linux-kernel - Re: [PATCH v3 1/3] pidfd: allow pidfd_open() on non-thread-group leaders

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Message-ID: <ZbVrRgIvudX242ZU@tycho.pizza>
Date: Sat, 27 Jan 2024 13:44:54 -0700
From: Tycho Andersen <tycho@...ho.pizza>
To: Oleg Nesterov <oleg@...hat.com>
Cc: Christian Brauner <brauner@...nel.org>, linux-kernel@...r.kernel.org,
	linux-api@...r.kernel.org, Tycho Andersen <tandersen@...flix.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>
Subject: Re: [PATCH v3 1/3] pidfd: allow pidfd_open() on non-thread-group
 leaders

On Sat, Jan 27, 2024 at 08:31:27PM +0100, Oleg Nesterov wrote:
> On 01/27, Tycho Andersen wrote:
> >
> > > > > exit_notify() is called after exit_files(). pidfd_getfd() returns
> > > > > ESRCH if the exiting thread completes release_task(), otherwise it
> > > > > returns EBADF because ->files == NULL. This too doesn't really
> > > > > depend on PIDFD_THREAD.
> > > >
> > > > Yup, understood. It just seems like an inconsistency we might want to
> > > > fix.
> > >
> > > Not sure this worth "fixing"...
> >
> > Yep, maybe not. Just wanted to point it out.
> 
> On the second thought I am starting to understand your concern...
> 
> Indeed, in this case -EBADF is technically correct but it can confuse
> the user which doesn't or can't know that this task/thread is exiting,
> because EBADF looks as if the "int fd" argument was wrong.
> 
> Sorry I missed your point before.

No worries. I realized it's not so hard to fix with your new
xxx_exited() helper from the PIDFD_THREAD patch, so maybe worth
cleaning up after all?

Tycho