On Wed, May 27, 2009 at 01:32:49PM -0400, Oren Laadan wrote: > Restarting of multiple processes expects all restarting tasks to call > sys_restart(). Once inside the system call, each task will restart > itself at the same order that they were saved. The internals of the > syscall will take care of in-kernel synchronization bewteen tasks. > > This patch does _not_ create the task tree in the kernel. Instead it > assumes that all tasks are created in some way and then invoke the > restart syscall. You can use the userspace mktree.c program to do > that. > > The init task (*) has a special role: it allocates the restart context > (ctx), and coordinates the operation. In particular, it first waits > until all participating tasks enter the kernel, and provides them the > common restart context. Once everyone in ready, it begins to restart > itself. > > In contrast, the other tasks enter the kernel, locate the init task (*) > and grab its restart context, and then wait for their turn to restore. > > When a task (init or not) completes its restart, it hands the control > over to the next in line, by waking that task. > > An array of pids (the one saved during the checkpoint) is used to > synchronize the operation. The first task in the array is the init > task (*). The restart context (ctx) maintain a "current position" in > the array, which indicates which task is currently active. Once the > currently active task completes its own restart, it increments that > position and wakes up the next task. > > Restart assumes that userspace provides meaningful data, otherwise > it's garbage-in-garbage-out. In this case, the syscall may block > indefinitely, but in TASK_INTERRUPTIBLE, so the user can ctrl-c or > otherwise kill the stray restarting tasks. > > In terms of security, restart runs as the user the invokes it, so it > will not allow a user to do more than is otherwise permitted by the > usual system semantics and policy. > > Currently we ignore threads and zombies Let's discuss threads and zombies. 1. Will zombie end up in a image? 2. If yes, how it will be restored. Will it be forked, call restart(2) and then somehow zombified inside kernel? 3. How thread group will be restored, will every thread be CLONE_THREAD'ed? What to do with exited thread group leaders, will they be forked, then CLONE_THREAD thread group? _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/containers
