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| author | Oleg Nesterov <oleg@redhat.com> | 2024-01-31 14:26:02 +0100 |
|---|---|---|
| committer | Christian Brauner <brauner@kernel.org> | 2024-02-02 13:12:28 +0100 |
| commit | 64bef697d33b75fc06c5789b3f8108680271529f (patch) | |
| tree | dacc56670ce9a76cb7252e69dd88fcdeb7d72f2f /kernel/exit.c | |
| parent | 21e25205d7f9b6d7d3807546dd12ea93844b7c8e (diff) | |
| download | linux-64bef697d33b75fc06c5789b3f8108680271529f.tar.gz linux-64bef697d33b75fc06c5789b3f8108680271529f.tar.bz2 linux-64bef697d33b75fc06c5789b3f8108680271529f.zip | |
pidfd: implement PIDFD_THREAD flag for pidfd_open()
With this flag:
- pidfd_open() doesn't require that the target task must be
a thread-group leader
- pidfd_poll() succeeds when the task exits and becomes a
zombie (iow, passes exit_notify()), even if it is a leader
and thread-group is not empty.
This means that the behaviour of pidfd_poll(PIDFD_THREAD,
pid-of-group-leader) is not well defined if it races with
exec() from its sub-thread; pidfd_poll() can succeed or not
depending on whether pidfd_task_exited() is called before
or after exchange_tids().
Perhaps we can improve this behaviour later, pidfd_poll()
can probably take sig->group_exec_task into account. But
this doesn't really differ from the case when the leader
exits before other threads (so pidfd_poll() succeeds) and
then another thread execs and pidfd_poll() will block again.
thread_group_exited() is no longer used, perhaps it can die.
Co-developed-by: Tycho Andersen <tycho@tycho.pizza>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Link: https://lore.kernel.org/r/20240131132602.GA23641@redhat.com
Tested-by: Tycho Andersen <tandersen@netflix.com>
Reviewed-by: Tycho Andersen <tandersen@netflix.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
Diffstat (limited to 'kernel/exit.c')
| -rw-r--r-- | kernel/exit.c | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/kernel/exit.c b/kernel/exit.c index 3988a02efaef..c038d10dfb38 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -739,6 +739,13 @@ static void exit_notify(struct task_struct *tsk, int group_dead) kill_orphaned_pgrp(tsk->group_leader, NULL); tsk->exit_state = EXIT_ZOMBIE; + /* + * sub-thread or delay_group_leader(), wake up the + * PIDFD_THREAD waiters. + */ + if (!thread_group_empty(tsk)) + do_notify_pidfd(tsk); + if (unlikely(tsk->ptrace)) { int sig = thread_group_leader(tsk) && thread_group_empty(tsk) && |