linux-kernel - Re: [RFC PATCH] pidfs: ensure consistent ENOENT/ESRCH reporting

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Message-ID: <20250411112532.GC5322@redhat.com>
Date: Fri, 11 Apr 2025 13:25:33 +0200
From: Oleg Nesterov <oleg@...hat.com>
To: Christian Brauner <brauner@...nel.org>
Cc: linux-fsdevel@...r.kernel.org, Jeff Layton <jlayton@...nel.org>,
	Lennart Poettering <lennart@...ttering.net>,
	Daan De Meyer <daan.j.demeyer@...il.com>,
	Mike Yuan <me@...dnzj.com>, linux-kernel@...r.kernel.org,
	Peter Ziljstra <peterz@...radead.org>
Subject: Re: [RFC PATCH] pidfs: ensure consistent ENOENT/ESRCH reporting

On 04/11, Christian Brauner wrote:
>
> > Looking close at this. Why is:
> >
> >         if (type == PIDTYPE_PID) {
> >                 WARN_ON_ONCE(pid_has_task(pid, PIDTYPE_PID));
> >                 wake_up_all(&pid->wait_pidfd);
> >         }
> >
> > located in __change_pid()? The only valid call to __change_pid() with a NULL
> > argument and PIDTYPE_PID is from __unhash_process(), no?
>
> We used to perform free_pid() directly from __change_pid() so prior to
> v6.15 changes it wasn't possible.

Yes, exactly ;)

> Now that we free the pids separately let's
> just move the notification into __unhash_process(). I have a patch ready
> for this.

Agreed,

Acked-by: Oleg Nesterov <oleg@...hat.com>