public-mirrors/linux
1
0
Fork 0
mirror of git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git synced 2025-09-18 22:14:16 +00:00
Code Issues Projects Releases Packages Wiki Activity Actions

pidfs: cleanup the usage of do_notify_pidfd()

Browse source 
If a single-threaded process exits do_notify_pidfd() will be called twice,
from exit_notify() and right after that from do_notify_parent().

1. Change exit_notify() to call do_notify_pidfd() if the exiting task is
   not ptraced and it is not a group leader.

2. Change do_notify_parent() to call do_notify_pidfd() unconditionally.

   If tsk is not ptraced, do_notify_parent() will only be called when it
   is a group-leader and thread_group_empty() is true.

This means that if tsk is ptraced, do_notify_pidfd() will be called from
do_notify_parent() even if tsk is a delay_group_leader(). But this case is
less common, and apart from the unnecessary __wake_up() is harmless.

Granted, this unnecessary __wake_up() can be avoided, but I don't want to
do it in this patch because it's just a consequence of another historical
oddity: we notify the tracer even if !thread_group_empty(), but do_wait()
from debugger can't work until all other threads exit. With or without this
patch we should either eliminate do_notify_parent() in this case, or change
do_wait(WEXITED) to untrace the ptraced delay_group_leader() at least when
ptrace_reparented().

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Link: https://lore.kernel.org/r/20250323171955.GA834@redhat.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
Oleg Nesterov 2025-03-23 18:19:55 +01:00 • committed by Christian Brauner
parent 2df0c02dab
commit 0b7747a547
No known key found for this signature in database
GPG key ID: 91C61BC06578DCA2
2 changed files with 5 additions and 11 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

8
kernel/exit.c
View file

@ -756,12 +756,6 @@ static void exit_notify(struct task_struct *tsk, int group_dead)
kill_orphaned_pgrp(tsk->group_leader, NULL);
tsk->exit_state = EXIT_ZOMBIE;
/*
* Ignore thread-group leaders that exited before all
* subthreads did.
*/
if (!delay_group_leader(tsk))
do_notify_pidfd(tsk);
if (unlikely(tsk->ptrace)) {
int sig = thread_group_leader(tsk) &&
@ -774,6 +768,8 @@ static void exit_notify(struct task_struct *tsk, int group_dead)
do_notify_parent(tsk, tsk->exit_signal);
} else {
autoreap = true;
/* untraced sub-thread */
do_notify_pidfd(tsk);
}
if (autoreap) {

8
kernel/signal.c
View file

@ -2179,11 +2179,9 @@ bool do_notify_parent(struct task_struct *tsk, int sig)
WARN_ON_ONCE(!tsk->ptrace &&
(tsk->group_leader != tsk || !thread_group_empty(tsk)));
/*
* Notify for thread-group leaders without subthreads.
*/
if (thread_group_empty(tsk))
do_notify_pidfd(tsk);
/* ptraced, or group-leader without sub-threads */
do_notify_pidfd(tsk);
if (sig != SIGCHLD) {
/*