Jamie Lokier [jamie@xxxxxxxxxxxxx] wrote: | Sukadev Bhattiprolu wrote: | > Checkpoint/restart of file-owner. | > | > Add uid, euid parameters to f_modown(). These parameters will be needed | > when restarting an application (and hence restoring the file information), | > from a checkpoint image. | | This is used to make sure I/O signals on sockets, ttys, devices and so | on are delivered to a particular process. Good point. | | If any of those signals are lost when an event happens around the same Well, signals are not lost across C/R - if they were pending at checkpoint, they will be pending on restart. | time as c/r (for example, more data arriving on a pipe, a device | becomes readable/writable, or room becoming available to write, or | urgent data on a socket), a process depending on it can get stuck - | unless the process knows that c/r happened, so it knows to call | select() on all those fds after the c/r. Real devices like ttys are still TBD from C/R perspective - so data arriving from the tty is still a problem. Applications using such devices cannot be checkpointed. But for pipes, (and sockets ?) we expect that both ends are checkpointed as a container. So before the container is frozen for checkpoint, either both the write() and SIGIO (due to new data on the pipe) both happen or neither. Sukadev -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
