Re: [bug] SLOB crash, 2.6.24-rc2

[David Miller <davem@davemloft.net>]

From: Ingo Molnar <mingo@elte.hu>
Date: Thu, 15 Nov 2007 11:43:32 +0100

> The crash logs contain this:
> 
>  VFS: Mounted root (ext3 filesystem) readonly.
>  Freeing unused kernel memory: 396k freed
>  Write protecting the kernel read-only data: 2056k
>  udev: renamed network interface eth1 to eth0
>  udev: renamed network interface eth0_rename to eth1
>  eth0: link down
>  ADDRCONF(NETDEV_UP): eth0: link is not ready
>  EXT3 FS on sda6, internal journal
>  kjournald starting.  Commit interval 5 seconds
> 
> followed by the crash shortly afterwards (but not immediately). With the 
> non-crashing kernel i dont get those "renamed network interface" 
> messages.
> 
> network interface renaming has been a historic source of pain for me so 
> i frequently have to 'twiddle' the networking config to make it work 
> again on new kernels. Perhaps because i'm using bzImage kernels. 
> User-space is Fedora 8, so fairly recent.

Yeah I wish udev would just leave the damn devices alone.

It even does things like try to rename a network device to the same
name it already has, and other strange stuff.

But that log difference is a good clue.

Because udev can try to rename a network device stupidly to a name the
device already has we added a patch to just short circuit this case in
the networking.  We did this because otherwise the generic device
layer gives an ugly stack backtrace via dev_rename().

Therefore, you might want to see if reverting that patch (attached
below) has some effect, once you are able to trigger it again.

Thanks Ingo.

commit c8d90dca3211966ba5189e0f3d4bccd558d9ae08
Author: Stephen Hemminger <shemminger@linux-foundation.org>
Date:   Fri Oct 26 03:53:42 2007 -0700

    [NET] dev_change_name: ignore changes to same name
    
    Prevent error/backtrace from dev_rename() when changing
    name of network device to the same name. This is a common
    situation with udev and other scripts that bind addr to device.
    
    Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org>
    Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/core/dev.c b/net/core/dev.c
index f1647d7..ddfef3b 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -883,6 +883,9 @@ int dev_change_name(struct net_device *dev, char *newname)
 	if (!dev_valid_name(newname))
 		return -EINVAL;
 
+	if (strncmp(newname, dev->name, IFNAMSIZ) == 0)
+		return 0;
+
 	memcpy(oldname, dev->name, IFNAMSIZ);
 
 	if (strchr(newname, '%')) {