Serge E. Hallyn [EMAIL PROTECTED] wrote: | Quoting Srivatsa Vaddagiri ([EMAIL PROTECTED]): | > On Fri, Nov 09, 2007 at 09:45:21AM +0100, Dmitry Adamushko wrote: | > > Humm... the 'current' is not kept within the tree but | > > current->se.on_rq is supposed to be '1' , | > > so the old code looks ok to me (at least for the 'leaf' elements). | > | > You are damned right! Sorry my mistake with the previous analysis and | > (as I now find out) testing :( | > | > There are couple of problems discovered by Suka's test: | > | > - The test requires the cgroup filesystem to be mounted with | > atleast the cpu and ns options (i.e both namespace and cpu | > controllers are active in the same hierarchy). | > | > # mkdir /dev/cpuctl | > # mount -t cgroup -ocpu,ns none cpuctl | > (or simply) | > # mount -t cgroup none cpuctl -> Will activate all controllers | > in same hierarchy. | > | > - The test invokes clone() with CLONE_NEWNS set. This causes a a new child | > to be created, also a new group (do_fork->copy_namespaces->ns_cgroup_clone-> | > cgroup_clone) and the child is attached to the new group (cgroup_clone-> | > attach_task->sched_move_task). At this point in time, the child's scheduler | > related fields are uninitialized (including its on_rq field, which it has | > inherited from parent). As a result sched_move_task thinks its on | > runqueue, when it isn't. | > | > As a solution to this problem, I moved sched_fork() call, which | > initializes scheduler related fields on a new task, before | > copy_namespaces(). I am not sure though whether moving up will | > cause other side-effects. Do you see any issue? | > | > - The second problem exposed by this test is that task_new_fair() | > assumes that parent and child will be part of the same group (which | > needn't be as this test shows). As a result, cfs_rq->curr can be NULL | > for the child. | > | > The solution is to test for curr pointer being NULL in | > task_new_fair(). | > | > | > With the patch below, I could run ns_exec() fine w/o a crash. | > | > Suka, can you verify whether this patch fixes your problem? | | Works on my machine. Thanks!
And mine too. Thanks, | | > -- | > | > Fix copy_namespace() <-> sched_fork() dependency in do_fork, by moving | > up sched_fork(). | > | > Also introduce a NULL pointer check for 'curr' in task_new_fair(). | > | > Signed-off-by : Srivatsa Vaddagiri <[EMAIL PROTECTED]> | | Tested-by: Serge Hallyn <[EMAIL PROTECTED]> Tested-by: Sukadev Bhattiprolu <[EMAIL PROTECTED]> - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
