Messages in this thread | | | Date | Wed, 26 Oct 2011 13:27:45 -0700 (PDT) | From | David Rientjes <> | Subject | Re: [patch-final] Re: patch] cpusets, cgroups: disallow attaching kthreadd |
| |
On Wed, 19 Oct 2011, Mike Galbraith wrote:
> cpusets, cgroups: disallow attaching kthreadd > > Allowing kthreadd to be moved to a non-root group makes no sense, it being > a global resource, and needlessly leads unsuspecting users toward trouble. > > 1. An RT workqueue worker thread spawned in a task group with no rt_runtime > allocated is not schedulable. Simple user error, but harmful to the box. > > 2. A worker thread which acquires PF_THREAD_BOUND can never leave a cpuset, > rendering the cpuset immortal. > > Save the user some unexpected trouble, just say no. > > Signed-off-by: Mike Galbraith <efault@gmx.de> > Acked-by: David Rientjes <rientjes@google.com> > Acked-by: Paul Menage <paul@paulmenage.org> >
Let's add Andrew to the cc so we can get it in -mm, I haven't seen it hit linux-next yet.
> --- > kernel/cpuset.c | 6 ++++-- > kernel/sched.c | 10 ++++++++++ > 2 files changed, 14 insertions(+), 2 deletions(-) > > Index: linux-3.0-tip/kernel/cpuset.c > =================================================================== > --- linux-3.0-tip.orig/kernel/cpuset.c > +++ linux-3.0-tip/kernel/cpuset.c > @@ -59,6 +59,7 @@ > #include <linux/mutex.h> > #include <linux/workqueue.h> > #include <linux/cgroup.h> > +#include <linux/kthread.h> > > /* > * Workqueue for cpuset related tasks. > @@ -1382,9 +1383,10 @@ static int cpuset_can_attach(struct cgro > * set of allowed nodes is unnecessary. Thus, cpusets are not > * applicable for such threads. This prevents checking for success of > * set_cpus_allowed_ptr() on all attached tasks before cpus_allowed may > - * be changed. > + * be changed. We also disallow attaching kthreadd, to prevent it's > + * child from becoming trapped should it then acquire PF_THREAD_BOUND. > */ > - if (tsk->flags & PF_THREAD_BOUND) > + if (tsk->flags & PF_THREAD_BOUND || tsk == kthreadd_task) > return -EINVAL; > > return 0; > Index: linux-3.0-tip/kernel/sched.c > =================================================================== > --- linux-3.0-tip.orig/kernel/sched.c > +++ linux-3.0-tip/kernel/sched.c > @@ -71,6 +71,7 @@ > #include <linux/ctype.h> > #include <linux/ftrace.h> > #include <linux/slab.h> > +#include <linux/kthread.h> > > #include <asm/tlb.h> > #include <asm/irq_regs.h> > @@ -9141,6 +9142,15 @@ cpu_cgroup_destroy(struct cgroup_subsys > static int > cpu_cgroup_can_attach_task(struct cgroup *cgrp, struct task_struct *tsk) > { > + /* > + * kthreadd can fork workers for an RT workqueue in a cgroup > + * which may or may not have rt_runtime allocated. Just say no, > + * as attaching a global resource to a non-root group doesn't > + * make any sense anyway. > + */ > + if (tsk == kthreadd_task) > + return -EINVAL; > + > #ifdef CONFIG_RT_GROUP_SCHED > if (!sched_rt_can_attach(cgroup_tg(cgrp), tsk)) > return -EINVAL;
| |