If you are querying v$asm_disk or v$asm_diskgroup and the query is hanging, and tracing shows that RBAL is waiting for the "GPnP Get Item" event, then more than likely you are hitting a bug.

This don't really hamper your ASM instance working, but its prudent to restart

the instance, though the blocking of RBAL also tend to disappear after a while.

MOS is your friend in this case.