On Wed, Apr 17, 2019 at 03:50:03PM +0200, Oleg Nesterov wrote: > On 04/17, Christian Brauner wrote: > > > > On Wed, Apr 17, 2019 at 03:16:03PM +0200, Oleg Nesterov wrote: > > > On 04/17, Christian Brauner wrote: > > > > > > > > On Mon, Apr 08, 2019 at 03:13:16PM +0200, Oleg Nesterov wrote: > > > > > > > > > > but perhaps it should always fail, even if task_pid(current) == pid. > > > > > > > > > > sys_rt_sigqueueinfo() allows to send any siginfo to yourself, but > > > > > this is only needed > > > > > for checkpoint/restart. > > > > > > > > Yes, that's why this was added. I would leave it in exactly because of > > > > checkpoint/restart. > > > > > > I don't understand... > > > > > > c/r doesn't need this "feature" in pidfd_send_signal(), so it can be > > > removed. > > > But, > > > > Just out of curiosity: in what sense? They don't need it since they have > > other ways of doing this > > Yes. The restarting process needs to "restore" the pending signals, including > the > signals with si_code >= 0. It does this using tgsigqueueinfo() and that is > why we > allow this if the signal sent to itself. > > So criu simply doesn't need pidfd_send_signal() to do this. And at the same > time, > > > or they *can't* use it for some other reason > > Yes again. pidfd_send_signal() does kill_pid_info(), so it can't be used to > restore > the "per-thread" task->pending signals.
In the future pidfd_send_signal() will gain the flag PIDFD_SIGNAL_THREAD. Jann and I already have a patch for this but we're holding off until the need arises. Christian
