Re: locking api self-test hanging

On Mon, 4 Feb 2008 04:43:04 -0800 Andrew Morton [off-list ref] wrote:

On Sun, 3 Feb 2008 15:07:44 -0800 Andrew Morton [off-list ref] wrote:

quoted

On Sun, 3 Feb 2008 15:02:46 -0800 Andrew Morton [off-list ref] wrote:

quoted

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.

quoted

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 [off-list ref]
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.