How can I put process into "uninterruptible sleep"?

Question

I'm testing some functionality to monitor processes and I need to emulate long core dump with determined "delay" (for example I need to make a process to "dump core" for 30 seconds). I'm noticed that process that dumping a core is in uninterruptible sleep, so it can't be killed with SIGKILL, but when I'm trying to emulate this behavior using pipe commands that receives coredump I can easily kill such process. So is there some way to make process to get into uninterruptible sleep (with such status in ps) and make it ignore the SIGKILL?

Answer 1

Most proper way is to use freezer cgroup. It puts process to uninterruptible sleep in case of FROZEN cgroup state.

# mkdir /sys/fs/cgroup/freezer
# mount -t cgroup -ofreezer freezer /sys/fs/cgroup/freezer
# mkdir /sys/fs/cgroup/freezer/frozen
# echo FROZEN > /sys/fs/cgroup/freezer/frozen/freezer.state
# echo `pidof you_process` > /sys/fs/cgroup/freezer/frozen/tasks

To put again to interruptible sleep, just change cgroup state to THAWED.