wait: use EXIT_TRACE only if thread_group_leader(zombie) (b4360690) · Commits · 戴 / test

wait_task_zombie() always uses EXIT_TRACE/ptrace_unlink() if ptrace_reparented(). This is suboptimal and a bit confusing: we do not need do_notify_parent(p) if !thread_group_leader(p) and in this case we also do not need ptrace_unlink(), we can rely on ptrace_release_task(). Change wait_task_zombie() to check thread_group_leader() along with ptrace_reparented() and simplify the final p->exit_state transition. Signed-off-by:

Oleg Nesterov <oleg@redhat.com> Tested-by:

Michal Schmidt <mschmidt@redhat.com> Cc: Jan Kratochvil <jan.kratochvil@redhat.com> Cc: Al Viro <viro@ZenIV.linux.org.uk> Cc: Lennart Poettering <lpoetter@redhat.com> Cc: Roland McGrath <roland@hack.frob.com> Cc: Tejun Heo <tj@kernel.org> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

kernel/exit.c

+7 −10

Original line number	Diff line number	Diff line
		@@ -1040,7 +1040,7 @@ static int wait_task_zombie(struct wait_opts wo, struct task_struct p)
		/*
		* Move the task's state to DEAD/TRACE, only one thread can do this.
		*/
		state = traced ? EXIT_TRACE : EXIT_DEAD;
		state = traced && thread_group_leader(p) ? EXIT_TRACE : EXIT_DEAD;
		if (cmpxchg(&p->exit_state, EXIT_ZOMBIE, state) != EXIT_ZOMBIE)
		return 0;
		/*
		@@ -1140,18 +1140,15 @@ static int wait_task_zombie(struct wait_opts wo, struct task_struct p)
		if (!retval)
		retval = pid;

		if (traced) {
		if (state == EXIT_TRACE) {
		write_lock_irq(&tasklist_lock);
		/* We dropped tasklist, ptracer could die and untrace */
		ptrace_unlink(p);
		/*
		* If this is not a sub-thread, notify the parent.
		* If parent wants a zombie, don't release it now.
		*/
		state = EXIT_DEAD;
		if (thread_group_leader(p) &&
		!do_notify_parent(p, p->exit_signal))

		/* If parent wants a zombie, don't release it now */
		state = EXIT_ZOMBIE;
		if (do_notify_parent(p, p->exit_signal))
		state = EXIT_DEAD;
		p->exit_state = state;
		write_unlock_irq(&tasklist_lock);
		}

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