Comment # 18 on bug 920368 from Jan Engelhardt

>udevd calls BLKRRPART on close() a write-opened device precisely to _detect_ any changes to the partition table. And this of course races with the BLKRRPART from parted.

So, why does parted close the device? fdisk does not do that:

open("/dev/sdb", O_RDWR|O_CLOEXEC)      = 3
ioctl(3, BLKGETSIZE64, 8589934592)      = 0
[...]
Device does not contain a recognized partition table.
open("/dev/urandom", O_RDONLY|O_CLOEXEC) = 4
close(4)                                = 0
Created a new DOS disklabel with disk identifier 0xd1ec9bdd.

Command (m for help): w
The partition table has been altered.
Calling ioctl() to re-read partition table.
ioctl(3, BLKRRPART, 0x7f3c9adb7658)     = 0
close(3)                                = 0
Syncing disks.