From 38fd525a4c61e7ecdc9ad4dcbf7b767d0a007962 Mon Sep 17 00:00:00 2001 From: "Eric W. Biederman" Date: Wed, 1 Jul 2020 07:30:06 -0500 Subject: exit: Factor thread_group_exited out of pidfd_poll Create an independent helper thread_group_exited which returns true when all threads have passed exit_notify in do_exit. AKA all of the threads are at least zombies and might be dead or completely gone. Create this helper by taking the logic out of pidfd_poll where it is already tested, and adding a READ_ONCE on the read of task->exit_state. I will be changing the user mode driver code to use this same logic to know when a user mode driver needs to be restarted. Place the new helper thread_group_exited in kernel/exit.c and EXPORT it so it can be used by modules. Link: https://lkml.kernel.org/r/20200702164140.4468-13-ebiederm@xmission.com Acked-by: Christian Brauner Acked-by: Alexei Starovoitov Tested-by: Alexei Starovoitov Signed-off-by: "Eric W. Biederman" --- kernel/fork.c | 6 +----- 1 file changed, 1 insertion(+), 5 deletions(-) (limited to 'kernel/fork.c') diff --git a/kernel/fork.c b/kernel/fork.c index 142b23645d82..bf215af7a904 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -1787,22 +1787,18 @@ static void pidfd_show_fdinfo(struct seq_file *m, struct file *f) */ static __poll_t pidfd_poll(struct file *file, struct poll_table_struct *pts) { - struct task_struct *task; struct pid *pid = file->private_data; __poll_t poll_flags = 0; poll_wait(file, &pid->wait_pidfd, pts); - rcu_read_lock(); - task = pid_task(pid, PIDTYPE_PID); /* * Inform pollers only when the whole thread group exits. * If the thread group leader exits before all other threads in the * group, then poll(2) should block, similar to the wait(2) family. */ - if (!task || (task->exit_state && thread_group_empty(task))) + if (thread_group_exited(pid)) poll_flags = EPOLLIN | EPOLLRDNORM; - rcu_read_unlock(); return poll_flags; } -- cgit v1.2.3