linux-kernel - Re: [PATCH] pidfd: change pidfd_send_signal() to respect PIDFD

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Message-ID: <20240208-babybett-nachjagen-ed354d2192f8@brauner>
Date: Thu, 8 Feb 2024 15:33:46 +0100
From: Christian Brauner <brauner@...nel.org>
To: Oleg Nesterov <oleg@...hat.com>
Cc: Andy Lutomirski <luto@...capital.net>, 
	"Eric W. Biederman" <ebiederm@...ssion.com>, Tycho Andersen <tycho@...ho.pizza>, linux-api@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] pidfd: change pidfd_send_signal() to respect PIDFD_THREAD

On Thu, Feb 08, 2024 at 03:06:10PM +0100, Oleg Nesterov wrote:
> On 02/08, Christian Brauner wrote:
> >
> > I would also suggest we update the obsolete comment on top of
> > pidfd_send_signal() along the lines of:
> 
> Yes, but...
> 
> > + * If the @pidfd refers to a thread-group leader the signal is thread-group
> > + * directed. If @pidfd referes to a thread then the signal is thread directed.
> 
> No, this depends on PIDFD_THREAD only.

Sorry, yes, that is what I meant to say but obviously wrote unclearly. I
mean that if pidfd->f_flags & PIDFD_THREAD then it's thread-directed.
That's what I meant by type of pidfd. Not type as in PIDTYPE_PID in
struct pid.

> 
> If it is set then the signal is always "thread directed" even if @pidfd refers
> to a thread-group leader.
> 
> Otherwise the target task must be a group leader and the signal will be
> "thread-group directed".
> 
> Right?

Yes, please feel free to update the comment!