After bootup (runlevel 5) I found this in dmesg:

WARNING: at mm/slab.c:777 __find_general_cachep()
 [<c0165fe1>] __kmalloc+0x40/0xc3
 [<f8f4d5ed>] drm_rmdraw+0x126/0x24e [drm]
 [<c023e68b>] skb_dequeue+0x39/0x3f
 [<f8f4d4c7>] drm_rmdraw+0x0/0x24e [drm]
 [<f8f4e10e>] drm_ioctl+0x14c/0x192 [drm]
 [<c0172cb0>] do_ioctl+0x4c/0x62
 [<c0172efd>] vfs_ioctl+0x237/0x249
 [<c017aff3>] mntput_no_expire+0x11/0x68
 [<c0172f5b>] sys_ioctl+0x4c/0x65
 [<c0103cde>] sysenter_past_esp+0x5f/0x85
 =======================

Kernel is Linus' git of yesterday, the first occurence of this in my logs was 
on May 16th.

Greetings,

Eike