>From the original thread, we tried the suggestion, but when the do_execve is >done from kernel_init
for Busybox /sbin/init (to start PID=1) all process zombies are flushed (the usermode helper that kicks Busybox /sbin/poweroff started by PID=2, before PID=1 is do_execve'd from kernel init). So when the line is crossed when PID=1 begins all zombies and pre-work are flushed, so nothing is carried over into the life of PID=1 to synchronize with or detect when the signals are properly setup. The only solution which worked was doing the abstract socket handshake which stays persistent across the boundary from PID=0 heritage to when PID=1 is properly instantiated. proc_flush_task_mnt from linux/fs/proc/base.c On 02/13/2018 08:32 PM, Laurent Bercot wrote: >> Even when process=1 is started, it still leaves a window when the >> signal handler setup has not been completed. > > Yes, but you can still use kill(pid, 0) to check whether init is > ready to receive signals: doublefork a zombie and repeatedly kill it > with signal 0. When you get -1 ESRCH, it means init has reapt the > zombie, so it's in its reaping loop, and at that point you know it > has installed its signal handlers. > > See http://lists.busybox.net/pipermail/busybox/2017-October/085888.html > > That's arguably uglier than using abstract sockets, but it can > be done without modifying the init code at all. > > -- > Laurent > _______________________________________________ busybox mailing list [email protected] http://lists.busybox.net/mailman/listinfo/busybox
