Messages in this thread | ![/](/images/icornerl.gif) | | Date | Sat, 10 Feb 2024 13:30:33 +0100 | From | Oleg Nesterov <> | Subject | Re: [PATCH v2 2/2] pidfd: change pidfd_send_signal() to respect PIDFD_THREAD |
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Christian,
Thanks again! the last 2 commits in vfs.pidfd look good to me.
As for this patch, I am not sure I understand your concerns, and I have another concern, please see below.
For the moment, please forget about PIDFD_THREAD.
On 02/10, Christian Brauner wrote: > > (1) kill(-1234) => kill process group with id 1234 > (2) kill(0) => kill process group of @current > > which implementation wise is indicated by > > __kill_pgrp_info(..., pid ? find_vpid(-pid) ? task_pgrp(current)) > > We're obviously not going to implement (2) as that doesn't really make a > sense for pidfd_send_signal().
Sure,
> But (1) is also wrong for pidfd_send_signal(). If we'd ever implement > (1) it should be via pidfd_open(1234, PIDFD_PROCESS_GROUP).
Why do you think we need another flag for open() ?
To me it looks fine if we allow to send the signal to pgrp if flags & PIDFD_SIGNAL_PROCESS_GROUP.
And pidfd_send_signal() can just do
if (PIDFD_SIGNAL_THREAD_GROUP) ret = __kill_pgrp_info(sig, kinfo, pid); else ret = kill_pid_info_type(...); (yes, yes, this needs tasklist, just a pseudo code to simpliy)
Now lets recall about PIDFD_THREAD.
If the target task is a group leader - there is no difference.
If it is not a leader - then __kill_pgrp_info() will always return -ESRCH, do_each_pid_task(PIDTYPE_PGID) won't find any task.
And personally I think this is all we need.
------------------------------------------------------------------------------ But if you want to make PIDFD_SIGNAL_THREAD_GROUP work even if the target task is not a leader, then yes, we need something like
task_pgrp(pid_task(pid, PIDTYPE_PID))
like you did in the new kill_pgrp_info() helper in this patch.
I won't argue, but do you think this makes a lot of sense?
Oleg.
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