Re: [PATCH v4] signal: add taskfd_send_signal() syscall

On Thu, 2018-12-06 at 13:30 +0100, Florian Weimer wrote:

* Christian Brauner:

quoted

/* zombies */
Zombies can be signaled just as any other process. No special error will be
reported since a zombie state is an unreliable state (cf. [3]).

I still disagree with this analysis.  If I know that the target process
is still alive, and it is not, this is a persistent error condition
which can be reliably reported.  Given that someone might send SIGKILL
to the process behind my back, detecting this error condition could be
useful.

As I understand it, kill() behaves the same way. I think it's good that
this new syscall keeps the behavior as close as possible to kill().
E.g., this would allow emulating kill() (or a higher level API
equivalent) on top of taskfds without subtle differences in behavior.

As the new syscall supports flags, we could consider introducing a flag
that changes the behavior in the zombie case. However, I think that
should be a separate discussion (after merge of the syscall) and the
default behavior makes sense as is.

Jürg