We can now assume that the css_set reference held by the task will not go away for an exiting task. PF_EXITING state can be trusted throughout migration by checking it after locking threadgroup. While at it, renamed css_set_check_fetched to css_set_fetched. !css_set_fetched() seems to read better than !css_set_check_fetched(). Changes in V4: * https://lkml.org/lkml/2011/12/20/368 (Tejun Heo) * Fix typo in commit message * Undid the rename of css_set_check_fetched * https://lkml.org/lkml/2011/12/20/427 (Li Zefan) * Fix comment in cgroup_task_migrate() Changes in V3: * https://lkml.org/lkml/2011/12/20/255 (Frederic Weisbecker) * Fixed to put error in retval Changes in V2: * https://lkml.org/lkml/2011/12/19/289 (Tejun Heo) * Updated commit message Signed-off-by: Mandeep Singh Baines <msb@xxxxxxxxxxxx> Cc: Tejun Heo <tj@xxxxxxxxxx> Cc: Li Zefan <lizf@xxxxxxxxxxxxxx> Cc: containers@xxxxxxxxxxxxxxxxxxxxxxxxxx Cc: cgroups@xxxxxxxxxxxxxxx Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx> Cc: Oleg Nesterov <oleg@xxxxxxxxxx> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Cc: Paul Menage <paul@xxxxxxxxxxxxxx> --- kernel/cgroup.c | 28 ++++++++-------------------- 1 files changed, 8 insertions(+), 20 deletions(-) diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 4936d88..8228808 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -1850,14 +1850,12 @@ static int cgroup_task_migrate(struct cgroup *cgrp, struct cgroup *oldcgrp, struct css_set *newcg; /* - * get old css_set. We are synchronized through threadgroup_lock() - * against PF_EXITING setting such that we can't race against - * cgroup_exit() changing the css_set to init_css_set and dropping the - * old one. + * We are synchronized through threadgroup_lock() against PF_EXITING + * setting such that we can't race against cgroup_exit() changing the + * css_set to init_css_set and dropping the old one. */ WARN_ON_ONCE(tsk->flags & PF_EXITING); oldcg = tsk->cgroups; - get_css_set(oldcg); /* locate or allocate a new css_set for this task. */ if (guarantee) { @@ -1872,12 +1870,9 @@ static int cgroup_task_migrate(struct cgroup *cgrp, struct cgroup *oldcgrp, might_sleep(); /* find_css_set will give us newcg already referenced. */ newcg = find_css_set(oldcg, cgrp); - if (!newcg) { - put_css_set(oldcg); + if (!newcg) return -ENOMEM; - } } - put_css_set(oldcg); task_lock(tsk); rcu_assign_pointer(tsk->cgroups, newcg); @@ -2186,18 +2181,11 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader) * init_css_set. */ oldcg = tc->task->cgroups; - get_css_set(oldcg); - /* see if the new one for us is already in the list? */ - if (css_set_check_fetched(cgrp, tc->task, oldcg, &newcg_list)) { - /* was already there, nothing to do. */ - put_css_set(oldcg); - } else { - /* we don't already have it. get new one. */ - retval = css_set_prefetch(cgrp, oldcg, &newcg_list); - put_css_set(oldcg); - if (retval) + + /* if we don't already have it in the list get a new one */ + if (!css_set_check_fetched(cgrp, tc->task, oldcg, &newcg_list)) + if (retval = css_set_prefetch(cgrp, oldcg, &newcg_list)) goto out_list_teardown; - } } /* -- 1.7.3.1 _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/containers
