# Re: \[PATCH 1/1\] mm: introduce process\_reap system call

- From: Jan Engelhardt \<hidden\>
- Date: 2021-07-12 13:00:22 
- List: linux-api
- Page: https://ratatoskr.run/linux-api/2021/07/1441934
- Thread: https://ratatoskr.run/linux-api/2021/07/1436125/t.md

```text

On Thursday 2021-07-08 08:05, Suren Baghdasaryan wrote:
>>
>> That explains very clearly the requirement, but it raises the question
>> why this isn't an si_code flag for rt_sigqueueinfo, reusing the existing
>> system call.
>
>I think you are suggesting to use sigqueue() to deliver the signal and
>perform the reaping when a special value accompanies it. This would be
>somewhat similar to my early suggestion to use a flag in
>pidfd_send_signal() (see:
>https://lore.kernel.org/patchwork/patch/1060407) to implement memory
>reaping which has another advantage of operation on PIDFDs instead of
>PIDs which can be recycled.
>kill()/pidfd_send_signal()/sigqueue() are supposed to deliver the
>signal and return without blocking. Changing that behavior was
>considered unacceptable in these discussions.

The way I understood the request is that a userspace program (or perhaps two,
if so desired) should issue _two_ calls, one to deliver the signal,
one to perform the reap portion:

	uinfo.si_code = SI_QUEUE;
	sigqueue(pid, SIGKILL, &uinfo);
	uinfo.si_code = SI_REAP;
	sigqueue(pid, SIGKILL, &uinfo);
```