I can leave them for a very long time and they do not appear to go away.
From the dmesg output I suspect we have the same or similar chipsets in our mainboards. I do not have this issue with the Precise kernel (3.2.0-x), but it is definitely there with 3.5.0-19 and 3.5.0-21
I have the same thing on my Asus P5WDG WS PRO board. Like you it has Intel sound, and the Intel sound device is one of the "stuck" modprobe processes.
In my case I get 2-3 modprobe processes stuck with a 'D' state (waiting on I/O). This causes my system load average to sit at 2.0 or higher.
root 879 0.0 0.0 4412 708 ? D 12:47 0:00 /sbin/modprobe -bv pci:v00008086d0 00027D8sv000010 43sd000081F6bc0 4sc03i00 000032Csv000000 00sd00000000bc0 6sc04i00 00027B8sv000010 43sd00008179bc0 6sc01i00
root 881 0.0 0.0 4404 680 ? D 12:47 0:00 /sbin/modprobe -bv pci:v00008086d0
root 889 0.0 0.0 4376 720 ? D 12:47 0:00 /sbin/modprobe -bv pci:v00008086d0
I can leave them for a very long time and they do not appear to go away.
From the dmesg output I suspect we have the same or similar chipsets in our mainboards. I do not have this issue with the Precise kernel (3.2.0-x), but it is definitely there with 3.5.0-19 and 3.5.0-21