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

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Message-ID: <ZWoKbHJ0152tiGeD@tycho.pizza>
Date:   Fri, 1 Dec 2023 09:31:40 -0700
From:   Tycho Andersen <tycho@...ho.pizza>
To:     Oleg Nesterov <oleg@...hat.com>
Cc:     Christian Brauner <brauner@...nel.org>,
        "Eric W . Biederman" <ebiederm@...ssion.com>,
        linux-kernel@...r.kernel.org, linux-api@...r.kernel.org,
        Tycho Andersen <tandersen@...flix.com>
Subject: Re: [RFC 1/3] pidfd: allow pidfd_open() on non-thread-group leaders

On Thu, Nov 30, 2023 at 10:57:01AM -0700, Tycho Andersen wrote:
> On Thu, Nov 30, 2023 at 06:39:39PM +0100, Oleg Nesterov wrote:
> > I think that wake_up_all(wait_pidfd) should have a single caller,
> > do_notify_pidfd(). This probably means it should be shiftef from
> > do_notify_parent() to exit_notify(), I am not sure...

Indeed, below passes the tests without issue and is much less ugly.
I'll respin with that later next week sometime.

Thanks,

Tycho


diff --git a/include/linux/sched/signal.h b/include/linux/sched/signal.h
index 3499c1a8b929..04c4423ebed0 100644
--- a/include/linux/sched/signal.h
+++ b/include/linux/sched/signal.h
@@ -332,6 +332,7 @@ extern int kill_pid_usb_asyncio(int sig, int errno, sigval_t addr, struct pid *,
 extern int kill_pgrp(struct pid *pid, int sig, int priv);
 extern int kill_pid(struct pid *pid, int sig, int priv);
 extern __must_check bool do_notify_parent(struct task_struct *, int);
+extern void do_notify_pidfd(struct task_struct *);
 extern void __wake_up_parent(struct task_struct *p, struct task_struct *parent);
 extern void force_sig(int);
 extern void force_fatal_sig(int);
diff --git a/kernel/exit.c b/kernel/exit.c
index 34eeefc7ee21..fd6048c20c48 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -769,6 +769,8 @@ static void exit_notify(struct task_struct *tsk, int group_dead)
 		wake_up_process(tsk->signal->group_exec_task);
 	write_unlock_irq(&tasklist_lock);
 
+	do_notify_pidfd(tsk);
+
 	list_for_each_entry_safe(p, n, &dead, ptrace_entry) {
 		list_del_init(&p->ptrace_entry);
 		release_task(p);
diff --git a/kernel/signal.c b/kernel/signal.c
index 47a7602dfe8d..7b3a1e147225 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -2028,7 +2028,7 @@ int send_sigqueue(struct sigqueue *q, struct pid *pid, enum pid_type type)
 	return ret;
 }
 
-static void do_notify_pidfd(struct task_struct *task)
+void do_notify_pidfd(struct task_struct *task)
 {
 	struct pid *pid;
 
@@ -2060,9 +2060,6 @@ bool do_notify_parent(struct task_struct *tsk, int sig)
 	WARN_ON_ONCE(!tsk->ptrace &&
 	       (tsk->group_leader != tsk || !thread_group_empty(tsk)));
 
-	/* Wake up all pidfd waiters */
-	do_notify_pidfd(tsk);
-
 	if (sig != SIGCHLD) {
 		/*
 		 * This is only possible if parent == real_parent.