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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/signal.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/signal.c')
| -rw-r--r-- | kernel/signal.c | 6 |
1 files changed, 4 insertions, 2 deletions
diff --git a/kernel/signal.c b/kernel/signal.c index 9561a3962ca6..9b40109f0c56 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -2019,7 +2019,7 @@ ret: return ret; } -static void do_notify_pidfd(struct task_struct *task) +void do_notify_pidfd(struct task_struct *task) { struct pid *pid; @@ -2051,7 +2051,8 @@ bool do_notify_parent(struct task_struct *tsk, int sig) WARN_ON_ONCE(!tsk->ptrace && (tsk->group_leader != tsk || !thread_group_empty(tsk))); /* - * tsk is a group leader and has no threads, wake up the pidfd waiters. + * tsk is a group leader and has no threads, wake up the + * non-PIDFD_THREAD waiters. */ if (thread_group_empty(tsk)) do_notify_pidfd(tsk); @@ -3926,6 +3927,7 @@ SYSCALL_DEFINE4(pidfd_send_signal, int, pidfd, int, sig, prepare_kill_siginfo(sig, &kinfo); } + /* TODO: respect PIDFD_THREAD */ ret = kill_pid_info(sig, &kinfo, pid); err: |