Quoting Eric W. Biederman (ebiederm at xmission.com): > "Serge E. Hallyn" <serue at us.ibm.com> writes: > > > Quoting Eric W. Biederman (ebiederm at xmission.com): > >> Yes. We all so need something like that list to support kill -1. > >> Although walking the list of all processes may be sufficient for a first > >> pass. > >> > >> The real trick is handing nested pid namespaces, properly. > > > > Not if, as you've suggested in the past, pid_ns 5 has valid pids in its > > own pid_ns for every process in pid_namespaces nested under it. > > > > It should be simple to implement, should not impact the non-container > > cases, and should only start to impact performance as the nesting gets > > deep, which AFAIK we all believe won't happen (max nesting of 2 AFAICS, > > one checkpointable application container under one vserver-thingie) > > > > And it makes kill -1 trivial, as in pid_ns 5 we just kill all processes > > in pid_ns 5, without worrying about finding the ones in it's decendent > > pid namespaces. > > If you do it correctly I agree. But you have to be very careful where > you put the list. > > My point being not that we can't get this correct with simple code, but > that it is easy to get it wrong. True. I should think the list has to go into the struct pid, not the task_struct. There is one struct pid per (pid_ns, pid), so we can keep just one simple list to walk the pid_ns processes. If we were to put it in the task_struct, well there's really no clean way to go about it then :) thanks, -serge
