On 10/15, Christian Brauner wrote: > > On Tue, Oct 15, 2019 at 04:43:57PM +0200, Oleg Nesterov wrote: > > But in fact I'd suggest to simply use !hlist_empty(&pid->tasks[PIDTYPE_PID]) > > in pidfd_show_fdinfo() and do not add a new helper. > > Sounds good to me. But can't we then just do something similar just with > !hlist_empty(&pid->tasks[PIDTYPE_TGID]) > > in v5.4-rc3:kernel/pid.c:pidfd_open():514-517 ? Agreed. Actually, it seems to me I suggested to use rcu_lock_acquire() rather than rcu_read_lock() in pidfd_open() too. But hlist_empty(pid->tasks[type]) looks even better. If you decide to add a new helper, you can also change do_wait() which checks hlist_empty(&wo->wo_pid->tasks[wo->wo_type]). May be even __change_pid(). Oleg.
