> 2 parallel enters? I meant you have pid 0 in the entered pid namespace. > You have pid 0 because your pid simply does not map. Oh, I see. > There is nothing that makes to parallel enters impossible in that. > Even today we have one thread per cpu that has task->pid == &init_struct_pid > which is pid 0. How about the forked processes then? Who will be their parent? > For the case of unshare where we are designed to be used with PAM I don't > think my proposed semantics work. For a join needed an extra fork before > you are really in the pid namespace should be minor. Hm... One more proposal - can we adopt the planned new fork_with_pids system call to fork the process right into a new pid namespace? > That doesn't handle the case of cached struct pids. A good example is > waitpid, where it waits for a specific struct pid. Which means that > allocating a new struct pid and changing task->pid will cause > waitpid(pid) to wait forever... OK. Good example. Thanks. > To change struct pid would require the refcount on struct pid to show > no references from anywhere except the task_struct. I think this is OK to return -EBUSY for this. And fix the waitpid respectively not to block this common case. All the others I think can be stayed as is. > At the cost of a little memory we can solve that problem for unshare > if we have a an extra upid in struct pid, how we verify there is space > in struct pid I'm not certain. > > I do think that at least until someone calls exec the namespace pids are > reported to the process itself should not change. That is kill and Wait a second - in that case the wait will be blocked too! No? > waitpid etc. Which suggests an implementation the opposite of what > I proposed. With ns_of_pid(task_pid(current)) being used as the > pid namespace of children, and current->nsproxy->pid_ns not changing > in the case of unshare. > > Shrug. > > Or perhaps this is a case where we use we can implement join with > an extra process but we can't implement unshare, because the effect > cannot be immediate. Well, I'm talking only about the join now. > Eric > -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
