On Wed, 16 Apr 2008 21:17:34 -0700 "Paul Menage" <menage@xxxxxxxxxx> wrote: > On Wed, Apr 16, 2008 at 9:11 PM, Andrew Morton > <akpm@xxxxxxxxxxxxxxxxxxxx> wrote: > > > > I don't fully understand the race. Both paths hold css_set_lock. > > > > Can you describe it in more detail please? > > Task A starts exiting, passes the check for unlinking current->cg_list. So cgroup_exit() sees !list_empty(tsk->cg_list) And the list_del() sets tsk->cg_list to LIST_POISON[12], which still means !list_empty(). Or we remove that debugging code and avoid writing to tsk->cg_list, and it _still_ is !list_empty(). > Before it completely exits task B does the very first > cgroup_iter_begin() call (via reading a cgroups tasks file) which > links all tasks in to their css_set objects via tsk->cg_list. But it won't link this task, because it's !list_empty(). > Then task A finishes exiting and is freed, but doesn't unlink from the cg_list. > > > > > afacit the task at *p could set PF_EXITING immediately after this code has > > tested PF_EXITING and then the task at *p could proceed until we hit the > > same race (whatever that is). > > The important fact there is that the task sets PF_EXITING *before* it > checks whether it needs to unlink from current->cg_list. > > Paul _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/containers
