From 0b7747a5477eb22d041997bc085fa8d492fa9b96 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Sun, 23 Mar 2025 18:19:55 +0100 Subject: pidfs: cleanup the usage of do_notify_pidfd() 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 Link: https://lore.kernel.org/r/20250323171955.GA834@redhat.com Signed-off-by: Christian Brauner --- kernel/exit.c | 8 ++------ 1 file changed, 2 insertions(+), 6 deletions(-) (limited to 'kernel/exit.c') diff --git a/kernel/exit.c b/kernel/exit.c index c2e6c7b7779f..5d1226fdfadc 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -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) { -- cgit v1.2.3