On 2013/1/21 17:27, Daniel Wagner wrote: > On 21.01.2013 10:01, Li Zefan wrote: >> On 2013/1/21 16:50, Daniel Wagner wrote: >>> Hi Li, >>> >>> On 21.01.2013 07:08, Li Zefan wrote: >>>> I'm not a network developer, so correct me if I'm wrong. >>>> >>>> Since commit 7955490f732c2b8 >>>> ("net: netprio_cgroup: rework update socket logic"), sock->sk->sk_cgrp_prioidx >>>> is set when the socket is created, and won't be updated unless the task is >>>> moved to another cgroup. >>>> >>>> Now the problem is, a socket can be _shared_ by multiple processes (fork, SCM_RIGHT). >>>> If we place those processes in different cgroups, and each cgroup has >>>> different configs, but all of the processes will send data via this socket >>>> with the same network priority. >>> >>> Wouldn't that be addressed by 48a87cc26c13b68f6cce4e9d769fcb17a6b3e4b8 >>> >>> net: netprio: fd passed in SCM_RIGHTS datagram not set correctly >>> >>> A socket fd passed in a SCM_RIGHTS datagram was not getting >>> updated with the new tasks cgrp prioidx. This leaves IO on >>> the socket tagged with the old tasks priority. >>> >>> To fix this add a check in the scm recvmsg path to update the >>> sock cgrp prioidx with the new tasks value. >>> >>> As I read this this should work for net_prio. >>> >> >> But after process A passed the socket fd to B, both A and B can use the >> same socket to send data, right? Then if A and B were placed in different >> cgroups with differnt configs, A's config won't take effect anymore. >> >> Am I missing something? > > I don't know. I guess at one point the socket resources are shared and then > one configuration is taking preference. As you can see I am far away of > being > an expert in this field. Hopefully someone who understands this bits > can chip in. > > BTW, isn't this a similar to what should happen with the block io cgroup? > What is the behavior with a fd writing to a file in the scenario you > describe above? > It forbids task moving in this case: /* * We cannot support shared io contexts, as we have no mean to support * two tasks with the same ioc in two different groups without major rework * of the main cic data structures. For now we allow a task to change * its cgroup only if it's the only owner of its ioc. */ static int blkcg_can_attach(struct cgroup *cgrp, struct cgroup_taskset *tset) -- To unsubscribe from this list: send the line "unsubscribe cgroups" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html