> Two things which need perhaps more thinking, can netpoll_poll be called
    >> recursively (it didn't look like it to me)

    mpm> It can if the poll function does a printk or the like and wants to
    mpm> recurse via netconsole. We could short-circuit that with an in_netpoll
    mpm> flag, but let's worry about that separately.

    Hmm, ok.

    >> and do we care about the racy
    >> nature of the netpoll_set_trap interface?

    mpm> That should probably become an atomic now.

    Ouch. I wanted to avoid that, but if we can't, we can't. Will
    netpoll_set_trap then to an atomic_inc or an atomic_add? I've only seen it
    called with 1 and 0, is that all that was intended?

    >> You'll notice that I reverted part of an earlier changeset which caused us
    >> to call the hard_start_xmit function even if netif_queue_stopped returned
    >> true. This is a bug. I preserved the second part of that patch, which was
    >> correct.

    mpm> Ok, jgarzik pointed that out to me just a bit ago. I'm not sure if
    mpm> we're dealing with the behavior that was intended to address yet
    mpm> though. Stelian, can you try giving this a spin?

    Well, we kept the second part of the patch, which deals with the
    hard_start_xmit routine returning 1. That was a valid bug, I believe.

    >> I've also bumped the budget from 1 to 16. As I mentioned, this was a
    >> required change for netdump.

    mpm> Should be fine.

    >> This patch was tested on my dual hammer test system.

    mpm> I'll have to re-rig my kgdb-over-ethernet test setup to test this, but
    mpm> it looks good for now.

    Yah, and I just noticed we don't want the poll_lock to be per struct
    netpoll. It should be a static lock in the netpoll.c file. The problem is
    that more than one netpoll object can reference the same ethernet device.


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