> On Sep 23, 2022, at 15:53, Florian Weimer <fweimer@xxxxxxxxxx> wrote: > >> I don't quite understand what you mean, sorry. But if kill() returns >> -ESRCH for tid which is not equal to tgid, kill() can only send signal >> to thread group via main thread id, that is what BSD did and manual >> said. It seems not odd? > > It's still odd because there's one TID per process that's valid for > kill by accident. That's all. > > Thanks, > Florian As far as I know, there is no rule forbidding 'process ID'(TGID on Linux) equals to main thread ID, is it right? If one wants to send signal to a specific thread, tgkill() can do that. As far as I understand, the difference between kill() and tgkill() is whether the signal is set on shared_pending, whatever the ID is a process ID or a thread ID. For Linux, the main thread ID just equals to the process ID. So the meaning of kill(main_tid, sig) is sending signal to a process, of which the PID equals to the first argument. It's not odd, I think. Thanks, Cambda
