On 02/20, Christian Brauner wrote: > > On Fri, Feb 16, 2024 at 07:12:14PM +0100, Oleg Nesterov wrote: > > On 02/16, Christian Brauner wrote: > > > > > > > SI_USER means that the target can trust the values of si_pid/si_uid > > > > in siginfo. > > > > > > Bah, what an annoying nonsense. I see that this can be used to emulate > > > stuff like SI_TIMER and SI_ASYNCIO. But I very much doubt the value of > > > e.g., emulating SI_DETHREAD. Maybe I'm missing something very obvious. > > > > I don't understand... > > My question was what the purpose of being able to to set si_code to > e.g., SI_DETHREAD is and then to send a signal to yourself? Because it > looks like that's what rt_{tg}sigqueueinfo() and pidfd_send_signal() > allows the caller to do. I'm just trying to understand use-cases for > this. Ah. IIRC criu uses this hack to restore the pending (arbitrary) signals collected at dump time. I was a bit surprise sys_pidfd_send_signal() allows this hack too, I don't think that criu uses pidfd at restore time, but I do not know. Oleg.