On 02/08, Eric W. Biederman wrote: > > Oleg Nesterov <oleg@xxxxxxxxxx> writes: > > > Turn kill_pid_info() into kill_pid_info_type(), this allows to pass any > > pid_type to group_send_sig_info(), despite its name it should work fine > > even if type = PIDTYPE_PID. > > > > Change pidfd_send_signal() to use PIDTYPE_PID or PIDTYPE_TGID depending > > on PIDFD_THREAD. > > > > While at it kill another TODO comment in pidfd_show_fdinfo(). As Christian > > expains fdinfo reports f_flags, userspace can already detect PIDFD_THREAD. > > > > I have a question here. > > Why is this based on group_send_sig_info instead of send_sig_info? Well. send_sig_info() accepts "struct task_struct *", not "struct pid *", it doesn't do check_kill_permission(), and it doesn't handle the possible race with mt-exec. > In particular I am asking are the intended semantics that the signal is > sent to a single thread in a thread group and placed in the per thread > queue, or is the signal sent to the entire thread group and placed > in the thread group signal queue? This depends on PIDFD_THREAD. If it is set then the signal goes to the per thread queue. > Because honestly right now using group_send_sig_info when > the intended target of the signal is not the entire thread > group is very confusing when reading your change. Agreed, so perhaps it makes sense to rename it later. See despite its name it should work fine even if type = PIDTYPE_PID. in the changelog above. Oleg.
