On Fri, Apr 27, 2012 at 03:02:22PM +0900, KAMEZAWA Hiroyuki wrote: > attach_task() is done under cgroup_mutex() but ->pre_destroy() callback > in rmdir() isn't called under cgroup_mutex(). > > It's better to avoid attaching a task to a cgroup which > is under pre_destroy(). Considering memcg, the attached task may > increase resource usage after memcg's pre_destroy() confirms that > memcg is empty. This is not good. > > Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> > --- > kernel/cgroup.c | 5 ++++- > 1 files changed, 4 insertions(+), 1 deletions(-) > > diff --git a/kernel/cgroup.c b/kernel/cgroup.c > index ad8eae5..7a3076b 100644 > --- a/kernel/cgroup.c > +++ b/kernel/cgroup.c > @@ -1953,6 +1953,9 @@ int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk) > if (cgrp == oldcgrp) > return 0; > > + if (test_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags)) > + return -EBUSY; > + You probably need to update cgroup_attach_proc() as well? > tset.single.task = tsk; > tset.single.cgrp = oldcgrp; > > @@ -4181,7 +4184,6 @@ again: > mutex_unlock(&cgroup_mutex); > return -EBUSY; > } > - mutex_unlock(&cgroup_mutex); > > /* > * In general, subsystem has no css->refcnt after pre_destroy(). But > @@ -4193,6 +4195,7 @@ again: > * and css_tryget() and cgroup_wakeup_rmdir_waiter() implementation. > */ > set_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags); > + mutex_unlock(&cgroup_mutex); > > /* > * Call pre_destroy handlers of subsys. Notify subsystems > -- > 1.7.4.1 > > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>