Re: locking api self-test hanging

From: Andrew Morton
Date: Mon Feb 04 2008 - 08:18:54 EST


On Mon, 4 Feb 2008 04:43:04 -0800 Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote:

> On Sun, 3 Feb 2008 15:07:44 -0800 Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote:
>
> > On Sun, 3 Feb 2008 15:02:46 -0800 Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote:
> >
> > >
> > > With current mainline I'm getting intermittent hangs here:
> > >
> > > http://userweb.kernel.org/~akpm/p2033590.jpg
> > >
> > > with this config:
> > >
> > > http://userweb.kernel.org/~akpm/config-sony.txt
> > >
> > > on the Vaio. Sometimes it boots (then hits another different hang),
> > > sometimes it gets stuck there.
>
> CONFIG_DEBUG_LOCKING_API_SELFTESTS=n fixed that up.
>
> >
> > The second hang is in kobject_uevent_init(). All that function does is call
> > netlink_kernel_create().
>
> And I've fully bisected this hang twice and both times came up with
>
> commit 33f807ba0d9259e7c75c7a2ce8bd2787e5b540c7
> Author: Stephen Hemminger <shemminger@xxxxxxxxxxxxxxxxxxxx>
> Date: Mon Nov 19 19:24:52 2007 -0800
>
> [NETPOLL]: Kill NETPOLL_RX_DROP, set but never tested.
>
> which is stupid because that patch doesn't do anything.
>
> However I am using netconsole-over-e100 and the hang does go away when I
> disable netconsole on the kernel boot command line.
>
> I'd say it's some timing thing in netpoll/netconsole/napi/etc.
>

I expect the locking API self-tests are innocent - the netconsole lockup
happened to strike during the locking API tests and fooled me. When I
disabled those tests, the netconsole lockup struck later on.

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