From: Oleg Nesterov <oleg@redhat.com>
To: Christian Brauner <brauner@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>,
"Eric W. Biederman" <ebiederm@xmission.com>,
Tycho Andersen <tycho@tycho.pizza>,
linux-api@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 2/2] pidfd: change pidfd_send_signal() to respect PIDFD_THREAD
Date: Sat, 10 Feb 2024 13:30:33 +0100 [thread overview]
Message-ID: <20240210123033.GA27557@redhat.com> (raw)
In-Reply-To: <20240210-abfinden-beimessen-2dbfea59b0da@brauner>
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.
next prev parent reply other threads:[~2024-02-10 12:31 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-09 13:06 [PATCH v2 1/2] signal: add the "int si_code" arg to prepare_kill_siginfo() Oleg Nesterov
2024-02-09 13:06 ` [PATCH v2 2/2] pidfd: change pidfd_send_signal() to respect PIDFD_THREAD Oleg Nesterov
2024-02-09 15:11 ` Christian Brauner
2024-02-09 15:15 ` Christian Brauner
2024-02-09 15:43 ` Oleg Nesterov
2024-02-09 15:49 ` Christian Brauner
2024-02-09 15:56 ` Oleg Nesterov
2024-02-10 10:23 ` Christian Brauner
2024-02-10 12:30 ` Oleg Nesterov [this message]
2024-02-10 12:47 ` Oleg Nesterov
2024-02-10 12:54 ` Christian Brauner
2024-02-10 13:15 ` Oleg Nesterov
2024-02-10 14:26 ` Christian Brauner
2024-02-10 16:51 ` Oleg Nesterov
2024-02-10 17:22 ` Christian Brauner
2024-02-14 12:36 ` Oleg Nesterov
2024-02-16 12:28 ` Christian Brauner
2024-02-16 13:06 ` Oleg Nesterov
2024-02-16 14:46 ` Christian Brauner
2024-02-16 18:12 ` Oleg Nesterov
2024-02-20 8:34 ` Christian Brauner
2024-02-20 9:02 ` Oleg Nesterov
2024-02-20 9:22 ` Christian Brauner
2024-02-20 11:00 ` Oleg Nesterov
2024-02-20 12:59 ` Christian Brauner
2024-02-20 16:22 ` Oleg Nesterov
2024-02-21 7:42 ` Christian Brauner
2024-02-21 12:55 ` Oleg Nesterov
2024-02-21 13:35 ` Christian Brauner
2024-02-09 19:08 ` Tycho Andersen
2024-02-09 15:10 ` [PATCH v2 1/2] signal: add the "int si_code" arg to prepare_kill_siginfo() Christian Brauner
2024-02-09 16:13 ` Christian Brauner
2024-02-09 16:22 ` Eric W. Biederman
2024-02-09 16:39 ` Oleg Nesterov
2024-02-09 19:36 ` Christian Brauner
2024-02-09 19:53 ` Oleg Nesterov
2024-02-09 20:01 ` Tycho Andersen
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